KVM: Don't pre-reserve xarray entries when storing empty/NULL attributesgrafted

Skip the xarray reservation loop when clearing all memory attributes, as
storing NULL only erases the entry and never needs to allocate, so no
reservation (and no cleanup of a failed one) is required in that case.

Suggested-by: Sean Christopherson <seanjc@google.com>
Cc: David Ballesteros <davimaba.v@proton.me>
Signed-off-by: Zeng Chi <zengchi@kylinos.cn>
Link: https://patch.msgid.link/20260921102442.1232375-1-zeng_chi911@163.com
[sean: split to separate patch]
Signed-off-by: Sean Christopherson <seanjc@google.com>

41 files changed, 18333 insertions, 0 deletions

diff --git a/net/rds/Kconfig b/net/rds/Kconfig
new file mode 100644
index 000000000..f007730aa
--- /dev/null
+++ b/net/rds/Kconfig
@@ -0,0 +1,37 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+config RDS
+	tristate "The Reliable Datagram Sockets Protocol"
+	depends on INET
+	help
+	  The RDS (Reliable Datagram Sockets) protocol provides reliable,
+	  sequenced delivery of datagrams over Infiniband or TCP.
+
+config RDS_RDMA
+	tristate "RDS over Infiniband"
+	depends on RDS && INFINIBAND && INFINIBAND_ADDR_TRANS
+	help
+	  Allow RDS to use Infiniband as a transport.
+	  This transport supports RDMA operations.
+
+config RDS_TCP
+	tristate "RDS over TCP"
+	depends on RDS
+	depends on IPV6 || !IPV6
+	help
+	  Allow RDS to use TCP as a transport.
+	  This transport does not support RDMA operations.
+
+config RDS_DEBUG
+	bool "RDS debugging messages"
+	depends on RDS
+	default n
+
+config GCOV_PROFILE_RDS
+	bool "Enable GCOV profiling on RDS"
+	depends on GCOV_KERNEL
+	help
+	  Enable GCOV profiling on RDS for checking which functions/lines
+	  are executed.
+
+	  If unsure, say N.
diff --git a/net/rds/Makefile b/net/rds/Makefile
new file mode 100644
index 000000000..3af1ca1d9
--- /dev/null
+++ b/net/rds/Makefile
@@ -0,0 +1,22 @@
+# SPDX-License-Identifier: GPL-2.0
+obj-$(CONFIG_RDS) += rds.o
+rds-y :=	af_rds.o bind.o cong.o connection.o info.o message.o   \
+			recv.o send.o stats.o sysctl.o threads.o transport.o \
+			loop.o page.o rdma.o
+
+obj-$(CONFIG_RDS_RDMA) += rds_rdma.o
+rds_rdma-y :=	rdma_transport.o \
+			ib.o ib_cm.o ib_recv.o ib_ring.o ib_send.o ib_stats.o \
+			ib_sysctl.o ib_rdma.o ib_frmr.o
+
+
+obj-$(CONFIG_RDS_TCP) += rds_tcp.o
+rds_tcp-y :=		tcp.o tcp_connect.o tcp_listen.o tcp_recv.o \
+			tcp_send.o tcp_stats.o
+
+ccflags-$(CONFIG_RDS_DEBUG)	:=	-DRDS_DEBUG
+
+# for GCOV coverage profiling
+ifdef CONFIG_GCOV_PROFILE_RDS
+GCOV_PROFILE := y
+endif
diff --git a/net/rds/af_rds.c b/net/rds/af_rds.c
new file mode 100644
index 000000000..d5defe917
--- /dev/null
+++ b/net/rds/af_rds.c
@@ -0,0 +1,1013 @@
+/*
+ * Copyright (c) 2006, 2019 Oracle and/or its affiliates. All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+#include <linux/module.h>
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/gfp.h>
+#include <linux/in.h>
+#include <linux/ipv6.h>
+#include <linux/poll.h>
+#include <linux/uio.h>
+#include <net/sock.h>
+
+#include "rds.h"
+
+/* this is just used for stats gathering :/ */
+static DEFINE_SPINLOCK(rds_sock_lock);
+static LIST_HEAD(rds_sock_list);
+DECLARE_WAIT_QUEUE_HEAD(rds_poll_waitq);
+
+/*
+ * This is called as the final descriptor referencing this socket is closed.
+ * We have to unbind the socket so that another socket can be bound to the
+ * address it was using.
+ *
+ * We have to be careful about racing with the incoming path.  sock_orphan()
+ * sets SOCK_DEAD and we use that as an indicator to the rx path that new
+ * messages shouldn't be queued.
+ */
+static int rds_release(struct socket *sock)
+{
+	struct sock *sk = sock->sk;
+	struct rds_sock *rs;
+
+	if (!sk)
+		goto out;
+
+	rs = rds_sk_to_rs(sk);
+
+	sock_orphan(sk);
+	/* Note - rds_clear_recv_queue grabs rs_recv_lock, so
+	 * that ensures the recv path has completed messing
+	 * with the socket. */
+	rds_clear_recv_queue(rs);
+	rds_cong_remove_socket(rs);
+
+	rds_remove_bound(rs);
+
+	rds_send_drop_to(rs, NULL);
+	rds_rdma_drop_keys(rs);
+	rds_notify_queue_get(rs, NULL);
+	rds_notify_msg_zcopy_purge(&rs->rs_zcookie_queue);
+
+	spin_lock_bh(&rds_sock_lock);
+	list_del_init(&rs->rs_item);
+	spin_unlock_bh(&rds_sock_lock);
+
+	rds_trans_put(rs->rs_transport);
+
+	sock->sk = NULL;
+	sock_put(sk);
+out:
+	return 0;
+}
+
+/*
+ * Careful not to race with rds_release -> sock_orphan which clears sk_sleep.
+ * _bh() isn't OK here, we're called from interrupt handlers.  It's probably OK
+ * to wake the waitqueue after sk_sleep is clear as we hold a sock ref, but
+ * this seems more conservative.
+ * NB - normally, one would use sk_callback_lock for this, but we can
+ * get here from interrupts, whereas the network code grabs sk_callback_lock
+ * with _lock_bh only - so relying on sk_callback_lock introduces livelocks.
+ */
+void rds_wake_sk_sleep(struct rds_sock *rs)
+{
+	unsigned long flags;
+
+	read_lock_irqsave(&rs->rs_recv_lock, flags);
+	__rds_wake_sk_sleep(rds_rs_to_sk(rs));
+	read_unlock_irqrestore(&rs->rs_recv_lock, flags);
+}
+
+static int rds_getname(struct socket *sock, struct sockaddr *uaddr,
+		       int peer)
+{
+	struct rds_sock *rs = rds_sk_to_rs(sock->sk);
+	struct sockaddr_in6 *sin6;
+	struct sockaddr_in *sin;
+	int uaddr_len;
+
+	/* racey, don't care */
+	if (peer) {
+		if (ipv6_addr_any(&rs->rs_conn_addr))
+			return -ENOTCONN;
+
+		if (ipv6_addr_v4mapped(&rs->rs_conn_addr)) {
+			sin = (struct sockaddr_in *)uaddr;
+			memset(sin->sin_zero, 0, sizeof(sin->sin_zero));
+			sin->sin_family = AF_INET;
+			sin->sin_port = rs->rs_conn_port;
+			sin->sin_addr.s_addr = rs->rs_conn_addr_v4;
+			uaddr_len = sizeof(*sin);
+		} else {
+			sin6 = (struct sockaddr_in6 *)uaddr;
+			sin6->sin6_family = AF_INET6;
+			sin6->sin6_port = rs->rs_conn_port;
+			sin6->sin6_addr = rs->rs_conn_addr;
+			sin6->sin6_flowinfo = 0;
+			/* scope_id is the same as in the bound address. */
+			sin6->sin6_scope_id = rs->rs_bound_scope_id;
+			uaddr_len = sizeof(*sin6);
+		}
+	} else {
+		/* If socket is not yet bound and the socket is connected,
+		 * set the return address family to be the same as the
+		 * connected address, but with 0 address value.  If it is not
+		 * connected, set the family to be AF_UNSPEC (value 0) and
+		 * the address size to be that of an IPv4 address.
+		 */
+		if (ipv6_addr_any(&rs->rs_bound_addr)) {
+			if (ipv6_addr_any(&rs->rs_conn_addr)) {
+				sin = (struct sockaddr_in *)uaddr;
+				memset(sin, 0, sizeof(*sin));
+				sin->sin_family = AF_UNSPEC;
+				return sizeof(*sin);
+			}
+
+#if IS_ENABLED(CONFIG_IPV6)
+			if (!(ipv6_addr_type(&rs->rs_conn_addr) &
+			      IPV6_ADDR_MAPPED)) {
+				sin6 = (struct sockaddr_in6 *)uaddr;
+				memset(sin6, 0, sizeof(*sin6));
+				sin6->sin6_family = AF_INET6;
+				return sizeof(*sin6);
+			}
+#endif
+
+			sin = (struct sockaddr_in *)uaddr;
+			memset(sin, 0, sizeof(*sin));
+			sin->sin_family = AF_INET;
+			return sizeof(*sin);
+		}
+		if (ipv6_addr_v4mapped(&rs->rs_bound_addr)) {
+			sin = (struct sockaddr_in *)uaddr;
+			memset(sin->sin_zero, 0, sizeof(sin->sin_zero));
+			sin->sin_family = AF_INET;
+			sin->sin_port = rs->rs_bound_port;
+			sin->sin_addr.s_addr = rs->rs_bound_addr_v4;
+			uaddr_len = sizeof(*sin);
+		} else {
+			sin6 = (struct sockaddr_in6 *)uaddr;
+			sin6->sin6_family = AF_INET6;
+			sin6->sin6_port = rs->rs_bound_port;
+			sin6->sin6_addr = rs->rs_bound_addr;
+			sin6->sin6_flowinfo = 0;
+			sin6->sin6_scope_id = rs->rs_bound_scope_id;
+			uaddr_len = sizeof(*sin6);
+		}
+	}
+
+	return uaddr_len;
+}
+
+/*
+ * RDS' poll is without a doubt the least intuitive part of the interface,
+ * as EPOLLIN and EPOLLOUT do not behave entirely as you would expect from
+ * a network protocol.
+ *
+ * EPOLLIN is asserted if
+ *  -	there is data on the receive queue.
+ *  -	to signal that a previously congested destination may have become
+ *	uncongested
+ *  -	A notification has been queued to the socket (this can be a congestion
+ *	update, or a RDMA completion, or a MSG_ZEROCOPY completion).
+ *
+ * EPOLLOUT is asserted if there is room on the send queue. This does not mean
+ * however, that the next sendmsg() call will succeed. If the application tries
+ * to send to a congested destination, the system call may still fail (and
+ * return ENOBUFS).
+ */
+static __poll_t rds_poll(struct file *file, struct socket *sock,
+			     poll_table *wait)
+{
+	struct sock *sk = sock->sk;
+	struct rds_sock *rs = rds_sk_to_rs(sk);
+	__poll_t mask = 0;
+	unsigned long flags;
+
+	poll_wait(file, sk_sleep(sk), wait);
+
+	if (READ_ONCE(rs->rs_seen_congestion))
+		poll_wait(file, &rds_poll_waitq, wait);
+
+	read_lock_irqsave(&rs->rs_recv_lock, flags);
+	if (!rs->rs_cong_monitor) {
+		/* When a congestion map was updated, we signal EPOLLIN for
+		 * "historical" reasons. Applications can also poll for
+		 * WRBAND instead. */
+		if (rds_cong_updated_since(&rs->rs_cong_track))
+			mask |= (EPOLLIN | EPOLLRDNORM | EPOLLWRBAND);
+	} else {
+		spin_lock(&rs->rs_lock);
+		if (rs->rs_cong_notify)
+			mask |= (EPOLLIN | EPOLLRDNORM);
+		spin_unlock(&rs->rs_lock);
+	}
+	if (!list_empty(&rs->rs_recv_queue) ||
+	    !list_empty(&rs->rs_notify_queue) ||
+	    !list_empty(&rs->rs_zcookie_queue.zcookie_head))
+		mask |= (EPOLLIN | EPOLLRDNORM);
+	if (rs->rs_snd_bytes < rds_sk_sndbuf(rs))
+		mask |= (EPOLLOUT | EPOLLWRNORM);
+	if (sk->sk_err || !skb_queue_empty(&sk->sk_error_queue))
+		mask |= EPOLLERR;
+	read_unlock_irqrestore(&rs->rs_recv_lock, flags);
+
+	/* clear state any time we wake a seen-congested socket */
+	if (mask)
+		WRITE_ONCE(rs->rs_seen_congestion, 0);
+
+	return mask;
+}
+
+static int rds_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
+{
+	struct rds_sock *rs = rds_sk_to_rs(sock->sk);
+	rds_tos_t utos, tos = 0;
+
+	switch (cmd) {
+	case SIOCRDSSETTOS:
+		if (get_user(utos, (rds_tos_t __user *)arg))
+			return -EFAULT;
+
+		if (rs->rs_transport &&
+		    rs->rs_transport->get_tos_map)
+			tos = rs->rs_transport->get_tos_map(utos);
+		else
+			return -ENOIOCTLCMD;
+
+		spin_lock_bh(&rds_sock_lock);
+		if (rs->rs_tos || rs->rs_conn) {
+			spin_unlock_bh(&rds_sock_lock);
+			return -EINVAL;
+		}
+		rs->rs_tos = tos;
+		spin_unlock_bh(&rds_sock_lock);
+		break;
+	case SIOCRDSGETTOS:
+		spin_lock_bh(&rds_sock_lock);
+		tos = rs->rs_tos;
+		spin_unlock_bh(&rds_sock_lock);
+		if (put_user(tos, (rds_tos_t __user *)arg))
+			return -EFAULT;
+		break;
+	default:
+		return -ENOIOCTLCMD;
+	}
+
+	return 0;
+}
+
+static int rds_cancel_sent_to(struct rds_sock *rs, sockptr_t optval, int len)
+{
+	struct sockaddr_in6 sin6;
+	struct sockaddr_in sin;
+	int ret = 0;
+
+	/* racing with another thread binding seems ok here */
+	if (ipv6_addr_any(&rs->rs_bound_addr)) {
+		ret = -ENOTCONN; /* XXX not a great errno */
+		goto out;
+	}
+
+	if (len < sizeof(struct sockaddr_in)) {
+		ret = -EINVAL;
+		goto out;
+	} else if (len < sizeof(struct sockaddr_in6)) {
+		/* Assume IPv4 */
+		if (copy_from_sockptr(&sin, optval,
+				sizeof(struct sockaddr_in))) {
+			ret = -EFAULT;
+			goto out;
+		}
+		ipv6_addr_set_v4mapped(sin.sin_addr.s_addr, &sin6.sin6_addr);
+		sin6.sin6_port = sin.sin_port;
+	} else {
+		if (copy_from_sockptr(&sin6, optval,
+				   sizeof(struct sockaddr_in6))) {
+			ret = -EFAULT;
+			goto out;
+		}
+	}
+
+	rds_send_drop_to(rs, &sin6);
+out:
+	return ret;
+}
+
+static int rds_set_bool_option(unsigned char *optvar, sockptr_t optval,
+			       int optlen)
+{
+	int value;
+
+	if (optlen < sizeof(int))
+		return -EINVAL;
+	if (copy_from_sockptr(&value, optval, sizeof(int)))
+		return -EFAULT;
+	*optvar = !!value;
+	return 0;
+}
+
+static int rds_cong_monitor(struct rds_sock *rs, sockptr_t optval, int optlen)
+{
+	int ret;
+
+	ret = rds_set_bool_option(&rs->rs_cong_monitor, optval, optlen);
+	if (ret == 0) {
+		if (rs->rs_cong_monitor) {
+			rds_cong_add_socket(rs);
+		} else {
+			rds_cong_remove_socket(rs);
+			rs->rs_cong_mask = 0;
+			rs->rs_cong_notify = 0;
+		}
+	}
+	return ret;
+}
+
+static int rds_set_transport(struct net *net, struct rds_sock *rs,
+			     sockptr_t optval, int optlen)
+{
+	int t_type;
+
+	if (rs->rs_transport)
+		return -EOPNOTSUPP; /* previously attached to transport */
+
+	if (optlen != sizeof(int))
+		return -EINVAL;
+
+	if (copy_from_sockptr(&t_type, optval, sizeof(t_type)))
+		return -EFAULT;
+
+	if (t_type < 0 || t_type >= RDS_TRANS_COUNT)
+		return -EINVAL;
+
+	/* RDS/IB is restricted to the initial network namespace */
+	if (t_type != RDS_TRANS_TCP && !net_eq(net, &init_net))
+		return -EPROTOTYPE;
+
+	rs->rs_transport = rds_trans_get(t_type);
+
+	return rs->rs_transport ? 0 : -ENOPROTOOPT;
+}
+
+static int rds_enable_recvtstamp(struct sock *sk, sockptr_t optval,
+				 int optlen, int optname)
+{
+	int val, valbool;
+
+	if (optlen != sizeof(int))
+		return -EFAULT;
+
+	if (copy_from_sockptr(&val, optval, sizeof(int)))
+		return -EFAULT;
+
+	valbool = val ? 1 : 0;
+
+	if (optname == SO_TIMESTAMP_NEW)
+		sock_set_flag(sk, SOCK_TSTAMP_NEW);
+
+	if (valbool)
+		sock_set_flag(sk, SOCK_RCVTSTAMP);
+	else
+		sock_reset_flag(sk, SOCK_RCVTSTAMP);
+
+	return 0;
+}
+
+static int rds_recv_track_latency(struct rds_sock *rs, sockptr_t optval,
+				  int optlen)
+{
+	struct rds_rx_trace_so trace;
+	int i;
+
+	if (optlen != sizeof(struct rds_rx_trace_so))
+		return -EFAULT;
+
+	if (copy_from_sockptr(&trace, optval, sizeof(trace)))
+		return -EFAULT;
+
+	if (trace.rx_traces > RDS_MSG_RX_DGRAM_TRACE_MAX)
+		return -EFAULT;
+
+	rs->rs_rx_traces = trace.rx_traces;
+	for (i = 0; i < rs->rs_rx_traces; i++) {
+		if (trace.rx_trace_pos[i] >= RDS_MSG_RX_DGRAM_TRACE_MAX) {
+			rs->rs_rx_traces = 0;
+			return -EFAULT;
+		}
+		rs->rs_rx_trace[i] = trace.rx_trace_pos[i];
+	}
+
+	return 0;
+}
+
+static int rds_setsockopt(struct socket *sock, int level, int optname,
+			  sockptr_t optval, unsigned int optlen)
+{
+	struct rds_sock *rs = rds_sk_to_rs(sock->sk);
+	struct net *net = sock_net(sock->sk);
+	int ret;
+
+	if (level != SOL_RDS) {
+		ret = -ENOPROTOOPT;
+		goto out;
+	}
+
+	switch (optname) {
+	case RDS_CANCEL_SENT_TO:
+		ret = rds_cancel_sent_to(rs, optval, optlen);
+		break;
+	case RDS_GET_MR:
+		ret = rds_get_mr(rs, optval, optlen);
+		break;
+	case RDS_GET_MR_FOR_DEST:
+		ret = rds_get_mr_for_dest(rs, optval, optlen);
+		break;
+	case RDS_FREE_MR:
+		ret = rds_free_mr(rs, optval, optlen);
+		break;
+	case RDS_RECVERR:
+		ret = rds_set_bool_option(&rs->rs_recverr, optval, optlen);
+		break;
+	case RDS_CONG_MONITOR:
+		ret = rds_cong_monitor(rs, optval, optlen);
+		break;
+	case SO_RDS_TRANSPORT:
+		lock_sock(sock->sk);
+		ret = rds_set_transport(net, rs, optval, optlen);
+		release_sock(sock->sk);
+		break;
+	case SO_TIMESTAMP_OLD:
+	case SO_TIMESTAMP_NEW:
+		lock_sock(sock->sk);
+		ret = rds_enable_recvtstamp(sock->sk, optval, optlen, optname);
+		release_sock(sock->sk);
+		break;
+	case SO_RDS_MSG_RXPATH_LATENCY:
+		ret = rds_recv_track_latency(rs, optval, optlen);
+		break;
+	default:
+		ret = -ENOPROTOOPT;
+	}
+out:
+	return ret;
+}
+
+static int rds_getsockopt(struct socket *sock, int level, int optname,
+			  sockopt_t *opt)
+{
+	struct rds_sock *rs = rds_sk_to_rs(sock->sk);
+	int ret = -ENOPROTOOPT, len;
+	int trans;
+	int val;
+
+	if (level != SOL_RDS)
+		goto out;
+
+	len = opt->optlen;
+
+	switch (optname) {
+	case RDS_INFO_FIRST ... RDS_INFO_LAST:
+		ret = rds_info_getsockopt(sock, optname, opt);
+		break;
+
+	case RDS_RECVERR:
+		if (len < sizeof(int)) {
+			ret = -EINVAL;
+			break;
+		}
+		val = rs->rs_recverr;
+		if (copy_to_iter(&val, sizeof(int), &opt->iter_out) !=
+		    sizeof(int)) {
+			ret = -EFAULT;
+		} else {
+			opt->optlen = sizeof(int);
+			ret = 0;
+		}
+		break;
+	case SO_RDS_TRANSPORT:
+		if (len < sizeof(int)) {
+			ret = -EINVAL;
+			break;
+		}
+		trans = (rs->rs_transport ? rs->rs_transport->t_type :
+			 RDS_TRANS_NONE); /* unbound */
+		if (copy_to_iter(&trans, sizeof(int), &opt->iter_out) !=
+		    sizeof(int)) {
+			ret = -EFAULT;
+		} else {
+			opt->optlen = sizeof(int);
+			ret = 0;
+		}
+		break;
+	default:
+		break;
+	}
+
+out:
+	return ret;
+
+}
+
+static int rds_connect(struct socket *sock, struct sockaddr_unsized *uaddr,
+		       int addr_len, int flags)
+{
+	struct sock *sk = sock->sk;
+	struct sockaddr_in *sin;
+	struct rds_sock *rs = rds_sk_to_rs(sk);
+	int ret = 0;
+
+	if (addr_len < offsetofend(struct sockaddr, sa_family))
+		return -EINVAL;
+
+	lock_sock(sk);
+
+	switch (uaddr->sa_family) {
+	case AF_INET:
+		sin = (struct sockaddr_in *)uaddr;
+		if (addr_len < sizeof(struct sockaddr_in)) {
+			ret = -EINVAL;
+			break;
+		}
+		if (sin->sin_addr.s_addr == htonl(INADDR_ANY)) {
+			ret = -EDESTADDRREQ;
+			break;
+		}
+		if (ipv4_is_multicast(sin->sin_addr.s_addr) ||
+		    sin->sin_addr.s_addr == htonl(INADDR_BROADCAST)) {
+			ret = -EINVAL;
+			break;
+		}
+		ipv6_addr_set_v4mapped(sin->sin_addr.s_addr, &rs->rs_conn_addr);
+		rs->rs_conn_port = sin->sin_port;
+		break;
+
+#if IS_ENABLED(CONFIG_IPV6)
+	case AF_INET6: {
+		struct sockaddr_in6 *sin6;
+		int addr_type;
+
+		sin6 = (struct sockaddr_in6 *)uaddr;
+		if (addr_len < sizeof(struct sockaddr_in6)) {
+			ret = -EINVAL;
+			break;
+		}
+		addr_type = ipv6_addr_type(&sin6->sin6_addr);
+		if (!(addr_type & IPV6_ADDR_UNICAST)) {
+			__be32 addr4;
+
+			if (!(addr_type & IPV6_ADDR_MAPPED)) {
+				ret = -EPROTOTYPE;
+				break;
+			}
+
+			/* It is a mapped address.  Need to do some sanity
+			 * checks.
+			 */
+			addr4 = sin6->sin6_addr.s6_addr32[3];
+			if (addr4 == htonl(INADDR_ANY) ||
+			    addr4 == htonl(INADDR_BROADCAST) ||
+			    ipv4_is_multicast(addr4)) {
+				ret = -EPROTOTYPE;
+				break;
+			}
+		}
+
+		if (addr_type & IPV6_ADDR_LINKLOCAL) {
+			/* If socket is already bound to a link local address,
+			 * the peer address must be on the same link.
+			 */
+			if (sin6->sin6_scope_id == 0 ||
+			    (!ipv6_addr_any(&rs->rs_bound_addr) &&
+			     rs->rs_bound_scope_id &&
+			     sin6->sin6_scope_id != rs->rs_bound_scope_id)) {
+				ret = -EINVAL;
+				break;
+			}
+			/* Remember the connected address scope ID.  It will
+			 * be checked against the binding local address when
+			 * the socket is bound.
+			 */
+			rs->rs_bound_scope_id = sin6->sin6_scope_id;
+		}
+		rs->rs_conn_addr = sin6->sin6_addr;
+		rs->rs_conn_port = sin6->sin6_port;
+		break;
+	}
+#endif
+
+	default:
+		ret = -EAFNOSUPPORT;
+		break;
+	}
+
+	release_sock(sk);
+	return ret;
+}
+
+static struct proto rds_proto = {
+	.name	  = "RDS",
+	.owner	  = THIS_MODULE,
+	.obj_size = sizeof(struct rds_sock),
+};
+
+static const struct proto_ops rds_proto_ops = {
+	.family =	AF_RDS,
+	.owner =	THIS_MODULE,
+	.release =	rds_release,
+	.bind =		rds_bind,
+	.connect =	rds_connect,
+	.socketpair =	sock_no_socketpair,
+	.accept =	sock_no_accept,
+	.getname =	rds_getname,
+	.poll =		rds_poll,
+	.ioctl =	rds_ioctl,
+	.listen =	sock_no_listen,
+	.shutdown =	sock_no_shutdown,
+	.setsockopt =	rds_setsockopt,
+	.getsockopt_iter =	rds_getsockopt,
+	.sendmsg =	rds_sendmsg,
+	.recvmsg =	rds_recvmsg,
+	.mmap =		sock_no_mmap,
+};
+
+static void rds_sock_destruct(struct sock *sk)
+{
+	struct rds_sock *rs = rds_sk_to_rs(sk);
+
+	WARN_ON((&rs->rs_item != rs->rs_item.next ||
+		 &rs->rs_item != rs->rs_item.prev));
+}
+
+static int __rds_create(struct socket *sock, struct sock *sk, int protocol)
+{
+	struct rds_sock *rs;
+
+	sock_init_data(sock, sk);
+	sock->ops		= &rds_proto_ops;
+	sk->sk_protocol		= protocol;
+	sk->sk_destruct		= rds_sock_destruct;
+
+	rs = rds_sk_to_rs(sk);
+	spin_lock_init(&rs->rs_lock);
+	rwlock_init(&rs->rs_recv_lock);
+	INIT_LIST_HEAD(&rs->rs_send_queue);
+	INIT_LIST_HEAD(&rs->rs_recv_queue);
+	INIT_LIST_HEAD(&rs->rs_notify_queue);
+	INIT_LIST_HEAD(&rs->rs_cong_list);
+	rds_message_zcopy_queue_init(&rs->rs_zcookie_queue);
+	spin_lock_init(&rs->rs_rdma_lock);
+	rs->rs_rdma_keys = RB_ROOT;
+	rs->rs_rx_traces = 0;
+	rs->rs_tos = 0;
+	rs->rs_conn = NULL;
+
+	spin_lock_bh(&rds_sock_lock);
+	list_add_tail(&rs->rs_item, &rds_sock_list);
+	spin_unlock_bh(&rds_sock_lock);
+
+	return 0;
+}
+
+static int rds_create(struct net *net, struct socket *sock, int protocol,
+		      int kern)
+{
+	struct sock *sk;
+
+	if (sock->type != SOCK_SEQPACKET || protocol)
+		return -ESOCKTNOSUPPORT;
+
+	sk = sk_alloc(net, AF_RDS, GFP_KERNEL, &rds_proto, kern);
+	if (!sk)
+		return -ENOMEM;
+
+	return __rds_create(sock, sk, protocol);
+}
+
+void rds_sock_addref(struct rds_sock *rs)
+{
+	sock_hold(rds_rs_to_sk(rs));
+}
+
+void rds_sock_put(struct rds_sock *rs)
+{
+	sock_put(rds_rs_to_sk(rs));
+}
+
+static const struct net_proto_family rds_family_ops = {
+	.family =	AF_RDS,
+	.create =	rds_create,
+	.owner	=	THIS_MODULE,
+};
+
+static void rds_sock_inc_info(struct socket *sock, unsigned int len,
+			      struct rds_info_iterator *iter,
+			      struct rds_info_lengths *lens)
+{
+	struct net *net = sock_net(sock->sk);
+	struct rds_sock *rs;
+	struct rds_incoming *inc;
+	unsigned int total = 0;
+
+	len /= sizeof(struct rds_info_message);
+
+	spin_lock_bh(&rds_sock_lock);
+
+	list_for_each_entry(rs, &rds_sock_list, rs_item) {
+		/* Only show sockets in the caller's netns. */
+		if (!net_eq(sock_net(rds_rs_to_sk(rs)), net))
+			continue;
+		/* This option only supports IPv4 sockets. */
+		if (!ipv6_addr_v4mapped(&rs->rs_bound_addr))
+			continue;
+
+		read_lock(&rs->rs_recv_lock);
+
+		/* XXX too lazy to maintain counts.. */
+		list_for_each_entry(inc, &rs->rs_recv_queue, i_item) {
+			total++;
+			if (total <= len)
+				rds_inc_info_copy(inc, iter,
+						  inc->i_saddr.s6_addr32[3],
+						  rs->rs_bound_addr_v4,
+						  1);
+		}
+
+		read_unlock(&rs->rs_recv_lock);
+	}
+
+	spin_unlock_bh(&rds_sock_lock);
+
+	lens->nr = total;
+	lens->each = sizeof(struct rds_info_message);
+}
+
+#if IS_ENABLED(CONFIG_IPV6)
+static void rds6_sock_inc_info(struct socket *sock, unsigned int len,
+			       struct rds_info_iterator *iter,
+			       struct rds_info_lengths *lens)
+{
+	struct net *net = sock_net(sock->sk);
+	struct rds_incoming *inc;
+	unsigned int total = 0;
+	struct rds_sock *rs;
+
+	len /= sizeof(struct rds6_info_message);
+
+	spin_lock_bh(&rds_sock_lock);
+
+	list_for_each_entry(rs, &rds_sock_list, rs_item) {
+		/* Only show sockets in the caller's netns. */
+		if (!net_eq(sock_net(rds_rs_to_sk(rs)), net))
+			continue;
+		read_lock(&rs->rs_recv_lock);
+
+		list_for_each_entry(inc, &rs->rs_recv_queue, i_item) {
+			total++;
+			if (total <= len)
+				rds6_inc_info_copy(inc, iter, &inc->i_saddr,
+						   &rs->rs_bound_addr, 1);
+		}
+
+		read_unlock(&rs->rs_recv_lock);
+	}
+
+	spin_unlock_bh(&rds_sock_lock);
+
+	lens->nr = total;
+	lens->each = sizeof(struct rds6_info_message);
+}
+#endif
+
+static void rds_sock_info(struct socket *sock, unsigned int len,
+			  struct rds_info_iterator *iter,
+			  struct rds_info_lengths *lens)
+{
+	struct net *net = sock_net(sock->sk);
+	struct rds_info_socket sinfo;
+	unsigned int copied = 0;
+	unsigned int cnt = 0;
+	struct rds_sock *rs;
+
+	len /= sizeof(struct rds_info_socket);
+
+	spin_lock_bh(&rds_sock_lock);
+
+	/* First pass: count entries visible in the caller's netns. */
+	list_for_each_entry(rs, &rds_sock_list, rs_item) {
+		if (!net_eq(sock_net(rds_rs_to_sk(rs)), net))
+			continue;
+		if (!ipv6_addr_v4mapped(&rs->rs_bound_addr))
+			continue;
+		cnt++;
+	}
+
+	if (len < cnt)
+		goto out;
+
+	list_for_each_entry(rs, &rds_sock_list, rs_item) {
+		if (copied >= cnt)
+			break;
+		/* Only show sockets in the caller's netns. */
+		if (!net_eq(sock_net(rds_rs_to_sk(rs)), net))
+			continue;
+		/* This option only supports IPv4 sockets. */
+		if (!ipv6_addr_v4mapped(&rs->rs_bound_addr))
+			continue;
+		sinfo.sndbuf = rds_sk_sndbuf(rs);
+		sinfo.rcvbuf = rds_sk_rcvbuf(rs);
+		sinfo.bound_addr = rs->rs_bound_addr_v4;
+		sinfo.connected_addr = rs->rs_conn_addr_v4;
+		sinfo.bound_port = rs->rs_bound_port;
+		sinfo.connected_port = rs->rs_conn_port;
+		sinfo.inum = sock_i_ino(rds_rs_to_sk(rs));
+
+		rds_info_copy(iter, &sinfo, sizeof(sinfo));
+		copied++;
+	}
+	/* A concurrent rds_bind() can change rs_bound_addr between the
+	 * two passes without holding rds_sock_lock, so copied may be
+	 * less than cnt. Report what was actually copied.
+	 */
+	cnt = copied;
+
+out:
+	lens->nr = cnt;
+	lens->each = sizeof(struct rds_info_socket);
+
+	spin_unlock_bh(&rds_sock_lock);
+}
+
+#if IS_ENABLED(CONFIG_IPV6)
+static void rds6_sock_info(struct socket *sock, unsigned int len,
+			   struct rds_info_iterator *iter,
+			   struct rds_info_lengths *lens)
+{
+	struct net *net = sock_net(sock->sk);
+	struct rds6_info_socket sinfo6;
+	unsigned int copied = 0;
+	unsigned int cnt = 0;
+	struct rds_sock *rs;
+
+	len /= sizeof(struct rds6_info_socket);
+
+	spin_lock_bh(&rds_sock_lock);
+
+	/* First pass: count entries visible in the caller's netns. */
+	list_for_each_entry(rs, &rds_sock_list, rs_item) {
+		if (!net_eq(sock_net(rds_rs_to_sk(rs)), net))
+			continue;
+		cnt++;
+	}
+
+	if (len < cnt)
+		goto out;
+
+	list_for_each_entry(rs, &rds_sock_list, rs_item) {
+		if (copied >= cnt)
+			break;
+		/* Only show sockets in the caller's netns. */
+		if (!net_eq(sock_net(rds_rs_to_sk(rs)), net))
+			continue;
+		sinfo6.sndbuf = rds_sk_sndbuf(rs);
+		sinfo6.rcvbuf = rds_sk_rcvbuf(rs);
+		sinfo6.bound_addr = rs->rs_bound_addr;
+		sinfo6.connected_addr = rs->rs_conn_addr;
+		sinfo6.bound_port = rs->rs_bound_port;
+		sinfo6.connected_port = rs->rs_conn_port;
+		sinfo6.inum = sock_i_ino(rds_rs_to_sk(rs));
+
+		rds_info_copy(iter, &sinfo6, sizeof(sinfo6));
+		copied++;
+	}
+	cnt = copied;
+
+ out:
+	lens->nr = cnt;
+	lens->each = sizeof(struct rds6_info_socket);
+
+	spin_unlock_bh(&rds_sock_lock);
+}
+#endif
+
+static void rds_exit(void)
+{
+	sock_unregister(rds_family_ops.family);
+	proto_unregister(&rds_proto);
+	rds_conn_exit();
+	rds_cong_exit();
+	rds_sysctl_exit();
+	rds_threads_exit();
+	rds_stats_exit();
+	rds_page_exit();
+	rds_bind_lock_destroy();
+	rds_info_deregister_func(RDS_INFO_SOCKETS, rds_sock_info);
+	rds_info_deregister_func(RDS_INFO_RECV_MESSAGES, rds_sock_inc_info);
+#if IS_ENABLED(CONFIG_IPV6)
+	rds_info_deregister_func(RDS6_INFO_SOCKETS, rds6_sock_info);
+	rds_info_deregister_func(RDS6_INFO_RECV_MESSAGES, rds6_sock_inc_info);
+#endif
+}
+module_exit(rds_exit);
+
+u32 rds_gen_num;
+
+static int __init rds_init(void)
+{
+	int ret;
+
+	net_get_random_once(&rds_gen_num, sizeof(rds_gen_num));
+
+	ret = rds_bind_lock_init();
+	if (ret)
+		goto out;
+
+	ret = rds_conn_init();
+	if (ret)
+		goto out_bind;
+
+	ret = rds_threads_init();
+	if (ret)
+		goto out_conn;
+	ret = rds_sysctl_init();
+	if (ret)
+		goto out_threads;
+	ret = rds_stats_init();
+	if (ret)
+		goto out_sysctl;
+	ret = proto_register(&rds_proto, 1);
+	if (ret)
+		goto out_stats;
+	ret = sock_register(&rds_family_ops);
+	if (ret)
+		goto out_proto;
+
+	rds_info_register_func(RDS_INFO_SOCKETS, rds_sock_info);
+	rds_info_register_func(RDS_INFO_RECV_MESSAGES, rds_sock_inc_info);
+#if IS_ENABLED(CONFIG_IPV6)
+	rds_info_register_func(RDS6_INFO_SOCKETS, rds6_sock_info);
+	rds_info_register_func(RDS6_INFO_RECV_MESSAGES, rds6_sock_inc_info);
+#endif
+
+	goto out;
+
+out_proto:
+	proto_unregister(&rds_proto);
+out_stats:
+	rds_stats_exit();
+out_sysctl:
+	rds_sysctl_exit();
+out_threads:
+	rds_threads_exit();
+out_conn:
+	rds_conn_exit();
+	rds_cong_exit();
+	rds_page_exit();
+out_bind:
+	rds_bind_lock_destroy();
+out:
+	return ret;
+}
+module_init(rds_init);
+
+#define DRV_VERSION     "4.0"
+#define DRV_RELDATE     "Feb 12, 2009"
+
+MODULE_AUTHOR("Oracle Corporation <rds-devel@oss.oracle.com>");
+MODULE_DESCRIPTION("RDS: Reliable Datagram Sockets"
+		   " v" DRV_VERSION " (" DRV_RELDATE ")");
+MODULE_VERSION(DRV_VERSION);
+MODULE_LICENSE("Dual BSD/GPL");
+MODULE_ALIAS_NETPROTO(PF_RDS);
diff --git a/net/rds/bind.c b/net/rds/bind.c
new file mode 100644
index 000000000..f800d920d
--- /dev/null
+++ b/net/rds/bind.c
@@ -0,0 +1,283 @@
+/*
+ * Copyright (c) 2006, 2019 Oracle and/or its affiliates. All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+#include <linux/kernel.h>
+#include <net/sock.h>
+#include <linux/in.h>
+#include <linux/ipv6.h>
+#include <linux/if_arp.h>
+#include <linux/jhash.h>
+#include <linux/ratelimit.h>
+#include "rds.h"
+
+static struct rhashtable bind_hash_table;
+
+static const struct rhashtable_params ht_parms = {
+	.nelem_hint = 768,
+	.key_len = RDS_BOUND_KEY_LEN,
+	.key_offset = offsetof(struct rds_sock, rs_bound_key),
+	.head_offset = offsetof(struct rds_sock, rs_bound_node),
+	.max_size = 16384,
+	.min_size = 1024,
+};
+
+/* Create a key for the bind hash table manipulation.  Port is in network byte
+ * order.
+ */
+static inline void __rds_create_bind_key(u8 *key, const struct in6_addr *addr,
+					 __be16 port, __u32 scope_id)
+{
+	memcpy(key, addr, sizeof(*addr));
+	key += sizeof(*addr);
+	memcpy(key, &port, sizeof(port));
+	key += sizeof(port);
+	memcpy(key, &scope_id, sizeof(scope_id));
+}
+
+/*
+ * Return the rds_sock bound at the given local address.
+ *
+ * The rx path can race with rds_release.  We notice if rds_release() has
+ * marked this socket and don't return a rs ref to the rx path.
+ */
+struct rds_sock *rds_find_bound(const struct in6_addr *addr, __be16 port,
+				__u32 scope_id)
+{
+	u8 key[RDS_BOUND_KEY_LEN];
+	struct rds_sock *rs;
+
+	__rds_create_bind_key(key, addr, port, scope_id);
+	rcu_read_lock();
+	rs = rhashtable_lookup(&bind_hash_table, key, ht_parms);
+	if (rs && (sock_flag(rds_rs_to_sk(rs), SOCK_DEAD) ||
+		   !refcount_inc_not_zero(&rds_rs_to_sk(rs)->sk_refcnt)))
+		rs = NULL;
+
+	rcu_read_unlock();
+
+	rdsdebug("returning rs %p for %pI6c:%u\n", rs, addr,
+		 ntohs(port));
+
+	return rs;
+}
+
+/* returns -ve errno or +ve port */
+static int rds_add_bound(struct rds_sock *rs, const struct in6_addr *addr,
+			 __be16 *port, __u32 scope_id)
+{
+	int ret = -EADDRINUSE;
+	u16 rover, last;
+	u8 key[RDS_BOUND_KEY_LEN];
+
+	if (*port != 0) {
+		rover = be16_to_cpu(*port);
+		if (rover == RDS_FLAG_PROBE_PORT)
+			return -EINVAL;
+		last = rover;
+	} else {
+		rover = max_t(u16, get_random_u16(), 2);
+		last = rover - 1;
+	}
+
+	do {
+		if (rover == 0)
+			rover++;
+
+		if (rover == RDS_FLAG_PROBE_PORT)
+			continue;
+		__rds_create_bind_key(key, addr, cpu_to_be16(rover),
+				      scope_id);
+		if (rhashtable_lookup_fast(&bind_hash_table, key, ht_parms))
+			continue;
+
+		memcpy(rs->rs_bound_key, key, sizeof(rs->rs_bound_key));
+		rs->rs_bound_addr = *addr;
+		net_get_random_once(&rs->rs_hash_initval,
+				    sizeof(rs->rs_hash_initval));
+		rs->rs_bound_port = cpu_to_be16(rover);
+		rs->rs_bound_node.next = NULL;
+		rds_sock_addref(rs);
+		if (!rhashtable_insert_fast(&bind_hash_table,
+					    &rs->rs_bound_node, ht_parms)) {
+			*port = rs->rs_bound_port;
+			rs->rs_bound_scope_id = scope_id;
+			ret = 0;
+			rdsdebug("rs %p binding to %pI6c:%d\n",
+				 rs, addr, (int)ntohs(*port));
+			break;
+		} else {
+			rs->rs_bound_addr = in6addr_any;
+			rds_sock_put(rs);
+			ret = -ENOMEM;
+			break;
+		}
+	} while (rover++ != last);
+
+	return ret;
+}
+
+void rds_remove_bound(struct rds_sock *rs)
+{
+
+	if (ipv6_addr_any(&rs->rs_bound_addr))
+		return;
+
+	rdsdebug("rs %p unbinding from %pI6c:%d\n",
+		 rs, &rs->rs_bound_addr,
+		 ntohs(rs->rs_bound_port));
+
+	rhashtable_remove_fast(&bind_hash_table, &rs->rs_bound_node, ht_parms);
+	rds_sock_put(rs);
+	rs->rs_bound_addr = in6addr_any;
+}
+
+int rds_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int addr_len)
+{
+	struct sock *sk = sock->sk;
+	struct rds_sock *rs = rds_sk_to_rs(sk);
+	struct in6_addr v6addr, *binding_addr;
+	struct rds_transport *trans;
+	__u32 scope_id = 0;
+	int ret = 0;
+	__be16 port;
+
+	/* We allow an RDS socket to be bound to either IPv4 or IPv6
+	 * address.
+	 */
+	if (addr_len < offsetofend(struct sockaddr, sa_family))
+		return -EINVAL;
+	if (uaddr->sa_family == AF_INET) {
+		struct sockaddr_in *sin = (struct sockaddr_in *)uaddr;
+
+		if (addr_len < sizeof(struct sockaddr_in) ||
+		    sin->sin_addr.s_addr == htonl(INADDR_ANY) ||
+		    sin->sin_addr.s_addr == htonl(INADDR_BROADCAST) ||
+		    ipv4_is_multicast(sin->sin_addr.s_addr))
+			return -EINVAL;
+		ipv6_addr_set_v4mapped(sin->sin_addr.s_addr, &v6addr);
+		binding_addr = &v6addr;
+		port = sin->sin_port;
+#if IS_ENABLED(CONFIG_IPV6)
+	} else if (uaddr->sa_family == AF_INET6) {
+		struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)uaddr;
+		int addr_type;
+
+		if (addr_len < sizeof(struct sockaddr_in6))
+			return -EINVAL;
+		addr_type = ipv6_addr_type(&sin6->sin6_addr);
+		if (!(addr_type & IPV6_ADDR_UNICAST)) {
+			__be32 addr4;
+
+			if (!(addr_type & IPV6_ADDR_MAPPED))
+				return -EINVAL;
+
+			/* It is a mapped address.  Need to do some sanity
+			 * checks.
+			 */
+			addr4 = sin6->sin6_addr.s6_addr32[3];
+			if (addr4 == htonl(INADDR_ANY) ||
+			    addr4 == htonl(INADDR_BROADCAST) ||
+			    ipv4_is_multicast(addr4))
+				return -EINVAL;
+		}
+		/* The scope ID must be specified for link local address. */
+		if (addr_type & IPV6_ADDR_LINKLOCAL) {
+			if (sin6->sin6_scope_id == 0)
+				return -EINVAL;
+			scope_id = sin6->sin6_scope_id;
+		}
+		binding_addr = &sin6->sin6_addr;
+		port = sin6->sin6_port;
+#endif
+	} else {
+		return -EINVAL;
+	}
+	lock_sock(sk);
+
+	/* RDS socket does not allow re-binding. */
+	if (!ipv6_addr_any(&rs->rs_bound_addr)) {
+		ret = -EINVAL;
+		goto out;
+	}
+	/* Socket is connected.  The binding address should have the same
+	 * scope ID as the connected address, except the case when one is
+	 * non-link local address (scope_id is 0).
+	 */
+	if (!ipv6_addr_any(&rs->rs_conn_addr) && scope_id &&
+	    rs->rs_bound_scope_id &&
+	    scope_id != rs->rs_bound_scope_id) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	/* The transport can be set using SO_RDS_TRANSPORT option before the
+	 * socket is bound.
+	 */
+	if (rs->rs_transport) {
+		trans = rs->rs_transport;
+		if (!trans->laddr_check ||
+		    trans->laddr_check(sock_net(sock->sk),
+				       binding_addr, scope_id) != 0) {
+			ret = -ENOPROTOOPT;
+			goto out;
+		}
+	} else {
+		trans = rds_trans_get_preferred(sock_net(sock->sk),
+						binding_addr, scope_id);
+		if (!trans) {
+			ret = -EADDRNOTAVAIL;
+			pr_info_ratelimited("RDS: %s could not find a transport for %pI6c, load rds_tcp or rds_rdma?\n",
+					    __func__, binding_addr);
+			goto out;
+		}
+		rs->rs_transport = trans;
+	}
+
+	sock_set_flag(sk, SOCK_RCU_FREE);
+	ret = rds_add_bound(rs, binding_addr, &port, scope_id);
+	if (ret)
+		rs->rs_transport = NULL;
+
+out:
+	release_sock(sk);
+	return ret;
+}
+
+void rds_bind_lock_destroy(void)
+{
+	rhashtable_destroy(&bind_hash_table);
+}
+
+int rds_bind_lock_init(void)
+{
+	return rhashtable_init(&bind_hash_table, &ht_parms);
+}
diff --git a/net/rds/cong.c b/net/rds/cong.c
new file mode 100644
index 000000000..f7634ce3f
--- /dev/null
+++ b/net/rds/cong.c
@@ -0,0 +1,428 @@
+/*
+ * Copyright (c) 2007, 2017 Oracle and/or its affiliates. All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <linux/rbtree.h>
+#include <linux/bitops.h>
+#include <linux/export.h>
+
+#include "rds.h"
+
+/*
+ * This file implements the receive side of the unconventional congestion
+ * management in RDS.
+ *
+ * Messages waiting in the receive queue on the receiving socket are accounted
+ * against the sockets SO_RCVBUF option value.  Only the payload bytes in the
+ * message are accounted for.  If the number of bytes queued equals or exceeds
+ * rcvbuf then the socket is congested.  All sends attempted to this socket's
+ * address should return block or return -EWOULDBLOCK.
+ *
+ * Applications are expected to be reasonably tuned such that this situation
+ * very rarely occurs.  An application encountering this "back-pressure" is
+ * considered a bug.
+ *
+ * This is implemented by having each node maintain bitmaps which indicate
+ * which ports on bound addresses are congested.  As the bitmap changes it is
+ * sent through all the connections which terminate in the local address of the
+ * bitmap which changed.
+ *
+ * The bitmaps are allocated as connections are brought up.  This avoids
+ * allocation in the interrupt handling path which queues messages on sockets.
+ * The dense bitmaps let transports send the entire bitmap on any bitmap change
+ * reasonably efficiently.  This is much easier to implement than some
+ * finer-grained communication of per-port congestion.  The sender does a very
+ * inexpensive bit test to test if the port it's about to send to is congested
+ * or not.
+ */
+
+/*
+ * Interaction with poll is a tad tricky. We want all processes stuck in
+ * poll to wake up and check whether a congested destination became uncongested.
+ * The really sad thing is we have no idea which destinations the application
+ * wants to send to - we don't even know which rds_connections are involved.
+ * So until we implement a more flexible rds poll interface, we have to make
+ * do with this:
+ * We maintain a global counter that is incremented each time a congestion map
+ * update is received. Each rds socket tracks this value, and if rds_poll
+ * finds that the saved generation number is smaller than the global generation
+ * number, it wakes up the process.
+ */
+static atomic_t		rds_cong_generation = ATOMIC_INIT(0);
+
+/*
+ * Congestion monitoring
+ */
+static LIST_HEAD(rds_cong_monitor);
+static DEFINE_RWLOCK(rds_cong_monitor_lock);
+
+/*
+ * Yes, a global lock.  It's used so infrequently that it's worth keeping it
+ * global to simplify the locking.  It's only used in the following
+ * circumstances:
+ *
+ *  - on connection buildup to associate a conn with its maps
+ *  - on map changes to inform conns of a new map to send
+ *
+ *  It's sadly ordered under the socket callback lock and the connection lock.
+ *  Receive paths can mark ports congested from interrupt context so the
+ *  lock masks interrupts.
+ */
+static DEFINE_SPINLOCK(rds_cong_lock);
+static struct rb_root rds_cong_tree = RB_ROOT;
+
+static struct rds_cong_map *rds_cong_tree_walk(const struct in6_addr *addr,
+					       struct rds_cong_map *insert)
+{
+	struct rb_node **p = &rds_cong_tree.rb_node;
+	struct rb_node *parent = NULL;
+	struct rds_cong_map *map;
+
+	while (*p) {
+		int diff;
+
+		parent = *p;
+		map = rb_entry(parent, struct rds_cong_map, m_rb_node);
+
+		diff = rds_addr_cmp(addr, &map->m_addr);
+		if (diff < 0)
+			p = &(*p)->rb_left;
+		else if (diff > 0)
+			p = &(*p)->rb_right;
+		else
+			return map;
+	}
+
+	if (insert) {
+		rb_link_node(&insert->m_rb_node, parent, p);
+		rb_insert_color(&insert->m_rb_node, &rds_cong_tree);
+	}
+	return NULL;
+}
+
+/*
+ * There is only ever one bitmap for any address.  Connections try and allocate
+ * these bitmaps in the process getting pointers to them.  The bitmaps are only
+ * ever freed as the module is removed after all connections have been freed.
+ */
+static struct rds_cong_map *rds_cong_from_addr(const struct in6_addr *addr)
+{
+	struct rds_cong_map *map;
+	struct rds_cong_map *ret = NULL;
+	unsigned long zp;
+	unsigned long i;
+	unsigned long flags;
+
+	map = kzalloc_obj(struct rds_cong_map);
+	if (!map)
+		return NULL;
+
+	map->m_addr = *addr;
+	init_waitqueue_head(&map->m_waitq);
+	INIT_LIST_HEAD(&map->m_conn_list);
+
+	for (i = 0; i < RDS_CONG_MAP_PAGES; i++) {
+		zp = get_zeroed_page(GFP_KERNEL);
+		if (zp == 0)
+			goto out;
+		map->m_page_addrs[i] = zp;
+	}
+
+	spin_lock_irqsave(&rds_cong_lock, flags);
+	ret = rds_cong_tree_walk(addr, map);
+	spin_unlock_irqrestore(&rds_cong_lock, flags);
+
+	if (!ret) {
+		ret = map;
+		map = NULL;
+	}
+
+out:
+	if (map) {
+		for (i = 0; i < RDS_CONG_MAP_PAGES && map->m_page_addrs[i]; i++)
+			free_page(map->m_page_addrs[i]);
+		kfree(map);
+	}
+
+	rdsdebug("map %p for addr %pI6c\n", ret, addr);
+
+	return ret;
+}
+
+/*
+ * Put the conn on its local map's list.  This is called when the conn is
+ * really added to the hash.  It's nested under the rds_conn_lock, sadly.
+ */
+void rds_cong_add_conn(struct rds_connection *conn)
+{
+	unsigned long flags;
+
+	rdsdebug("conn %p now on map %p\n", conn, conn->c_lcong);
+	spin_lock_irqsave(&rds_cong_lock, flags);
+	list_add_tail(&conn->c_map_item, &conn->c_lcong->m_conn_list);
+	spin_unlock_irqrestore(&rds_cong_lock, flags);
+}
+
+void rds_cong_remove_conn(struct rds_connection *conn)
+{
+	unsigned long flags;
+
+	rdsdebug("removing conn %p from map %p\n", conn, conn->c_lcong);
+	spin_lock_irqsave(&rds_cong_lock, flags);
+	list_del_init(&conn->c_map_item);
+	spin_unlock_irqrestore(&rds_cong_lock, flags);
+}
+
+int rds_cong_get_maps(struct rds_connection *conn)
+{
+	conn->c_lcong = rds_cong_from_addr(&conn->c_laddr);
+	conn->c_fcong = rds_cong_from_addr(&conn->c_faddr);
+
+	if (!(conn->c_lcong && conn->c_fcong))
+		return -ENOMEM;
+
+	return 0;
+}
+
+void rds_cong_queue_updates(struct rds_cong_map *map)
+{
+	struct rds_connection *conn;
+	unsigned long flags;
+
+	spin_lock_irqsave(&rds_cong_lock, flags);
+
+	list_for_each_entry(conn, &map->m_conn_list, c_map_item) {
+		struct rds_conn_path *cp = &conn->c_path[0];
+
+		rcu_read_lock();
+		if (!test_and_set_bit(0, &conn->c_map_queued) &&
+		    !rds_destroy_pending(cp->cp_conn)) {
+			rds_stats_inc(s_cong_update_queued);
+			/* We cannot inline the call to rds_send_xmit() here
+			 * for two reasons (both pertaining to a TCP transport):
+			 * 1. When we get here from the receive path, we
+			 *    are already holding the sock_lock (held by
+			 *    tcp_v4_rcv()). So inlining calls to
+			 *    tcp_setsockopt and/or tcp_sendmsg will deadlock
+			 *    when it tries to get the sock_lock())
+			 * 2. Interrupts are masked so that we can mark the
+			 *    port congested from both send and recv paths.
+			 *    (See comment around declaration of rdc_cong_lock).
+			 *    An attempt to get the sock_lock() here will
+			 *    therefore trigger warnings.
+			 * Defer the xmit to rds_send_worker() instead.
+			 */
+			queue_delayed_work(cp->cp_wq, &cp->cp_send_w, 0);
+		}
+		rcu_read_unlock();
+	}
+
+	spin_unlock_irqrestore(&rds_cong_lock, flags);
+}
+
+void rds_cong_map_updated(struct rds_cong_map *map, uint64_t portmask)
+{
+	rdsdebug("waking map %p for %pI4\n",
+	  map, &map->m_addr);
+	rds_stats_inc(s_cong_update_received);
+	atomic_inc(&rds_cong_generation);
+	if (wq_has_sleeper(&map->m_waitq))
+		wake_up(&map->m_waitq);
+	if (wq_has_sleeper(&rds_poll_waitq))
+		wake_up_all(&rds_poll_waitq);
+
+	if (portmask && !list_empty(&rds_cong_monitor)) {
+		unsigned long flags;
+		struct rds_sock *rs;
+
+		read_lock_irqsave(&rds_cong_monitor_lock, flags);
+		list_for_each_entry(rs, &rds_cong_monitor, rs_cong_list) {
+			spin_lock(&rs->rs_lock);
+			rs->rs_cong_notify |= (rs->rs_cong_mask & portmask);
+			rs->rs_cong_mask &= ~portmask;
+			spin_unlock(&rs->rs_lock);
+			if (rs->rs_cong_notify)
+				rds_wake_sk_sleep(rs);
+		}
+		read_unlock_irqrestore(&rds_cong_monitor_lock, flags);
+	}
+}
+EXPORT_SYMBOL_GPL(rds_cong_map_updated);
+
+int rds_cong_updated_since(unsigned long *recent)
+{
+	unsigned long gen = atomic_read(&rds_cong_generation);
+
+	if (likely(*recent == gen))
+		return 0;
+	*recent = gen;
+	return 1;
+}
+
+/*
+ * We're called under the locking that protects the sockets receive buffer
+ * consumption.  This makes it a lot easier for the caller to only call us
+ * when it knows that an existing set bit needs to be cleared, and vice versa.
+ * We can't block and we need to deal with concurrent sockets working against
+ * the same per-address map.
+ */
+void rds_cong_set_bit(struct rds_cong_map *map, __be16 port)
+{
+	unsigned long i;
+	unsigned long off;
+
+	rdsdebug("setting congestion for %pI4:%u in map %p\n",
+	  &map->m_addr, ntohs(port), map);
+
+	i = be16_to_cpu(port) / RDS_CONG_MAP_PAGE_BITS;
+	off = be16_to_cpu(port) % RDS_CONG_MAP_PAGE_BITS;
+
+	set_bit_le(off, (void *)map->m_page_addrs[i]);
+}
+
+void rds_cong_clear_bit(struct rds_cong_map *map, __be16 port)
+{
+	unsigned long i;
+	unsigned long off;
+
+	rdsdebug("clearing congestion for %pI4:%u in map %p\n",
+	  &map->m_addr, ntohs(port), map);
+
+	i = be16_to_cpu(port) / RDS_CONG_MAP_PAGE_BITS;
+	off = be16_to_cpu(port) % RDS_CONG_MAP_PAGE_BITS;
+
+	clear_bit_le(off, (void *)map->m_page_addrs[i]);
+}
+
+static int rds_cong_test_bit(struct rds_cong_map *map, __be16 port)
+{
+	unsigned long i;
+	unsigned long off;
+
+	i = be16_to_cpu(port) / RDS_CONG_MAP_PAGE_BITS;
+	off = be16_to_cpu(port) % RDS_CONG_MAP_PAGE_BITS;
+
+	return test_bit_le(off, (void *)map->m_page_addrs[i]);
+}
+
+void rds_cong_add_socket(struct rds_sock *rs)
+{
+	unsigned long flags;
+
+	write_lock_irqsave(&rds_cong_monitor_lock, flags);
+	if (list_empty(&rs->rs_cong_list))
+		list_add(&rs->rs_cong_list, &rds_cong_monitor);
+	write_unlock_irqrestore(&rds_cong_monitor_lock, flags);
+}
+
+void rds_cong_remove_socket(struct rds_sock *rs)
+{
+	unsigned long flags;
+	struct rds_cong_map *map;
+
+	write_lock_irqsave(&rds_cong_monitor_lock, flags);
+	list_del_init(&rs->rs_cong_list);
+	write_unlock_irqrestore(&rds_cong_monitor_lock, flags);
+
+	/* update congestion map for now-closed port */
+	spin_lock_irqsave(&rds_cong_lock, flags);
+	map = rds_cong_tree_walk(&rs->rs_bound_addr, NULL);
+	spin_unlock_irqrestore(&rds_cong_lock, flags);
+
+	if (map && rds_cong_test_bit(map, rs->rs_bound_port)) {
+		rds_cong_clear_bit(map, rs->rs_bound_port);
+		rds_cong_queue_updates(map);
+	}
+}
+
+int rds_cong_wait(struct rds_cong_map *map, __be16 port, int nonblock,
+		  struct rds_sock *rs)
+{
+	if (!rds_cong_test_bit(map, port))
+		return 0;
+	if (nonblock) {
+		if (rs && rs->rs_cong_monitor) {
+			unsigned long flags;
+
+			/* It would have been nice to have an atomic set_bit on
+			 * a uint64_t. */
+			spin_lock_irqsave(&rs->rs_lock, flags);
+			rs->rs_cong_mask |= RDS_CONG_MONITOR_MASK(ntohs(port));
+			spin_unlock_irqrestore(&rs->rs_lock, flags);
+
+			/* Test again - a congestion update may have arrived in
+			 * the meantime. */
+			if (!rds_cong_test_bit(map, port))
+				return 0;
+		}
+		rds_stats_inc(s_cong_send_error);
+		return -ENOBUFS;
+	}
+
+	rds_stats_inc(s_cong_send_blocked);
+	rdsdebug("waiting on map %p for port %u\n", map, be16_to_cpu(port));
+
+	return wait_event_interruptible(map->m_waitq,
+					!rds_cong_test_bit(map, port));
+}
+
+void rds_cong_exit(void)
+{
+	struct rb_node *node;
+	struct rds_cong_map *map;
+	unsigned long i;
+
+	while ((node = rb_first(&rds_cong_tree))) {
+		map = rb_entry(node, struct rds_cong_map, m_rb_node);
+		rdsdebug("freeing map %p\n", map);
+		rb_erase(&map->m_rb_node, &rds_cong_tree);
+		for (i = 0; i < RDS_CONG_MAP_PAGES && map->m_page_addrs[i]; i++)
+			free_page(map->m_page_addrs[i]);
+		kfree(map);
+	}
+}
+
+/*
+ * Allocate a RDS message containing a congestion update.
+ */
+struct rds_message *rds_cong_update_alloc(struct rds_connection *conn)
+{
+	struct rds_cong_map *map = conn->c_lcong;
+	struct rds_message *rm;
+
+	rm = rds_message_map_pages(map->m_page_addrs, RDS_CONG_MAP_BYTES);
+	if (!IS_ERR(rm))
+		rm->m_inc.i_hdr.h_flags = RDS_FLAG_CONG_BITMAP;
+
+	return rm;
+}
diff --git a/net/rds/connection.c b/net/rds/connection.c
new file mode 100644
index 000000000..7c8ab8e97
--- /dev/null
+++ b/net/rds/connection.c
@@ -0,0 +1,1003 @@
+/*
+ * Copyright (c) 2006, 2018 Oracle and/or its affiliates. All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/slab.h>
+#include <linux/export.h>
+#include <net/ipv6.h>
+#include <net/inet6_hashtables.h>
+#include <net/addrconf.h>
+
+#include "rds.h"
+#include "loop.h"
+
+#define RDS_CONNECTION_HASH_BITS 12
+#define RDS_CONNECTION_HASH_ENTRIES (1 << RDS_CONNECTION_HASH_BITS)
+#define RDS_CONNECTION_HASH_MASK (RDS_CONNECTION_HASH_ENTRIES - 1)
+
+/* converting this to RCU is a chore for another day.. */
+static DEFINE_SPINLOCK(rds_conn_lock);
+static unsigned long rds_conn_count;
+static struct hlist_head rds_conn_hash[RDS_CONNECTION_HASH_ENTRIES];
+static struct kmem_cache *rds_conn_slab;
+
+static struct hlist_head *rds_conn_bucket(const struct in6_addr *laddr,
+					  const struct in6_addr *faddr)
+{
+	static u32 rds6_hash_secret __read_mostly;
+	static u32 rds_hash_secret __read_mostly;
+
+	__be32 lhash, fhash;
+	u32 hash;
+
+	net_get_random_once(&rds_hash_secret, sizeof(rds_hash_secret));
+	net_get_random_once(&rds6_hash_secret, sizeof(rds6_hash_secret));
+
+	lhash = laddr->s6_addr32[3];
+#if IS_ENABLED(CONFIG_IPV6)
+	fhash = (__force __be32)__ipv6_addr_jhash(faddr, rds6_hash_secret);
+#else
+	fhash = faddr->s6_addr32[3];
+#endif
+	hash = __inet_ehashfn(lhash, 0, fhash, 0, rds_hash_secret);
+
+	return &rds_conn_hash[hash & RDS_CONNECTION_HASH_MASK];
+}
+
+#define rds_conn_info_set(var, test, suffix) do {		\
+	if (test)						\
+		var |= RDS_INFO_CONNECTION_FLAG_##suffix;	\
+} while (0)
+
+/* rcu read lock must be held or the connection spinlock */
+static struct rds_connection *rds_conn_lookup(struct net *net,
+					      struct hlist_head *head,
+					      const struct in6_addr *laddr,
+					      const struct in6_addr *faddr,
+					      struct rds_transport *trans,
+					      u8 tos, int dev_if)
+{
+	struct rds_connection *conn, *ret = NULL;
+
+	hlist_for_each_entry_rcu(conn, head, c_hash_node) {
+		if (ipv6_addr_equal(&conn->c_faddr, faddr) &&
+		    ipv6_addr_equal(&conn->c_laddr, laddr) &&
+		    conn->c_trans == trans &&
+		    conn->c_tos == tos &&
+		    net == rds_conn_net(conn) &&
+		    conn->c_dev_if == dev_if) {
+			ret = conn;
+			break;
+		}
+	}
+	rdsdebug("returning conn %p for %pI6c -> %pI6c\n", ret,
+		 laddr, faddr);
+	return ret;
+}
+
+/*
+ * This is called by transports as they're bringing down a connection.
+ * It clears partial message state so that the transport can start sending
+ * and receiving over this connection again in the future.  It is up to
+ * the transport to have serialized this call with its send and recv.
+ */
+static void rds_conn_path_reset(struct rds_conn_path *cp)
+{
+	struct rds_connection *conn = cp->cp_conn;
+
+	rdsdebug("connection %pI6c to %pI6c reset\n",
+		 &conn->c_laddr, &conn->c_faddr);
+
+	rds_stats_inc(s_conn_reset);
+	rds_send_path_reset(cp);
+	cp->cp_flags = 0;
+
+	/* Do not clear next_rx_seq here, else we cannot distinguish
+	 * retransmitted packets from new packets, and will hand all
+	 * of them to the application. That is not consistent with the
+	 * reliability guarantees of RDS. */
+}
+
+static void __rds_conn_path_init(struct rds_connection *conn,
+				 struct rds_conn_path *cp, bool is_outgoing)
+{
+	spin_lock_init(&cp->cp_lock);
+	cp->cp_next_tx_seq = 1;
+	init_waitqueue_head(&cp->cp_waitq);
+	INIT_LIST_HEAD(&cp->cp_send_queue);
+	INIT_LIST_HEAD(&cp->cp_retrans);
+
+	cp->cp_conn = conn;
+	atomic_set(&cp->cp_state, RDS_CONN_DOWN);
+	cp->cp_send_gen = 0;
+	cp->cp_reconnect_jiffies = 0;
+	cp->cp_conn->c_proposed_version = RDS_PROTOCOL_VERSION;
+	INIT_DELAYED_WORK(&cp->cp_send_w, rds_send_worker);
+	INIT_DELAYED_WORK(&cp->cp_recv_w, rds_recv_worker);
+	INIT_DELAYED_WORK(&cp->cp_conn_w, rds_connect_worker);
+	INIT_WORK(&cp->cp_down_w, rds_shutdown_worker);
+	mutex_init(&cp->cp_cm_lock);
+	cp->cp_flags = 0;
+}
+
+/*
+ * There is only every one 'conn' for a given pair of addresses in the
+ * system at a time.  They contain messages to be retransmitted and so
+ * span the lifetime of the actual underlying transport connections.
+ *
+ * For now they are not garbage collected once they're created.  They
+ * are torn down as the module is removed, if ever.
+ */
+static struct rds_connection *__rds_conn_create(struct net *net,
+						const struct in6_addr *laddr,
+						const struct in6_addr *faddr,
+						struct rds_transport *trans,
+						gfp_t gfp, u8 tos,
+						int is_outgoing,
+						int dev_if)
+{
+	struct rds_connection *conn, *parent = NULL;
+	struct hlist_head *head = rds_conn_bucket(laddr, faddr);
+	struct rds_transport *loop_trans;
+	struct rds_conn_path *free_cp = NULL;
+	unsigned long flags;
+	int ret, i;
+	int npaths = (trans->t_mp_capable ? RDS_MPATH_WORKERS : 1);
+
+	rcu_read_lock();
+	conn = rds_conn_lookup(net, head, laddr, faddr, trans, tos, dev_if);
+	if (conn &&
+	    conn->c_loopback &&
+	    conn->c_trans != &rds_loop_transport &&
+	    ipv6_addr_equal(laddr, faddr) &&
+	    !is_outgoing) {
+		/* This is a looped back IB connection, and we're
+		 * called by the code handling the incoming connect.
+		 * We need a second connection object into which we
+		 * can stick the other QP. */
+		parent = conn;
+		conn = parent->c_passive;
+	}
+	rcu_read_unlock();
+	if (conn)
+		goto out;
+
+	conn = kmem_cache_zalloc(rds_conn_slab, gfp);
+	if (!conn) {
+		conn = ERR_PTR(-ENOMEM);
+		goto out;
+	}
+	conn->c_path = kzalloc_objs(struct rds_conn_path, npaths, gfp);
+	if (!conn->c_path) {
+		kmem_cache_free(rds_conn_slab, conn);
+		conn = ERR_PTR(-ENOMEM);
+		goto out;
+	}
+
+	INIT_HLIST_NODE(&conn->c_hash_node);
+	conn->c_laddr = *laddr;
+	conn->c_isv6 = !ipv6_addr_v4mapped(laddr);
+	conn->c_faddr = *faddr;
+	conn->c_dev_if = dev_if;
+	conn->c_tos = tos;
+
+#if IS_ENABLED(CONFIG_IPV6)
+	/* If the local address is link local, set c_bound_if to be the
+	 * index used for this connection.  Otherwise, set it to 0 as
+	 * the socket is not bound to an interface.  c_bound_if is used
+	 * to look up a socket when a packet is received
+	 */
+	if (ipv6_addr_type(laddr) & IPV6_ADDR_LINKLOCAL)
+		conn->c_bound_if = dev_if;
+	else
+#endif
+		conn->c_bound_if = 0;
+
+	rds_conn_net_set(conn, net);
+
+	ret = rds_cong_get_maps(conn);
+	if (ret) {
+		kfree(conn->c_path);
+		kmem_cache_free(rds_conn_slab, conn);
+		conn = ERR_PTR(ret);
+		goto out;
+	}
+
+	/*
+	 * This is where a connection becomes loopback.  If *any* RDS sockets
+	 * can bind to the destination address then we'd rather the messages
+	 * flow through loopback rather than either transport.
+	 */
+	loop_trans = rds_trans_get_preferred(net, faddr, conn->c_dev_if);
+	if (loop_trans) {
+		rds_trans_put(loop_trans);
+		conn->c_loopback = 1;
+		if (trans->t_prefer_loopback) {
+			if (likely(is_outgoing)) {
+				/* "outgoing" connection to local address.
+				 * Protocol says it wants the connection
+				 * handled by the loopback transport.
+				 * This is what TCP does.
+				 */
+				trans = &rds_loop_transport;
+			} else {
+				/* No transport currently in use
+				 * should end up here, but if it
+				 * does, reset/destroy the connection.
+				 */
+				kfree(conn->c_path);
+				kmem_cache_free(rds_conn_slab, conn);
+				conn = ERR_PTR(-EOPNOTSUPP);
+				goto out;
+			}
+		}
+	}
+
+	conn->c_trans = trans;
+
+	init_waitqueue_head(&conn->c_hs_waitq);
+	for (i = 0; i < npaths; i++) {
+		__rds_conn_path_init(conn, &conn->c_path[i],
+				     is_outgoing);
+		conn->c_path[i].cp_index = i;
+		conn->c_path[i].cp_wq =
+			alloc_ordered_workqueue("krds_cp_wq#%lu/%d", 0,
+						rds_conn_count, i);
+		if (!conn->c_path[i].cp_wq)
+			conn->c_path[i].cp_wq = rds_wq;
+	}
+	rcu_read_lock();
+	if (rds_destroy_pending(conn))
+		ret = -ENETDOWN;
+	else
+		ret = trans->conn_alloc(conn, GFP_ATOMIC);
+	if (ret) {
+		rcu_read_unlock();
+		free_cp = conn->c_path;
+		kmem_cache_free(rds_conn_slab, conn);
+		conn = ERR_PTR(ret);
+		goto out;
+	}
+
+	rdsdebug("allocated conn %p for %pI6c -> %pI6c over %s %s\n",
+		 conn, laddr, faddr,
+		 strnlen(trans->t_name, sizeof(trans->t_name)) ?
+		 trans->t_name : "[unknown]", is_outgoing ? "(outgoing)" : "");
+
+	/*
+	 * Since we ran without holding the conn lock, someone could
+	 * have created the same conn (either normal or passive) in the
+	 * interim. We check while holding the lock. If we won, we complete
+	 * init and return our conn. If we lost, we rollback and return the
+	 * other one.
+	 */
+	spin_lock_irqsave(&rds_conn_lock, flags);
+	if (parent) {
+		/* Creating passive conn */
+		if (parent->c_passive) {
+			trans->conn_free(conn->c_path[0].cp_transport_data);
+			free_cp = conn->c_path;
+			kmem_cache_free(rds_conn_slab, conn);
+			conn = parent->c_passive;
+		} else {
+			parent->c_passive = conn;
+			rds_cong_add_conn(conn);
+			rds_conn_count++;
+		}
+	} else {
+		/* Creating normal conn */
+		struct rds_connection *found;
+
+		found = rds_conn_lookup(net, head, laddr, faddr, trans,
+					tos, dev_if);
+		if (found) {
+			struct rds_conn_path *cp;
+			int i;
+
+			for (i = 0; i < npaths; i++) {
+				cp = &conn->c_path[i];
+				/* The ->conn_alloc invocation may have
+				 * allocated resource for all paths, so all
+				 * of them may have to be freed here.
+				 */
+				if (cp->cp_transport_data)
+					trans->conn_free(cp->cp_transport_data);
+			}
+			free_cp = conn->c_path;
+			kmem_cache_free(rds_conn_slab, conn);
+			conn = found;
+		} else {
+			conn->c_my_gen_num = rds_gen_num;
+			conn->c_peer_gen_num = 0;
+			hlist_add_head_rcu(&conn->c_hash_node, head);
+			rds_cong_add_conn(conn);
+			rds_conn_count++;
+		}
+	}
+	spin_unlock_irqrestore(&rds_conn_lock, flags);
+	rcu_read_unlock();
+
+out:
+	if (free_cp) {
+		for (i = 0; i < npaths; i++)
+			if (free_cp[i].cp_wq != rds_wq)
+				destroy_workqueue(free_cp[i].cp_wq);
+		kfree(free_cp);
+	}
+
+	return conn;
+}
+
+struct rds_connection *rds_conn_create(struct net *net,
+				       const struct in6_addr *laddr,
+				       const struct in6_addr *faddr,
+				       struct rds_transport *trans, u8 tos,
+				       gfp_t gfp, int dev_if)
+{
+	return __rds_conn_create(net, laddr, faddr, trans, gfp, tos, 0, dev_if);
+}
+EXPORT_SYMBOL_GPL(rds_conn_create);
+
+struct rds_connection *rds_conn_create_outgoing(struct net *net,
+						const struct in6_addr *laddr,
+						const struct in6_addr *faddr,
+						struct rds_transport *trans,
+						u8 tos, gfp_t gfp, int dev_if)
+{
+	return __rds_conn_create(net, laddr, faddr, trans, gfp, tos, 1, dev_if);
+}
+EXPORT_SYMBOL_GPL(rds_conn_create_outgoing);
+
+void rds_conn_shutdown(struct rds_conn_path *cp)
+{
+	struct rds_connection *conn = cp->cp_conn;
+
+	/* shut it down unless it's down already */
+	if (!rds_conn_path_transition(cp, RDS_CONN_DOWN, RDS_CONN_DOWN)) {
+		/*
+		 * Quiesce the connection mgmt handlers before we start tearing
+		 * things down. We don't hold the mutex for the entire
+		 * duration of the shutdown operation, else we may be
+		 * deadlocking with the CM handler. Instead, the CM event
+		 * handler is supposed to check for state DISCONNECTING
+		 */
+		mutex_lock(&cp->cp_cm_lock);
+		if (!rds_conn_path_transition(cp, RDS_CONN_UP,
+					      RDS_CONN_DISCONNECTING) &&
+		    !rds_conn_path_transition(cp, RDS_CONN_ERROR,
+					      RDS_CONN_DISCONNECTING) &&
+		    !rds_conn_path_transition(cp, RDS_CONN_RESETTING,
+					      RDS_CONN_DISCONNECTING)) {
+			rds_conn_path_error(cp,
+					    "shutdown called in state %d\n",
+					    atomic_read(&cp->cp_state));
+			mutex_unlock(&cp->cp_cm_lock);
+			return;
+		}
+		mutex_unlock(&cp->cp_cm_lock);
+
+		wait_event(cp->cp_waitq,
+			   !test_bit(RDS_IN_XMIT, &cp->cp_flags));
+		wait_event(cp->cp_waitq,
+			   !test_bit(RDS_RECV_REFILL, &cp->cp_flags));
+
+		conn->c_trans->conn_path_shutdown(cp);
+		rds_conn_path_reset(cp);
+
+		if (!rds_conn_path_transition(cp, RDS_CONN_DISCONNECTING,
+					      RDS_CONN_DOWN) &&
+		    !rds_conn_path_transition(cp, RDS_CONN_ERROR,
+					      RDS_CONN_DOWN)) {
+			/* This can happen - eg when we're in the middle of tearing
+			 * down the connection, and someone unloads the rds module.
+			 * Quite reproducible with loopback connections.
+			 * Mostly harmless.
+			 *
+			 * Note that this also happens with rds-tcp because
+			 * we could have triggered rds_conn_path_drop in irq
+			 * mode from rds_tcp_state change on the receipt of
+			 * a FIN, thus we need to recheck for RDS_CONN_ERROR
+			 * here.
+			 */
+			rds_conn_path_error(cp, "%s: failed to transition "
+					    "to state DOWN, current state "
+					    "is %d\n", __func__,
+					    atomic_read(&cp->cp_state));
+			return;
+		}
+	}
+
+	/* Then reconnect if it's still live.
+	 * The passive side of an IB loopback connection is never added
+	 * to the conn hash, so we never trigger a reconnect on this
+	 * conn - the reconnect is always triggered by the active peer. */
+	cancel_delayed_work_sync(&cp->cp_conn_w);
+
+	clear_bit(RDS_RECONNECT_PENDING, &cp->cp_flags);
+	rcu_read_lock();
+	if (!hlist_unhashed(&conn->c_hash_node)) {
+		rcu_read_unlock();
+		if (conn->c_trans->t_mp_capable &&
+		    cp->cp_index == 0)
+			rds_send_ping(conn, 0);
+		rds_queue_reconnect(cp);
+	} else {
+		rcu_read_unlock();
+	}
+
+	/* we do not hold the socket lock here but it is safe because
+	 * fan-out is disabled when calling conn_slots_available()
+	 */
+	if (conn->c_trans->conn_slots_available)
+		conn->c_trans->conn_slots_available(conn, false);
+}
+
+/* destroy a single rds_conn_path. rds_conn_destroy() iterates over
+ * all paths using rds_conn_path_destroy()
+ */
+static void rds_conn_path_destroy(struct rds_conn_path *cp)
+{
+	struct rds_message *rm, *rtmp;
+
+	if (!cp->cp_transport_data)
+		return;
+
+	/* make sure lingering queued work won't try to ref the conn */
+	cancel_delayed_work_sync(&cp->cp_send_w);
+	cancel_delayed_work_sync(&cp->cp_recv_w);
+
+	rds_conn_path_drop(cp, true);
+	flush_work(&cp->cp_down_w);
+
+	/* tear down queued messages */
+	list_for_each_entry_safe(rm, rtmp,
+				 &cp->cp_send_queue,
+				 m_conn_item) {
+		list_del_init(&rm->m_conn_item);
+		BUG_ON(!list_empty(&rm->m_sock_item));
+		rds_message_put(rm);
+	}
+	if (cp->cp_xmit_rm)
+		rds_message_put(cp->cp_xmit_rm);
+
+	WARN_ON(delayed_work_pending(&cp->cp_send_w));
+	WARN_ON(delayed_work_pending(&cp->cp_recv_w));
+	WARN_ON(delayed_work_pending(&cp->cp_conn_w));
+	WARN_ON(work_pending(&cp->cp_down_w));
+
+	if (cp->cp_wq != rds_wq) {
+		destroy_workqueue(cp->cp_wq);
+		cp->cp_wq = NULL;
+	}
+
+	cp->cp_conn->c_trans->conn_free(cp->cp_transport_data);
+}
+
+/*
+ * Stop and free a connection.
+ *
+ * This can only be used in very limited circumstances.  It assumes that once
+ * the conn has been shutdown that no one else is referencing the connection.
+ * We can only ensure this in the rmmod path in the current code.
+ */
+void rds_conn_destroy(struct rds_connection *conn)
+{
+	unsigned long flags;
+	int i;
+	struct rds_conn_path *cp;
+	int npaths = (conn->c_trans->t_mp_capable ? RDS_MPATH_WORKERS : 1);
+
+	rdsdebug("freeing conn %p for %pI4 -> "
+		 "%pI4\n", conn, &conn->c_laddr,
+		 &conn->c_faddr);
+
+	/* Ensure conn will not be scheduled for reconnect */
+	spin_lock_irq(&rds_conn_lock);
+	hlist_del_init_rcu(&conn->c_hash_node);
+	spin_unlock_irq(&rds_conn_lock);
+	synchronize_rcu();
+
+	/* shut the connection down */
+	for (i = 0; i < npaths; i++) {
+		cp = &conn->c_path[i];
+		rds_conn_path_destroy(cp);
+		BUG_ON(!list_empty(&cp->cp_retrans));
+	}
+
+	/*
+	 * The congestion maps aren't freed up here.  They're
+	 * freed by rds_cong_exit() after all the connections
+	 * have been freed.
+	 */
+	rds_cong_remove_conn(conn);
+
+	kfree(conn->c_path);
+	kmem_cache_free(rds_conn_slab, conn);
+
+	spin_lock_irqsave(&rds_conn_lock, flags);
+	rds_conn_count--;
+	spin_unlock_irqrestore(&rds_conn_lock, flags);
+}
+EXPORT_SYMBOL_GPL(rds_conn_destroy);
+
+static void __rds_inc_msg_cp(struct rds_incoming *inc,
+			     struct rds_info_iterator *iter,
+			     void *saddr, void *daddr, int flip, bool isv6)
+{
+#if IS_ENABLED(CONFIG_IPV6)
+	if (isv6)
+		rds6_inc_info_copy(inc, iter, saddr, daddr, flip);
+	else
+#endif
+		rds_inc_info_copy(inc, iter, *(__be32 *)saddr,
+				  *(__be32 *)daddr, flip);
+}
+
+static void rds_conn_message_info_cmn(struct socket *sock, unsigned int len,
+				      struct rds_info_iterator *iter,
+				      struct rds_info_lengths *lens,
+				      int want_send, bool isv6)
+{
+	struct net *net = sock_net(sock->sk);
+	struct hlist_head *head;
+	struct list_head *list;
+	struct rds_connection *conn;
+	struct rds_message *rm;
+	unsigned int total = 0;
+	unsigned long flags;
+	size_t i;
+	int j;
+
+	if (isv6)
+		len /= sizeof(struct rds6_info_message);
+	else
+		len /= sizeof(struct rds_info_message);
+
+	rcu_read_lock();
+
+	for (i = 0, head = rds_conn_hash; i < ARRAY_SIZE(rds_conn_hash);
+	     i++, head++) {
+		hlist_for_each_entry_rcu(conn, head, c_hash_node) {
+			struct rds_conn_path *cp;
+			int npaths;
+
+			/* Only show connections in the caller's netns. */
+			if (!net_eq(rds_conn_net(conn), net))
+				continue;
+			if (!isv6 && conn->c_isv6)
+				continue;
+
+			npaths = (conn->c_trans->t_mp_capable ?
+				 RDS_MPATH_WORKERS : 1);
+
+			for (j = 0; j < npaths; j++) {
+				cp = &conn->c_path[j];
+				if (want_send)
+					list = &cp->cp_send_queue;
+				else
+					list = &cp->cp_retrans;
+
+				spin_lock_irqsave(&cp->cp_lock, flags);
+
+				/* XXX too lazy to maintain counts.. */
+				list_for_each_entry(rm, list, m_conn_item) {
+					total++;
+					if (total <= len)
+						__rds_inc_msg_cp(&rm->m_inc,
+								 iter,
+								 &conn->c_laddr,
+								 &conn->c_faddr,
+								 0, isv6);
+				}
+
+				spin_unlock_irqrestore(&cp->cp_lock, flags);
+			}
+		}
+	}
+	rcu_read_unlock();
+
+	lens->nr = total;
+	if (isv6)
+		lens->each = sizeof(struct rds6_info_message);
+	else
+		lens->each = sizeof(struct rds_info_message);
+}
+
+static void rds_conn_message_info(struct socket *sock, unsigned int len,
+				  struct rds_info_iterator *iter,
+				  struct rds_info_lengths *lens,
+				  int want_send)
+{
+	rds_conn_message_info_cmn(sock, len, iter, lens, want_send, false);
+}
+
+#if IS_ENABLED(CONFIG_IPV6)
+static void rds6_conn_message_info(struct socket *sock, unsigned int len,
+				   struct rds_info_iterator *iter,
+				   struct rds_info_lengths *lens,
+				   int want_send)
+{
+	rds_conn_message_info_cmn(sock, len, iter, lens, want_send, true);
+}
+#endif
+
+static void rds_conn_message_info_send(struct socket *sock, unsigned int len,
+				       struct rds_info_iterator *iter,
+				       struct rds_info_lengths *lens)
+{
+	rds_conn_message_info(sock, len, iter, lens, 1);
+}
+
+#if IS_ENABLED(CONFIG_IPV6)
+static void rds6_conn_message_info_send(struct socket *sock, unsigned int len,
+					struct rds_info_iterator *iter,
+					struct rds_info_lengths *lens)
+{
+	rds6_conn_message_info(sock, len, iter, lens, 1);
+}
+#endif
+
+static void rds_conn_message_info_retrans(struct socket *sock,
+					  unsigned int len,
+					  struct rds_info_iterator *iter,
+					  struct rds_info_lengths *lens)
+{
+	rds_conn_message_info(sock, len, iter, lens, 0);
+}
+
+#if IS_ENABLED(CONFIG_IPV6)
+static void rds6_conn_message_info_retrans(struct socket *sock,
+					   unsigned int len,
+					   struct rds_info_iterator *iter,
+					   struct rds_info_lengths *lens)
+{
+	rds6_conn_message_info(sock, len, iter, lens, 0);
+}
+#endif
+
+void rds_for_each_conn_info(struct socket *sock, unsigned int len,
+			  struct rds_info_iterator *iter,
+			  struct rds_info_lengths *lens,
+			  int (*visitor)(struct rds_connection *, void *),
+			  u64 *buffer,
+			  size_t item_len)
+{
+	struct net *net = sock_net(sock->sk);
+	struct hlist_head *head;
+	struct rds_connection *conn;
+	size_t i;
+
+	rcu_read_lock();
+
+	lens->nr = 0;
+	lens->each = item_len;
+
+	for (i = 0, head = rds_conn_hash; i < ARRAY_SIZE(rds_conn_hash);
+	     i++, head++) {
+		hlist_for_each_entry_rcu(conn, head, c_hash_node) {
+			/* Only show connections in the caller's netns. */
+			if (!net_eq(rds_conn_net(conn), net))
+				continue;
+
+			/* Zero the per-item buffer before handing it to the
+			 * visitor so any field the visitor does not write -
+			 * including implicit alignment padding - cannot leak
+			 * stack contents to user space via rds_info_copy().
+			 */
+			memset(buffer, 0, item_len);
+
+			/* XXX no c_lock usage.. */
+			if (!visitor(conn, buffer))
+				continue;
+
+			/* We copy as much as we can fit in the buffer,
+			 * but we count all items so that the caller
+			 * can resize the buffer. */
+			if (len >= item_len) {
+				rds_info_copy(iter, buffer, item_len);
+				len -= item_len;
+			}
+			lens->nr++;
+		}
+	}
+	rcu_read_unlock();
+}
+EXPORT_SYMBOL_GPL(rds_for_each_conn_info);
+
+static void rds_walk_conn_path_info(struct socket *sock, unsigned int len,
+				    struct rds_info_iterator *iter,
+				    struct rds_info_lengths *lens,
+				    int (*visitor)(struct rds_conn_path *, void *),
+				    u64 *buffer,
+				    size_t item_len)
+{
+	struct net *net = sock_net(sock->sk);
+	struct hlist_head *head;
+	struct rds_connection *conn;
+	size_t i;
+
+	rcu_read_lock();
+
+	lens->nr = 0;
+	lens->each = item_len;
+
+	for (i = 0, head = rds_conn_hash; i < ARRAY_SIZE(rds_conn_hash);
+	     i++, head++) {
+		hlist_for_each_entry_rcu(conn, head, c_hash_node) {
+			struct rds_conn_path *cp;
+
+			/* Only show connections in the caller's netns. */
+			if (!net_eq(rds_conn_net(conn), net))
+				continue;
+
+			/* XXX We only copy the information from the first
+			 * path for now.  The problem is that if there are
+			 * more than one underlying paths, we cannot report
+			 * information of all of them using the existing
+			 * API.  For example, there is only one next_tx_seq,
+			 * which path's next_tx_seq should we report?  It is
+			 * a bug in the design of MPRDS.
+			 */
+			cp = conn->c_path;
+
+			/* Zero the per-item buffer for the same reason as
+			 * rds_for_each_conn_info(): any byte the visitor
+			 * does not write (including alignment padding) must
+			 * not leak stack contents via rds_info_copy().
+			 */
+			memset(buffer, 0, item_len);
+
+			/* XXX no cp_lock usage.. */
+			if (!visitor(cp, buffer))
+				continue;
+
+			/* We copy as much as we can fit in the buffer,
+			 * but we count all items so that the caller
+			 * can resize the buffer.
+			 */
+			if (len >= item_len) {
+				rds_info_copy(iter, buffer, item_len);
+				len -= item_len;
+			}
+			lens->nr++;
+		}
+	}
+	rcu_read_unlock();
+}
+
+static int rds_conn_info_visitor(struct rds_conn_path *cp, void *buffer)
+{
+	struct rds_info_connection *cinfo = buffer;
+	struct rds_connection *conn = cp->cp_conn;
+
+	if (conn->c_isv6)
+		return 0;
+
+	cinfo->next_tx_seq = cp->cp_next_tx_seq;
+	cinfo->next_rx_seq = cp->cp_next_rx_seq;
+	cinfo->laddr = conn->c_laddr.s6_addr32[3];
+	cinfo->faddr = conn->c_faddr.s6_addr32[3];
+	cinfo->tos = conn->c_tos;
+	strscpy_pad(cinfo->transport, conn->c_trans->t_name);
+	cinfo->flags = 0;
+
+	rds_conn_info_set(cinfo->flags, test_bit(RDS_IN_XMIT, &cp->cp_flags),
+			  SENDING);
+	/* XXX Future: return the state rather than these funky bits */
+	rds_conn_info_set(cinfo->flags,
+			  atomic_read(&cp->cp_state) == RDS_CONN_CONNECTING,
+			  CONNECTING);
+	rds_conn_info_set(cinfo->flags,
+			  atomic_read(&cp->cp_state) == RDS_CONN_UP,
+			  CONNECTED);
+	return 1;
+}
+
+#if IS_ENABLED(CONFIG_IPV6)
+static int rds6_conn_info_visitor(struct rds_conn_path *cp, void *buffer)
+{
+	struct rds6_info_connection *cinfo6 = buffer;
+	struct rds_connection *conn = cp->cp_conn;
+
+	cinfo6->next_tx_seq = cp->cp_next_tx_seq;
+	cinfo6->next_rx_seq = cp->cp_next_rx_seq;
+	cinfo6->laddr = conn->c_laddr;
+	cinfo6->faddr = conn->c_faddr;
+	strscpy_pad(cinfo6->transport, conn->c_trans->t_name);
+	cinfo6->flags = 0;
+
+	rds_conn_info_set(cinfo6->flags, test_bit(RDS_IN_XMIT, &cp->cp_flags),
+			  SENDING);
+	/* XXX Future: return the state rather than these funky bits */
+	rds_conn_info_set(cinfo6->flags,
+			  atomic_read(&cp->cp_state) == RDS_CONN_CONNECTING,
+			  CONNECTING);
+	rds_conn_info_set(cinfo6->flags,
+			  atomic_read(&cp->cp_state) == RDS_CONN_UP,
+			  CONNECTED);
+	/* Just return 1 as there is no error case. This is a helper function
+	 * for rds_walk_conn_path_info() and it wants a return value.
+	 */
+	return 1;
+}
+#endif
+
+static void rds_conn_info(struct socket *sock, unsigned int len,
+			  struct rds_info_iterator *iter,
+			  struct rds_info_lengths *lens)
+{
+	u64 buffer[(sizeof(struct rds_info_connection) + 7) / 8];
+
+	rds_walk_conn_path_info(sock, len, iter, lens,
+				rds_conn_info_visitor,
+				buffer,
+				sizeof(struct rds_info_connection));
+}
+
+#if IS_ENABLED(CONFIG_IPV6)
+static void rds6_conn_info(struct socket *sock, unsigned int len,
+			   struct rds_info_iterator *iter,
+			   struct rds_info_lengths *lens)
+{
+	u64 buffer[(sizeof(struct rds6_info_connection) + 7) / 8];
+
+	rds_walk_conn_path_info(sock, len, iter, lens,
+				rds6_conn_info_visitor,
+				buffer,
+				sizeof(struct rds6_info_connection));
+}
+#endif
+
+int rds_conn_init(void)
+{
+	int ret;
+
+	ret = rds_loop_net_init(); /* register pernet callback */
+	if (ret)
+		return ret;
+
+	rds_conn_slab = KMEM_CACHE(rds_connection, 0);
+	if (!rds_conn_slab) {
+		rds_loop_net_exit();
+		return -ENOMEM;
+	}
+
+	rds_info_register_func(RDS_INFO_CONNECTIONS, rds_conn_info);
+	rds_info_register_func(RDS_INFO_SEND_MESSAGES,
+			       rds_conn_message_info_send);
+	rds_info_register_func(RDS_INFO_RETRANS_MESSAGES,
+			       rds_conn_message_info_retrans);
+#if IS_ENABLED(CONFIG_IPV6)
+	rds_info_register_func(RDS6_INFO_CONNECTIONS, rds6_conn_info);
+	rds_info_register_func(RDS6_INFO_SEND_MESSAGES,
+			       rds6_conn_message_info_send);
+	rds_info_register_func(RDS6_INFO_RETRANS_MESSAGES,
+			       rds6_conn_message_info_retrans);
+#endif
+	return 0;
+}
+
+void rds_conn_exit(void)
+{
+	rds_loop_net_exit(); /* unregister pernet callback */
+	rds_loop_exit();
+
+	WARN_ON(!hlist_empty(rds_conn_hash));
+
+	kmem_cache_destroy(rds_conn_slab);
+
+	rds_info_deregister_func(RDS_INFO_CONNECTIONS, rds_conn_info);
+	rds_info_deregister_func(RDS_INFO_SEND_MESSAGES,
+				 rds_conn_message_info_send);
+	rds_info_deregister_func(RDS_INFO_RETRANS_MESSAGES,
+				 rds_conn_message_info_retrans);
+#if IS_ENABLED(CONFIG_IPV6)
+	rds_info_deregister_func(RDS6_INFO_CONNECTIONS, rds6_conn_info);
+	rds_info_deregister_func(RDS6_INFO_SEND_MESSAGES,
+				 rds6_conn_message_info_send);
+	rds_info_deregister_func(RDS6_INFO_RETRANS_MESSAGES,
+				 rds6_conn_message_info_retrans);
+#endif
+}
+
+/*
+ * Force a disconnect
+ */
+void rds_conn_path_drop(struct rds_conn_path *cp, bool destroy)
+{
+	atomic_set(&cp->cp_state, RDS_CONN_ERROR);
+
+	rcu_read_lock();
+	if (!destroy && rds_destroy_pending(cp->cp_conn)) {
+		rcu_read_unlock();
+		return;
+	}
+	queue_work(cp->cp_wq, &cp->cp_down_w);
+	rcu_read_unlock();
+}
+EXPORT_SYMBOL_GPL(rds_conn_path_drop);
+
+void rds_conn_drop(struct rds_connection *conn)
+{
+	WARN_ON(conn->c_trans->t_mp_capable);
+	rds_conn_path_drop(&conn->c_path[0], false);
+}
+EXPORT_SYMBOL_GPL(rds_conn_drop);
+
+/*
+ * If the connection is down, trigger a connect. We may have scheduled a
+ * delayed reconnect however - in this case we should not interfere.
+ */
+void rds_conn_path_connect_if_down(struct rds_conn_path *cp)
+{
+	rcu_read_lock();
+	if (rds_destroy_pending(cp->cp_conn)) {
+		rcu_read_unlock();
+		return;
+	}
+	if (rds_conn_path_state(cp) == RDS_CONN_DOWN &&
+	    !test_and_set_bit(RDS_RECONNECT_PENDING, &cp->cp_flags))
+		queue_delayed_work(cp->cp_wq, &cp->cp_conn_w, 0);
+	rcu_read_unlock();
+}
+EXPORT_SYMBOL_GPL(rds_conn_path_connect_if_down);
+
+/* Check connectivity of all paths
+ */
+void rds_check_all_paths(struct rds_connection *conn)
+{
+	int i = 0;
+
+	do {
+		rds_conn_path_connect_if_down(&conn->c_path[i]);
+	} while (++i < conn->c_npaths);
+}
+
+void rds_conn_connect_if_down(struct rds_connection *conn)
+{
+	WARN_ON(conn->c_trans->t_mp_capable);
+	rds_conn_path_connect_if_down(&conn->c_path[0]);
+}
+EXPORT_SYMBOL_GPL(rds_conn_connect_if_down);
+
+void
+__rds_conn_path_error(struct rds_conn_path *cp, const char *fmt, ...)
+{
+	va_list ap;
+
+	va_start(ap, fmt);
+	vprintk(fmt, ap);
+	va_end(ap);
+
+	rds_conn_path_drop(cp, false);
+}
diff --git a/net/rds/ib.c b/net/rds/ib.c
new file mode 100644
index 000000000..786f39169
--- /dev/null
+++ b/net/rds/ib.c
@@ -0,0 +1,629 @@
+/*
+ * Copyright (c) 2006, 2019 Oracle and/or its affiliates. All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+#include <linux/kernel.h>
+#include <linux/in.h>
+#include <linux/if.h>
+#include <linux/netdevice.h>
+#include <linux/inetdevice.h>
+#include <linux/if_arp.h>
+#include <linux/delay.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <net/addrconf.h>
+
+#include "rds_single_path.h"
+#include "rds.h"
+#include "ib.h"
+#include "ib_mr.h"
+
+static unsigned int rds_ib_mr_1m_pool_size = RDS_MR_1M_POOL_SIZE;
+static unsigned int rds_ib_mr_8k_pool_size = RDS_MR_8K_POOL_SIZE;
+unsigned int rds_ib_retry_count = RDS_IB_DEFAULT_RETRY_COUNT;
+static atomic_t rds_ib_unloading;
+
+module_param(rds_ib_mr_1m_pool_size, int, 0444);
+MODULE_PARM_DESC(rds_ib_mr_1m_pool_size, " Max number of 1M mr per HCA");
+module_param(rds_ib_mr_8k_pool_size, int, 0444);
+MODULE_PARM_DESC(rds_ib_mr_8k_pool_size, " Max number of 8K mr per HCA");
+module_param(rds_ib_retry_count, int, 0444);
+MODULE_PARM_DESC(rds_ib_retry_count, " Number of hw retries before reporting an error");
+
+/*
+ * we have a clumsy combination of RCU and a rwsem protecting this list
+ * because it is used both in the get_mr fast path and while blocking in
+ * the FMR flushing path.
+ */
+DECLARE_RWSEM(rds_ib_devices_lock);
+struct list_head rds_ib_devices;
+
+/* NOTE: if also grabbing ibdev lock, grab this first */
+DEFINE_SPINLOCK(ib_nodev_conns_lock);
+LIST_HEAD(ib_nodev_conns);
+
+static void rds_ib_nodev_connect(void)
+{
+	struct rds_ib_connection *ic;
+
+	spin_lock(&ib_nodev_conns_lock);
+	list_for_each_entry(ic, &ib_nodev_conns, ib_node)
+		rds_conn_connect_if_down(ic->conn);
+	spin_unlock(&ib_nodev_conns_lock);
+}
+
+static void rds_ib_dev_shutdown(struct rds_ib_device *rds_ibdev)
+{
+	struct rds_ib_connection *ic;
+	unsigned long flags;
+
+	spin_lock_irqsave(&rds_ibdev->spinlock, flags);
+	list_for_each_entry(ic, &rds_ibdev->conn_list, ib_node)
+		rds_conn_path_drop(&ic->conn->c_path[0], true);
+	spin_unlock_irqrestore(&rds_ibdev->spinlock, flags);
+}
+
+/*
+ * rds_ib_destroy_mr_pool() blocks on a few things and mrs drop references
+ * from interrupt context so we push freing off into a work struct in krdsd.
+ */
+static void rds_ib_dev_free(struct work_struct *work)
+{
+	struct rds_ib_ipaddr *i_ipaddr, *i_next;
+	struct rds_ib_device *rds_ibdev = container_of(work,
+					struct rds_ib_device, free_work);
+
+	if (rds_ibdev->mr_8k_pool)
+		rds_ib_destroy_mr_pool(rds_ibdev->mr_8k_pool);
+	if (rds_ibdev->mr_1m_pool)
+		rds_ib_destroy_mr_pool(rds_ibdev->mr_1m_pool);
+	if (rds_ibdev->pd)
+		ib_dealloc_pd(rds_ibdev->pd);
+
+	list_for_each_entry_safe(i_ipaddr, i_next, &rds_ibdev->ipaddr_list, list) {
+		list_del(&i_ipaddr->list);
+		kfree(i_ipaddr);
+	}
+
+	kfree(rds_ibdev->vector_load);
+
+	kfree(rds_ibdev);
+}
+
+void rds_ib_dev_put(struct rds_ib_device *rds_ibdev)
+{
+	BUG_ON(refcount_read(&rds_ibdev->refcount) == 0);
+	if (refcount_dec_and_test(&rds_ibdev->refcount))
+		queue_work(rds_wq, &rds_ibdev->free_work);
+}
+
+static int rds_ib_add_one(struct ib_device *device)
+{
+	struct rds_ib_device *rds_ibdev;
+	int ret;
+
+	/* Only handle IB (no iWARP) devices */
+	if (device->node_type != RDMA_NODE_IB_CA)
+		return -EOPNOTSUPP;
+
+	/* Device must support FRWR */
+	if (!(device->attrs.device_cap_flags & IB_DEVICE_MEM_MGT_EXTENSIONS))
+		return -EOPNOTSUPP;
+
+	rds_ibdev = kzalloc_node(sizeof(struct rds_ib_device), GFP_KERNEL,
+				 ibdev_to_node(device));
+	if (!rds_ibdev)
+		return -ENOMEM;
+
+	spin_lock_init(&rds_ibdev->spinlock);
+	refcount_set(&rds_ibdev->refcount, 1);
+	INIT_WORK(&rds_ibdev->free_work, rds_ib_dev_free);
+
+	INIT_LIST_HEAD(&rds_ibdev->ipaddr_list);
+	INIT_LIST_HEAD(&rds_ibdev->conn_list);
+
+	rds_ibdev->max_wrs = device->attrs.max_qp_wr;
+	rds_ibdev->max_sge = min(device->attrs.max_send_sge, RDS_IB_MAX_SGE);
+
+	rds_ibdev->odp_capable =
+		!!(device->attrs.kernel_cap_flags &
+		   IBK_ON_DEMAND_PAGING) &&
+		!!(device->attrs.odp_caps.per_transport_caps.rc_odp_caps &
+		   IB_ODP_SUPPORT_WRITE) &&
+		!!(device->attrs.odp_caps.per_transport_caps.rc_odp_caps &
+		   IB_ODP_SUPPORT_READ);
+
+	rds_ibdev->max_1m_mrs = device->attrs.max_mr ?
+		min(device->attrs.max_mr / 2,
+		    rds_ib_mr_1m_pool_size) : rds_ib_mr_1m_pool_size;
+
+	rds_ibdev->max_8k_mrs = device->attrs.max_mr ?
+		min((device->attrs.max_mr / 2) * RDS_MR_8K_SCALE,
+		    rds_ib_mr_8k_pool_size) : rds_ib_mr_8k_pool_size;
+
+	rds_ibdev->max_initiator_depth = device->attrs.max_qp_init_rd_atom;
+	rds_ibdev->max_responder_resources = device->attrs.max_qp_rd_atom;
+
+	rds_ibdev->vector_load = kzalloc_objs(int, device->num_comp_vectors);
+	if (!rds_ibdev->vector_load) {
+		pr_err("RDS/IB: %s failed to allocate vector memory\n",
+			__func__);
+		ret = -ENOMEM;
+		goto put_dev;
+	}
+
+	rds_ibdev->dev = device;
+	rds_ibdev->pd = ib_alloc_pd(device, 0);
+	if (IS_ERR(rds_ibdev->pd)) {
+		ret = PTR_ERR(rds_ibdev->pd);
+		rds_ibdev->pd = NULL;
+		goto put_dev;
+	}
+
+	rds_ibdev->mr_1m_pool =
+		rds_ib_create_mr_pool(rds_ibdev, RDS_IB_MR_1M_POOL);
+	if (IS_ERR(rds_ibdev->mr_1m_pool)) {
+		ret = PTR_ERR(rds_ibdev->mr_1m_pool);
+		rds_ibdev->mr_1m_pool = NULL;
+		goto put_dev;
+	}
+
+	rds_ibdev->mr_8k_pool =
+		rds_ib_create_mr_pool(rds_ibdev, RDS_IB_MR_8K_POOL);
+	if (IS_ERR(rds_ibdev->mr_8k_pool)) {
+		ret = PTR_ERR(rds_ibdev->mr_8k_pool);
+		rds_ibdev->mr_8k_pool = NULL;
+		goto put_dev;
+	}
+
+	rdsdebug("RDS/IB: max_mr = %u, max_wrs = %d, max_sge = %d, max_1m_mrs = %d, max_8k_mrs = %d\n",
+		 device->attrs.max_mr, rds_ibdev->max_wrs, rds_ibdev->max_sge,
+		 rds_ibdev->max_1m_mrs, rds_ibdev->max_8k_mrs);
+
+	pr_info("RDS/IB: %s: added\n", device->name);
+
+	down_write(&rds_ib_devices_lock);
+	list_add_tail_rcu(&rds_ibdev->list, &rds_ib_devices);
+	up_write(&rds_ib_devices_lock);
+	refcount_inc(&rds_ibdev->refcount);
+
+	ib_set_client_data(device, &rds_ib_client, rds_ibdev);
+
+	rds_ib_nodev_connect();
+	return 0;
+
+put_dev:
+	rds_ib_dev_put(rds_ibdev);
+	return ret;
+}
+
+/*
+ * New connections use this to find the device to associate with the
+ * connection.  It's not in the fast path so we're not concerned about the
+ * performance of the IB call.  (As of this writing, it uses an interrupt
+ * blocking spinlock to serialize walking a per-device list of all registered
+ * clients.)
+ *
+ * RCU is used to handle incoming connections racing with device teardown.
+ * Rather than use a lock to serialize removal from the client_data and
+ * getting a new reference, we use an RCU grace period.  The destruction
+ * path removes the device from client_data and then waits for all RCU
+ * readers to finish.
+ *
+ * A new connection can get NULL from this if its arriving on a
+ * device that is in the process of being removed.
+ */
+struct rds_ib_device *rds_ib_get_client_data(struct ib_device *device)
+{
+	struct rds_ib_device *rds_ibdev;
+
+	rcu_read_lock();
+	rds_ibdev = ib_get_client_data(device, &rds_ib_client);
+	if (rds_ibdev)
+		refcount_inc(&rds_ibdev->refcount);
+	rcu_read_unlock();
+	return rds_ibdev;
+}
+
+/*
+ * The IB stack is letting us know that a device is going away.  This can
+ * happen if the underlying HCA driver is removed or if PCI hotplug is removing
+ * the pci function, for example.
+ *
+ * This can be called at any time and can be racing with any other RDS path.
+ */
+static void rds_ib_remove_one(struct ib_device *device, void *client_data)
+{
+	struct rds_ib_device *rds_ibdev = client_data;
+
+	rds_ib_dev_shutdown(rds_ibdev);
+
+	/* stop connection attempts from getting a reference to this device. */
+	ib_set_client_data(device, &rds_ib_client, NULL);
+
+	down_write(&rds_ib_devices_lock);
+	list_del_rcu(&rds_ibdev->list);
+	up_write(&rds_ib_devices_lock);
+
+	/*
+	 * This synchronize rcu is waiting for readers of both the ib
+	 * client data and the devices list to finish before we drop
+	 * both of those references.
+	 */
+	synchronize_rcu();
+	rds_ib_dev_put(rds_ibdev);
+	rds_ib_dev_put(rds_ibdev);
+}
+
+struct ib_client rds_ib_client = {
+	.name   = "rds_ib",
+	.add    = rds_ib_add_one,
+	.remove = rds_ib_remove_one
+};
+
+static int rds_ib_conn_info_visitor(struct rds_connection *conn,
+				    void *buffer)
+{
+	struct rds_info_rdma_connection *iinfo = buffer;
+	struct rds_ib_connection *ic = conn->c_transport_data;
+
+	/* We will only ever look at IB transports */
+	if (conn->c_trans != &rds_ib_transport)
+		return 0;
+	if (conn->c_isv6)
+		return 0;
+
+	iinfo->src_addr = conn->c_laddr.s6_addr32[3];
+	iinfo->dst_addr = conn->c_faddr.s6_addr32[3];
+	if (ic) {
+		iinfo->tos = conn->c_tos;
+		iinfo->sl = ic->i_sl;
+	}
+
+	memset(&iinfo->src_gid, 0, sizeof(iinfo->src_gid));
+	memset(&iinfo->dst_gid, 0, sizeof(iinfo->dst_gid));
+	if (rds_conn_state(conn) == RDS_CONN_UP) {
+		struct rds_ib_device *rds_ibdev;
+
+		rdma_read_gids(ic->i_cm_id, (union ib_gid *)&iinfo->src_gid,
+			       (union ib_gid *)&iinfo->dst_gid);
+
+		rds_ibdev = ic->rds_ibdev;
+		iinfo->max_send_wr = ic->i_send_ring.w_nr;
+		iinfo->max_recv_wr = ic->i_recv_ring.w_nr;
+		iinfo->max_send_sge = rds_ibdev->max_sge;
+		rds_ib_get_mr_info(rds_ibdev, iinfo);
+		iinfo->cache_allocs = atomic_read(&ic->i_cache_allocs);
+	}
+	return 1;
+}
+
+#if IS_ENABLED(CONFIG_IPV6)
+/* IPv6 version of rds_ib_conn_info_visitor(). */
+static int rds6_ib_conn_info_visitor(struct rds_connection *conn,
+				     void *buffer)
+{
+	struct rds6_info_rdma_connection *iinfo6 = buffer;
+	struct rds_ib_connection *ic = conn->c_transport_data;
+
+	/* We will only ever look at IB transports */
+	if (conn->c_trans != &rds_ib_transport)
+		return 0;
+
+	iinfo6->src_addr = conn->c_laddr;
+	iinfo6->dst_addr = conn->c_faddr;
+	if (ic) {
+		iinfo6->tos = conn->c_tos;
+		iinfo6->sl = ic->i_sl;
+	}
+
+	memset(&iinfo6->src_gid, 0, sizeof(iinfo6->src_gid));
+	memset(&iinfo6->dst_gid, 0, sizeof(iinfo6->dst_gid));
+
+	if (rds_conn_state(conn) == RDS_CONN_UP) {
+		struct rds_ib_device *rds_ibdev;
+
+		rdma_read_gids(ic->i_cm_id, (union ib_gid *)&iinfo6->src_gid,
+			       (union ib_gid *)&iinfo6->dst_gid);
+		rds_ibdev = ic->rds_ibdev;
+		iinfo6->max_send_wr = ic->i_send_ring.w_nr;
+		iinfo6->max_recv_wr = ic->i_recv_ring.w_nr;
+		iinfo6->max_send_sge = rds_ibdev->max_sge;
+		rds6_ib_get_mr_info(rds_ibdev, iinfo6);
+		iinfo6->cache_allocs = atomic_read(&ic->i_cache_allocs);
+	}
+	return 1;
+}
+#endif
+
+static void rds_ib_ic_info(struct socket *sock, unsigned int len,
+			   struct rds_info_iterator *iter,
+			   struct rds_info_lengths *lens)
+{
+	u64 buffer[(sizeof(struct rds_info_rdma_connection) + 7) / 8];
+
+	rds_for_each_conn_info(sock, len, iter, lens,
+				rds_ib_conn_info_visitor,
+				buffer,
+				sizeof(struct rds_info_rdma_connection));
+}
+
+#if IS_ENABLED(CONFIG_IPV6)
+/* IPv6 version of rds_ib_ic_info(). */
+static void rds6_ib_ic_info(struct socket *sock, unsigned int len,
+			    struct rds_info_iterator *iter,
+			    struct rds_info_lengths *lens)
+{
+	u64 buffer[(sizeof(struct rds6_info_rdma_connection) + 7) / 8];
+
+	rds_for_each_conn_info(sock, len, iter, lens,
+			       rds6_ib_conn_info_visitor,
+			       buffer,
+			       sizeof(struct rds6_info_rdma_connection));
+}
+#endif
+
+/*
+ * Early RDS/IB was built to only bind to an address if there is an IPoIB
+ * device with that address set.
+ *
+ * If it were me, I'd advocate for something more flexible.  Sending and
+ * receiving should be device-agnostic.  Transports would try and maintain
+ * connections between peers who have messages queued.  Userspace would be
+ * allowed to influence which paths have priority.  We could call userspace
+ * asserting this policy "routing".
+ */
+static int rds_ib_laddr_check_cm(struct net *net, const struct in6_addr *addr,
+				 __u32 scope_id)
+{
+	int ret;
+	struct rdma_cm_id *cm_id;
+#if IS_ENABLED(CONFIG_IPV6)
+	struct sockaddr_in6 sin6;
+#endif
+	struct sockaddr_in sin;
+	struct sockaddr *sa;
+	bool isv4;
+
+	isv4 = ipv6_addr_v4mapped(addr);
+	/* Create a CMA ID and try to bind it. This catches both
+	 * IB and iWARP capable NICs.
+	 */
+	cm_id = rdma_create_id(&init_net, rds_rdma_cm_event_handler,
+			       NULL, RDMA_PS_TCP, IB_QPT_RC);
+	if (IS_ERR(cm_id))
+		return PTR_ERR(cm_id);
+
+	if (isv4) {
+		memset(&sin, 0, sizeof(sin));
+		sin.sin_family = AF_INET;
+		sin.sin_addr.s_addr = addr->s6_addr32[3];
+		sa = (struct sockaddr *)&sin;
+	} else {
+#if IS_ENABLED(CONFIG_IPV6)
+		if (!ipv6_mod_enabled()) {
+			ret = -EADDRNOTAVAIL;
+			goto out;
+		}
+		memset(&sin6, 0, sizeof(sin6));
+		sin6.sin6_family = AF_INET6;
+		sin6.sin6_addr = *addr;
+		sin6.sin6_scope_id = scope_id;
+		sa = (struct sockaddr *)&sin6;
+
+		/* XXX Do a special IPv6 link local address check here.  The
+		 * reason is that rdma_bind_addr() always succeeds with IPv6
+		 * link local address regardless it is indeed configured in a
+		 * system.
+		 */
+		if (ipv6_addr_type(addr) & IPV6_ADDR_LINKLOCAL) {
+			struct net_device *dev;
+
+			if (scope_id == 0) {
+				ret = -EADDRNOTAVAIL;
+				goto out;
+			}
+
+			/* Use init_net for now as RDS is not network
+			 * name space aware.
+			 */
+			dev = dev_get_by_index(&init_net, scope_id);
+			if (!dev) {
+				ret = -EADDRNOTAVAIL;
+				goto out;
+			}
+			if (!ipv6_chk_addr(&init_net, addr, dev, 1)) {
+				dev_put(dev);
+				ret = -EADDRNOTAVAIL;
+				goto out;
+			}
+			dev_put(dev);
+		}
+#else
+		ret = -EADDRNOTAVAIL;
+		goto out;
+#endif
+	}
+
+	/* rdma_bind_addr will only succeed for IB & iWARP devices */
+	ret = rdma_bind_addr(cm_id, sa);
+	/* due to this, we will claim to support iWARP devices unless we
+	   check node_type. */
+	if (ret || !cm_id->device ||
+	    cm_id->device->node_type != RDMA_NODE_IB_CA)
+		ret = -EADDRNOTAVAIL;
+
+	rdsdebug("addr %pI6c%%%u ret %d node type %d\n",
+		 addr, scope_id, ret,
+		 cm_id->device ? cm_id->device->node_type : -1);
+
+out:
+	rdma_destroy_id(cm_id);
+
+	return ret;
+}
+
+static int rds_ib_laddr_check(struct net *net, const struct in6_addr *addr,
+			      __u32 scope_id)
+{
+	struct rds_ib_device *rds_ibdev = NULL;
+
+	/* RDS/IB is restricted to the initial network namespace */
+	if (!net_eq(net, &init_net))
+		return -EPROTOTYPE;
+
+	if (ipv6_addr_v4mapped(addr)) {
+		rds_ibdev = rds_ib_get_device(addr->s6_addr32[3]);
+		if (rds_ibdev) {
+			rds_ib_dev_put(rds_ibdev);
+			return 0;
+		}
+	}
+
+	return rds_ib_laddr_check_cm(net, addr, scope_id);
+}
+
+static void rds_ib_unregister_client(void)
+{
+	ib_unregister_client(&rds_ib_client);
+	/* wait for rds_ib_dev_free() to complete */
+	flush_workqueue(rds_wq);
+}
+
+static void rds_ib_set_unloading(void)
+{
+	atomic_set(&rds_ib_unloading, 1);
+}
+
+static bool rds_ib_is_unloading(struct rds_connection *conn)
+{
+	struct rds_conn_path *cp = &conn->c_path[0];
+
+	return (test_bit(RDS_DESTROY_PENDING, &cp->cp_flags) ||
+		atomic_read(&rds_ib_unloading) != 0);
+}
+
+void rds_ib_exit(void)
+{
+	rds_ib_set_unloading();
+	synchronize_rcu();
+	rds_info_deregister_func(RDS_INFO_IB_CONNECTIONS, rds_ib_ic_info);
+#if IS_ENABLED(CONFIG_IPV6)
+	rds_info_deregister_func(RDS6_INFO_IB_CONNECTIONS, rds6_ib_ic_info);
+#endif
+	rds_ib_unregister_client();
+	rds_ib_destroy_nodev_conns();
+	rds_ib_sysctl_exit();
+	rds_ib_recv_exit();
+	rds_trans_unregister(&rds_ib_transport);
+	rds_ib_mr_exit();
+}
+
+static u8 rds_ib_get_tos_map(u8 tos)
+{
+	/* 1:1 user to transport map for RDMA transport.
+	 * In future, if custom map is desired, hook can export
+	 * user configurable map.
+	 */
+	return tos;
+}
+
+struct rds_transport rds_ib_transport = {
+	.laddr_check		= rds_ib_laddr_check,
+	.xmit_path_complete	= rds_ib_xmit_path_complete,
+	.xmit			= rds_ib_xmit,
+	.xmit_rdma		= rds_ib_xmit_rdma,
+	.xmit_atomic		= rds_ib_xmit_atomic,
+	.recv_path		= rds_ib_recv_path,
+	.conn_alloc		= rds_ib_conn_alloc,
+	.conn_free		= rds_ib_conn_free,
+	.conn_path_connect	= rds_ib_conn_path_connect,
+	.conn_path_shutdown	= rds_ib_conn_path_shutdown,
+	.inc_copy_to_user	= rds_ib_inc_copy_to_user,
+	.inc_free		= rds_ib_inc_free,
+	.cm_initiate_connect	= rds_ib_cm_initiate_connect,
+	.cm_handle_connect	= rds_ib_cm_handle_connect,
+	.cm_connect_complete	= rds_ib_cm_connect_complete,
+	.stats_info_copy	= rds_ib_stats_info_copy,
+	.exit			= rds_ib_exit,
+	.get_mr			= rds_ib_get_mr,
+	.sync_mr		= rds_ib_sync_mr,
+	.free_mr		= rds_ib_free_mr,
+	.flush_mrs		= rds_ib_flush_mrs,
+	.get_tos_map		= rds_ib_get_tos_map,
+	.t_owner		= THIS_MODULE,
+	.t_name			= "infiniband",
+	.t_unloading		= rds_ib_is_unloading,
+	.t_type			= RDS_TRANS_IB
+};
+
+int rds_ib_init(void)
+{
+	int ret;
+
+	INIT_LIST_HEAD(&rds_ib_devices);
+
+	ret = rds_ib_mr_init();
+	if (ret)
+		goto out;
+
+	ret = ib_register_client(&rds_ib_client);
+	if (ret)
+		goto out_mr_exit;
+
+	ret = rds_ib_sysctl_init();
+	if (ret)
+		goto out_ibreg;
+
+	ret = rds_ib_recv_init();
+	if (ret)
+		goto out_sysctl;
+
+	rds_trans_register(&rds_ib_transport);
+
+	rds_info_register_func(RDS_INFO_IB_CONNECTIONS, rds_ib_ic_info);
+#if IS_ENABLED(CONFIG_IPV6)
+	rds_info_register_func(RDS6_INFO_IB_CONNECTIONS, rds6_ib_ic_info);
+#endif
+
+	goto out;
+
+out_sysctl:
+	rds_ib_sysctl_exit();
+out_ibreg:
+	rds_ib_unregister_client();
+out_mr_exit:
+	rds_ib_mr_exit();
+out:
+	return ret;
+}
+
+MODULE_LICENSE("GPL");
diff --git a/net/rds/ib.h b/net/rds/ib.h
new file mode 100644
index 000000000..5ff346a1e
--- /dev/null
+++ b/net/rds/ib.h
@@ -0,0 +1,455 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _RDS_IB_H
+#define _RDS_IB_H
+
+#include <rdma/ib_verbs.h>
+#include <rdma/rdma_cm.h>
+#include <linux/interrupt.h>
+#include <linux/pci.h>
+#include <linux/slab.h>
+#include "rds.h"
+#include "rdma_transport.h"
+
+#define RDS_IB_MAX_SGE			8
+#define RDS_IB_RECV_SGE 		2
+
+#define RDS_IB_DEFAULT_RECV_WR		1024
+#define RDS_IB_DEFAULT_SEND_WR		256
+#define RDS_IB_DEFAULT_FR_WR		512
+
+#define RDS_IB_DEFAULT_RETRY_COUNT	1
+
+#define RDS_IB_SUPPORTED_PROTOCOLS	0x00000003	/* minor versions supported */
+
+#define RDS_IB_RECYCLE_BATCH_COUNT	32
+
+#define RDS_IB_WC_MAX			32
+
+extern struct rw_semaphore rds_ib_devices_lock;
+extern struct list_head rds_ib_devices;
+
+/*
+ * IB posts RDS_FRAG_SIZE fragments of pages to the receive queues to
+ * try and minimize the amount of memory tied up both the device and
+ * socket receive queues.
+ */
+struct rds_page_frag {
+	struct list_head	f_item;
+	struct list_head	f_cache_entry;
+	struct scatterlist	f_sg;
+};
+
+struct rds_ib_incoming {
+	struct list_head	ii_frags;
+	struct list_head	ii_cache_entry;
+	struct rds_incoming	ii_inc;
+};
+
+struct rds_ib_cache_head {
+	struct list_head *first;
+	unsigned long count;
+};
+
+struct rds_ib_refill_cache {
+	struct rds_ib_cache_head __percpu *percpu;
+	struct list_head	 *xfer;
+	struct list_head	 *ready;
+};
+
+/* This is the common structure for the IB private data exchange in setting up
+ * an RDS connection.  The exchange is different for IPv4 and IPv6 connections.
+ * The reason is that the address size is different and the addresses
+ * exchanged are in the beginning of the structure.  Hence it is not possible
+ * for interoperability if same structure is used.
+ */
+struct rds_ib_conn_priv_cmn {
+	u8			ricpc_protocol_major;
+	u8			ricpc_protocol_minor;
+	__be16			ricpc_protocol_minor_mask;	/* bitmask */
+	u8			ricpc_dp_toss;
+	u8			ripc_reserved1;
+	__be16			ripc_reserved2;
+	__be64			ricpc_ack_seq;
+	__be32			ricpc_credit;	/* non-zero enables flow ctl */
+};
+
+struct rds_ib_connect_private {
+	/* Add new fields at the end, and don't permute existing fields. */
+	__be32				dp_saddr;
+	__be32				dp_daddr;
+	struct rds_ib_conn_priv_cmn	dp_cmn;
+};
+
+struct rds6_ib_connect_private {
+	/* Add new fields at the end, and don't permute existing fields. */
+	struct in6_addr			dp_saddr;
+	struct in6_addr			dp_daddr;
+	struct rds_ib_conn_priv_cmn	dp_cmn;
+};
+
+#define dp_protocol_major	dp_cmn.ricpc_protocol_major
+#define dp_protocol_minor	dp_cmn.ricpc_protocol_minor
+#define dp_protocol_minor_mask	dp_cmn.ricpc_protocol_minor_mask
+#define dp_ack_seq		dp_cmn.ricpc_ack_seq
+#define dp_credit		dp_cmn.ricpc_credit
+
+union rds_ib_conn_priv {
+	struct rds_ib_connect_private	ricp_v4;
+	struct rds6_ib_connect_private	ricp_v6;
+};
+
+struct rds_ib_send_work {
+	void			*s_op;
+	union {
+		struct ib_send_wr	s_wr;
+		struct ib_rdma_wr	s_rdma_wr;
+		struct ib_atomic_wr	s_atomic_wr;
+	};
+	struct ib_sge		s_sge[RDS_IB_MAX_SGE];
+	unsigned long		s_queued;
+};
+
+struct rds_ib_recv_work {
+	struct rds_ib_incoming 	*r_ibinc;
+	struct rds_page_frag	*r_frag;
+	struct ib_recv_wr	r_wr;
+	struct ib_sge		r_sge[2];
+};
+
+struct rds_ib_work_ring {
+	u32		w_nr;
+	u32		w_alloc_ptr;
+	u32		w_alloc_ctr;
+	u32		w_free_ptr;
+	atomic_t	w_free_ctr;
+};
+
+/* Rings are posted with all the allocations they'll need to queue the
+ * incoming message to the receiving socket so this can't fail.
+ * All fragments start with a header, so we can make sure we're not receiving
+ * garbage, and we can tell a small 8 byte fragment from an ACK frame.
+ */
+struct rds_ib_ack_state {
+	u64		ack_next;
+	u64		ack_recv;
+	unsigned int	ack_required:1;
+	unsigned int	ack_next_valid:1;
+	unsigned int	ack_recv_valid:1;
+};
+
+
+struct rds_ib_device;
+
+struct rds_ib_connection {
+
+	struct list_head	ib_node;
+	struct rds_ib_device	*rds_ibdev;
+	struct rds_connection	*conn;
+
+	/* alphabet soup, IBTA style */
+	struct rdma_cm_id	*i_cm_id;
+	struct ib_pd		*i_pd;
+	struct ib_cq		*i_send_cq;
+	struct ib_cq		*i_recv_cq;
+	struct ib_wc		i_send_wc[RDS_IB_WC_MAX];
+	struct ib_wc		i_recv_wc[RDS_IB_WC_MAX];
+
+	/* To control the number of wrs from fastreg */
+	atomic_t		i_fastreg_wrs;
+	atomic_t		i_fastreg_inuse_count;
+
+	/* interrupt handling */
+	struct tasklet_struct	i_send_tasklet;
+	struct tasklet_struct	i_recv_tasklet;
+
+	/* tx */
+	struct rds_ib_work_ring	i_send_ring;
+	struct rm_data_op	*i_data_op;
+	struct rds_header	**i_send_hdrs;
+	dma_addr_t		*i_send_hdrs_dma;
+	struct rds_ib_send_work *i_sends;
+	atomic_t		i_signaled_sends;
+
+	/* rx */
+	struct mutex		i_recv_mutex;
+	struct rds_ib_work_ring	i_recv_ring;
+	struct rds_ib_incoming	*i_ibinc;
+	u32			i_recv_data_rem;
+	struct rds_header	**i_recv_hdrs;
+	dma_addr_t		*i_recv_hdrs_dma;
+	struct rds_ib_recv_work *i_recvs;
+	u64			i_ack_recv;	/* last ACK received */
+	struct rds_ib_refill_cache i_cache_incs;
+	struct rds_ib_refill_cache i_cache_frags;
+	atomic_t		i_cache_allocs;
+
+	/* sending acks */
+	unsigned long		i_ack_flags;
+#ifdef KERNEL_HAS_ATOMIC64
+	atomic64_t		i_ack_next;	/* next ACK to send */
+#else
+	spinlock_t		i_ack_lock;	/* protect i_ack_next */
+	u64			i_ack_next;	/* next ACK to send */
+#endif
+	struct rds_header	*i_ack;
+	struct ib_send_wr	i_ack_wr;
+	struct ib_sge		i_ack_sge;
+	dma_addr_t		i_ack_dma;
+	unsigned long		i_ack_queued;
+
+	/* Flow control related information
+	 *
+	 * Our algorithm uses a pair variables that we need to access
+	 * atomically - one for the send credits, and one posted
+	 * recv credits we need to transfer to remote.
+	 * Rather than protect them using a slow spinlock, we put both into
+	 * a single atomic_t and update it using cmpxchg
+	 */
+	atomic_t		i_credits;
+
+	/* Protocol version specific information */
+	unsigned int		i_flowctl:1;	/* enable/disable flow ctl */
+
+	/* Batched completions */
+	unsigned int		i_unsignaled_wrs;
+
+	/* Endpoint role in connection */
+	bool			i_active_side;
+	atomic_t		i_cq_quiesce;
+
+	/* Send/Recv vectors */
+	int			i_scq_vector;
+	int			i_rcq_vector;
+	u8			i_sl;
+};
+
+/* This assumes that atomic_t is at least 32 bits */
+#define IB_GET_SEND_CREDITS(v)	((v) & 0xffff)
+#define IB_GET_POST_CREDITS(v)	((v) >> 16)
+#define IB_SET_SEND_CREDITS(v)	((v) & 0xffff)
+#define IB_SET_POST_CREDITS(v)	((v) << 16)
+
+struct rds_ib_ipaddr {
+	struct list_head	list;
+	__be32			ipaddr;
+	struct rcu_head		rcu;
+};
+
+enum {
+	RDS_IB_MR_8K_POOL,
+	RDS_IB_MR_1M_POOL,
+};
+
+struct rds_ib_device {
+	struct list_head	list;
+	struct list_head	ipaddr_list;
+	struct list_head	conn_list;
+	struct ib_device	*dev;
+	struct ib_pd		*pd;
+	u8			odp_capable:1;
+
+	unsigned int		max_mrs;
+	struct rds_ib_mr_pool	*mr_1m_pool;
+	struct rds_ib_mr_pool   *mr_8k_pool;
+	unsigned int		max_8k_mrs;
+	unsigned int		max_1m_mrs;
+	int			max_sge;
+	unsigned int		max_wrs;
+	unsigned int		max_initiator_depth;
+	unsigned int		max_responder_resources;
+	spinlock_t		spinlock;	/* protect the above */
+	refcount_t		refcount;
+	struct work_struct	free_work;
+	int			*vector_load;
+};
+
+#define rdsibdev_to_node(rdsibdev) ibdev_to_node(rdsibdev->dev)
+
+/* bits for i_ack_flags */
+#define IB_ACK_IN_FLIGHT	0
+#define IB_ACK_REQUESTED	1
+
+/* Magic WR_ID for ACKs */
+#define RDS_IB_ACK_WR_ID	(~(u64) 0)
+
+struct rds_ib_statistics {
+	uint64_t	s_ib_connect_raced;
+	uint64_t	s_ib_listen_closed_stale;
+	uint64_t	s_ib_evt_handler_call;
+	uint64_t	s_ib_tasklet_call;
+	uint64_t	s_ib_tx_cq_event;
+	uint64_t	s_ib_tx_ring_full;
+	uint64_t	s_ib_tx_throttle;
+	uint64_t	s_ib_tx_sg_mapping_failure;
+	uint64_t	s_ib_tx_stalled;
+	uint64_t	s_ib_tx_credit_updates;
+	uint64_t	s_ib_rx_cq_event;
+	uint64_t	s_ib_rx_ring_empty;
+	uint64_t	s_ib_rx_refill_from_cq;
+	uint64_t	s_ib_rx_refill_from_thread;
+	uint64_t	s_ib_rx_alloc_limit;
+	uint64_t	s_ib_rx_total_frags;
+	uint64_t	s_ib_rx_total_incs;
+	uint64_t	s_ib_rx_credit_updates;
+	uint64_t	s_ib_ack_sent;
+	uint64_t	s_ib_ack_send_failure;
+	uint64_t	s_ib_ack_send_delayed;
+	uint64_t	s_ib_ack_send_piggybacked;
+	uint64_t	s_ib_ack_received;
+	uint64_t	s_ib_rdma_mr_8k_alloc;
+	uint64_t	s_ib_rdma_mr_8k_free;
+	uint64_t	s_ib_rdma_mr_8k_used;
+	uint64_t	s_ib_rdma_mr_8k_pool_flush;
+	uint64_t	s_ib_rdma_mr_8k_pool_wait;
+	uint64_t	s_ib_rdma_mr_8k_pool_depleted;
+	uint64_t	s_ib_rdma_mr_1m_alloc;
+	uint64_t	s_ib_rdma_mr_1m_free;
+	uint64_t	s_ib_rdma_mr_1m_used;
+	uint64_t	s_ib_rdma_mr_1m_pool_flush;
+	uint64_t	s_ib_rdma_mr_1m_pool_wait;
+	uint64_t	s_ib_rdma_mr_1m_pool_depleted;
+	uint64_t	s_ib_rdma_mr_8k_reused;
+	uint64_t	s_ib_rdma_mr_1m_reused;
+	uint64_t	s_ib_atomic_cswp;
+	uint64_t	s_ib_atomic_fadd;
+	uint64_t	s_ib_recv_added_to_cache;
+	uint64_t	s_ib_recv_removed_from_cache;
+};
+
+extern struct workqueue_struct *rds_ib_wq;
+
+/*
+ * Fake ib_dma_sync_sg_for_{cpu,device} as long as ib_verbs.h
+ * doesn't define it.
+ */
+static inline void rds_ib_dma_sync_sg_for_cpu(struct ib_device *dev,
+					      struct scatterlist *sglist,
+					      unsigned int sg_dma_len,
+					      int direction)
+{
+	struct scatterlist *sg;
+	unsigned int i;
+
+	for_each_sg(sglist, sg, sg_dma_len, i) {
+		ib_dma_sync_single_for_cpu(dev, sg_dma_address(sg),
+					   sg_dma_len(sg), direction);
+	}
+}
+#define ib_dma_sync_sg_for_cpu	rds_ib_dma_sync_sg_for_cpu
+
+static inline void rds_ib_dma_sync_sg_for_device(struct ib_device *dev,
+						 struct scatterlist *sglist,
+						 unsigned int sg_dma_len,
+						 int direction)
+{
+	struct scatterlist *sg;
+	unsigned int i;
+
+	for_each_sg(sglist, sg, sg_dma_len, i) {
+		ib_dma_sync_single_for_device(dev, sg_dma_address(sg),
+					      sg_dma_len(sg), direction);
+	}
+}
+#define ib_dma_sync_sg_for_device	rds_ib_dma_sync_sg_for_device
+
+
+/* ib.c */
+extern struct rds_transport rds_ib_transport;
+struct rds_ib_device *rds_ib_get_client_data(struct ib_device *device);
+void rds_ib_dev_put(struct rds_ib_device *rds_ibdev);
+extern struct ib_client rds_ib_client;
+
+extern unsigned int rds_ib_retry_count;
+
+extern spinlock_t ib_nodev_conns_lock;
+extern struct list_head ib_nodev_conns;
+
+/* ib_cm.c */
+int rds_ib_conn_alloc(struct rds_connection *conn, gfp_t gfp);
+void rds_ib_conn_free(void *arg);
+int rds_ib_conn_path_connect(struct rds_conn_path *cp);
+void rds_ib_conn_path_shutdown(struct rds_conn_path *cp);
+__printf(2, 3)
+void __rds_ib_conn_error(struct rds_connection *conn, const char *, ...);
+int rds_ib_cm_handle_connect(struct rdma_cm_id *cm_id,
+			     struct rdma_cm_event *event, bool isv6);
+int rds_ib_cm_initiate_connect(struct rdma_cm_id *cm_id, bool isv6);
+void rds_ib_cm_connect_complete(struct rds_connection *conn,
+				struct rdma_cm_event *event);
+
+#define rds_ib_conn_error(conn, fmt...) \
+	__rds_ib_conn_error(conn, KERN_WARNING "RDS/IB: " fmt)
+
+/* ib_rdma.c */
+struct rds_ib_device *rds_ib_get_device(__be32 ipaddr);
+int rds_ib_update_ipaddr(struct rds_ib_device *rds_ibdev,
+			 struct in6_addr *ipaddr);
+void rds_ib_add_conn(struct rds_ib_device *rds_ibdev, struct rds_connection *conn);
+void rds_ib_remove_conn(struct rds_ib_device *rds_ibdev, struct rds_connection *conn);
+void rds_ib_destroy_nodev_conns(void);
+void rds_ib_mr_cqe_handler(struct rds_ib_connection *ic, struct ib_wc *wc);
+
+/* ib_recv.c */
+int rds_ib_recv_init(void);
+void rds_ib_recv_exit(void);
+int rds_ib_recv_path(struct rds_conn_path *conn);
+int rds_ib_recv_alloc_caches(struct rds_ib_connection *ic, gfp_t gfp);
+void rds_ib_recv_free_caches(struct rds_ib_connection *ic);
+void rds_ib_recv_refill(struct rds_connection *conn, int prefill, gfp_t gfp);
+void rds_ib_inc_free(struct rds_incoming *inc);
+int rds_ib_inc_copy_to_user(struct rds_incoming *inc, struct iov_iter *to);
+void rds_ib_recv_cqe_handler(struct rds_ib_connection *ic, struct ib_wc *wc,
+			     struct rds_ib_ack_state *state);
+void rds_ib_recv_init_ring(struct rds_ib_connection *ic);
+void rds_ib_recv_clear_ring(struct rds_ib_connection *ic);
+void rds_ib_recv_init_ack(struct rds_ib_connection *ic);
+void rds_ib_attempt_ack(struct rds_ib_connection *ic);
+void rds_ib_ack_send_complete(struct rds_ib_connection *ic);
+u64 rds_ib_piggyb_ack(struct rds_ib_connection *ic);
+void rds_ib_set_ack(struct rds_ib_connection *ic, u64 seq, int ack_required);
+
+/* ib_ring.c */
+void rds_ib_ring_init(struct rds_ib_work_ring *ring, u32 nr);
+void rds_ib_ring_resize(struct rds_ib_work_ring *ring, u32 nr);
+u32 rds_ib_ring_alloc(struct rds_ib_work_ring *ring, u32 val, u32 *pos);
+void rds_ib_ring_free(struct rds_ib_work_ring *ring, u32 val);
+void rds_ib_ring_unalloc(struct rds_ib_work_ring *ring, u32 val);
+int rds_ib_ring_empty(struct rds_ib_work_ring *ring);
+int rds_ib_ring_low(struct rds_ib_work_ring *ring);
+u32 rds_ib_ring_oldest(struct rds_ib_work_ring *ring);
+u32 rds_ib_ring_completed(struct rds_ib_work_ring *ring, u32 wr_id, u32 oldest);
+extern wait_queue_head_t rds_ib_ring_empty_wait;
+
+/* ib_send.c */
+void rds_ib_xmit_path_complete(struct rds_conn_path *cp);
+int rds_ib_xmit(struct rds_connection *conn, struct rds_message *rm,
+		unsigned int hdr_off, unsigned int sg, unsigned int off);
+void rds_ib_send_cqe_handler(struct rds_ib_connection *ic, struct ib_wc *wc);
+void rds_ib_send_init_ring(struct rds_ib_connection *ic);
+void rds_ib_send_clear_ring(struct rds_ib_connection *ic);
+int rds_ib_xmit_rdma(struct rds_connection *conn, struct rm_rdma_op *op);
+void rds_ib_send_add_credits(struct rds_connection *conn, unsigned int credits);
+void rds_ib_advertise_credits(struct rds_connection *conn, unsigned int posted);
+int rds_ib_send_grab_credits(struct rds_ib_connection *ic, u32 wanted,
+			     u32 *adv_credits, int need_posted, int max_posted);
+int rds_ib_xmit_atomic(struct rds_connection *conn, struct rm_atomic_op *op);
+
+/* ib_stats.c */
+DECLARE_PER_CPU_SHARED_ALIGNED(struct rds_ib_statistics, rds_ib_stats);
+#define rds_ib_stats_inc(member) rds_stats_inc_which(rds_ib_stats, member)
+#define rds_ib_stats_add(member, count) \
+		rds_stats_add_which(rds_ib_stats, member, count)
+unsigned int rds_ib_stats_info_copy(struct rds_info_iterator *iter,
+				    unsigned int avail);
+
+/* ib_sysctl.c */
+int rds_ib_sysctl_init(void);
+void rds_ib_sysctl_exit(void);
+extern unsigned long rds_ib_sysctl_max_send_wr;
+extern unsigned long rds_ib_sysctl_max_recv_wr;
+extern unsigned long rds_ib_sysctl_max_unsig_wrs;
+extern unsigned long rds_ib_sysctl_max_unsig_bytes;
+extern unsigned long rds_ib_sysctl_max_recv_allocation;
+extern unsigned int rds_ib_sysctl_flow_control;
+
+#endif
diff --git a/net/rds/ib_cm.c b/net/rds/ib_cm.c
new file mode 100644
index 000000000..4feb0edc3
--- /dev/null
+++ b/net/rds/ib_cm.c
@@ -0,0 +1,1307 @@
+/*
+ * Copyright (c) 2006, 2019 Oracle and/or its affiliates. All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+#include <linux/kernel.h>
+#include <linux/in.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+#include <linux/ratelimit.h>
+#include <net/addrconf.h>
+#include <rdma/ib_cm.h>
+
+#include "rds_single_path.h"
+#include "rds.h"
+#include "ib.h"
+#include "ib_mr.h"
+
+/*
+ * Set the selected protocol version
+ */
+static void rds_ib_set_protocol(struct rds_connection *conn, unsigned int version)
+{
+	conn->c_version = version;
+}
+
+/*
+ * Set up flow control
+ */
+static void rds_ib_set_flow_control(struct rds_connection *conn, u32 credits)
+{
+	struct rds_ib_connection *ic = conn->c_transport_data;
+
+	if (rds_ib_sysctl_flow_control && credits != 0) {
+		/* We're doing flow control */
+		ic->i_flowctl = 1;
+		rds_ib_send_add_credits(conn, credits);
+	} else {
+		ic->i_flowctl = 0;
+	}
+}
+
+/*
+ * Connection established.
+ * We get here for both outgoing and incoming connection.
+ */
+void rds_ib_cm_connect_complete(struct rds_connection *conn, struct rdma_cm_event *event)
+{
+	struct rds_ib_connection *ic = conn->c_transport_data;
+	const union rds_ib_conn_priv *dp = NULL;
+	__be64 ack_seq = 0;
+	__be32 credit = 0;
+	u8 major = 0;
+	u8 minor = 0;
+	int err;
+
+	dp = event->param.conn.private_data;
+	if (conn->c_isv6) {
+		if (event->param.conn.private_data_len >=
+		    sizeof(struct rds6_ib_connect_private)) {
+			major = dp->ricp_v6.dp_protocol_major;
+			minor = dp->ricp_v6.dp_protocol_minor;
+			credit = dp->ricp_v6.dp_credit;
+			/* dp structure start is not guaranteed to be 8 bytes
+			 * aligned.  Since dp_ack_seq is 64-bit extended load
+			 * operations can be used so go through get_unaligned
+			 * to avoid unaligned errors.
+			 */
+			ack_seq = get_unaligned(&dp->ricp_v6.dp_ack_seq);
+		}
+	} else if (event->param.conn.private_data_len >=
+		   sizeof(struct rds_ib_connect_private)) {
+		major = dp->ricp_v4.dp_protocol_major;
+		minor = dp->ricp_v4.dp_protocol_minor;
+		credit = dp->ricp_v4.dp_credit;
+		ack_seq = get_unaligned(&dp->ricp_v4.dp_ack_seq);
+	}
+
+	/* make sure it isn't empty data */
+	if (major) {
+		rds_ib_set_protocol(conn, RDS_PROTOCOL(major, minor));
+		rds_ib_set_flow_control(conn, be32_to_cpu(credit));
+	}
+
+	if (conn->c_version < RDS_PROTOCOL_VERSION) {
+		if (conn->c_version != RDS_PROTOCOL_COMPAT_VERSION) {
+			pr_notice("RDS/IB: Connection <%pI6c,%pI6c> version %u.%u no longer supported\n",
+				  &conn->c_laddr, &conn->c_faddr,
+				  RDS_PROTOCOL_MAJOR(conn->c_version),
+				  RDS_PROTOCOL_MINOR(conn->c_version));
+			rds_conn_destroy(conn);
+			return;
+		}
+	}
+
+	pr_notice("RDS/IB: %s conn connected <%pI6c,%pI6c,%d> version %u.%u%s\n",
+		  ic->i_active_side ? "Active" : "Passive",
+		  &conn->c_laddr, &conn->c_faddr, conn->c_tos,
+		  RDS_PROTOCOL_MAJOR(conn->c_version),
+		  RDS_PROTOCOL_MINOR(conn->c_version),
+		  ic->i_flowctl ? ", flow control" : "");
+
+	/* receive sl from the peer */
+	ic->i_sl = ic->i_cm_id->route.path_rec->sl;
+
+	atomic_set(&ic->i_cq_quiesce, 0);
+
+	/* Init rings and fill recv. this needs to wait until protocol
+	 * negotiation is complete, since ring layout is different
+	 * from 3.1 to 4.1.
+	 */
+	rds_ib_send_init_ring(ic);
+	rds_ib_recv_init_ring(ic);
+	/* Post receive buffers - as a side effect, this will update
+	 * the posted credit count. */
+	rds_ib_recv_refill(conn, 1, GFP_KERNEL);
+
+	/* update ib_device with this local ipaddr */
+	err = rds_ib_update_ipaddr(ic->rds_ibdev, &conn->c_laddr);
+	if (err)
+		printk(KERN_ERR "rds_ib_update_ipaddr failed (%d)\n",
+			err);
+
+	/* If the peer gave us the last packet it saw, process this as if
+	 * we had received a regular ACK. */
+	if (dp) {
+		if (ack_seq)
+			rds_send_drop_acked(conn, be64_to_cpu(ack_seq),
+					    NULL);
+	}
+
+	conn->c_proposed_version = conn->c_version;
+	rds_connect_complete(conn);
+}
+
+static void rds_ib_cm_fill_conn_param(struct rds_connection *conn,
+				      struct rdma_conn_param *conn_param,
+				      union rds_ib_conn_priv *dp,
+				      u32 protocol_version,
+				      u32 max_responder_resources,
+				      u32 max_initiator_depth,
+				      bool isv6)
+{
+	struct rds_ib_connection *ic = conn->c_transport_data;
+	struct rds_ib_device *rds_ibdev = ic->rds_ibdev;
+
+	memset(conn_param, 0, sizeof(struct rdma_conn_param));
+
+	conn_param->responder_resources = min3(rds_ibdev->max_responder_resources,
+					       max_responder_resources, U8_MAX);
+	conn_param->initiator_depth = min3(rds_ibdev->max_initiator_depth,
+					   max_initiator_depth, U8_MAX);
+	conn_param->retry_count = min(rds_ib_retry_count, 7U);
+	conn_param->rnr_retry_count = 7;
+
+	if (dp) {
+		memset(dp, 0, sizeof(*dp));
+		if (isv6) {
+			dp->ricp_v6.dp_saddr = conn->c_laddr;
+			dp->ricp_v6.dp_daddr = conn->c_faddr;
+			dp->ricp_v6.dp_protocol_major =
+			    RDS_PROTOCOL_MAJOR(protocol_version);
+			dp->ricp_v6.dp_protocol_minor =
+			    RDS_PROTOCOL_MINOR(protocol_version);
+			dp->ricp_v6.dp_protocol_minor_mask =
+			    cpu_to_be16(RDS_IB_SUPPORTED_PROTOCOLS);
+			dp->ricp_v6.dp_ack_seq =
+			    cpu_to_be64(rds_ib_piggyb_ack(ic));
+			dp->ricp_v6.dp_cmn.ricpc_dp_toss = conn->c_tos;
+
+			conn_param->private_data = &dp->ricp_v6;
+			conn_param->private_data_len = sizeof(dp->ricp_v6);
+		} else {
+			dp->ricp_v4.dp_saddr = conn->c_laddr.s6_addr32[3];
+			dp->ricp_v4.dp_daddr = conn->c_faddr.s6_addr32[3];
+			dp->ricp_v4.dp_protocol_major =
+			    RDS_PROTOCOL_MAJOR(protocol_version);
+			dp->ricp_v4.dp_protocol_minor =
+			    RDS_PROTOCOL_MINOR(protocol_version);
+			dp->ricp_v4.dp_protocol_minor_mask =
+			    cpu_to_be16(RDS_IB_SUPPORTED_PROTOCOLS);
+			dp->ricp_v4.dp_ack_seq =
+			    cpu_to_be64(rds_ib_piggyb_ack(ic));
+			dp->ricp_v4.dp_cmn.ricpc_dp_toss = conn->c_tos;
+
+			conn_param->private_data = &dp->ricp_v4;
+			conn_param->private_data_len = sizeof(dp->ricp_v4);
+		}
+
+		/* Advertise flow control */
+		if (ic->i_flowctl) {
+			unsigned int credits;
+
+			credits = IB_GET_POST_CREDITS
+				(atomic_read(&ic->i_credits));
+			if (isv6)
+				dp->ricp_v6.dp_credit = cpu_to_be32(credits);
+			else
+				dp->ricp_v4.dp_credit = cpu_to_be32(credits);
+			atomic_sub(IB_SET_POST_CREDITS(credits),
+				   &ic->i_credits);
+		}
+	}
+}
+
+static void rds_ib_cq_event_handler(struct ib_event *event, void *data)
+{
+	rdsdebug("event %u (%s) data %p\n",
+		 event->event, ib_event_msg(event->event), data);
+}
+
+/* Plucking the oldest entry from the ring can be done concurrently with
+ * the thread refilling the ring.  Each ring operation is protected by
+ * spinlocks and the transient state of refilling doesn't change the
+ * recording of which entry is oldest.
+ *
+ * This relies on IB only calling one cq comp_handler for each cq so that
+ * there will only be one caller of rds_recv_incoming() per RDS connection.
+ */
+static void rds_ib_cq_comp_handler_recv(struct ib_cq *cq, void *context)
+{
+	struct rds_connection *conn = context;
+	struct rds_ib_connection *ic = conn->c_transport_data;
+
+	rdsdebug("conn %p cq %p\n", conn, cq);
+
+	rds_ib_stats_inc(s_ib_evt_handler_call);
+
+	tasklet_schedule(&ic->i_recv_tasklet);
+}
+
+static void poll_scq(struct rds_ib_connection *ic, struct ib_cq *cq,
+		     struct ib_wc *wcs)
+{
+	int nr, i;
+	struct ib_wc *wc;
+
+	while ((nr = ib_poll_cq(cq, RDS_IB_WC_MAX, wcs)) > 0) {
+		for (i = 0; i < nr; i++) {
+			wc = wcs + i;
+			rdsdebug("wc wr_id 0x%llx status %u byte_len %u imm_data %u\n",
+				 (unsigned long long)wc->wr_id, wc->status,
+				 wc->byte_len, be32_to_cpu(wc->ex.imm_data));
+
+			if (wc->wr_id <= ic->i_send_ring.w_nr ||
+			    wc->wr_id == RDS_IB_ACK_WR_ID)
+				rds_ib_send_cqe_handler(ic, wc);
+			else
+				rds_ib_mr_cqe_handler(ic, wc);
+
+		}
+	}
+}
+
+static void rds_ib_tasklet_fn_send(unsigned long data)
+{
+	struct rds_ib_connection *ic = (struct rds_ib_connection *)data;
+	struct rds_connection *conn = ic->conn;
+
+	rds_ib_stats_inc(s_ib_tasklet_call);
+
+	/* if cq has been already reaped, ignore incoming cq event */
+	if (atomic_read(&ic->i_cq_quiesce))
+		return;
+
+	poll_scq(ic, ic->i_send_cq, ic->i_send_wc);
+	ib_req_notify_cq(ic->i_send_cq, IB_CQ_NEXT_COMP);
+	poll_scq(ic, ic->i_send_cq, ic->i_send_wc);
+
+	if (rds_conn_up(conn) &&
+	    (!test_bit(RDS_LL_SEND_FULL, &conn->c_flags) ||
+	    test_bit(0, &conn->c_map_queued)))
+		rds_send_xmit(&ic->conn->c_path[0]);
+}
+
+static void poll_rcq(struct rds_ib_connection *ic, struct ib_cq *cq,
+		     struct ib_wc *wcs,
+		     struct rds_ib_ack_state *ack_state)
+{
+	int nr, i;
+	struct ib_wc *wc;
+
+	while ((nr = ib_poll_cq(cq, RDS_IB_WC_MAX, wcs)) > 0) {
+		for (i = 0; i < nr; i++) {
+			wc = wcs + i;
+			rdsdebug("wc wr_id 0x%llx status %u byte_len %u imm_data %u\n",
+				 (unsigned long long)wc->wr_id, wc->status,
+				 wc->byte_len, be32_to_cpu(wc->ex.imm_data));
+
+			rds_ib_recv_cqe_handler(ic, wc, ack_state);
+		}
+	}
+}
+
+static void rds_ib_tasklet_fn_recv(unsigned long data)
+{
+	struct rds_ib_connection *ic = (struct rds_ib_connection *)data;
+	struct rds_connection *conn = ic->conn;
+	struct rds_ib_device *rds_ibdev = ic->rds_ibdev;
+	struct rds_ib_ack_state state;
+
+	if (!rds_ibdev)
+		rds_conn_drop(conn);
+
+	rds_ib_stats_inc(s_ib_tasklet_call);
+
+	/* if cq has been already reaped, ignore incoming cq event */
+	if (atomic_read(&ic->i_cq_quiesce))
+		return;
+
+	memset(&state, 0, sizeof(state));
+	poll_rcq(ic, ic->i_recv_cq, ic->i_recv_wc, &state);
+	ib_req_notify_cq(ic->i_recv_cq, IB_CQ_SOLICITED);
+	poll_rcq(ic, ic->i_recv_cq, ic->i_recv_wc, &state);
+
+	if (state.ack_next_valid)
+		rds_ib_set_ack(ic, state.ack_next, state.ack_required);
+	if (state.ack_recv_valid && state.ack_recv > ic->i_ack_recv) {
+		rds_send_drop_acked(conn, state.ack_recv, NULL);
+		ic->i_ack_recv = state.ack_recv;
+	}
+
+	if (rds_conn_up(conn))
+		rds_ib_attempt_ack(ic);
+}
+
+static void rds_ib_qp_event_handler(struct ib_event *event, void *data)
+{
+	struct rds_connection *conn = data;
+	struct rds_ib_connection *ic = conn->c_transport_data;
+
+	rdsdebug("conn %p ic %p event %u (%s)\n", conn, ic, event->event,
+		 ib_event_msg(event->event));
+
+	switch (event->event) {
+	case IB_EVENT_COMM_EST:
+		rdma_notify(ic->i_cm_id, IB_EVENT_COMM_EST);
+		break;
+	default:
+		rdsdebug("Fatal QP Event %u (%s) - connection %pI6c->%pI6c, reconnecting\n",
+			 event->event, ib_event_msg(event->event),
+			 &conn->c_laddr, &conn->c_faddr);
+		rds_conn_drop(conn);
+		break;
+	}
+}
+
+static void rds_ib_cq_comp_handler_send(struct ib_cq *cq, void *context)
+{
+	struct rds_connection *conn = context;
+	struct rds_ib_connection *ic = conn->c_transport_data;
+
+	rdsdebug("conn %p cq %p\n", conn, cq);
+
+	rds_ib_stats_inc(s_ib_evt_handler_call);
+
+	tasklet_schedule(&ic->i_send_tasklet);
+}
+
+static inline int ibdev_get_unused_vector(struct rds_ib_device *rds_ibdev)
+{
+	int min = rds_ibdev->vector_load[rds_ibdev->dev->num_comp_vectors - 1];
+	int index = rds_ibdev->dev->num_comp_vectors - 1;
+	int i;
+
+	for (i = rds_ibdev->dev->num_comp_vectors - 1; i >= 0; i--) {
+		if (rds_ibdev->vector_load[i] < min) {
+			index = i;
+			min = rds_ibdev->vector_load[i];
+		}
+	}
+
+	rds_ibdev->vector_load[index]++;
+	return index;
+}
+
+static inline void ibdev_put_vector(struct rds_ib_device *rds_ibdev, int index)
+{
+	rds_ibdev->vector_load[index]--;
+}
+
+static void rds_dma_hdr_free(struct ib_device *dev, struct rds_header *hdr,
+		dma_addr_t dma_addr, enum dma_data_direction dir)
+{
+	ib_dma_unmap_single(dev, dma_addr, sizeof(*hdr), dir);
+	kfree(hdr);
+}
+
+static struct rds_header *rds_dma_hdr_alloc(struct ib_device *dev,
+		dma_addr_t *dma_addr, enum dma_data_direction dir)
+{
+	struct rds_header *hdr;
+
+	hdr = kzalloc_node(sizeof(*hdr), GFP_KERNEL, ibdev_to_node(dev));
+	if (!hdr)
+		return NULL;
+
+	*dma_addr = ib_dma_map_single(dev, hdr, sizeof(*hdr),
+				      DMA_BIDIRECTIONAL);
+	if (ib_dma_mapping_error(dev, *dma_addr)) {
+		kfree(hdr);
+		return NULL;
+	}
+
+	return hdr;
+}
+
+/* Free the DMA memory used to store struct rds_header.
+ *
+ * @dev: the RDS IB device
+ * @hdrs: pointer to the array storing DMA memory pointers
+ * @dma_addrs: pointer to the array storing DMA addresses
+ * @num_hdars: number of headers to free.
+ */
+static void rds_dma_hdrs_free(struct rds_ib_device *dev,
+		struct rds_header **hdrs, dma_addr_t *dma_addrs, u32 num_hdrs,
+		enum dma_data_direction dir)
+{
+	u32 i;
+
+	for (i = 0; i < num_hdrs; i++)
+		rds_dma_hdr_free(dev->dev, hdrs[i], dma_addrs[i], dir);
+	kvfree(hdrs);
+	kvfree(dma_addrs);
+}
+
+
+/* Allocate DMA coherent memory to be used to store struct rds_header for
+ * sending/receiving packets.  The pointers to the DMA memory and the
+ * associated DMA addresses are stored in two arrays.
+ *
+ * @dev: the RDS IB device
+ * @dma_addrs: pointer to the array for storing DMA addresses
+ * @num_hdrs: number of headers to allocate
+ *
+ * It returns the pointer to the array storing the DMA memory pointers.  On
+ * error, NULL pointer is returned.
+ */
+static struct rds_header **rds_dma_hdrs_alloc(struct rds_ib_device *dev,
+		dma_addr_t **dma_addrs, u32 num_hdrs,
+		enum dma_data_direction dir)
+{
+	struct rds_header **hdrs;
+	dma_addr_t *hdr_daddrs;
+	u32 i;
+
+	hdrs = kvmalloc_node(sizeof(*hdrs) * num_hdrs, GFP_KERNEL,
+			     ibdev_to_node(dev->dev));
+	if (!hdrs)
+		return NULL;
+
+	hdr_daddrs = kvmalloc_node(sizeof(*hdr_daddrs) * num_hdrs, GFP_KERNEL,
+				   ibdev_to_node(dev->dev));
+	if (!hdr_daddrs) {
+		kvfree(hdrs);
+		return NULL;
+	}
+
+	for (i = 0; i < num_hdrs; i++) {
+		hdrs[i] = rds_dma_hdr_alloc(dev->dev, &hdr_daddrs[i], dir);
+		if (!hdrs[i]) {
+			rds_dma_hdrs_free(dev, hdrs, hdr_daddrs, i, dir);
+			return NULL;
+		}
+	}
+
+	*dma_addrs = hdr_daddrs;
+	return hdrs;
+}
+
+/*
+ * This needs to be very careful to not leave IS_ERR pointers around for
+ * cleanup to trip over.
+ */
+static int rds_ib_setup_qp(struct rds_connection *conn)
+{
+	struct rds_ib_connection *ic = conn->c_transport_data;
+	struct ib_device *dev = ic->i_cm_id->device;
+	struct ib_qp_init_attr attr;
+	struct ib_cq_init_attr cq_attr = {};
+	struct rds_ib_device *rds_ibdev;
+	unsigned long max_wrs;
+	int ret, fr_queue_space;
+
+	/*
+	 * It's normal to see a null device if an incoming connection races
+	 * with device removal, so we don't print a warning.
+	 */
+	rds_ibdev = rds_ib_get_client_data(dev);
+	if (!rds_ibdev)
+		return -EOPNOTSUPP;
+
+	/* The fr_queue_space is currently set to 512, to add extra space on
+	 * completion queue and send queue. This extra space is used for FRWR
+	 * registration and invalidation work requests
+	 */
+	fr_queue_space = RDS_IB_DEFAULT_FR_WR;
+
+	/* add the conn now so that connection establishment has the dev */
+	rds_ib_add_conn(rds_ibdev, conn);
+
+	max_wrs = rds_ibdev->max_wrs < rds_ib_sysctl_max_send_wr + 1 ?
+		rds_ibdev->max_wrs - 1 : rds_ib_sysctl_max_send_wr;
+	if (ic->i_send_ring.w_nr != max_wrs)
+		rds_ib_ring_resize(&ic->i_send_ring, max_wrs);
+
+	max_wrs = rds_ibdev->max_wrs < rds_ib_sysctl_max_recv_wr + 1 ?
+		rds_ibdev->max_wrs - 1 : rds_ib_sysctl_max_recv_wr;
+	if (ic->i_recv_ring.w_nr != max_wrs)
+		rds_ib_ring_resize(&ic->i_recv_ring, max_wrs);
+
+	/* Protection domain and memory range */
+	ic->i_pd = rds_ibdev->pd;
+
+	ic->i_scq_vector = ibdev_get_unused_vector(rds_ibdev);
+	cq_attr.cqe = ic->i_send_ring.w_nr + fr_queue_space + 1;
+	cq_attr.comp_vector = ic->i_scq_vector;
+	ic->i_send_cq = ib_create_cq(dev, rds_ib_cq_comp_handler_send,
+				     rds_ib_cq_event_handler, conn,
+				     &cq_attr);
+	if (IS_ERR(ic->i_send_cq)) {
+		ret = PTR_ERR(ic->i_send_cq);
+		ic->i_send_cq = NULL;
+		ibdev_put_vector(rds_ibdev, ic->i_scq_vector);
+		rdsdebug("ib_create_cq send failed: %d\n", ret);
+		goto rds_ibdev_out;
+	}
+
+	ic->i_rcq_vector = ibdev_get_unused_vector(rds_ibdev);
+	cq_attr.cqe = ic->i_recv_ring.w_nr;
+	cq_attr.comp_vector = ic->i_rcq_vector;
+	ic->i_recv_cq = ib_create_cq(dev, rds_ib_cq_comp_handler_recv,
+				     rds_ib_cq_event_handler, conn,
+				     &cq_attr);
+	if (IS_ERR(ic->i_recv_cq)) {
+		ret = PTR_ERR(ic->i_recv_cq);
+		ic->i_recv_cq = NULL;
+		ibdev_put_vector(rds_ibdev, ic->i_rcq_vector);
+		rdsdebug("ib_create_cq recv failed: %d\n", ret);
+		goto send_cq_out;
+	}
+
+	ret = ib_req_notify_cq(ic->i_send_cq, IB_CQ_NEXT_COMP);
+	if (ret) {
+		rdsdebug("ib_req_notify_cq send failed: %d\n", ret);
+		goto recv_cq_out;
+	}
+
+	ret = ib_req_notify_cq(ic->i_recv_cq, IB_CQ_SOLICITED);
+	if (ret) {
+		rdsdebug("ib_req_notify_cq recv failed: %d\n", ret);
+		goto recv_cq_out;
+	}
+
+	/* XXX negotiate max send/recv with remote? */
+	memset(&attr, 0, sizeof(attr));
+	attr.event_handler = rds_ib_qp_event_handler;
+	attr.qp_context = conn;
+	/* + 1 to allow for the single ack message */
+	attr.cap.max_send_wr = ic->i_send_ring.w_nr + fr_queue_space + 1;
+	attr.cap.max_recv_wr = ic->i_recv_ring.w_nr + 1;
+	attr.cap.max_send_sge = rds_ibdev->max_sge;
+	attr.cap.max_recv_sge = RDS_IB_RECV_SGE;
+	attr.sq_sig_type = IB_SIGNAL_REQ_WR;
+	attr.qp_type = IB_QPT_RC;
+	attr.send_cq = ic->i_send_cq;
+	attr.recv_cq = ic->i_recv_cq;
+
+	/*
+	 * XXX this can fail if max_*_wr is too large?  Are we supposed
+	 * to back off until we get a value that the hardware can support?
+	 */
+	ret = rdma_create_qp(ic->i_cm_id, ic->i_pd, &attr);
+	if (ret) {
+		rdsdebug("rdma_create_qp failed: %d\n", ret);
+		goto recv_cq_out;
+	}
+
+	ic->i_send_hdrs = rds_dma_hdrs_alloc(rds_ibdev, &ic->i_send_hdrs_dma,
+					     ic->i_send_ring.w_nr,
+					     DMA_TO_DEVICE);
+	if (!ic->i_send_hdrs) {
+		ret = -ENOMEM;
+		rdsdebug("DMA send hdrs alloc failed\n");
+		goto qp_out;
+	}
+
+	ic->i_recv_hdrs = rds_dma_hdrs_alloc(rds_ibdev, &ic->i_recv_hdrs_dma,
+					     ic->i_recv_ring.w_nr,
+					     DMA_FROM_DEVICE);
+	if (!ic->i_recv_hdrs) {
+		ret = -ENOMEM;
+		rdsdebug("DMA recv hdrs alloc failed\n");
+		goto send_hdrs_dma_out;
+	}
+
+	ic->i_ack = rds_dma_hdr_alloc(rds_ibdev->dev, &ic->i_ack_dma,
+				      DMA_TO_DEVICE);
+	if (!ic->i_ack) {
+		ret = -ENOMEM;
+		rdsdebug("DMA ack header alloc failed\n");
+		goto recv_hdrs_dma_out;
+	}
+
+	ic->i_sends = vzalloc_node(array_size(sizeof(struct rds_ib_send_work),
+					      ic->i_send_ring.w_nr),
+				   ibdev_to_node(dev));
+	if (!ic->i_sends) {
+		ret = -ENOMEM;
+		rdsdebug("send allocation failed\n");
+		goto ack_dma_out;
+	}
+
+	ic->i_recvs = vzalloc_node(array_size(sizeof(struct rds_ib_recv_work),
+					      ic->i_recv_ring.w_nr),
+				   ibdev_to_node(dev));
+	if (!ic->i_recvs) {
+		ret = -ENOMEM;
+		rdsdebug("recv allocation failed\n");
+		goto sends_out;
+	}
+
+	rds_ib_recv_init_ack(ic);
+
+	rdsdebug("conn %p pd %p cq %p %p\n", conn, ic->i_pd,
+		 ic->i_send_cq, ic->i_recv_cq);
+
+	goto out;
+
+sends_out:
+	vfree(ic->i_sends);
+	ic->i_sends = NULL;
+
+ack_dma_out:
+	rds_dma_hdr_free(rds_ibdev->dev, ic->i_ack, ic->i_ack_dma,
+			 DMA_TO_DEVICE);
+	ic->i_ack = NULL;
+
+recv_hdrs_dma_out:
+	rds_dma_hdrs_free(rds_ibdev, ic->i_recv_hdrs, ic->i_recv_hdrs_dma,
+			  ic->i_recv_ring.w_nr, DMA_FROM_DEVICE);
+	ic->i_recv_hdrs = NULL;
+	ic->i_recv_hdrs_dma = NULL;
+
+send_hdrs_dma_out:
+	rds_dma_hdrs_free(rds_ibdev, ic->i_send_hdrs, ic->i_send_hdrs_dma,
+			  ic->i_send_ring.w_nr, DMA_TO_DEVICE);
+	ic->i_send_hdrs = NULL;
+	ic->i_send_hdrs_dma = NULL;
+
+qp_out:
+	rdma_destroy_qp(ic->i_cm_id);
+recv_cq_out:
+	ib_destroy_cq(ic->i_recv_cq);
+	ic->i_recv_cq = NULL;
+send_cq_out:
+	ib_destroy_cq(ic->i_send_cq);
+	ic->i_send_cq = NULL;
+rds_ibdev_out:
+	rds_ib_remove_conn(rds_ibdev, conn);
+out:
+	rds_ib_dev_put(rds_ibdev);
+
+	return ret;
+}
+
+static u32 rds_ib_protocol_compatible(struct rdma_cm_event *event, bool isv6)
+{
+	const union rds_ib_conn_priv *dp = event->param.conn.private_data;
+	u8 data_len, major, minor;
+	u32 version = 0;
+	__be16 mask;
+	u16 common;
+
+	/*
+	 * rdma_cm private data is odd - when there is any private data in the
+	 * request, we will be given a pretty large buffer without telling us the
+	 * original size. The only way to tell the difference is by looking at
+	 * the contents, which are initialized to zero.
+	 * If the protocol version fields aren't set, this is a connection attempt
+	 * from an older version. This could be 3.0 or 2.0 - we can't tell.
+	 * We really should have changed this for OFED 1.3 :-(
+	 */
+
+	/* Be paranoid. RDS always has privdata */
+	if (!event->param.conn.private_data_len) {
+		printk(KERN_NOTICE "RDS incoming connection has no private data, "
+			"rejecting\n");
+		return 0;
+	}
+
+	if (isv6) {
+		data_len = sizeof(struct rds6_ib_connect_private);
+		major = dp->ricp_v6.dp_protocol_major;
+		minor = dp->ricp_v6.dp_protocol_minor;
+		mask = dp->ricp_v6.dp_protocol_minor_mask;
+	} else {
+		data_len = sizeof(struct rds_ib_connect_private);
+		major = dp->ricp_v4.dp_protocol_major;
+		minor = dp->ricp_v4.dp_protocol_minor;
+		mask = dp->ricp_v4.dp_protocol_minor_mask;
+	}
+
+	/* Even if len is crap *now* I still want to check it. -ASG */
+	if (event->param.conn.private_data_len < data_len || major == 0)
+		return RDS_PROTOCOL_4_0;
+
+	common = be16_to_cpu(mask) & RDS_IB_SUPPORTED_PROTOCOLS;
+	if (major == 4 && common) {
+		version = RDS_PROTOCOL_4_0;
+		while ((common >>= 1) != 0)
+			version++;
+	} else if (RDS_PROTOCOL_COMPAT_VERSION ==
+		   RDS_PROTOCOL(major, minor)) {
+		version = RDS_PROTOCOL_COMPAT_VERSION;
+	} else {
+		if (isv6)
+			printk_ratelimited(KERN_NOTICE "RDS: Connection from %pI6c using incompatible protocol version %u.%u\n",
+					   &dp->ricp_v6.dp_saddr, major, minor);
+		else
+			printk_ratelimited(KERN_NOTICE "RDS: Connection from %pI4 using incompatible protocol version %u.%u\n",
+					   &dp->ricp_v4.dp_saddr, major, minor);
+	}
+	return version;
+}
+
+#if IS_ENABLED(CONFIG_IPV6)
+/* Given an IPv6 address, find the net_device which hosts that address and
+ * return its index.  This is used by the rds_ib_cm_handle_connect() code to
+ * find the interface index of where an incoming request comes from when
+ * the request is using a link local address.
+ *
+ * Note one problem in this search.  It is possible that two interfaces have
+ * the same link local address.  Unfortunately, this cannot be solved unless
+ * the underlying layer gives us the interface which an incoming RDMA connect
+ * request comes from.
+ */
+static u32 __rds_find_ifindex(struct net *net, const struct in6_addr *addr)
+{
+	struct net_device *dev;
+	int idx = 0;
+
+	rcu_read_lock();
+	for_each_netdev_rcu(net, dev) {
+		if (ipv6_chk_addr(net, addr, dev, 1)) {
+			idx = dev->ifindex;
+			break;
+		}
+	}
+	rcu_read_unlock();
+
+	return idx;
+}
+#endif
+
+int rds_ib_cm_handle_connect(struct rdma_cm_id *cm_id,
+			     struct rdma_cm_event *event, bool isv6)
+{
+	__be64 lguid = cm_id->route.path_rec->sgid.global.interface_id;
+	__be64 fguid = cm_id->route.path_rec->dgid.global.interface_id;
+	const struct rds_ib_conn_priv_cmn *dp_cmn;
+	struct rds_connection *conn = NULL;
+	struct rds_ib_connection *ic = NULL;
+	struct rdma_conn_param conn_param;
+	const union rds_ib_conn_priv *dp;
+	union rds_ib_conn_priv dp_rep;
+	struct in6_addr s_mapped_addr;
+	struct in6_addr d_mapped_addr;
+	const struct in6_addr *saddr6;
+	const struct in6_addr *daddr6;
+	int destroy = 1;
+	u32 ifindex = 0;
+	u32 version;
+	int err = 1;
+
+	/* Check whether the remote protocol version matches ours. */
+	version = rds_ib_protocol_compatible(event, isv6);
+	if (!version) {
+		err = RDS_RDMA_REJ_INCOMPAT;
+		goto out;
+	}
+
+	dp = event->param.conn.private_data;
+	if (isv6) {
+#if IS_ENABLED(CONFIG_IPV6)
+		if (!ipv6_mod_enabled()) {
+			err = -EOPNOTSUPP;
+			goto out;
+		}
+		dp_cmn = &dp->ricp_v6.dp_cmn;
+		saddr6 = &dp->ricp_v6.dp_saddr;
+		daddr6 = &dp->ricp_v6.dp_daddr;
+		/* If either address is link local, need to find the
+		 * interface index in order to create a proper RDS
+		 * connection.
+		 */
+		if (ipv6_addr_type(daddr6) & IPV6_ADDR_LINKLOCAL) {
+			/* Using init_net for now ..  */
+			ifindex = __rds_find_ifindex(&init_net, daddr6);
+			/* No index found...  Need to bail out. */
+			if (ifindex == 0) {
+				err = -EOPNOTSUPP;
+				goto out;
+			}
+		} else if (ipv6_addr_type(saddr6) & IPV6_ADDR_LINKLOCAL) {
+			/* Use our address to find the correct index. */
+			ifindex = __rds_find_ifindex(&init_net, daddr6);
+			/* No index found...  Need to bail out. */
+			if (ifindex == 0) {
+				err = -EOPNOTSUPP;
+				goto out;
+			}
+		}
+#else
+		err = -EOPNOTSUPP;
+		goto out;
+#endif
+	} else {
+		dp_cmn = &dp->ricp_v4.dp_cmn;
+		ipv6_addr_set_v4mapped(dp->ricp_v4.dp_saddr, &s_mapped_addr);
+		ipv6_addr_set_v4mapped(dp->ricp_v4.dp_daddr, &d_mapped_addr);
+		saddr6 = &s_mapped_addr;
+		daddr6 = &d_mapped_addr;
+	}
+
+	rdsdebug("saddr %pI6c daddr %pI6c RDSv%u.%u lguid 0x%llx fguid 0x%llx, tos:%d\n",
+		 saddr6, daddr6, RDS_PROTOCOL_MAJOR(version),
+		 RDS_PROTOCOL_MINOR(version),
+		 (unsigned long long)be64_to_cpu(lguid),
+		 (unsigned long long)be64_to_cpu(fguid), dp_cmn->ricpc_dp_toss);
+
+	/* RDS/IB is not currently netns aware, thus init_net */
+	conn = rds_conn_create(&init_net, daddr6, saddr6,
+			       &rds_ib_transport, dp_cmn->ricpc_dp_toss,
+			       GFP_KERNEL, ifindex);
+	if (IS_ERR(conn)) {
+		rdsdebug("rds_conn_create failed (%ld)\n", PTR_ERR(conn));
+		conn = NULL;
+		goto out;
+	}
+
+	/*
+	 * The connection request may occur while the
+	 * previous connection exist, e.g. in case of failover.
+	 * But as connections may be initiated simultaneously
+	 * by both hosts, we have a random backoff mechanism -
+	 * see the comment above rds_queue_reconnect()
+	 */
+	mutex_lock(&conn->c_cm_lock);
+	if (!rds_conn_transition(conn, RDS_CONN_DOWN, RDS_CONN_CONNECTING)) {
+		if (rds_conn_state(conn) == RDS_CONN_UP) {
+			rdsdebug("incoming connect while connecting\n");
+			rds_conn_drop(conn);
+			rds_ib_stats_inc(s_ib_listen_closed_stale);
+		} else
+		if (rds_conn_state(conn) == RDS_CONN_CONNECTING) {
+			/* Wait and see - our connect may still be succeeding */
+			rds_ib_stats_inc(s_ib_connect_raced);
+		}
+		goto out;
+	}
+
+	ic = conn->c_transport_data;
+
+	rds_ib_set_protocol(conn, version);
+	rds_ib_set_flow_control(conn, be32_to_cpu(dp_cmn->ricpc_credit));
+
+	/* If the peer gave us the last packet it saw, process this as if
+	 * we had received a regular ACK. */
+	if (dp_cmn->ricpc_ack_seq)
+		rds_send_drop_acked(conn, be64_to_cpu(dp_cmn->ricpc_ack_seq),
+				    NULL);
+
+	BUG_ON(cm_id->context);
+	BUG_ON(ic->i_cm_id);
+
+	ic->i_cm_id = cm_id;
+	cm_id->context = conn;
+
+	/* We got halfway through setting up the ib_connection, if we
+	 * fail now, we have to take the long route out of this mess. */
+	destroy = 0;
+
+	err = rds_ib_setup_qp(conn);
+	if (err) {
+		rds_ib_conn_error(conn, "rds_ib_setup_qp failed (%d)\n", err);
+		goto out;
+	}
+
+	rds_ib_cm_fill_conn_param(conn, &conn_param, &dp_rep, version,
+				  event->param.conn.responder_resources,
+				  event->param.conn.initiator_depth, isv6);
+
+	rdma_set_min_rnr_timer(cm_id, IB_RNR_TIMER_000_32);
+	/* rdma_accept() calls rdma_reject() internally if it fails */
+	if (rdma_accept(cm_id, &conn_param))
+		rds_ib_conn_error(conn, "rdma_accept failed\n");
+
+out:
+	if (conn)
+		mutex_unlock(&conn->c_cm_lock);
+	if (err)
+		rdma_reject(cm_id, &err, sizeof(int),
+			    IB_CM_REJ_CONSUMER_DEFINED);
+	return destroy;
+}
+
+
+int rds_ib_cm_initiate_connect(struct rdma_cm_id *cm_id, bool isv6)
+{
+	struct rds_connection *conn = cm_id->context;
+	struct rds_ib_connection *ic = conn->c_transport_data;
+	struct rdma_conn_param conn_param;
+	union rds_ib_conn_priv dp;
+	int ret;
+
+	/* If the peer doesn't do protocol negotiation, we must
+	 * default to RDSv3.0 */
+	rds_ib_set_protocol(conn, RDS_PROTOCOL_4_1);
+	ic->i_flowctl = rds_ib_sysctl_flow_control;	/* advertise flow control */
+
+	ret = rds_ib_setup_qp(conn);
+	if (ret) {
+		rds_ib_conn_error(conn, "rds_ib_setup_qp failed (%d)\n", ret);
+		goto out;
+	}
+
+	rds_ib_cm_fill_conn_param(conn, &conn_param, &dp,
+				  conn->c_proposed_version,
+				  UINT_MAX, UINT_MAX, isv6);
+	ret = rdma_connect_locked(cm_id, &conn_param);
+	if (ret)
+		rds_ib_conn_error(conn, "rdma_connect_locked failed (%d)\n",
+				  ret);
+
+out:
+	/* Beware - returning non-zero tells the rdma_cm to destroy
+	 * the cm_id. We should certainly not do it as long as we still
+	 * "own" the cm_id. */
+	if (ret) {
+		if (ic->i_cm_id == cm_id)
+			ret = 0;
+	}
+	ic->i_active_side = true;
+	return ret;
+}
+
+int rds_ib_conn_path_connect(struct rds_conn_path *cp)
+{
+	struct rds_connection *conn = cp->cp_conn;
+	struct sockaddr_storage src, dest;
+	rdma_cm_event_handler handler;
+	struct rds_ib_connection *ic;
+	int ret;
+
+	ic = conn->c_transport_data;
+
+	/* XXX I wonder what affect the port space has */
+	/* delegate cm event handler to rdma_transport */
+#if IS_ENABLED(CONFIG_IPV6)
+	if (conn->c_isv6)
+		handler = rds6_rdma_cm_event_handler;
+	else
+#endif
+		handler = rds_rdma_cm_event_handler;
+	ic->i_cm_id = rdma_create_id(&init_net, handler, conn,
+				     RDMA_PS_TCP, IB_QPT_RC);
+	if (IS_ERR(ic->i_cm_id)) {
+		ret = PTR_ERR(ic->i_cm_id);
+		ic->i_cm_id = NULL;
+		rdsdebug("rdma_create_id() failed: %d\n", ret);
+		goto out;
+	}
+
+	rdsdebug("created cm id %p for conn %p\n", ic->i_cm_id, conn);
+
+	if (ipv6_addr_v4mapped(&conn->c_faddr)) {
+		struct sockaddr_in *sin;
+
+		sin = (struct sockaddr_in *)&src;
+		sin->sin_family = AF_INET;
+		sin->sin_addr.s_addr = conn->c_laddr.s6_addr32[3];
+		sin->sin_port = 0;
+
+		sin = (struct sockaddr_in *)&dest;
+		sin->sin_family = AF_INET;
+		sin->sin_addr.s_addr = conn->c_faddr.s6_addr32[3];
+		sin->sin_port = htons(RDS_PORT);
+	} else {
+		struct sockaddr_in6 *sin6;
+
+		sin6 = (struct sockaddr_in6 *)&src;
+		sin6->sin6_family = AF_INET6;
+		sin6->sin6_addr = conn->c_laddr;
+		sin6->sin6_port = 0;
+		sin6->sin6_scope_id = conn->c_dev_if;
+
+		sin6 = (struct sockaddr_in6 *)&dest;
+		sin6->sin6_family = AF_INET6;
+		sin6->sin6_addr = conn->c_faddr;
+		sin6->sin6_port = htons(RDS_CM_PORT);
+		sin6->sin6_scope_id = conn->c_dev_if;
+	}
+
+	ret = rdma_resolve_addr(ic->i_cm_id, (struct sockaddr *)&src,
+				(struct sockaddr *)&dest,
+				RDS_RDMA_RESOLVE_TIMEOUT_MS);
+	if (ret) {
+		rdsdebug("addr resolve failed for cm id %p: %d\n", ic->i_cm_id,
+			 ret);
+		rdma_destroy_id(ic->i_cm_id);
+		ic->i_cm_id = NULL;
+	}
+
+out:
+	return ret;
+}
+
+static unsigned long rds_ib_conn_path_shutdown_check_wait(struct rds_conn_path *cp)
+{
+	struct rds_connection *conn = cp->cp_conn;
+	struct rds_ib_connection *ic = conn->c_transport_data;
+
+	return (!ic->i_cm_id ||
+		(rds_ib_ring_empty(&ic->i_recv_ring) &&
+		 (atomic_read(&ic->i_signaled_sends) == 0) &&
+		 (atomic_read(&ic->i_fastreg_inuse_count)) == 0 &&
+		 (atomic_read(&ic->i_fastreg_wrs) == RDS_IB_DEFAULT_FR_WR))) ? 0
+		: msecs_to_jiffies(1000);
+}
+
+/*
+ * This is so careful about only cleaning up resources that were built up
+ * so that it can be called at any point during startup.  In fact it
+ * can be called multiple times for a given connection.
+ */
+void rds_ib_conn_path_shutdown(struct rds_conn_path *cp)
+{
+	struct rds_connection *conn = cp->cp_conn;
+	struct rds_ib_connection *ic = conn->c_transport_data;
+	int err = 0;
+
+	rdsdebug("cm %p pd %p cq %p %p qp %p\n", ic->i_cm_id,
+		 ic->i_pd, ic->i_send_cq, ic->i_recv_cq,
+		 ic->i_cm_id ? ic->i_cm_id->qp : NULL);
+
+	if (ic->i_cm_id) {
+		rdsdebug("disconnecting cm %p\n", ic->i_cm_id);
+		err = rdma_disconnect(ic->i_cm_id);
+		if (err) {
+			/* Actually this may happen quite frequently, when
+			 * an outgoing connect raced with an incoming connect.
+			 */
+			rdsdebug("failed to disconnect, cm: %p err %d\n",
+				ic->i_cm_id, err);
+		}
+
+		/* kick off "flush_worker" for all pools in order to reap
+		 * all FRMR registrations that are still marked "FRMR_IS_INUSE"
+		 */
+		rds_ib_flush_mrs();
+
+		/*
+		 * We want to wait for tx and rx completion to finish
+		 * before we tear down the connection, but we have to be
+		 * careful not to get stuck waiting on a send ring that
+		 * only has unsignaled sends in it.  We've shutdown new
+		 * sends before getting here so by waiting for signaled
+		 * sends to complete we're ensured that there will be no
+		 * more tx processing.
+		 */
+		while (!wait_event_timeout(rds_ib_ring_empty_wait,
+					   rds_ib_conn_path_shutdown_check_wait(cp) == 0,
+					   msecs_to_jiffies(1000))) {
+			tasklet_schedule(&ic->i_send_tasklet);
+			tasklet_schedule(&ic->i_recv_tasklet);
+		}
+
+		tasklet_kill(&ic->i_send_tasklet);
+		tasklet_kill(&ic->i_recv_tasklet);
+
+		atomic_set(&ic->i_cq_quiesce, 1);
+
+		/* first destroy the ib state that generates callbacks */
+		if (ic->i_cm_id->qp)
+			rdma_destroy_qp(ic->i_cm_id);
+		if (ic->i_send_cq) {
+			if (ic->rds_ibdev)
+				ibdev_put_vector(ic->rds_ibdev, ic->i_scq_vector);
+			ib_destroy_cq(ic->i_send_cq);
+		}
+
+		if (ic->i_recv_cq) {
+			if (ic->rds_ibdev)
+				ibdev_put_vector(ic->rds_ibdev, ic->i_rcq_vector);
+			ib_destroy_cq(ic->i_recv_cq);
+		}
+
+		if (ic->rds_ibdev) {
+			/* then free the resources that ib callbacks use */
+			if (ic->i_send_hdrs) {
+				rds_dma_hdrs_free(ic->rds_ibdev,
+						  ic->i_send_hdrs,
+						  ic->i_send_hdrs_dma,
+						  ic->i_send_ring.w_nr,
+						  DMA_TO_DEVICE);
+				ic->i_send_hdrs = NULL;
+				ic->i_send_hdrs_dma = NULL;
+			}
+
+			if (ic->i_recv_hdrs) {
+				rds_dma_hdrs_free(ic->rds_ibdev,
+						  ic->i_recv_hdrs,
+						  ic->i_recv_hdrs_dma,
+						  ic->i_recv_ring.w_nr,
+						  DMA_FROM_DEVICE);
+				ic->i_recv_hdrs = NULL;
+				ic->i_recv_hdrs_dma = NULL;
+			}
+
+			if (ic->i_ack) {
+				rds_dma_hdr_free(ic->rds_ibdev->dev, ic->i_ack,
+						 ic->i_ack_dma, DMA_TO_DEVICE);
+				ic->i_ack = NULL;
+			}
+		} else {
+			WARN_ON(ic->i_send_hdrs);
+			WARN_ON(ic->i_send_hdrs_dma);
+			WARN_ON(ic->i_recv_hdrs);
+			WARN_ON(ic->i_recv_hdrs_dma);
+			WARN_ON(ic->i_ack);
+		}
+
+		if (ic->i_sends)
+			rds_ib_send_clear_ring(ic);
+		if (ic->i_recvs)
+			rds_ib_recv_clear_ring(ic);
+
+		rdma_destroy_id(ic->i_cm_id);
+
+		/*
+		 * Move connection back to the nodev list.
+		 */
+		if (ic->rds_ibdev)
+			rds_ib_remove_conn(ic->rds_ibdev, conn);
+
+		ic->i_cm_id = NULL;
+		ic->i_pd = NULL;
+		ic->i_send_cq = NULL;
+		ic->i_recv_cq = NULL;
+	}
+	BUG_ON(ic->rds_ibdev);
+
+	/* Clear pending transmit */
+	if (ic->i_data_op) {
+		struct rds_message *rm;
+
+		rm = container_of(ic->i_data_op, struct rds_message, data);
+		rds_message_put(rm);
+		ic->i_data_op = NULL;
+	}
+
+	/* Clear the ACK state */
+	clear_bit(IB_ACK_IN_FLIGHT, &ic->i_ack_flags);
+#ifdef KERNEL_HAS_ATOMIC64
+	atomic64_set(&ic->i_ack_next, 0);
+#else
+	ic->i_ack_next = 0;
+#endif
+	ic->i_ack_recv = 0;
+
+	/* Clear flow control state */
+	ic->i_flowctl = 0;
+	atomic_set(&ic->i_credits, 0);
+
+	/* Re-init rings, but retain sizes. */
+	rds_ib_ring_init(&ic->i_send_ring, ic->i_send_ring.w_nr);
+	rds_ib_ring_init(&ic->i_recv_ring, ic->i_recv_ring.w_nr);
+
+	if (ic->i_ibinc) {
+		rds_inc_put(&ic->i_ibinc->ii_inc);
+		ic->i_ibinc = NULL;
+	}
+
+	vfree(ic->i_sends);
+	ic->i_sends = NULL;
+	vfree(ic->i_recvs);
+	ic->i_recvs = NULL;
+	ic->i_active_side = false;
+}
+
+int rds_ib_conn_alloc(struct rds_connection *conn, gfp_t gfp)
+{
+	struct rds_ib_connection *ic;
+	unsigned long flags;
+	int ret;
+
+	/* XXX too lazy? */
+	ic = kzalloc_obj(struct rds_ib_connection, gfp);
+	if (!ic)
+		return -ENOMEM;
+
+	ret = rds_ib_recv_alloc_caches(ic, gfp);
+	if (ret) {
+		kfree(ic);
+		return ret;
+	}
+
+	INIT_LIST_HEAD(&ic->ib_node);
+	tasklet_init(&ic->i_send_tasklet, rds_ib_tasklet_fn_send,
+		     (unsigned long)ic);
+	tasklet_init(&ic->i_recv_tasklet, rds_ib_tasklet_fn_recv,
+		     (unsigned long)ic);
+	mutex_init(&ic->i_recv_mutex);
+#ifndef KERNEL_HAS_ATOMIC64
+	spin_lock_init(&ic->i_ack_lock);
+#endif
+	atomic_set(&ic->i_signaled_sends, 0);
+	atomic_set(&ic->i_fastreg_wrs, RDS_IB_DEFAULT_FR_WR);
+
+	/*
+	 * rds_ib_conn_shutdown() waits for these to be emptied so they
+	 * must be initialized before it can be called.
+	 */
+	rds_ib_ring_init(&ic->i_send_ring, 0);
+	rds_ib_ring_init(&ic->i_recv_ring, 0);
+
+	ic->conn = conn;
+	conn->c_transport_data = ic;
+
+	spin_lock_irqsave(&ib_nodev_conns_lock, flags);
+	list_add_tail(&ic->ib_node, &ib_nodev_conns);
+	spin_unlock_irqrestore(&ib_nodev_conns_lock, flags);
+
+
+	rdsdebug("conn %p conn ic %p\n", conn, conn->c_transport_data);
+	return 0;
+}
+
+/*
+ * Free a connection. Connection must be shut down and not set for reconnect.
+ */
+void rds_ib_conn_free(void *arg)
+{
+	struct rds_ib_connection *ic = arg;
+	spinlock_t	*lock_ptr;
+
+	rdsdebug("ic %p\n", ic);
+
+	/*
+	 * Conn is either on a dev's list or on the nodev list.
+	 * A race with shutdown() or connect() would cause problems
+	 * (since rds_ibdev would change) but that should never happen.
+	 */
+	lock_ptr = ic->rds_ibdev ? &ic->rds_ibdev->spinlock : &ib_nodev_conns_lock;
+
+	spin_lock_irq(lock_ptr);
+	list_del(&ic->ib_node);
+	spin_unlock_irq(lock_ptr);
+
+	rds_ib_recv_free_caches(ic);
+
+	kfree(ic);
+}
+
+
+/*
+ * An error occurred on the connection
+ */
+void
+__rds_ib_conn_error(struct rds_connection *conn, const char *fmt, ...)
+{
+	va_list ap;
+
+	rds_conn_drop(conn);
+
+	va_start(ap, fmt);
+	vprintk(fmt, ap);
+	va_end(ap);
+}
diff --git a/net/rds/ib_frmr.c b/net/rds/ib_frmr.c
new file mode 100644
index 000000000..bd8611911
--- /dev/null
+++ b/net/rds/ib_frmr.c
@@ -0,0 +1,450 @@
+/*
+ * Copyright (c) 2016 Oracle.  All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "ib_mr.h"
+
+static inline void
+rds_transition_frwr_state(struct rds_ib_mr *ibmr,
+			  enum rds_ib_fr_state old_state,
+			  enum rds_ib_fr_state new_state)
+{
+	if (cmpxchg(&ibmr->u.frmr.fr_state,
+		    old_state, new_state) == old_state &&
+	    old_state == FRMR_IS_INUSE) {
+		/* enforce order of ibmr->u.frmr.fr_state update
+		 * before decrementing i_fastreg_inuse_count
+		 */
+		smp_mb__before_atomic();
+		atomic_dec(&ibmr->ic->i_fastreg_inuse_count);
+		if (waitqueue_active(&rds_ib_ring_empty_wait))
+			wake_up(&rds_ib_ring_empty_wait);
+	}
+}
+
+static struct rds_ib_mr *rds_ib_alloc_frmr(struct rds_ib_device *rds_ibdev,
+					   int npages)
+{
+	struct rds_ib_mr_pool *pool;
+	struct rds_ib_mr *ibmr = NULL;
+	struct rds_ib_frmr *frmr;
+	int err = 0;
+
+	if (npages <= RDS_MR_8K_MSG_SIZE)
+		pool = rds_ibdev->mr_8k_pool;
+	else
+		pool = rds_ibdev->mr_1m_pool;
+
+	ibmr = rds_ib_try_reuse_ibmr(pool);
+	if (ibmr)
+		return ibmr;
+
+	ibmr = kzalloc_node(sizeof(*ibmr), GFP_KERNEL,
+			    rdsibdev_to_node(rds_ibdev));
+	if (!ibmr) {
+		err = -ENOMEM;
+		goto out_no_cigar;
+	}
+
+	frmr = &ibmr->u.frmr;
+	frmr->mr = ib_alloc_mr(rds_ibdev->pd, IB_MR_TYPE_MEM_REG,
+			 pool->max_pages);
+	if (IS_ERR(frmr->mr)) {
+		pr_warn("RDS/IB: %s failed to allocate MR", __func__);
+		err = PTR_ERR(frmr->mr);
+		goto out_no_cigar;
+	}
+
+	ibmr->pool = pool;
+	if (pool->pool_type == RDS_IB_MR_8K_POOL)
+		rds_ib_stats_inc(s_ib_rdma_mr_8k_alloc);
+	else
+		rds_ib_stats_inc(s_ib_rdma_mr_1m_alloc);
+
+	if (atomic_read(&pool->item_count) > pool->max_items_soft)
+		pool->max_items_soft = pool->max_items;
+
+	frmr->fr_state = FRMR_IS_FREE;
+	init_waitqueue_head(&frmr->fr_inv_done);
+	init_waitqueue_head(&frmr->fr_reg_done);
+	return ibmr;
+
+out_no_cigar:
+	kfree(ibmr);
+	atomic_dec(&pool->item_count);
+	return ERR_PTR(err);
+}
+
+static void rds_ib_free_frmr(struct rds_ib_mr *ibmr, bool drop)
+{
+	struct rds_ib_mr_pool *pool = ibmr->pool;
+
+	if (drop)
+		llist_add(&ibmr->llnode, &pool->drop_list);
+	else
+		llist_add(&ibmr->llnode, &pool->free_list);
+	atomic_add(ibmr->sg_len, &pool->free_pinned);
+	atomic_inc(&pool->dirty_count);
+
+	/* If we've pinned too many pages, request a flush */
+	if (atomic_read(&pool->free_pinned) >= pool->max_free_pinned ||
+	    atomic_read(&pool->dirty_count) >= pool->max_items / 5)
+		queue_delayed_work(rds_ib_mr_wq, &pool->flush_worker, 10);
+}
+
+static int rds_ib_post_reg_frmr(struct rds_ib_mr *ibmr)
+{
+	struct rds_ib_frmr *frmr = &ibmr->u.frmr;
+	struct ib_reg_wr reg_wr;
+	int ret, off = 0;
+
+	while (atomic_dec_return(&ibmr->ic->i_fastreg_wrs) <= 0) {
+		atomic_inc(&ibmr->ic->i_fastreg_wrs);
+		cpu_relax();
+	}
+
+	ret = ib_map_mr_sg_zbva(frmr->mr, ibmr->sg, ibmr->sg_dma_len,
+				&off, PAGE_SIZE);
+	if (unlikely(ret != ibmr->sg_dma_len)) {
+		ret = ret < 0 ? ret : -EINVAL;
+		goto out_inc;
+	}
+
+	if (cmpxchg(&frmr->fr_state, FRMR_IS_FREE, FRMR_IS_INUSE) != FRMR_IS_FREE) {
+		ret = -EBUSY;
+		goto out_inc;
+	}
+
+	atomic_inc(&ibmr->ic->i_fastreg_inuse_count);
+
+	/* Perform a WR for the fast_reg_mr. Each individual page
+	 * in the sg list is added to the fast reg page list and placed
+	 * inside the fast_reg_mr WR.  The key used is a rolling 8bit
+	 * counter, which should guarantee uniqueness.
+	 */
+	ib_update_fast_reg_key(frmr->mr, ibmr->remap_count++);
+	frmr->fr_reg = true;
+
+	memset(&reg_wr, 0, sizeof(reg_wr));
+	reg_wr.wr.wr_id = (unsigned long)(void *)ibmr;
+	reg_wr.wr.opcode = IB_WR_REG_MR;
+	reg_wr.wr.num_sge = 0;
+	reg_wr.mr = frmr->mr;
+	reg_wr.key = frmr->mr->rkey;
+	reg_wr.access = IB_ACCESS_LOCAL_WRITE |
+			IB_ACCESS_REMOTE_READ |
+			IB_ACCESS_REMOTE_WRITE;
+	reg_wr.wr.send_flags = IB_SEND_SIGNALED;
+
+	ret = ib_post_send(ibmr->ic->i_cm_id->qp, &reg_wr.wr, NULL);
+	if (unlikely(ret)) {
+		/* Failure here can be because of -ENOMEM as well */
+		rds_transition_frwr_state(ibmr, FRMR_IS_INUSE, FRMR_IS_STALE);
+
+		if (printk_ratelimit())
+			pr_warn("RDS/IB: %s returned error(%d)\n",
+				__func__, ret);
+		goto out_inc;
+	}
+
+	/* Wait for the registration to complete in order to prevent an invalid
+	 * access error resulting from a race between the memory region already
+	 * being accessed while registration is still pending.
+	 */
+	wait_event(frmr->fr_reg_done, !frmr->fr_reg);
+
+	return ret;
+
+out_inc:
+	atomic_inc(&ibmr->ic->i_fastreg_wrs);
+	return ret;
+}
+
+static int rds_ib_map_frmr(struct rds_ib_device *rds_ibdev,
+			   struct rds_ib_mr_pool *pool,
+			   struct rds_ib_mr *ibmr,
+			   struct scatterlist *sg, unsigned int sg_len)
+{
+	struct ib_device *dev = rds_ibdev->dev;
+	struct rds_ib_frmr *frmr = &ibmr->u.frmr;
+	int i;
+	u32 len;
+	int ret = 0;
+
+	/* We want to teardown old ibmr values here and fill it up with
+	 * new sg values
+	 */
+	rds_ib_teardown_mr(ibmr);
+
+	ibmr->sg = sg;
+	ibmr->sg_len = sg_len;
+	ibmr->sg_dma_len = 0;
+	frmr->sg_byte_len = 0;
+	WARN_ON(ibmr->sg_dma_len);
+	ibmr->sg_dma_len = ib_dma_map_sg(dev, ibmr->sg, ibmr->sg_len,
+					 DMA_BIDIRECTIONAL);
+	if (unlikely(!ibmr->sg_dma_len)) {
+		pr_warn("RDS/IB: %s failed!\n", __func__);
+		return -EBUSY;
+	}
+
+	frmr->sg_byte_len = 0;
+	frmr->dma_npages = 0;
+	len = 0;
+
+	ret = -EINVAL;
+	for (i = 0; i < ibmr->sg_dma_len; ++i) {
+		unsigned int dma_len = sg_dma_len(&ibmr->sg[i]);
+		u64 dma_addr = sg_dma_address(&ibmr->sg[i]);
+
+		frmr->sg_byte_len += dma_len;
+		if (dma_addr & ~PAGE_MASK) {
+			if (i > 0)
+				goto out_unmap;
+			else
+				++frmr->dma_npages;
+		}
+
+		if ((dma_addr + dma_len) & ~PAGE_MASK) {
+			if (i < ibmr->sg_dma_len - 1)
+				goto out_unmap;
+			else
+				++frmr->dma_npages;
+		}
+
+		len += dma_len;
+	}
+	frmr->dma_npages += len >> PAGE_SHIFT;
+
+	if (frmr->dma_npages > ibmr->pool->max_pages) {
+		ret = -EMSGSIZE;
+		goto out_unmap;
+	}
+
+	ret = rds_ib_post_reg_frmr(ibmr);
+	if (ret)
+		goto out_unmap;
+
+	if (ibmr->pool->pool_type == RDS_IB_MR_8K_POOL)
+		rds_ib_stats_inc(s_ib_rdma_mr_8k_used);
+	else
+		rds_ib_stats_inc(s_ib_rdma_mr_1m_used);
+
+	return ret;
+
+out_unmap:
+	ib_dma_unmap_sg(rds_ibdev->dev, ibmr->sg, ibmr->sg_len,
+			DMA_BIDIRECTIONAL);
+	ibmr->sg_dma_len = 0;
+	return ret;
+}
+
+static int rds_ib_post_inv(struct rds_ib_mr *ibmr)
+{
+	struct ib_send_wr *s_wr;
+	struct rds_ib_frmr *frmr = &ibmr->u.frmr;
+	struct rdma_cm_id *i_cm_id = ibmr->ic->i_cm_id;
+	int ret = -EINVAL;
+
+	if (!i_cm_id || !i_cm_id->qp || !frmr->mr)
+		goto out;
+
+	if (frmr->fr_state != FRMR_IS_INUSE)
+		goto out;
+
+	while (atomic_dec_return(&ibmr->ic->i_fastreg_wrs) <= 0) {
+		atomic_inc(&ibmr->ic->i_fastreg_wrs);
+		cpu_relax();
+	}
+
+	frmr->fr_inv = true;
+	s_wr = &frmr->fr_wr;
+
+	memset(s_wr, 0, sizeof(*s_wr));
+	s_wr->wr_id = (unsigned long)(void *)ibmr;
+	s_wr->opcode = IB_WR_LOCAL_INV;
+	s_wr->ex.invalidate_rkey = frmr->mr->rkey;
+	s_wr->send_flags = IB_SEND_SIGNALED;
+
+	ret = ib_post_send(i_cm_id->qp, s_wr, NULL);
+	if (unlikely(ret)) {
+		rds_transition_frwr_state(ibmr, FRMR_IS_INUSE, FRMR_IS_STALE);
+		frmr->fr_inv = false;
+		/* enforce order of frmr->fr_inv update
+		 * before incrementing i_fastreg_wrs
+		 */
+		smp_mb__before_atomic();
+		atomic_inc(&ibmr->ic->i_fastreg_wrs);
+		pr_err("RDS/IB: %s returned error(%d)\n", __func__, ret);
+		goto out;
+	}
+
+	/* Wait for the FRMR_IS_FREE (or FRMR_IS_STALE) transition in order to
+	 * 1) avoid a silly bouncing between "clean_list" and "drop_list"
+	 *    triggered by function "rds_ib_reg_frmr" as it is releases frmr
+	 *    regions whose state is not "FRMR_IS_FREE" right away.
+	 * 2) prevents an invalid access error in a race
+	 *    from a pending "IB_WR_LOCAL_INV" operation
+	 *    with a teardown ("dma_unmap_sg", "put_page")
+	 *    and de-registration ("ib_dereg_mr") of the corresponding
+	 *    memory region.
+	 */
+	wait_event(frmr->fr_inv_done, frmr->fr_state != FRMR_IS_INUSE);
+
+out:
+	return ret;
+}
+
+void rds_ib_mr_cqe_handler(struct rds_ib_connection *ic, struct ib_wc *wc)
+{
+	struct rds_ib_mr *ibmr = (void *)(unsigned long)wc->wr_id;
+	struct rds_ib_frmr *frmr = &ibmr->u.frmr;
+
+	if (wc->status != IB_WC_SUCCESS) {
+		rds_transition_frwr_state(ibmr, FRMR_IS_INUSE, FRMR_IS_STALE);
+		if (rds_conn_up(ic->conn))
+			rds_ib_conn_error(ic->conn,
+					  "frmr completion <%pI4,%pI4> status %u(%s), vendor_err 0x%x, disconnecting and reconnecting\n",
+					  &ic->conn->c_laddr,
+					  &ic->conn->c_faddr,
+					  wc->status,
+					  ib_wc_status_msg(wc->status),
+					  wc->vendor_err);
+	}
+
+	if (frmr->fr_inv) {
+		rds_transition_frwr_state(ibmr, FRMR_IS_INUSE, FRMR_IS_FREE);
+		frmr->fr_inv = false;
+		wake_up(&frmr->fr_inv_done);
+	}
+
+	if (frmr->fr_reg) {
+		frmr->fr_reg = false;
+		wake_up(&frmr->fr_reg_done);
+	}
+
+	/* enforce order of frmr->{fr_reg,fr_inv} update
+	 * before incrementing i_fastreg_wrs
+	 */
+	smp_mb__before_atomic();
+	atomic_inc(&ic->i_fastreg_wrs);
+}
+
+void rds_ib_unreg_frmr(struct list_head *list, unsigned int *nfreed,
+		       unsigned long *unpinned, unsigned int goal)
+{
+	struct rds_ib_mr *ibmr, *next;
+	struct rds_ib_frmr *frmr;
+	int ret = 0, ret2;
+	unsigned int freed = *nfreed;
+
+	/* String all ib_mr's onto one list and hand them to ib_unmap_fmr */
+	list_for_each_entry(ibmr, list, unmap_list) {
+		if (ibmr->sg_dma_len) {
+			ret2 = rds_ib_post_inv(ibmr);
+			if (ret2 && !ret)
+				ret = ret2;
+		}
+	}
+
+	if (ret)
+		pr_warn("RDS/IB: %s failed (err=%d)\n", __func__, ret);
+
+	/* Now we can destroy the DMA mapping and unpin any pages */
+	list_for_each_entry_safe(ibmr, next, list, unmap_list) {
+		*unpinned += ibmr->sg_len;
+		frmr = &ibmr->u.frmr;
+		__rds_ib_teardown_mr(ibmr);
+		if (freed < goal || frmr->fr_state == FRMR_IS_STALE) {
+			/* Don't de-allocate if the MR is not free yet */
+			if (frmr->fr_state == FRMR_IS_INUSE)
+				continue;
+
+			if (ibmr->pool->pool_type == RDS_IB_MR_8K_POOL)
+				rds_ib_stats_inc(s_ib_rdma_mr_8k_free);
+			else
+				rds_ib_stats_inc(s_ib_rdma_mr_1m_free);
+			list_del(&ibmr->unmap_list);
+			if (frmr->mr)
+				ib_dereg_mr(frmr->mr);
+			kfree(ibmr);
+			freed++;
+		}
+	}
+	*nfreed = freed;
+}
+
+struct rds_ib_mr *rds_ib_reg_frmr(struct rds_ib_device *rds_ibdev,
+				  struct rds_ib_connection *ic,
+				  struct scatterlist *sg,
+				  unsigned long nents, u32 *key)
+{
+	struct rds_ib_mr *ibmr = NULL;
+	struct rds_ib_frmr *frmr;
+	int ret;
+
+	if (!ic) {
+		/* TODO: Add FRWR support for RDS_GET_MR using proxy qp*/
+		return ERR_PTR(-EOPNOTSUPP);
+	}
+
+	do {
+		if (ibmr)
+			rds_ib_free_frmr(ibmr, true);
+		ibmr = rds_ib_alloc_frmr(rds_ibdev, nents);
+		if (IS_ERR(ibmr))
+			return ibmr;
+		frmr = &ibmr->u.frmr;
+	} while (frmr->fr_state != FRMR_IS_FREE);
+
+	ibmr->ic = ic;
+	ibmr->device = rds_ibdev;
+	ret = rds_ib_map_frmr(rds_ibdev, ibmr->pool, ibmr, sg, nents);
+	if (ret == 0) {
+		*key = frmr->mr->rkey;
+	} else {
+		rds_ib_free_frmr(ibmr, false);
+		ibmr = ERR_PTR(ret);
+	}
+
+	return ibmr;
+}
+
+void rds_ib_free_frmr_list(struct rds_ib_mr *ibmr)
+{
+	struct rds_ib_mr_pool *pool = ibmr->pool;
+	struct rds_ib_frmr *frmr = &ibmr->u.frmr;
+
+	if (frmr->fr_state == FRMR_IS_STALE)
+		llist_add(&ibmr->llnode, &pool->drop_list);
+	else
+		llist_add(&ibmr->llnode, &pool->free_list);
+}
diff --git a/net/rds/ib_mr.h b/net/rds/ib_mr.h
new file mode 100644
index 000000000..5884de8c6
--- /dev/null
+++ b/net/rds/ib_mr.h
@@ -0,0 +1,142 @@
+/*
+ * Copyright (c) 2016 Oracle.  All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+#ifndef _RDS_IB_MR_H
+#define _RDS_IB_MR_H
+
+#include <linux/kernel.h>
+
+#include "rds.h"
+#include "ib.h"
+
+#define RDS_MR_1M_POOL_SIZE		(8192 / 2)
+#define RDS_MR_1M_MSG_SIZE		256
+#define RDS_MR_8K_MSG_SIZE		2
+#define RDS_MR_8K_SCALE			(256 / (RDS_MR_8K_MSG_SIZE + 1))
+#define RDS_MR_8K_POOL_SIZE		(RDS_MR_8K_SCALE * (8192 / 2))
+
+enum rds_ib_fr_state {
+	FRMR_IS_FREE,	/* mr invalidated & ready for use */
+	FRMR_IS_INUSE,	/* mr is in use or used & can be invalidated */
+	FRMR_IS_STALE,	/* Stale MR and needs to be dropped  */
+};
+
+struct rds_ib_frmr {
+	struct ib_mr		*mr;
+	enum rds_ib_fr_state	fr_state;
+	bool			fr_inv;
+	wait_queue_head_t	fr_inv_done;
+	bool			fr_reg;
+	wait_queue_head_t	fr_reg_done;
+	struct ib_send_wr	fr_wr;
+	unsigned int		dma_npages;
+	unsigned int		sg_byte_len;
+};
+
+/* This is stored as mr->r_trans_private. */
+struct rds_ib_mr {
+	struct delayed_work		work;
+	struct rds_ib_device		*device;
+	struct rds_ib_mr_pool		*pool;
+	struct rds_ib_connection	*ic;
+
+	struct llist_node		llnode;
+
+	/* unmap_list is for freeing */
+	struct list_head		unmap_list;
+	unsigned int			remap_count;
+
+	struct scatterlist		*sg;
+	unsigned int			sg_len;
+	int				sg_dma_len;
+
+	u8				odp:1;
+	union {
+		struct rds_ib_frmr	frmr;
+		struct ib_mr		*mr;
+	} u;
+};
+
+/* Our own little MR pool */
+struct rds_ib_mr_pool {
+	unsigned int            pool_type;
+	struct mutex		flush_lock;	/* serialize fmr invalidate */
+	struct delayed_work	flush_worker;	/* flush worker */
+
+	atomic_t		item_count;	/* total # of MRs */
+	atomic_t		dirty_count;	/* # dirty of MRs */
+
+	struct llist_head	drop_list;	/* MRs not reached max_maps */
+	struct llist_head	free_list;	/* unused MRs */
+	struct llist_head	clean_list;	/* unused & unmapped MRs */
+	wait_queue_head_t	flush_wait;
+	spinlock_t		clean_lock;	/* "clean_list" concurrency */
+
+	atomic_t		free_pinned;	/* memory pinned by free MRs */
+	unsigned long		max_items;
+	unsigned long		max_items_soft;
+	unsigned long		max_free_pinned;
+	unsigned int		max_pages;
+};
+
+extern struct workqueue_struct *rds_ib_mr_wq;
+
+struct rds_ib_mr_pool *rds_ib_create_mr_pool(struct rds_ib_device *rds_dev,
+					     int npages);
+void rds_ib_get_mr_info(struct rds_ib_device *rds_ibdev,
+			struct rds_info_rdma_connection *iinfo);
+void rds6_ib_get_mr_info(struct rds_ib_device *rds_ibdev,
+			 struct rds6_info_rdma_connection *iinfo6);
+void rds_ib_destroy_mr_pool(struct rds_ib_mr_pool *);
+void *rds_ib_get_mr(struct scatterlist *sg, unsigned long nents,
+		    struct rds_sock *rs, u32 *key_ret,
+		    struct rds_connection *conn, u64 start, u64 length,
+		    int need_odp);
+void rds_ib_sync_mr(void *trans_private, int dir);
+void rds_ib_free_mr(void *trans_private, int invalidate);
+void rds_ib_flush_mrs(void);
+int rds_ib_mr_init(void);
+void rds_ib_mr_exit(void);
+u32 rds_ib_get_lkey(void *trans_private);
+
+void __rds_ib_teardown_mr(struct rds_ib_mr *);
+void rds_ib_teardown_mr(struct rds_ib_mr *);
+struct rds_ib_mr *rds_ib_reuse_mr(struct rds_ib_mr_pool *);
+int rds_ib_flush_mr_pool(struct rds_ib_mr_pool *, int, struct rds_ib_mr **);
+struct rds_ib_mr *rds_ib_try_reuse_ibmr(struct rds_ib_mr_pool *);
+struct rds_ib_mr *rds_ib_reg_frmr(struct rds_ib_device *rds_ibdev,
+				  struct rds_ib_connection *ic,
+				  struct scatterlist *sg,
+				  unsigned long nents, u32 *key);
+void rds_ib_unreg_frmr(struct list_head *list, unsigned int *nfreed,
+		       unsigned long *unpinned, unsigned int goal);
+void rds_ib_free_frmr_list(struct rds_ib_mr *);
+#endif
diff --git a/net/rds/ib_rdma.c b/net/rds/ib_rdma.c
new file mode 100644
index 000000000..db7e92e7b
--- /dev/null
+++ b/net/rds/ib_rdma.c
@@ -0,0 +1,701 @@
+/*
+ * Copyright (c) 2006, 2018 Oracle and/or its affiliates. All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/rculist.h>
+#include <linux/llist.h>
+
+#include "rds_single_path.h"
+#include "ib_mr.h"
+#include "rds.h"
+
+struct workqueue_struct *rds_ib_mr_wq;
+
+static void rds_ib_odp_mr_worker(struct work_struct *work);
+
+struct rds_ib_device *rds_ib_get_device(__be32 ipaddr)
+{
+	struct rds_ib_device *rds_ibdev;
+	struct rds_ib_ipaddr *i_ipaddr;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(rds_ibdev, &rds_ib_devices, list) {
+		list_for_each_entry_rcu(i_ipaddr, &rds_ibdev->ipaddr_list, list) {
+			if (i_ipaddr->ipaddr == ipaddr) {
+				refcount_inc(&rds_ibdev->refcount);
+				rcu_read_unlock();
+				return rds_ibdev;
+			}
+		}
+	}
+	rcu_read_unlock();
+
+	return NULL;
+}
+
+static int rds_ib_add_ipaddr(struct rds_ib_device *rds_ibdev, __be32 ipaddr)
+{
+	struct rds_ib_ipaddr *i_ipaddr;
+
+	i_ipaddr = kmalloc_obj(*i_ipaddr);
+	if (!i_ipaddr)
+		return -ENOMEM;
+
+	i_ipaddr->ipaddr = ipaddr;
+
+	spin_lock_irq(&rds_ibdev->spinlock);
+	list_add_tail_rcu(&i_ipaddr->list, &rds_ibdev->ipaddr_list);
+	spin_unlock_irq(&rds_ibdev->spinlock);
+
+	return 0;
+}
+
+static void rds_ib_remove_ipaddr(struct rds_ib_device *rds_ibdev, __be32 ipaddr)
+{
+	struct rds_ib_ipaddr *i_ipaddr;
+	struct rds_ib_ipaddr *to_free = NULL;
+
+
+	spin_lock_irq(&rds_ibdev->spinlock);
+	list_for_each_entry_rcu(i_ipaddr, &rds_ibdev->ipaddr_list, list) {
+		if (i_ipaddr->ipaddr == ipaddr) {
+			list_del_rcu(&i_ipaddr->list);
+			to_free = i_ipaddr;
+			break;
+		}
+	}
+	spin_unlock_irq(&rds_ibdev->spinlock);
+
+	if (to_free)
+		kfree_rcu(to_free, rcu);
+}
+
+int rds_ib_update_ipaddr(struct rds_ib_device *rds_ibdev,
+			 struct in6_addr *ipaddr)
+{
+	struct rds_ib_device *rds_ibdev_old;
+
+	rds_ibdev_old = rds_ib_get_device(ipaddr->s6_addr32[3]);
+	if (!rds_ibdev_old)
+		return rds_ib_add_ipaddr(rds_ibdev, ipaddr->s6_addr32[3]);
+
+	if (rds_ibdev_old != rds_ibdev) {
+		rds_ib_remove_ipaddr(rds_ibdev_old, ipaddr->s6_addr32[3]);
+		rds_ib_dev_put(rds_ibdev_old);
+		return rds_ib_add_ipaddr(rds_ibdev, ipaddr->s6_addr32[3]);
+	}
+	rds_ib_dev_put(rds_ibdev_old);
+
+	return 0;
+}
+
+void rds_ib_add_conn(struct rds_ib_device *rds_ibdev, struct rds_connection *conn)
+{
+	struct rds_ib_connection *ic = conn->c_transport_data;
+
+	/* conn was previously on the nodev_conns_list */
+	spin_lock_irq(&ib_nodev_conns_lock);
+	BUG_ON(list_empty(&ib_nodev_conns));
+	BUG_ON(list_empty(&ic->ib_node));
+	list_del(&ic->ib_node);
+
+	spin_lock(&rds_ibdev->spinlock);
+	list_add_tail(&ic->ib_node, &rds_ibdev->conn_list);
+	spin_unlock(&rds_ibdev->spinlock);
+	spin_unlock_irq(&ib_nodev_conns_lock);
+
+	ic->rds_ibdev = rds_ibdev;
+	refcount_inc(&rds_ibdev->refcount);
+}
+
+void rds_ib_remove_conn(struct rds_ib_device *rds_ibdev, struct rds_connection *conn)
+{
+	struct rds_ib_connection *ic = conn->c_transport_data;
+
+	/* place conn on nodev_conns_list */
+	spin_lock(&ib_nodev_conns_lock);
+
+	spin_lock_irq(&rds_ibdev->spinlock);
+	BUG_ON(list_empty(&ic->ib_node));
+	list_del(&ic->ib_node);
+	spin_unlock_irq(&rds_ibdev->spinlock);
+
+	list_add_tail(&ic->ib_node, &ib_nodev_conns);
+
+	spin_unlock(&ib_nodev_conns_lock);
+
+	ic->rds_ibdev = NULL;
+	rds_ib_dev_put(rds_ibdev);
+}
+
+void rds_ib_destroy_nodev_conns(void)
+{
+	struct rds_ib_connection *ic, *_ic;
+	LIST_HEAD(tmp_list);
+
+	/* avoid calling conn_destroy with irqs off */
+	spin_lock_irq(&ib_nodev_conns_lock);
+	list_splice(&ib_nodev_conns, &tmp_list);
+	spin_unlock_irq(&ib_nodev_conns_lock);
+
+	list_for_each_entry_safe(ic, _ic, &tmp_list, ib_node)
+		rds_conn_destroy(ic->conn);
+}
+
+void rds_ib_get_mr_info(struct rds_ib_device *rds_ibdev, struct rds_info_rdma_connection *iinfo)
+{
+	struct rds_ib_mr_pool *pool_1m = rds_ibdev->mr_1m_pool;
+
+	iinfo->rdma_mr_max = pool_1m->max_items;
+	iinfo->rdma_mr_size = pool_1m->max_pages;
+}
+
+#if IS_ENABLED(CONFIG_IPV6)
+void rds6_ib_get_mr_info(struct rds_ib_device *rds_ibdev,
+			 struct rds6_info_rdma_connection *iinfo6)
+{
+	struct rds_ib_mr_pool *pool_1m = rds_ibdev->mr_1m_pool;
+
+	iinfo6->rdma_mr_max = pool_1m->max_items;
+	iinfo6->rdma_mr_size = pool_1m->max_pages;
+}
+#endif
+
+struct rds_ib_mr *rds_ib_reuse_mr(struct rds_ib_mr_pool *pool)
+{
+	struct rds_ib_mr *ibmr = NULL;
+	struct llist_node *ret;
+	unsigned long flags;
+
+	spin_lock_irqsave(&pool->clean_lock, flags);
+	ret = llist_del_first(&pool->clean_list);
+	spin_unlock_irqrestore(&pool->clean_lock, flags);
+	if (ret) {
+		ibmr = llist_entry(ret, struct rds_ib_mr, llnode);
+		if (pool->pool_type == RDS_IB_MR_8K_POOL)
+			rds_ib_stats_inc(s_ib_rdma_mr_8k_reused);
+		else
+			rds_ib_stats_inc(s_ib_rdma_mr_1m_reused);
+	}
+
+	return ibmr;
+}
+
+void rds_ib_sync_mr(void *trans_private, int direction)
+{
+	struct rds_ib_mr *ibmr = trans_private;
+	struct rds_ib_device *rds_ibdev = ibmr->device;
+
+	if (ibmr->odp)
+		return;
+
+	switch (direction) {
+	case DMA_FROM_DEVICE:
+		ib_dma_sync_sg_for_cpu(rds_ibdev->dev, ibmr->sg,
+			ibmr->sg_dma_len, DMA_BIDIRECTIONAL);
+		break;
+	case DMA_TO_DEVICE:
+		ib_dma_sync_sg_for_device(rds_ibdev->dev, ibmr->sg,
+			ibmr->sg_dma_len, DMA_BIDIRECTIONAL);
+		break;
+	}
+}
+
+void __rds_ib_teardown_mr(struct rds_ib_mr *ibmr)
+{
+	struct rds_ib_device *rds_ibdev = ibmr->device;
+
+	if (ibmr->sg_dma_len) {
+		ib_dma_unmap_sg(rds_ibdev->dev,
+				ibmr->sg, ibmr->sg_len,
+				DMA_BIDIRECTIONAL);
+		ibmr->sg_dma_len = 0;
+	}
+
+	/* Release the s/g list */
+	if (ibmr->sg_len) {
+		unsigned int i;
+
+		for (i = 0; i < ibmr->sg_len; ++i) {
+			struct page *page = sg_page(&ibmr->sg[i]);
+
+			/* FIXME we need a way to tell a r/w MR
+			 * from a r/o MR */
+			unpin_user_pages_dirty_lock(&page, 1, true);
+		}
+		kfree(ibmr->sg);
+
+		ibmr->sg = NULL;
+		ibmr->sg_len = 0;
+	}
+}
+
+void rds_ib_teardown_mr(struct rds_ib_mr *ibmr)
+{
+	unsigned int pinned = ibmr->sg_len;
+
+	__rds_ib_teardown_mr(ibmr);
+	if (pinned) {
+		struct rds_ib_mr_pool *pool = ibmr->pool;
+
+		atomic_sub(pinned, &pool->free_pinned);
+	}
+}
+
+static inline unsigned int rds_ib_flush_goal(struct rds_ib_mr_pool *pool, int free_all)
+{
+	unsigned int item_count;
+
+	item_count = atomic_read(&pool->item_count);
+	if (free_all)
+		return item_count;
+
+	return 0;
+}
+
+/*
+ * given an llist of mrs, put them all into the list_head for more processing
+ */
+static unsigned int llist_append_to_list(struct llist_head *llist,
+					 struct list_head *list)
+{
+	struct rds_ib_mr *ibmr;
+	struct llist_node *node;
+	struct llist_node *next;
+	unsigned int count = 0;
+
+	node = llist_del_all(llist);
+	while (node) {
+		next = node->next;
+		ibmr = llist_entry(node, struct rds_ib_mr, llnode);
+		list_add_tail(&ibmr->unmap_list, list);
+		node = next;
+		count++;
+	}
+	return count;
+}
+
+/*
+ * this takes a list head of mrs and turns it into linked llist nodes
+ * of clusters.  Each cluster has linked llist nodes of
+ * MR_CLUSTER_SIZE mrs that are ready for reuse.
+ */
+static void list_to_llist_nodes(struct list_head *list,
+				struct llist_node **nodes_head,
+				struct llist_node **nodes_tail)
+{
+	struct rds_ib_mr *ibmr;
+	struct llist_node *cur = NULL;
+	struct llist_node **next = nodes_head;
+
+	list_for_each_entry(ibmr, list, unmap_list) {
+		cur = &ibmr->llnode;
+		*next = cur;
+		next = &cur->next;
+	}
+	*next = NULL;
+	*nodes_tail = cur;
+}
+
+/*
+ * Flush our pool of MRs.
+ * At a minimum, all currently unused MRs are unmapped.
+ * If the number of MRs allocated exceeds the limit, we also try
+ * to free as many MRs as needed to get back to this limit.
+ */
+int rds_ib_flush_mr_pool(struct rds_ib_mr_pool *pool,
+			 int free_all, struct rds_ib_mr **ibmr_ret)
+{
+	struct rds_ib_mr *ibmr;
+	struct llist_node *clean_nodes;
+	struct llist_node *clean_tail;
+	LIST_HEAD(unmap_list);
+	unsigned long unpinned = 0;
+	unsigned int nfreed = 0, dirty_to_clean = 0, free_goal;
+
+	if (pool->pool_type == RDS_IB_MR_8K_POOL)
+		rds_ib_stats_inc(s_ib_rdma_mr_8k_pool_flush);
+	else
+		rds_ib_stats_inc(s_ib_rdma_mr_1m_pool_flush);
+
+	if (ibmr_ret) {
+		DEFINE_WAIT(wait);
+		while (!mutex_trylock(&pool->flush_lock)) {
+			ibmr = rds_ib_reuse_mr(pool);
+			if (ibmr) {
+				*ibmr_ret = ibmr;
+				finish_wait(&pool->flush_wait, &wait);
+				goto out_nolock;
+			}
+
+			prepare_to_wait(&pool->flush_wait, &wait,
+					TASK_UNINTERRUPTIBLE);
+			if (llist_empty(&pool->clean_list))
+				schedule();
+
+			ibmr = rds_ib_reuse_mr(pool);
+			if (ibmr) {
+				*ibmr_ret = ibmr;
+				finish_wait(&pool->flush_wait, &wait);
+				goto out_nolock;
+			}
+		}
+		finish_wait(&pool->flush_wait, &wait);
+	} else
+		mutex_lock(&pool->flush_lock);
+
+	if (ibmr_ret) {
+		ibmr = rds_ib_reuse_mr(pool);
+		if (ibmr) {
+			*ibmr_ret = ibmr;
+			goto out;
+		}
+	}
+
+	/* Get the list of all MRs to be dropped. Ordering matters -
+	 * we want to put drop_list ahead of free_list.
+	 */
+	dirty_to_clean = llist_append_to_list(&pool->drop_list, &unmap_list);
+	dirty_to_clean += llist_append_to_list(&pool->free_list, &unmap_list);
+	if (free_all) {
+		unsigned long flags;
+
+		spin_lock_irqsave(&pool->clean_lock, flags);
+		llist_append_to_list(&pool->clean_list, &unmap_list);
+		spin_unlock_irqrestore(&pool->clean_lock, flags);
+	}
+
+	free_goal = rds_ib_flush_goal(pool, free_all);
+
+	if (list_empty(&unmap_list))
+		goto out;
+
+	rds_ib_unreg_frmr(&unmap_list, &nfreed, &unpinned, free_goal);
+
+	if (!list_empty(&unmap_list)) {
+		unsigned long flags;
+
+		list_to_llist_nodes(&unmap_list, &clean_nodes, &clean_tail);
+		if (ibmr_ret) {
+			*ibmr_ret = llist_entry(clean_nodes, struct rds_ib_mr, llnode);
+			clean_nodes = clean_nodes->next;
+		}
+		/* more than one entry in llist nodes */
+		if (clean_nodes) {
+			spin_lock_irqsave(&pool->clean_lock, flags);
+			llist_add_batch(clean_nodes, clean_tail,
+					&pool->clean_list);
+			spin_unlock_irqrestore(&pool->clean_lock, flags);
+		}
+	}
+
+	atomic_sub(unpinned, &pool->free_pinned);
+	atomic_sub(dirty_to_clean, &pool->dirty_count);
+	atomic_sub(nfreed, &pool->item_count);
+
+out:
+	mutex_unlock(&pool->flush_lock);
+	if (waitqueue_active(&pool->flush_wait))
+		wake_up(&pool->flush_wait);
+out_nolock:
+	return 0;
+}
+
+struct rds_ib_mr *rds_ib_try_reuse_ibmr(struct rds_ib_mr_pool *pool)
+{
+	struct rds_ib_mr *ibmr = NULL;
+	int iter = 0;
+
+	while (1) {
+		ibmr = rds_ib_reuse_mr(pool);
+		if (ibmr)
+			return ibmr;
+
+		if (atomic_inc_return(&pool->item_count) <= pool->max_items)
+			break;
+
+		atomic_dec(&pool->item_count);
+
+		if (++iter > 2) {
+			if (pool->pool_type == RDS_IB_MR_8K_POOL)
+				rds_ib_stats_inc(s_ib_rdma_mr_8k_pool_depleted);
+			else
+				rds_ib_stats_inc(s_ib_rdma_mr_1m_pool_depleted);
+			break;
+		}
+
+		/* We do have some empty MRs. Flush them out. */
+		if (pool->pool_type == RDS_IB_MR_8K_POOL)
+			rds_ib_stats_inc(s_ib_rdma_mr_8k_pool_wait);
+		else
+			rds_ib_stats_inc(s_ib_rdma_mr_1m_pool_wait);
+
+		rds_ib_flush_mr_pool(pool, 0, &ibmr);
+		if (ibmr)
+			return ibmr;
+	}
+
+	return NULL;
+}
+
+static void rds_ib_mr_pool_flush_worker(struct work_struct *work)
+{
+	struct rds_ib_mr_pool *pool = container_of(work, struct rds_ib_mr_pool, flush_worker.work);
+
+	rds_ib_flush_mr_pool(pool, 0, NULL);
+}
+
+void rds_ib_free_mr(void *trans_private, int invalidate)
+{
+	struct rds_ib_mr *ibmr = trans_private;
+	struct rds_ib_mr_pool *pool = ibmr->pool;
+	struct rds_ib_device *rds_ibdev = ibmr->device;
+
+	rdsdebug("RDS/IB: free_mr nents %u\n", ibmr->sg_len);
+
+	if (ibmr->odp) {
+		/* A MR created and marked as use_once. We use delayed work,
+		 * because there is a change that we are in interrupt and can't
+		 * call to ib_dereg_mr() directly.
+		 */
+		INIT_DELAYED_WORK(&ibmr->work, rds_ib_odp_mr_worker);
+		queue_delayed_work(rds_ib_mr_wq, &ibmr->work, 0);
+		return;
+	}
+
+	/* Return it to the pool's free list */
+	rds_ib_free_frmr_list(ibmr);
+
+	atomic_add(ibmr->sg_len, &pool->free_pinned);
+	atomic_inc(&pool->dirty_count);
+
+	/* If we've pinned too many pages, request a flush */
+	if (atomic_read(&pool->free_pinned) >= pool->max_free_pinned ||
+	    atomic_read(&pool->dirty_count) >= pool->max_items / 5)
+		queue_delayed_work(rds_ib_mr_wq, &pool->flush_worker, 10);
+
+	if (invalidate) {
+		if (likely(!in_interrupt())) {
+			rds_ib_flush_mr_pool(pool, 0, NULL);
+		} else {
+			/* We get here if the user created a MR marked
+			 * as use_once and invalidate at the same time.
+			 */
+			queue_delayed_work(rds_ib_mr_wq,
+					   &pool->flush_worker, 10);
+		}
+	}
+
+	rds_ib_dev_put(rds_ibdev);
+}
+
+void rds_ib_flush_mrs(void)
+{
+	struct rds_ib_device *rds_ibdev;
+
+	down_read(&rds_ib_devices_lock);
+	list_for_each_entry(rds_ibdev, &rds_ib_devices, list) {
+		if (rds_ibdev->mr_8k_pool)
+			rds_ib_flush_mr_pool(rds_ibdev->mr_8k_pool, 0, NULL);
+
+		if (rds_ibdev->mr_1m_pool)
+			rds_ib_flush_mr_pool(rds_ibdev->mr_1m_pool, 0, NULL);
+	}
+	up_read(&rds_ib_devices_lock);
+}
+
+u32 rds_ib_get_lkey(void *trans_private)
+{
+	struct rds_ib_mr *ibmr = trans_private;
+
+	return ibmr->u.mr->lkey;
+}
+
+void *rds_ib_get_mr(struct scatterlist *sg, unsigned long nents,
+		    struct rds_sock *rs, u32 *key_ret,
+		    struct rds_connection *conn,
+		    u64 start, u64 length, int need_odp)
+{
+	struct rds_ib_device *rds_ibdev;
+	struct rds_ib_mr *ibmr = NULL;
+	struct rds_ib_connection *ic = NULL;
+	int ret;
+
+	rds_ibdev = rds_ib_get_device(rs->rs_bound_addr.s6_addr32[3]);
+	if (!rds_ibdev) {
+		ret = -ENODEV;
+		goto out;
+	}
+
+	if (need_odp == ODP_ZEROBASED || need_odp == ODP_VIRTUAL) {
+		u64 virt_addr = need_odp == ODP_ZEROBASED ? 0 : start;
+		int access_flags =
+			(IB_ACCESS_LOCAL_WRITE | IB_ACCESS_REMOTE_READ |
+			 IB_ACCESS_REMOTE_WRITE | IB_ACCESS_REMOTE_ATOMIC |
+			 IB_ACCESS_ON_DEMAND);
+		struct ib_sge sge = {};
+		struct ib_mr *ib_mr;
+
+		if (!rds_ibdev->odp_capable) {
+			ret = -EOPNOTSUPP;
+			goto out;
+		}
+
+		ib_mr = ib_reg_user_mr(rds_ibdev->pd, start, length, virt_addr,
+				       access_flags);
+
+		if (IS_ERR(ib_mr)) {
+			rdsdebug("rds_ib_get_user_mr returned %d\n",
+				 IS_ERR(ib_mr));
+			ret = PTR_ERR(ib_mr);
+			goto out;
+		}
+		if (key_ret)
+			*key_ret = ib_mr->rkey;
+
+		ibmr = kzalloc_obj(*ibmr);
+		if (!ibmr) {
+			ib_dereg_mr(ib_mr);
+			ret = -ENOMEM;
+			goto out;
+		}
+		ibmr->u.mr = ib_mr;
+		ibmr->odp = 1;
+
+		sge.addr = virt_addr;
+		sge.length = length;
+		sge.lkey = ib_mr->lkey;
+
+		ib_advise_mr(rds_ibdev->pd,
+			     IB_UVERBS_ADVISE_MR_ADVICE_PREFETCH_WRITE,
+			     IB_UVERBS_ADVISE_MR_FLAG_FLUSH, &sge, 1);
+		return ibmr;
+	}
+
+	if (conn) {
+		ic = conn->c_transport_data;
+		if (!ic || !ic->i_cm_id || !ic->i_cm_id->qp) {
+			ret = -ENODEV;
+			goto out;
+		}
+	}
+
+	if (!rds_ibdev->mr_8k_pool || !rds_ibdev->mr_1m_pool) {
+		ret = -ENODEV;
+		goto out;
+	}
+
+	ibmr = rds_ib_reg_frmr(rds_ibdev, ic, sg, nents, key_ret);
+	if (IS_ERR(ibmr)) {
+		ret = PTR_ERR(ibmr);
+		pr_warn("RDS/IB: rds_ib_get_mr failed (errno=%d)\n", ret);
+	} else {
+		return ibmr;
+	}
+
+ out:
+	if (rds_ibdev)
+		rds_ib_dev_put(rds_ibdev);
+
+	return ERR_PTR(ret);
+}
+
+void rds_ib_destroy_mr_pool(struct rds_ib_mr_pool *pool)
+{
+	cancel_delayed_work_sync(&pool->flush_worker);
+	rds_ib_flush_mr_pool(pool, 1, NULL);
+	WARN_ON(atomic_read(&pool->item_count));
+	WARN_ON(atomic_read(&pool->free_pinned));
+	kfree(pool);
+}
+
+struct rds_ib_mr_pool *rds_ib_create_mr_pool(struct rds_ib_device *rds_ibdev,
+					     int pool_type)
+{
+	struct rds_ib_mr_pool *pool;
+
+	pool = kzalloc_obj(*pool);
+	if (!pool)
+		return ERR_PTR(-ENOMEM);
+
+	pool->pool_type = pool_type;
+	init_llist_head(&pool->free_list);
+	init_llist_head(&pool->drop_list);
+	init_llist_head(&pool->clean_list);
+	spin_lock_init(&pool->clean_lock);
+	mutex_init(&pool->flush_lock);
+	init_waitqueue_head(&pool->flush_wait);
+	INIT_DELAYED_WORK(&pool->flush_worker, rds_ib_mr_pool_flush_worker);
+
+	if (pool_type == RDS_IB_MR_1M_POOL) {
+		/* +1 allows for unaligned MRs */
+		pool->max_pages = RDS_MR_1M_MSG_SIZE + 1;
+		pool->max_items = rds_ibdev->max_1m_mrs;
+	} else {
+		/* pool_type == RDS_IB_MR_8K_POOL */
+		pool->max_pages = RDS_MR_8K_MSG_SIZE + 1;
+		pool->max_items = rds_ibdev->max_8k_mrs;
+	}
+
+	pool->max_free_pinned = pool->max_items * pool->max_pages / 4;
+	pool->max_items_soft = rds_ibdev->max_mrs * 3 / 4;
+
+	return pool;
+}
+
+int rds_ib_mr_init(void)
+{
+	rds_ib_mr_wq = alloc_workqueue("rds_mr_flushd",
+				       WQ_MEM_RECLAIM | WQ_PERCPU, 0);
+	if (!rds_ib_mr_wq)
+		return -ENOMEM;
+	return 0;
+}
+
+/* By the time this is called all the IB devices should have been torn down and
+ * had their pools freed.  As each pool is freed its work struct is waited on,
+ * so the pool flushing work queue should be idle by the time we get here.
+ */
+void rds_ib_mr_exit(void)
+{
+	destroy_workqueue(rds_ib_mr_wq);
+}
+
+static void rds_ib_odp_mr_worker(struct work_struct  *work)
+{
+	struct rds_ib_mr *ibmr;
+
+	ibmr = container_of(work, struct rds_ib_mr, work.work);
+	ib_dereg_mr(ibmr->u.mr);
+	kfree(ibmr);
+}
diff --git a/net/rds/ib_recv.c b/net/rds/ib_recv.c
new file mode 100644
index 000000000..357128d34
--- /dev/null
+++ b/net/rds/ib_recv.c
@@ -0,0 +1,1095 @@
+/*
+ * Copyright (c) 2006, 2019 Oracle and/or its affiliates. All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+#include <linux/kernel.h>
+#include <linux/sched/clock.h>
+#include <linux/slab.h>
+#include <linux/pci.h>
+#include <linux/dma-mapping.h>
+#include <rdma/rdma_cm.h>
+
+#include "rds_single_path.h"
+#include "rds.h"
+#include "ib.h"
+
+static struct kmem_cache *rds_ib_incoming_slab;
+static struct kmem_cache *rds_ib_frag_slab;
+static atomic_t	rds_ib_allocation = ATOMIC_INIT(0);
+
+void rds_ib_recv_init_ring(struct rds_ib_connection *ic)
+{
+	struct rds_ib_recv_work *recv;
+	u32 i;
+
+	for (i = 0, recv = ic->i_recvs; i < ic->i_recv_ring.w_nr; i++, recv++) {
+		struct ib_sge *sge;
+
+		recv->r_ibinc = NULL;
+		recv->r_frag = NULL;
+
+		recv->r_wr.next = NULL;
+		recv->r_wr.wr_id = i;
+		recv->r_wr.sg_list = recv->r_sge;
+		recv->r_wr.num_sge = RDS_IB_RECV_SGE;
+
+		sge = &recv->r_sge[0];
+		sge->addr = ic->i_recv_hdrs_dma[i];
+		sge->length = sizeof(struct rds_header);
+		sge->lkey = ic->i_pd->local_dma_lkey;
+
+		sge = &recv->r_sge[1];
+		sge->addr = 0;
+		sge->length = RDS_FRAG_SIZE;
+		sge->lkey = ic->i_pd->local_dma_lkey;
+	}
+}
+
+/*
+ * The entire 'from' list, including the from element itself, is put on
+ * to the tail of the 'to' list.
+ */
+static void list_splice_entire_tail(struct list_head *from,
+				    struct list_head *to)
+{
+	struct list_head *from_last = from->prev;
+
+	list_splice_tail(from_last, to);
+	list_add_tail(from_last, to);
+}
+
+static void rds_ib_cache_xfer_to_ready(struct rds_ib_refill_cache *cache)
+{
+	struct list_head *tmp;
+
+	tmp = xchg(&cache->xfer, NULL);
+	if (tmp) {
+		if (cache->ready)
+			list_splice_entire_tail(tmp, cache->ready);
+		else
+			cache->ready = tmp;
+	}
+}
+
+static int rds_ib_recv_alloc_cache(struct rds_ib_refill_cache *cache, gfp_t gfp)
+{
+	struct rds_ib_cache_head *head;
+	int cpu;
+
+	cache->percpu = alloc_percpu_gfp(struct rds_ib_cache_head, gfp);
+	if (!cache->percpu)
+	       return -ENOMEM;
+
+	for_each_possible_cpu(cpu) {
+		head = per_cpu_ptr(cache->percpu, cpu);
+		head->first = NULL;
+		head->count = 0;
+	}
+	cache->xfer = NULL;
+	cache->ready = NULL;
+
+	return 0;
+}
+
+int rds_ib_recv_alloc_caches(struct rds_ib_connection *ic, gfp_t gfp)
+{
+	int ret;
+
+	ret = rds_ib_recv_alloc_cache(&ic->i_cache_incs, gfp);
+	if (!ret) {
+		ret = rds_ib_recv_alloc_cache(&ic->i_cache_frags, gfp);
+		if (ret)
+			free_percpu(ic->i_cache_incs.percpu);
+	}
+
+	return ret;
+}
+
+static void rds_ib_cache_splice_all_lists(struct rds_ib_refill_cache *cache,
+					  struct list_head *caller_list)
+{
+	struct rds_ib_cache_head *head;
+	int cpu;
+
+	for_each_possible_cpu(cpu) {
+		head = per_cpu_ptr(cache->percpu, cpu);
+		if (head->first) {
+			list_splice_entire_tail(head->first, caller_list);
+			head->first = NULL;
+		}
+	}
+
+	if (cache->ready) {
+		list_splice_entire_tail(cache->ready, caller_list);
+		cache->ready = NULL;
+	}
+}
+
+void rds_ib_recv_free_caches(struct rds_ib_connection *ic)
+{
+	struct rds_ib_incoming *inc;
+	struct rds_ib_incoming *inc_tmp;
+	struct rds_page_frag *frag;
+	struct rds_page_frag *frag_tmp;
+	LIST_HEAD(list);
+
+	rds_ib_cache_xfer_to_ready(&ic->i_cache_incs);
+	rds_ib_cache_splice_all_lists(&ic->i_cache_incs, &list);
+	free_percpu(ic->i_cache_incs.percpu);
+
+	list_for_each_entry_safe(inc, inc_tmp, &list, ii_cache_entry) {
+		list_del(&inc->ii_cache_entry);
+		WARN_ON(!list_empty(&inc->ii_frags));
+		kmem_cache_free(rds_ib_incoming_slab, inc);
+		atomic_dec(&rds_ib_allocation);
+	}
+
+	rds_ib_cache_xfer_to_ready(&ic->i_cache_frags);
+	rds_ib_cache_splice_all_lists(&ic->i_cache_frags, &list);
+	free_percpu(ic->i_cache_frags.percpu);
+
+	list_for_each_entry_safe(frag, frag_tmp, &list, f_cache_entry) {
+		list_del(&frag->f_cache_entry);
+		WARN_ON(!list_empty(&frag->f_item));
+		kmem_cache_free(rds_ib_frag_slab, frag);
+	}
+}
+
+/* fwd decl */
+static void rds_ib_recv_cache_put(struct list_head *new_item,
+				  struct rds_ib_refill_cache *cache);
+static struct list_head *rds_ib_recv_cache_get(struct rds_ib_refill_cache *cache);
+
+
+/* Recycle frag and attached recv buffer f_sg */
+static void rds_ib_frag_free(struct rds_ib_connection *ic,
+			     struct rds_page_frag *frag)
+{
+	rdsdebug("frag %p page %p\n", frag, sg_page(&frag->f_sg));
+
+	rds_ib_recv_cache_put(&frag->f_cache_entry, &ic->i_cache_frags);
+	atomic_add(RDS_FRAG_SIZE / SZ_1K, &ic->i_cache_allocs);
+	rds_ib_stats_add(s_ib_recv_added_to_cache, RDS_FRAG_SIZE);
+}
+
+/* Recycle inc after freeing attached frags */
+void rds_ib_inc_free(struct rds_incoming *inc)
+{
+	struct rds_ib_incoming *ibinc;
+	struct rds_page_frag *frag;
+	struct rds_page_frag *pos;
+	struct rds_ib_connection *ic = inc->i_conn->c_transport_data;
+
+	ibinc = container_of(inc, struct rds_ib_incoming, ii_inc);
+
+	/* Free attached frags */
+	list_for_each_entry_safe(frag, pos, &ibinc->ii_frags, f_item) {
+		list_del_init(&frag->f_item);
+		rds_ib_frag_free(ic, frag);
+	}
+	BUG_ON(!list_empty(&ibinc->ii_frags));
+
+	rdsdebug("freeing ibinc %p inc %p\n", ibinc, inc);
+	rds_ib_recv_cache_put(&ibinc->ii_cache_entry, &ic->i_cache_incs);
+}
+
+static void rds_ib_recv_clear_one(struct rds_ib_connection *ic,
+				  struct rds_ib_recv_work *recv)
+{
+	if (recv->r_ibinc) {
+		rds_inc_put(&recv->r_ibinc->ii_inc);
+		recv->r_ibinc = NULL;
+	}
+	if (recv->r_frag) {
+		ib_dma_unmap_sg(ic->i_cm_id->device, &recv->r_frag->f_sg, 1, DMA_FROM_DEVICE);
+		rds_ib_frag_free(ic, recv->r_frag);
+		recv->r_frag = NULL;
+	}
+}
+
+void rds_ib_recv_clear_ring(struct rds_ib_connection *ic)
+{
+	u32 i;
+
+	for (i = 0; i < ic->i_recv_ring.w_nr; i++)
+		rds_ib_recv_clear_one(ic, &ic->i_recvs[i]);
+}
+
+static struct rds_ib_incoming *rds_ib_refill_one_inc(struct rds_ib_connection *ic,
+						     gfp_t slab_mask)
+{
+	struct rds_ib_incoming *ibinc;
+	struct list_head *cache_item;
+	int avail_allocs;
+
+	cache_item = rds_ib_recv_cache_get(&ic->i_cache_incs);
+	if (cache_item) {
+		ibinc = container_of(cache_item, struct rds_ib_incoming, ii_cache_entry);
+	} else {
+		avail_allocs = atomic_add_unless(&rds_ib_allocation,
+						 1, rds_ib_sysctl_max_recv_allocation);
+		if (!avail_allocs) {
+			rds_ib_stats_inc(s_ib_rx_alloc_limit);
+			return NULL;
+		}
+		ibinc = kmem_cache_alloc(rds_ib_incoming_slab, slab_mask);
+		if (!ibinc) {
+			atomic_dec(&rds_ib_allocation);
+			return NULL;
+		}
+		rds_ib_stats_inc(s_ib_rx_total_incs);
+	}
+	INIT_LIST_HEAD(&ibinc->ii_frags);
+	rds_inc_init(&ibinc->ii_inc, ic->conn, &ic->conn->c_faddr);
+
+	return ibinc;
+}
+
+static struct rds_page_frag *rds_ib_refill_one_frag(struct rds_ib_connection *ic,
+						    gfp_t slab_mask, gfp_t page_mask)
+{
+	struct rds_page_frag *frag;
+	struct list_head *cache_item;
+	int ret;
+
+	cache_item = rds_ib_recv_cache_get(&ic->i_cache_frags);
+	if (cache_item) {
+		frag = container_of(cache_item, struct rds_page_frag, f_cache_entry);
+		atomic_sub(RDS_FRAG_SIZE / SZ_1K, &ic->i_cache_allocs);
+		rds_ib_stats_add(s_ib_recv_added_to_cache, RDS_FRAG_SIZE);
+	} else {
+		frag = kmem_cache_alloc(rds_ib_frag_slab, slab_mask);
+		if (!frag)
+			return NULL;
+
+		sg_init_table(&frag->f_sg, 1);
+		ret = rds_page_remainder_alloc(&frag->f_sg,
+					       RDS_FRAG_SIZE, page_mask);
+		if (ret) {
+			kmem_cache_free(rds_ib_frag_slab, frag);
+			return NULL;
+		}
+		rds_ib_stats_inc(s_ib_rx_total_frags);
+	}
+
+	INIT_LIST_HEAD(&frag->f_item);
+
+	return frag;
+}
+
+static int rds_ib_recv_refill_one(struct rds_connection *conn,
+				  struct rds_ib_recv_work *recv, gfp_t gfp)
+{
+	struct rds_ib_connection *ic = conn->c_transport_data;
+	struct ib_sge *sge;
+	int ret = -ENOMEM;
+	gfp_t slab_mask = gfp;
+	gfp_t page_mask = gfp;
+
+	if (gfp & __GFP_DIRECT_RECLAIM) {
+		slab_mask = GFP_KERNEL;
+		page_mask = GFP_HIGHUSER;
+	}
+
+	if (!ic->i_cache_incs.ready)
+		rds_ib_cache_xfer_to_ready(&ic->i_cache_incs);
+	if (!ic->i_cache_frags.ready)
+		rds_ib_cache_xfer_to_ready(&ic->i_cache_frags);
+
+	/*
+	 * ibinc was taken from recv if recv contained the start of a message.
+	 * recvs that were continuations will still have this allocated.
+	 */
+	if (!recv->r_ibinc) {
+		recv->r_ibinc = rds_ib_refill_one_inc(ic, slab_mask);
+		if (!recv->r_ibinc)
+			goto out;
+	}
+
+	WARN_ON(recv->r_frag); /* leak! */
+	recv->r_frag = rds_ib_refill_one_frag(ic, slab_mask, page_mask);
+	if (!recv->r_frag)
+		goto out;
+
+	ret = ib_dma_map_sg(ic->i_cm_id->device, &recv->r_frag->f_sg,
+			    1, DMA_FROM_DEVICE);
+	WARN_ON(ret != 1);
+
+	sge = &recv->r_sge[0];
+	sge->addr = ic->i_recv_hdrs_dma[recv - ic->i_recvs];
+	sge->length = sizeof(struct rds_header);
+
+	sge = &recv->r_sge[1];
+	sge->addr = sg_dma_address(&recv->r_frag->f_sg);
+	sge->length = sg_dma_len(&recv->r_frag->f_sg);
+
+	ret = 0;
+out:
+	return ret;
+}
+
+static int acquire_refill(struct rds_connection *conn)
+{
+	return test_and_set_bit(RDS_RECV_REFILL, &conn->c_flags) == 0;
+}
+
+static void release_refill(struct rds_connection *conn)
+{
+	clear_bit(RDS_RECV_REFILL, &conn->c_flags);
+	smp_mb__after_atomic();
+
+	/* We don't use wait_on_bit()/wake_up_bit() because our waking is in a
+	 * hot path and finding waiters is very rare.  We don't want to walk
+	 * the system-wide hashed waitqueue buckets in the fast path only to
+	 * almost never find waiters.
+	 */
+	if (waitqueue_active(&conn->c_waitq))
+		wake_up_all(&conn->c_waitq);
+}
+
+/*
+ * This tries to allocate and post unused work requests after making sure that
+ * they have all the allocations they need to queue received fragments into
+ * sockets.
+ */
+void rds_ib_recv_refill(struct rds_connection *conn, int prefill, gfp_t gfp)
+{
+	struct rds_ib_connection *ic = conn->c_transport_data;
+	struct rds_ib_recv_work *recv;
+	unsigned int posted = 0;
+	int ret = 0;
+	bool can_wait = !!(gfp & __GFP_DIRECT_RECLAIM);
+	bool must_wake = false;
+	u32 pos;
+
+	/* the goal here is to just make sure that someone, somewhere
+	 * is posting buffers.  If we can't get the refill lock,
+	 * let them do their thing
+	 */
+	if (!acquire_refill(conn))
+		return;
+
+	while ((prefill || rds_conn_up(conn)) &&
+	       rds_ib_ring_alloc(&ic->i_recv_ring, 1, &pos)) {
+		if (pos >= ic->i_recv_ring.w_nr) {
+			printk(KERN_NOTICE "Argh - ring alloc returned pos=%u\n",
+					pos);
+			break;
+		}
+
+		recv = &ic->i_recvs[pos];
+		ret = rds_ib_recv_refill_one(conn, recv, gfp);
+		if (ret) {
+			must_wake = true;
+			break;
+		}
+
+		rdsdebug("recv %p ibinc %p page %p addr %lu\n", recv,
+			 recv->r_ibinc, sg_page(&recv->r_frag->f_sg),
+			 (long)sg_dma_address(&recv->r_frag->f_sg));
+
+		/* XXX when can this fail? */
+		ret = ib_post_recv(ic->i_cm_id->qp, &recv->r_wr, NULL);
+		if (ret) {
+			rds_ib_conn_error(conn, "recv post on "
+			       "%pI6c returned %d, disconnecting and "
+			       "reconnecting\n", &conn->c_faddr,
+			       ret);
+			break;
+		}
+
+		posted++;
+
+		if ((posted > 128 && need_resched()) || posted > 8192) {
+			must_wake = true;
+			break;
+		}
+	}
+
+	/* We're doing flow control - update the window. */
+	if (ic->i_flowctl && posted)
+		rds_ib_advertise_credits(conn, posted);
+
+	if (ret)
+		rds_ib_ring_unalloc(&ic->i_recv_ring, 1);
+
+	release_refill(conn);
+
+	/* if we're called from the softirq handler, we'll be GFP_NOWAIT.
+	 * in this case the ring being low is going to lead to more interrupts
+	 * and we can safely let the softirq code take care of it unless the
+	 * ring is completely empty.
+	 *
+	 * if we're called from krdsd, we'll be GFP_KERNEL.  In this case
+	 * we might have raced with the softirq code while we had the refill
+	 * lock held.  Use rds_ib_ring_low() instead of ring_empty to decide
+	 * if we should requeue.
+	 */
+	if (rds_conn_up(conn) &&
+	    (must_wake ||
+	    (can_wait && rds_ib_ring_low(&ic->i_recv_ring)) ||
+	    rds_ib_ring_empty(&ic->i_recv_ring))) {
+		queue_delayed_work(conn->c_path->cp_wq, &conn->c_recv_w, 1);
+	}
+	if (can_wait)
+		cond_resched();
+}
+
+/*
+ * We want to recycle several types of recv allocations, like incs and frags.
+ * To use this, the *_free() function passes in the ptr to a list_head within
+ * the recyclee, as well as the cache to put it on.
+ *
+ * First, we put the memory on a percpu list. When this reaches a certain size,
+ * We move it to an intermediate non-percpu list in a lockless manner, with some
+ * xchg/compxchg wizardry.
+ *
+ * N.B. Instead of a list_head as the anchor, we use a single pointer, which can
+ * be NULL and xchg'd. The list is actually empty when the pointer is NULL, and
+ * list_empty() will return true with one element is actually present.
+ */
+static void rds_ib_recv_cache_put(struct list_head *new_item,
+				 struct rds_ib_refill_cache *cache)
+{
+	unsigned long flags;
+	struct list_head *old, *chpfirst;
+
+	local_irq_save(flags);
+
+	chpfirst = __this_cpu_read(cache->percpu->first);
+	if (!chpfirst)
+		INIT_LIST_HEAD(new_item);
+	else /* put on front */
+		list_add_tail(new_item, chpfirst);
+
+	__this_cpu_write(cache->percpu->first, new_item);
+	__this_cpu_inc(cache->percpu->count);
+
+	if (__this_cpu_read(cache->percpu->count) < RDS_IB_RECYCLE_BATCH_COUNT)
+		goto end;
+
+	/*
+	 * Return our per-cpu first list to the cache's xfer by atomically
+	 * grabbing the current xfer list, appending it to our per-cpu list,
+	 * and then atomically returning that entire list back to the
+	 * cache's xfer list as long as it's still empty.
+	 */
+	do {
+		old = xchg(&cache->xfer, NULL);
+		if (old)
+			list_splice_entire_tail(old, chpfirst);
+		old = cmpxchg(&cache->xfer, NULL, chpfirst);
+	} while (old);
+
+
+	__this_cpu_write(cache->percpu->first, NULL);
+	__this_cpu_write(cache->percpu->count, 0);
+end:
+	local_irq_restore(flags);
+}
+
+static struct list_head *rds_ib_recv_cache_get(struct rds_ib_refill_cache *cache)
+{
+	struct list_head *head = cache->ready;
+
+	if (head) {
+		if (!list_empty(head)) {
+			cache->ready = head->next;
+			list_del_init(head);
+		} else
+			cache->ready = NULL;
+	}
+
+	return head;
+}
+
+int rds_ib_inc_copy_to_user(struct rds_incoming *inc, struct iov_iter *to)
+{
+	struct rds_ib_incoming *ibinc;
+	struct rds_page_frag *frag;
+	unsigned long to_copy;
+	unsigned long frag_off = 0;
+	int copied = 0;
+	int ret;
+	u32 len;
+
+	ibinc = container_of(inc, struct rds_ib_incoming, ii_inc);
+	frag = list_entry(ibinc->ii_frags.next, struct rds_page_frag, f_item);
+	len = be32_to_cpu(inc->i_hdr.h_len);
+
+	while (iov_iter_count(to) && copied < len) {
+		if (frag_off == RDS_FRAG_SIZE) {
+			frag = list_entry(frag->f_item.next,
+					  struct rds_page_frag, f_item);
+			frag_off = 0;
+		}
+		to_copy = min_t(unsigned long, iov_iter_count(to),
+				RDS_FRAG_SIZE - frag_off);
+		to_copy = min_t(unsigned long, to_copy, len - copied);
+
+		/* XXX needs + offset for multiple recvs per page */
+		rds_stats_add(s_copy_to_user, to_copy);
+		ret = copy_page_to_iter(sg_page(&frag->f_sg),
+					frag->f_sg.offset + frag_off,
+					to_copy,
+					to);
+		if (ret != to_copy)
+			return -EFAULT;
+
+		frag_off += to_copy;
+		copied += to_copy;
+	}
+
+	return copied;
+}
+
+/* ic starts out kzalloc()ed */
+void rds_ib_recv_init_ack(struct rds_ib_connection *ic)
+{
+	struct ib_send_wr *wr = &ic->i_ack_wr;
+	struct ib_sge *sge = &ic->i_ack_sge;
+
+	sge->addr = ic->i_ack_dma;
+	sge->length = sizeof(struct rds_header);
+	sge->lkey = ic->i_pd->local_dma_lkey;
+
+	wr->sg_list = sge;
+	wr->num_sge = 1;
+	wr->opcode = IB_WR_SEND;
+	wr->wr_id = RDS_IB_ACK_WR_ID;
+	wr->send_flags = IB_SEND_SIGNALED | IB_SEND_SOLICITED;
+}
+
+/*
+ * You'd think that with reliable IB connections you wouldn't need to ack
+ * messages that have been received.  The problem is that IB hardware generates
+ * an ack message before it has DMAed the message into memory.  This creates a
+ * potential message loss if the HCA is disabled for any reason between when it
+ * sends the ack and before the message is DMAed and processed.  This is only a
+ * potential issue if another HCA is available for fail-over.
+ *
+ * When the remote host receives our ack they'll free the sent message from
+ * their send queue.  To decrease the latency of this we always send an ack
+ * immediately after we've received messages.
+ *
+ * For simplicity, we only have one ack in flight at a time.  This puts
+ * pressure on senders to have deep enough send queues to absorb the latency of
+ * a single ack frame being in flight.  This might not be good enough.
+ *
+ * This is implemented by have a long-lived send_wr and sge which point to a
+ * statically allocated ack frame.  This ack wr does not fall under the ring
+ * accounting that the tx and rx wrs do.  The QP attribute specifically makes
+ * room for it beyond the ring size.  Send completion notices its special
+ * wr_id and avoids working with the ring in that case.
+ */
+#ifndef KERNEL_HAS_ATOMIC64
+void rds_ib_set_ack(struct rds_ib_connection *ic, u64 seq, int ack_required)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&ic->i_ack_lock, flags);
+	ic->i_ack_next = seq;
+	if (ack_required)
+		set_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
+	spin_unlock_irqrestore(&ic->i_ack_lock, flags);
+}
+
+static u64 rds_ib_get_ack(struct rds_ib_connection *ic)
+{
+	unsigned long flags;
+	u64 seq;
+
+	clear_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
+
+	spin_lock_irqsave(&ic->i_ack_lock, flags);
+	seq = ic->i_ack_next;
+	spin_unlock_irqrestore(&ic->i_ack_lock, flags);
+
+	return seq;
+}
+#else
+void rds_ib_set_ack(struct rds_ib_connection *ic, u64 seq, int ack_required)
+{
+	atomic64_set(&ic->i_ack_next, seq);
+	if (ack_required) {
+		smp_mb__before_atomic();
+		set_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
+	}
+}
+
+static u64 rds_ib_get_ack(struct rds_ib_connection *ic)
+{
+	clear_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
+	smp_mb__after_atomic();
+
+	return atomic64_read(&ic->i_ack_next);
+}
+#endif
+
+
+static void rds_ib_send_ack(struct rds_ib_connection *ic, unsigned int adv_credits)
+{
+	struct rds_header *hdr = ic->i_ack;
+	u64 seq;
+	int ret;
+
+	seq = rds_ib_get_ack(ic);
+
+	rdsdebug("send_ack: ic %p ack %llu\n", ic, (unsigned long long) seq);
+
+	ib_dma_sync_single_for_cpu(ic->rds_ibdev->dev, ic->i_ack_dma,
+				   sizeof(*hdr), DMA_TO_DEVICE);
+	rds_message_populate_header(hdr, 0, 0, 0);
+	hdr->h_ack = cpu_to_be64(seq);
+	hdr->h_credit = adv_credits;
+	rds_message_make_checksum(hdr);
+	ib_dma_sync_single_for_device(ic->rds_ibdev->dev, ic->i_ack_dma,
+				      sizeof(*hdr), DMA_TO_DEVICE);
+
+	ic->i_ack_queued = jiffies;
+
+	ret = ib_post_send(ic->i_cm_id->qp, &ic->i_ack_wr, NULL);
+	if (unlikely(ret)) {
+		/* Failed to send. Release the WR, and
+		 * force another ACK.
+		 */
+		clear_bit(IB_ACK_IN_FLIGHT, &ic->i_ack_flags);
+		set_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
+
+		rds_ib_stats_inc(s_ib_ack_send_failure);
+
+		rds_ib_conn_error(ic->conn, "sending ack failed\n");
+	} else
+		rds_ib_stats_inc(s_ib_ack_sent);
+}
+
+/*
+ * There are 3 ways of getting acknowledgements to the peer:
+ *  1.	We call rds_ib_attempt_ack from the recv completion handler
+ *	to send an ACK-only frame.
+ *	However, there can be only one such frame in the send queue
+ *	at any time, so we may have to postpone it.
+ *  2.	When another (data) packet is transmitted while there's
+ *	an ACK in the queue, we piggyback the ACK sequence number
+ *	on the data packet.
+ *  3.	If the ACK WR is done sending, we get called from the
+ *	send queue completion handler, and check whether there's
+ *	another ACK pending (postponed because the WR was on the
+ *	queue). If so, we transmit it.
+ *
+ * We maintain 2 variables:
+ *  -	i_ack_flags, which keeps track of whether the ACK WR
+ *	is currently in the send queue or not (IB_ACK_IN_FLIGHT)
+ *  -	i_ack_next, which is the last sequence number we received
+ *
+ * Potentially, send queue and receive queue handlers can run concurrently.
+ * It would be nice to not have to use a spinlock to synchronize things,
+ * but the one problem that rules this out is that 64bit updates are
+ * not atomic on all platforms. Things would be a lot simpler if
+ * we had atomic64 or maybe cmpxchg64 everywhere.
+ *
+ * Reconnecting complicates this picture just slightly. When we
+ * reconnect, we may be seeing duplicate packets. The peer
+ * is retransmitting them, because it hasn't seen an ACK for
+ * them. It is important that we ACK these.
+ *
+ * ACK mitigation adds a header flag "ACK_REQUIRED"; any packet with
+ * this flag set *MUST* be acknowledged immediately.
+ */
+
+/*
+ * When we get here, we're called from the recv queue handler.
+ * Check whether we ought to transmit an ACK.
+ */
+void rds_ib_attempt_ack(struct rds_ib_connection *ic)
+{
+	unsigned int adv_credits;
+
+	if (!test_bit(IB_ACK_REQUESTED, &ic->i_ack_flags))
+		return;
+
+	if (test_and_set_bit(IB_ACK_IN_FLIGHT, &ic->i_ack_flags)) {
+		rds_ib_stats_inc(s_ib_ack_send_delayed);
+		return;
+	}
+
+	/* Can we get a send credit? */
+	if (!rds_ib_send_grab_credits(ic, 1, &adv_credits, 0, RDS_MAX_ADV_CREDIT)) {
+		rds_ib_stats_inc(s_ib_tx_throttle);
+		clear_bit(IB_ACK_IN_FLIGHT, &ic->i_ack_flags);
+		return;
+	}
+
+	clear_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
+	rds_ib_send_ack(ic, adv_credits);
+}
+
+/*
+ * We get here from the send completion handler, when the
+ * adapter tells us the ACK frame was sent.
+ */
+void rds_ib_ack_send_complete(struct rds_ib_connection *ic)
+{
+	clear_bit(IB_ACK_IN_FLIGHT, &ic->i_ack_flags);
+	rds_ib_attempt_ack(ic);
+}
+
+/*
+ * This is called by the regular xmit code when it wants to piggyback
+ * an ACK on an outgoing frame.
+ */
+u64 rds_ib_piggyb_ack(struct rds_ib_connection *ic)
+{
+	if (test_and_clear_bit(IB_ACK_REQUESTED, &ic->i_ack_flags))
+		rds_ib_stats_inc(s_ib_ack_send_piggybacked);
+	return rds_ib_get_ack(ic);
+}
+
+/*
+ * It's kind of lame that we're copying from the posted receive pages into
+ * long-lived bitmaps.  We could have posted the bitmaps and rdma written into
+ * them.  But receiving new congestion bitmaps should be a *rare* event, so
+ * hopefully we won't need to invest that complexity in making it more
+ * efficient.  By copying we can share a simpler core with TCP which has to
+ * copy.
+ */
+static void rds_ib_cong_recv(struct rds_connection *conn,
+			      struct rds_ib_incoming *ibinc)
+{
+	struct rds_cong_map *map;
+	unsigned int map_off;
+	unsigned int map_page;
+	struct rds_page_frag *frag;
+	unsigned long frag_off;
+	unsigned long to_copy;
+	unsigned long copied;
+	__le64 uncongested = 0;
+	void *addr;
+
+	/* catch completely corrupt packets */
+	if (be32_to_cpu(ibinc->ii_inc.i_hdr.h_len) != RDS_CONG_MAP_BYTES)
+		return;
+
+	map = conn->c_fcong;
+	map_page = 0;
+	map_off = 0;
+
+	frag = list_entry(ibinc->ii_frags.next, struct rds_page_frag, f_item);
+	frag_off = 0;
+
+	copied = 0;
+
+	while (copied < RDS_CONG_MAP_BYTES) {
+		__le64 *src, *dst;
+		unsigned int k;
+
+		to_copy = min(RDS_FRAG_SIZE - frag_off, PAGE_SIZE - map_off);
+		BUG_ON(to_copy & 7); /* Must be 64bit aligned. */
+
+		addr = kmap_atomic(sg_page(&frag->f_sg));
+
+		src = addr + frag->f_sg.offset + frag_off;
+		dst = (void *)map->m_page_addrs[map_page] + map_off;
+		for (k = 0; k < to_copy; k += 8) {
+			/* Record ports that became uncongested, ie
+			 * bits that changed from 0 to 1. */
+			uncongested |= ~(*src) & *dst;
+			*dst++ = *src++;
+		}
+		kunmap_atomic(addr);
+
+		copied += to_copy;
+
+		map_off += to_copy;
+		if (map_off == PAGE_SIZE) {
+			map_off = 0;
+			map_page++;
+		}
+
+		frag_off += to_copy;
+		if (frag_off == RDS_FRAG_SIZE) {
+			frag = list_entry(frag->f_item.next,
+					  struct rds_page_frag, f_item);
+			frag_off = 0;
+		}
+	}
+
+	/* the congestion map is in little endian order */
+	rds_cong_map_updated(map, le64_to_cpu(uncongested));
+}
+
+static void rds_ib_process_recv(struct rds_connection *conn,
+				struct rds_ib_recv_work *recv, u32 data_len,
+				struct rds_ib_ack_state *state)
+{
+	struct rds_ib_connection *ic = conn->c_transport_data;
+	struct rds_ib_incoming *ibinc = ic->i_ibinc;
+	struct rds_header *ihdr, *hdr;
+	dma_addr_t dma_addr = ic->i_recv_hdrs_dma[recv - ic->i_recvs];
+
+	/* XXX shut down the connection if port 0,0 are seen? */
+
+	rdsdebug("ic %p ibinc %p recv %p byte len %u\n", ic, ibinc, recv,
+		 data_len);
+
+	if (data_len < sizeof(struct rds_header)) {
+		rds_ib_conn_error(conn, "incoming message "
+		       "from %pI6c didn't include a "
+		       "header, disconnecting and "
+		       "reconnecting\n",
+		       &conn->c_faddr);
+		return;
+	}
+	data_len -= sizeof(struct rds_header);
+
+	ihdr = ic->i_recv_hdrs[recv - ic->i_recvs];
+
+	ib_dma_sync_single_for_cpu(ic->rds_ibdev->dev, dma_addr,
+				   sizeof(*ihdr), DMA_FROM_DEVICE);
+	/* Validate the checksum. */
+	if (!rds_message_verify_checksum(ihdr)) {
+		rds_ib_conn_error(conn, "incoming message "
+		       "from %pI6c has corrupted header - "
+		       "forcing a reconnect\n",
+		       &conn->c_faddr);
+		rds_stats_inc(s_recv_drop_bad_checksum);
+		goto done;
+	}
+
+	/* Process the ACK sequence which comes with every packet */
+	state->ack_recv = be64_to_cpu(ihdr->h_ack);
+	state->ack_recv_valid = 1;
+
+	/* Process the credits update if there was one */
+	if (ihdr->h_credit)
+		rds_ib_send_add_credits(conn, ihdr->h_credit);
+
+	if (ihdr->h_sport == 0 && ihdr->h_dport == 0 && data_len == 0) {
+		/* This is an ACK-only packet. The fact that it gets
+		 * special treatment here is that historically, ACKs
+		 * were rather special beasts.
+		 */
+		rds_ib_stats_inc(s_ib_ack_received);
+
+		/*
+		 * Usually the frags make their way on to incs and are then freed as
+		 * the inc is freed.  We don't go that route, so we have to drop the
+		 * page ref ourselves.  We can't just leave the page on the recv
+		 * because that confuses the dma mapping of pages and each recv's use
+		 * of a partial page.
+		 *
+		 * FIXME: Fold this into the code path below.
+		 */
+		rds_ib_frag_free(ic, recv->r_frag);
+		recv->r_frag = NULL;
+		goto done;
+	}
+
+	/*
+	 * If we don't already have an inc on the connection then this
+	 * fragment has a header and starts a message.. copy its header
+	 * into the inc and save the inc so we can hang upcoming fragments
+	 * off its list.
+	 */
+	if (!ibinc) {
+		ibinc = recv->r_ibinc;
+		recv->r_ibinc = NULL;
+		ic->i_ibinc = ibinc;
+
+		hdr = &ibinc->ii_inc.i_hdr;
+		ibinc->ii_inc.i_rx_lat_trace[RDS_MSG_RX_HDR] =
+				local_clock();
+		memcpy(hdr, ihdr, sizeof(*hdr));
+		ic->i_recv_data_rem = be32_to_cpu(hdr->h_len);
+		ibinc->ii_inc.i_rx_lat_trace[RDS_MSG_RX_START] =
+				local_clock();
+
+		rdsdebug("ic %p ibinc %p rem %u flag 0x%x\n", ic, ibinc,
+			 ic->i_recv_data_rem, hdr->h_flags);
+	} else {
+		hdr = &ibinc->ii_inc.i_hdr;
+		/* We can't just use memcmp here; fragments of a
+		 * single message may carry different ACKs */
+		if (hdr->h_sequence != ihdr->h_sequence ||
+		    hdr->h_len != ihdr->h_len ||
+		    hdr->h_sport != ihdr->h_sport ||
+		    hdr->h_dport != ihdr->h_dport) {
+			rds_ib_conn_error(conn,
+				"fragment header mismatch; forcing reconnect\n");
+			goto done;
+		}
+	}
+
+	list_add_tail(&recv->r_frag->f_item, &ibinc->ii_frags);
+	recv->r_frag = NULL;
+
+	if (ic->i_recv_data_rem > RDS_FRAG_SIZE)
+		ic->i_recv_data_rem -= RDS_FRAG_SIZE;
+	else {
+		ic->i_recv_data_rem = 0;
+		ic->i_ibinc = NULL;
+
+		if (ibinc->ii_inc.i_hdr.h_flags == RDS_FLAG_CONG_BITMAP) {
+			rds_ib_cong_recv(conn, ibinc);
+		} else {
+			rds_recv_incoming(conn, &conn->c_faddr, &conn->c_laddr,
+					  &ibinc->ii_inc, GFP_ATOMIC);
+			state->ack_next = be64_to_cpu(hdr->h_sequence);
+			state->ack_next_valid = 1;
+		}
+
+		/* Evaluate the ACK_REQUIRED flag *after* we received
+		 * the complete frame, and after bumping the next_rx
+		 * sequence. */
+		if (hdr->h_flags & RDS_FLAG_ACK_REQUIRED) {
+			rds_stats_inc(s_recv_ack_required);
+			state->ack_required = 1;
+		}
+
+		rds_inc_put(&ibinc->ii_inc);
+	}
+done:
+	ib_dma_sync_single_for_device(ic->rds_ibdev->dev, dma_addr,
+				      sizeof(*ihdr), DMA_FROM_DEVICE);
+}
+
+void rds_ib_recv_cqe_handler(struct rds_ib_connection *ic,
+			     struct ib_wc *wc,
+			     struct rds_ib_ack_state *state)
+{
+	struct rds_connection *conn = ic->conn;
+	struct rds_ib_recv_work *recv;
+
+	rdsdebug("wc wr_id 0x%llx status %u (%s) byte_len %u imm_data %u\n",
+		 (unsigned long long)wc->wr_id, wc->status,
+		 ib_wc_status_msg(wc->status), wc->byte_len,
+		 be32_to_cpu(wc->ex.imm_data));
+
+	rds_ib_stats_inc(s_ib_rx_cq_event);
+	recv = &ic->i_recvs[rds_ib_ring_oldest(&ic->i_recv_ring)];
+	ib_dma_unmap_sg(ic->i_cm_id->device, &recv->r_frag->f_sg, 1,
+			DMA_FROM_DEVICE);
+
+	/* Also process recvs in connecting state because it is possible
+	 * to get a recv completion _before_ the rdmacm ESTABLISHED
+	 * event is processed.
+	 */
+	if (wc->status == IB_WC_SUCCESS) {
+		rds_ib_process_recv(conn, recv, wc->byte_len, state);
+	} else {
+		/* We expect errors as the qp is drained during shutdown */
+		if (rds_conn_up(conn) || rds_conn_connecting(conn))
+			rds_ib_conn_error(conn, "recv completion on <%pI6c,%pI6c, %d> had status %u (%s), vendor err 0x%x, disconnecting and reconnecting\n",
+					  &conn->c_laddr, &conn->c_faddr,
+					  conn->c_tos, wc->status,
+					  ib_wc_status_msg(wc->status),
+					  wc->vendor_err);
+	}
+
+	/* rds_ib_process_recv() doesn't always consume the frag, and
+	 * we might not have called it at all if the wc didn't indicate
+	 * success. We already unmapped the frag's pages, though, and
+	 * the following rds_ib_ring_free() call tells the refill path
+	 * that it will not find an allocated frag here. Make sure we
+	 * keep that promise by freeing a frag that's still on the ring.
+	 */
+	if (recv->r_frag) {
+		rds_ib_frag_free(ic, recv->r_frag);
+		recv->r_frag = NULL;
+	}
+	rds_ib_ring_free(&ic->i_recv_ring, 1);
+
+	/* If we ever end up with a really empty receive ring, we're
+	 * in deep trouble, as the sender will definitely see RNR
+	 * timeouts. */
+	if (rds_ib_ring_empty(&ic->i_recv_ring))
+		rds_ib_stats_inc(s_ib_rx_ring_empty);
+
+	if (rds_ib_ring_low(&ic->i_recv_ring)) {
+		rds_ib_recv_refill(conn, 0, GFP_NOWAIT);
+		rds_ib_stats_inc(s_ib_rx_refill_from_cq);
+	}
+}
+
+int rds_ib_recv_path(struct rds_conn_path *cp)
+{
+	struct rds_connection *conn = cp->cp_conn;
+	struct rds_ib_connection *ic = conn->c_transport_data;
+
+	rdsdebug("conn %p\n", conn);
+	if (rds_conn_up(conn)) {
+		rds_ib_attempt_ack(ic);
+		rds_ib_recv_refill(conn, 0, GFP_KERNEL);
+		rds_ib_stats_inc(s_ib_rx_refill_from_thread);
+	}
+
+	return 0;
+}
+
+int rds_ib_recv_init(void)
+{
+	struct sysinfo si;
+	int ret = -ENOMEM;
+
+	/* Default to 30% of all available RAM for recv memory */
+	si_meminfo(&si);
+	rds_ib_sysctl_max_recv_allocation = si.totalram / 3 * PAGE_SIZE / RDS_FRAG_SIZE;
+
+	rds_ib_incoming_slab =
+		kmem_cache_create_usercopy("rds_ib_incoming",
+					   sizeof(struct rds_ib_incoming),
+					   0, SLAB_HWCACHE_ALIGN,
+					   offsetof(struct rds_ib_incoming,
+						    ii_inc.i_usercopy),
+					   sizeof(struct rds_inc_usercopy),
+					   NULL);
+	if (!rds_ib_incoming_slab)
+		goto out;
+
+	rds_ib_frag_slab = kmem_cache_create("rds_ib_frag",
+					sizeof(struct rds_page_frag),
+					0, SLAB_HWCACHE_ALIGN, NULL);
+	if (!rds_ib_frag_slab) {
+		kmem_cache_destroy(rds_ib_incoming_slab);
+		rds_ib_incoming_slab = NULL;
+	} else
+		ret = 0;
+out:
+	return ret;
+}
+
+void rds_ib_recv_exit(void)
+{
+	WARN_ON(atomic_read(&rds_ib_allocation));
+
+	kmem_cache_destroy(rds_ib_incoming_slab);
+	kmem_cache_destroy(rds_ib_frag_slab);
+}
diff --git a/net/rds/ib_ring.c b/net/rds/ib_ring.c
new file mode 100644
index 000000000..006b2e441
--- /dev/null
+++ b/net/rds/ib_ring.c
@@ -0,0 +1,168 @@
+/*
+ * Copyright (c) 2006 Oracle.  All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+#include <linux/kernel.h>
+
+#include "rds.h"
+#include "ib.h"
+
+/*
+ * Locking for IB rings.
+ * We assume that allocation is always protected by a mutex
+ * in the caller (this is a valid assumption for the current
+ * implementation).
+ *
+ * Freeing always happens in an interrupt, and hence only
+ * races with allocations, but not with other free()s.
+ *
+ * The interaction between allocation and freeing is that
+ * the alloc code has to determine the number of free entries.
+ * To this end, we maintain two counters; an allocation counter
+ * and a free counter. Both are allowed to run freely, and wrap
+ * around.
+ * The number of used entries is always (alloc_ctr - free_ctr) % NR.
+ *
+ * The current implementation makes free_ctr atomic. When the
+ * caller finds an allocation fails, it should set an "alloc fail"
+ * bit and retry the allocation. The "alloc fail" bit essentially tells
+ * the CQ completion handlers to wake it up after freeing some
+ * more entries.
+ */
+
+/*
+ * This only happens on shutdown.
+ */
+DECLARE_WAIT_QUEUE_HEAD(rds_ib_ring_empty_wait);
+
+void rds_ib_ring_init(struct rds_ib_work_ring *ring, u32 nr)
+{
+	memset(ring, 0, sizeof(*ring));
+	ring->w_nr = nr;
+	rdsdebug("ring %p nr %u\n", ring, ring->w_nr);
+}
+
+static inline u32 __rds_ib_ring_used(struct rds_ib_work_ring *ring)
+{
+	u32 diff;
+
+	/* This assumes that atomic_t has at least as many bits as u32 */
+	diff = ring->w_alloc_ctr - (u32) atomic_read(&ring->w_free_ctr);
+	BUG_ON(diff > ring->w_nr);
+
+	return diff;
+}
+
+void rds_ib_ring_resize(struct rds_ib_work_ring *ring, u32 nr)
+{
+	/* We only ever get called from the connection setup code,
+	 * prior to creating the QP. */
+	BUG_ON(__rds_ib_ring_used(ring));
+	ring->w_nr = nr;
+}
+
+static int __rds_ib_ring_empty(struct rds_ib_work_ring *ring)
+{
+	return __rds_ib_ring_used(ring) == 0;
+}
+
+u32 rds_ib_ring_alloc(struct rds_ib_work_ring *ring, u32 val, u32 *pos)
+{
+	u32 ret = 0, avail;
+
+	avail = ring->w_nr - __rds_ib_ring_used(ring);
+
+	rdsdebug("ring %p val %u next %u free %u\n", ring, val,
+		 ring->w_alloc_ptr, avail);
+
+	if (val && avail) {
+		ret = min(val, avail);
+		*pos = ring->w_alloc_ptr;
+
+		ring->w_alloc_ptr = (ring->w_alloc_ptr + ret) % ring->w_nr;
+		ring->w_alloc_ctr += ret;
+	}
+
+	return ret;
+}
+
+void rds_ib_ring_free(struct rds_ib_work_ring *ring, u32 val)
+{
+	ring->w_free_ptr = (ring->w_free_ptr + val) % ring->w_nr;
+	atomic_add(val, &ring->w_free_ctr);
+
+	if (__rds_ib_ring_empty(ring) &&
+	    waitqueue_active(&rds_ib_ring_empty_wait))
+		wake_up(&rds_ib_ring_empty_wait);
+}
+
+void rds_ib_ring_unalloc(struct rds_ib_work_ring *ring, u32 val)
+{
+	ring->w_alloc_ptr = (ring->w_alloc_ptr - val) % ring->w_nr;
+	ring->w_alloc_ctr -= val;
+}
+
+int rds_ib_ring_empty(struct rds_ib_work_ring *ring)
+{
+	return __rds_ib_ring_empty(ring);
+}
+
+int rds_ib_ring_low(struct rds_ib_work_ring *ring)
+{
+	return __rds_ib_ring_used(ring) <= (ring->w_nr >> 1);
+}
+
+/*
+ * returns the oldest allocated ring entry.  This will be the next one
+ * freed.  This can't be called if there are none allocated.
+ */
+u32 rds_ib_ring_oldest(struct rds_ib_work_ring *ring)
+{
+	return ring->w_free_ptr;
+}
+
+/*
+ * returns the number of completed work requests.
+ */
+
+u32 rds_ib_ring_completed(struct rds_ib_work_ring *ring, u32 wr_id, u32 oldest)
+{
+	u32 ret;
+
+	if (oldest <= (unsigned long long)wr_id)
+		ret = (unsigned long long)wr_id - oldest + 1;
+	else
+		ret = ring->w_nr - oldest + (unsigned long long)wr_id + 1;
+
+	rdsdebug("ring %p ret %u wr_id %u oldest %u\n", ring, ret,
+		 wr_id, oldest);
+	return ret;
+}
diff --git a/net/rds/ib_send.c b/net/rds/ib_send.c
new file mode 100644
index 000000000..d6be95542
--- /dev/null
+++ b/net/rds/ib_send.c
@@ -0,0 +1,1045 @@
+/*
+ * Copyright (c) 2006, 2019 Oracle and/or its affiliates. All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+#include <linux/kernel.h>
+#include <linux/in.h>
+#include <linux/device.h>
+#include <linux/dmapool.h>
+#include <linux/ratelimit.h>
+
+#include "rds_single_path.h"
+#include "rds.h"
+#include "ib.h"
+#include "ib_mr.h"
+
+/*
+ * Convert IB-specific error message to RDS error message and call core
+ * completion handler.
+ */
+static void rds_ib_send_complete(struct rds_message *rm,
+				 int wc_status,
+				 void (*complete)(struct rds_message *rm, int status))
+{
+	int notify_status;
+
+	switch (wc_status) {
+	case IB_WC_WR_FLUSH_ERR:
+		return;
+
+	case IB_WC_SUCCESS:
+		notify_status = RDS_RDMA_SUCCESS;
+		break;
+
+	case IB_WC_REM_ACCESS_ERR:
+		notify_status = RDS_RDMA_REMOTE_ERROR;
+		break;
+
+	default:
+		notify_status = RDS_RDMA_OTHER_ERROR;
+		break;
+	}
+	complete(rm, notify_status);
+}
+
+static void rds_ib_send_unmap_data(struct rds_ib_connection *ic,
+				   struct rm_data_op *op,
+				   int wc_status)
+{
+	if (op->op_nents)
+		ib_dma_unmap_sg(ic->i_cm_id->device,
+				op->op_sg, op->op_nents,
+				DMA_TO_DEVICE);
+}
+
+static void rds_ib_send_unmap_rdma(struct rds_ib_connection *ic,
+				   struct rm_rdma_op *op,
+				   int wc_status)
+{
+	if (op->op_mapped) {
+		ib_dma_unmap_sg(ic->i_cm_id->device,
+				op->op_sg, op->op_nents,
+				op->op_write ? DMA_TO_DEVICE : DMA_FROM_DEVICE);
+		op->op_mapped = 0;
+	}
+
+	/* If the user asked for a completion notification on this
+	 * message, we can implement three different semantics:
+	 *  1.	Notify when we received the ACK on the RDS message
+	 *	that was queued with the RDMA. This provides reliable
+	 *	notification of RDMA status at the expense of a one-way
+	 *	packet delay.
+	 *  2.	Notify when the IB stack gives us the completion event for
+	 *	the RDMA operation.
+	 *  3.	Notify when the IB stack gives us the completion event for
+	 *	the accompanying RDS messages.
+	 * Here, we implement approach #3. To implement approach #2,
+	 * we would need to take an event for the rdma WR. To implement #1,
+	 * don't call rds_rdma_send_complete at all, and fall back to the notify
+	 * handling in the ACK processing code.
+	 *
+	 * Note: There's no need to explicitly sync any RDMA buffers using
+	 * ib_dma_sync_sg_for_cpu - the completion for the RDMA
+	 * operation itself unmapped the RDMA buffers, which takes care
+	 * of synching.
+	 */
+	rds_ib_send_complete(container_of(op, struct rds_message, rdma),
+			     wc_status, rds_rdma_send_complete);
+
+	if (op->op_write)
+		rds_stats_add(s_send_rdma_bytes, op->op_bytes);
+	else
+		rds_stats_add(s_recv_rdma_bytes, op->op_bytes);
+}
+
+static void rds_ib_send_unmap_atomic(struct rds_ib_connection *ic,
+				     struct rm_atomic_op *op,
+				     int wc_status)
+{
+	/* unmap atomic recvbuf */
+	if (op->op_mapped) {
+		ib_dma_unmap_sg(ic->i_cm_id->device, op->op_sg, 1,
+				DMA_FROM_DEVICE);
+		op->op_mapped = 0;
+	}
+
+	rds_ib_send_complete(container_of(op, struct rds_message, atomic),
+			     wc_status, rds_atomic_send_complete);
+
+	if (op->op_type == RDS_ATOMIC_TYPE_CSWP)
+		rds_ib_stats_inc(s_ib_atomic_cswp);
+	else
+		rds_ib_stats_inc(s_ib_atomic_fadd);
+}
+
+/*
+ * Unmap the resources associated with a struct send_work.
+ *
+ * Returns the rm for no good reason other than it is unobtainable
+ * other than by switching on wr.opcode, currently, and the caller,
+ * the event handler, needs it.
+ */
+static struct rds_message *rds_ib_send_unmap_op(struct rds_ib_connection *ic,
+						struct rds_ib_send_work *send,
+						int wc_status)
+{
+	struct rds_message *rm = NULL;
+
+	/* In the error case, wc.opcode sometimes contains garbage */
+	switch (send->s_wr.opcode) {
+	case IB_WR_SEND:
+		if (send->s_op) {
+			rm = container_of(send->s_op, struct rds_message, data);
+			rds_ib_send_unmap_data(ic, send->s_op, wc_status);
+		}
+		break;
+	case IB_WR_RDMA_WRITE:
+	case IB_WR_RDMA_READ:
+		if (send->s_op) {
+			rm = container_of(send->s_op, struct rds_message, rdma);
+			rds_ib_send_unmap_rdma(ic, send->s_op, wc_status);
+		}
+		break;
+	case IB_WR_ATOMIC_FETCH_AND_ADD:
+	case IB_WR_ATOMIC_CMP_AND_SWP:
+	case IB_WR_MASKED_ATOMIC_FETCH_AND_ADD:
+	case IB_WR_MASKED_ATOMIC_CMP_AND_SWP:
+		if (send->s_op) {
+			rm = container_of(send->s_op, struct rds_message, atomic);
+			rds_ib_send_unmap_atomic(ic, send->s_op, wc_status);
+		}
+		break;
+	default:
+		printk_ratelimited(KERN_NOTICE
+			       "RDS/IB: %s: unexpected opcode 0x%x in WR!\n",
+			       __func__, send->s_wr.opcode);
+		break;
+	}
+
+	send->s_wr.opcode = 0xdead;
+
+	return rm;
+}
+
+void rds_ib_send_init_ring(struct rds_ib_connection *ic)
+{
+	struct rds_ib_send_work *send;
+	u32 i;
+
+	for (i = 0, send = ic->i_sends; i < ic->i_send_ring.w_nr; i++, send++) {
+		struct ib_sge *sge;
+
+		send->s_op = NULL;
+
+		send->s_wr.wr_id = i;
+		send->s_wr.sg_list = send->s_sge;
+		send->s_wr.ex.imm_data = 0;
+
+		sge = &send->s_sge[0];
+		sge->addr = ic->i_send_hdrs_dma[i];
+
+		sge->length = sizeof(struct rds_header);
+		sge->lkey = ic->i_pd->local_dma_lkey;
+
+		send->s_sge[1].lkey = ic->i_pd->local_dma_lkey;
+	}
+}
+
+void rds_ib_send_clear_ring(struct rds_ib_connection *ic)
+{
+	struct rds_ib_send_work *send;
+	u32 i;
+
+	for (i = 0, send = ic->i_sends; i < ic->i_send_ring.w_nr; i++, send++) {
+		if (send->s_op && send->s_wr.opcode != 0xdead)
+			rds_ib_send_unmap_op(ic, send, IB_WC_WR_FLUSH_ERR);
+	}
+}
+
+/*
+ * The only fast path caller always has a non-zero nr, so we don't
+ * bother testing nr before performing the atomic sub.
+ */
+static void rds_ib_sub_signaled(struct rds_ib_connection *ic, int nr)
+{
+	if ((atomic_sub_return(nr, &ic->i_signaled_sends) == 0) &&
+	    waitqueue_active(&rds_ib_ring_empty_wait))
+		wake_up(&rds_ib_ring_empty_wait);
+	BUG_ON(atomic_read(&ic->i_signaled_sends) < 0);
+}
+
+/*
+ * The _oldest/_free ring operations here race cleanly with the alloc/unalloc
+ * operations performed in the send path.  As the sender allocs and potentially
+ * unallocs the next free entry in the ring it doesn't alter which is
+ * the next to be freed, which is what this is concerned with.
+ */
+void rds_ib_send_cqe_handler(struct rds_ib_connection *ic, struct ib_wc *wc)
+{
+	struct rds_message *rm = NULL;
+	struct rds_connection *conn = ic->conn;
+	struct rds_ib_send_work *send;
+	u32 completed;
+	u32 oldest;
+	u32 i = 0;
+	int nr_sig = 0;
+
+
+	rdsdebug("wc wr_id 0x%llx status %u (%s) byte_len %u imm_data %u\n",
+		 (unsigned long long)wc->wr_id, wc->status,
+		 ib_wc_status_msg(wc->status), wc->byte_len,
+		 be32_to_cpu(wc->ex.imm_data));
+	rds_ib_stats_inc(s_ib_tx_cq_event);
+
+	if (wc->wr_id == RDS_IB_ACK_WR_ID) {
+		if (time_after(jiffies, ic->i_ack_queued + HZ / 2))
+			rds_ib_stats_inc(s_ib_tx_stalled);
+		rds_ib_ack_send_complete(ic);
+		return;
+	}
+
+	oldest = rds_ib_ring_oldest(&ic->i_send_ring);
+
+	completed = rds_ib_ring_completed(&ic->i_send_ring, wc->wr_id, oldest);
+
+	for (i = 0; i < completed; i++) {
+		send = &ic->i_sends[oldest];
+		if (send->s_wr.send_flags & IB_SEND_SIGNALED)
+			nr_sig++;
+
+		rm = rds_ib_send_unmap_op(ic, send, wc->status);
+
+		if (time_after(jiffies, send->s_queued + HZ / 2))
+			rds_ib_stats_inc(s_ib_tx_stalled);
+
+		if (send->s_op) {
+			if (send->s_op == rm->m_final_op) {
+				/* If anyone waited for this message to get
+				 * flushed out, wake them up now
+				 */
+				rds_message_unmapped(rm);
+			}
+			rds_message_put(rm);
+			send->s_op = NULL;
+		}
+
+		oldest = (oldest + 1) % ic->i_send_ring.w_nr;
+	}
+
+	rds_ib_ring_free(&ic->i_send_ring, completed);
+	rds_ib_sub_signaled(ic, nr_sig);
+
+	if (test_and_clear_bit(RDS_LL_SEND_FULL, &conn->c_flags) ||
+	    test_bit(0, &conn->c_map_queued))
+		queue_delayed_work(conn->c_path->cp_wq, &conn->c_send_w, 0);
+
+	/* We expect errors as the qp is drained during shutdown */
+	if (wc->status != IB_WC_SUCCESS && rds_conn_up(conn)) {
+		rds_ib_conn_error(conn, "send completion on <%pI6c,%pI6c,%d> had status %u (%s), vendor err 0x%x, disconnecting and reconnecting\n",
+				  &conn->c_laddr, &conn->c_faddr,
+				  conn->c_tos, wc->status,
+				  ib_wc_status_msg(wc->status), wc->vendor_err);
+	}
+}
+
+/*
+ * This is the main function for allocating credits when sending
+ * messages.
+ *
+ * Conceptually, we have two counters:
+ *  -	send credits: this tells us how many WRs we're allowed
+ *	to submit without overruning the receiver's queue. For
+ *	each SEND WR we post, we decrement this by one.
+ *
+ *  -	posted credits: this tells us how many WRs we recently
+ *	posted to the receive queue. This value is transferred
+ *	to the peer as a "credit update" in a RDS header field.
+ *	Every time we transmit credits to the peer, we subtract
+ *	the amount of transferred credits from this counter.
+ *
+ * It is essential that we avoid situations where both sides have
+ * exhausted their send credits, and are unable to send new credits
+ * to the peer. We achieve this by requiring that we send at least
+ * one credit update to the peer before exhausting our credits.
+ * When new credits arrive, we subtract one credit that is withheld
+ * until we've posted new buffers and are ready to transmit these
+ * credits (see rds_ib_send_add_credits below).
+ *
+ * The RDS send code is essentially single-threaded; rds_send_xmit
+ * sets RDS_IN_XMIT to ensure exclusive access to the send ring.
+ * However, the ACK sending code is independent and can race with
+ * message SENDs.
+ *
+ * In the send path, we need to update the counters for send credits
+ * and the counter of posted buffers atomically - when we use the
+ * last available credit, we cannot allow another thread to race us
+ * and grab the posted credits counter.  Hence, we have to use a
+ * spinlock to protect the credit counter, or use atomics.
+ *
+ * Spinlocks shared between the send and the receive path are bad,
+ * because they create unnecessary delays. An early implementation
+ * using a spinlock showed a 5% degradation in throughput at some
+ * loads.
+ *
+ * This implementation avoids spinlocks completely, putting both
+ * counters into a single atomic, and updating that atomic using
+ * atomic_add (in the receive path, when receiving fresh credits),
+ * and using atomic_cmpxchg when updating the two counters.
+ */
+int rds_ib_send_grab_credits(struct rds_ib_connection *ic,
+			     u32 wanted, u32 *adv_credits, int need_posted, int max_posted)
+{
+	unsigned int avail, posted, got = 0, advertise;
+	long oldval, newval;
+
+	*adv_credits = 0;
+	if (!ic->i_flowctl)
+		return wanted;
+
+try_again:
+	advertise = 0;
+	oldval = newval = atomic_read(&ic->i_credits);
+	posted = IB_GET_POST_CREDITS(oldval);
+	avail = IB_GET_SEND_CREDITS(oldval);
+
+	rdsdebug("wanted=%u credits=%u posted=%u\n",
+			wanted, avail, posted);
+
+	/* The last credit must be used to send a credit update. */
+	if (avail && !posted)
+		avail--;
+
+	if (avail < wanted) {
+		struct rds_connection *conn = ic->i_cm_id->context;
+
+		/* Oops, there aren't that many credits left! */
+		set_bit(RDS_LL_SEND_FULL, &conn->c_flags);
+		got = avail;
+	} else {
+		/* Sometimes you get what you want, lalala. */
+		got = wanted;
+	}
+	newval -= IB_SET_SEND_CREDITS(got);
+
+	/*
+	 * If need_posted is non-zero, then the caller wants
+	 * the posted regardless of whether any send credits are
+	 * available.
+	 */
+	if (posted && (got || need_posted)) {
+		advertise = min_t(unsigned int, posted, max_posted);
+		newval -= IB_SET_POST_CREDITS(advertise);
+	}
+
+	/* Finally bill everything */
+	if (atomic_cmpxchg(&ic->i_credits, oldval, newval) != oldval)
+		goto try_again;
+
+	*adv_credits = advertise;
+	return got;
+}
+
+void rds_ib_send_add_credits(struct rds_connection *conn, unsigned int credits)
+{
+	struct rds_ib_connection *ic = conn->c_transport_data;
+
+	if (credits == 0)
+		return;
+
+	rdsdebug("credits=%u current=%u%s\n",
+			credits,
+			IB_GET_SEND_CREDITS(atomic_read(&ic->i_credits)),
+			test_bit(RDS_LL_SEND_FULL, &conn->c_flags) ? ", ll_send_full" : "");
+
+	atomic_add(IB_SET_SEND_CREDITS(credits), &ic->i_credits);
+	if (test_and_clear_bit(RDS_LL_SEND_FULL, &conn->c_flags))
+		queue_delayed_work(conn->c_path->cp_wq, &conn->c_send_w, 0);
+
+	WARN_ON(IB_GET_SEND_CREDITS(credits) >= 16384);
+
+	rds_ib_stats_inc(s_ib_rx_credit_updates);
+}
+
+void rds_ib_advertise_credits(struct rds_connection *conn, unsigned int posted)
+{
+	struct rds_ib_connection *ic = conn->c_transport_data;
+
+	if (posted == 0)
+		return;
+
+	atomic_add(IB_SET_POST_CREDITS(posted), &ic->i_credits);
+
+	/* Decide whether to send an update to the peer now.
+	 * If we would send a credit update for every single buffer we
+	 * post, we would end up with an ACK storm (ACK arrives,
+	 * consumes buffer, we refill the ring, send ACK to remote
+	 * advertising the newly posted buffer... ad inf)
+	 *
+	 * Performance pretty much depends on how often we send
+	 * credit updates - too frequent updates mean lots of ACKs.
+	 * Too infrequent updates, and the peer will run out of
+	 * credits and has to throttle.
+	 * For the time being, 16 seems to be a good compromise.
+	 */
+	if (IB_GET_POST_CREDITS(atomic_read(&ic->i_credits)) >= 16)
+		set_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
+}
+
+static inline int rds_ib_set_wr_signal_state(struct rds_ib_connection *ic,
+					     struct rds_ib_send_work *send,
+					     bool notify)
+{
+	/*
+	 * We want to delay signaling completions just enough to get
+	 * the batching benefits but not so much that we create dead time
+	 * on the wire.
+	 */
+	if (ic->i_unsignaled_wrs-- == 0 || notify) {
+		ic->i_unsignaled_wrs = rds_ib_sysctl_max_unsig_wrs;
+		send->s_wr.send_flags |= IB_SEND_SIGNALED;
+		return 1;
+	}
+	return 0;
+}
+
+/*
+ * This can be called multiple times for a given message.  The first time
+ * we see a message we map its scatterlist into the IB device so that
+ * we can provide that mapped address to the IB scatter gather entries
+ * in the IB work requests.  We translate the scatterlist into a series
+ * of work requests that fragment the message.  These work requests complete
+ * in order so we pass ownership of the message to the completion handler
+ * once we send the final fragment.
+ *
+ * The RDS core uses the c_send_lock to only enter this function once
+ * per connection.  This makes sure that the tx ring alloc/unalloc pairs
+ * don't get out of sync and confuse the ring.
+ */
+int rds_ib_xmit(struct rds_connection *conn, struct rds_message *rm,
+		unsigned int hdr_off, unsigned int sg, unsigned int off)
+{
+	struct rds_ib_connection *ic = conn->c_transport_data;
+	struct ib_device *dev = ic->i_cm_id->device;
+	struct rds_ib_send_work *send = NULL;
+	struct rds_ib_send_work *first;
+	struct rds_ib_send_work *prev;
+	const struct ib_send_wr *failed_wr;
+	struct scatterlist *scat;
+	u32 pos;
+	u32 i;
+	u32 work_alloc;
+	u32 credit_alloc = 0;
+	u32 posted;
+	u32 adv_credits = 0;
+	int send_flags = 0;
+	int bytes_sent = 0;
+	int ret;
+	int flow_controlled = 0;
+	int nr_sig = 0;
+
+	BUG_ON(off % RDS_FRAG_SIZE);
+	BUG_ON(hdr_off != 0 && hdr_off != sizeof(struct rds_header));
+
+	/* Do not send cong updates to IB loopback */
+	if (conn->c_loopback
+	    && rm->m_inc.i_hdr.h_flags & RDS_FLAG_CONG_BITMAP) {
+		rds_cong_map_updated(conn->c_fcong, ~(u64) 0);
+		scat = &rm->data.op_sg[sg];
+		ret = max_t(int, RDS_CONG_MAP_BYTES, scat->length);
+		return sizeof(struct rds_header) + ret;
+	}
+
+	/* FIXME we may overallocate here */
+	if (be32_to_cpu(rm->m_inc.i_hdr.h_len) == 0)
+		i = 1;
+	else
+		i = DIV_ROUND_UP(be32_to_cpu(rm->m_inc.i_hdr.h_len), RDS_FRAG_SIZE);
+
+	work_alloc = rds_ib_ring_alloc(&ic->i_send_ring, i, &pos);
+	if (work_alloc == 0) {
+		set_bit(RDS_LL_SEND_FULL, &conn->c_flags);
+		rds_ib_stats_inc(s_ib_tx_ring_full);
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	if (ic->i_flowctl) {
+		credit_alloc = rds_ib_send_grab_credits(ic, work_alloc, &posted, 0, RDS_MAX_ADV_CREDIT);
+		adv_credits += posted;
+		if (credit_alloc < work_alloc) {
+			rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc - credit_alloc);
+			work_alloc = credit_alloc;
+			flow_controlled = 1;
+		}
+		if (work_alloc == 0) {
+			set_bit(RDS_LL_SEND_FULL, &conn->c_flags);
+			rds_ib_stats_inc(s_ib_tx_throttle);
+			ret = -ENOMEM;
+			goto out;
+		}
+	}
+
+	/* map the message the first time we see it */
+	if (!ic->i_data_op) {
+		if (rm->data.op_nents) {
+			rm->data.op_count = ib_dma_map_sg(dev,
+							  rm->data.op_sg,
+							  rm->data.op_nents,
+							  DMA_TO_DEVICE);
+			rdsdebug("ic %p mapping rm %p: %d\n", ic, rm, rm->data.op_count);
+			if (rm->data.op_count == 0) {
+				rds_ib_stats_inc(s_ib_tx_sg_mapping_failure);
+				rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc);
+				ret = -ENOMEM; /* XXX ? */
+				goto out;
+			}
+		} else {
+			rm->data.op_count = 0;
+		}
+
+		rds_message_addref(rm);
+		rm->data.op_dmasg = 0;
+		rm->data.op_dmaoff = 0;
+		ic->i_data_op = &rm->data;
+
+		/* Finalize the header */
+		if (test_bit(RDS_MSG_ACK_REQUIRED, &rm->m_flags))
+			rm->m_inc.i_hdr.h_flags |= RDS_FLAG_ACK_REQUIRED;
+		if (test_bit(RDS_MSG_RETRANSMITTED, &rm->m_flags))
+			rm->m_inc.i_hdr.h_flags |= RDS_FLAG_RETRANSMITTED;
+
+		/* If it has a RDMA op, tell the peer we did it. This is
+		 * used by the peer to release use-once RDMA MRs. */
+		if (rm->rdma.op_active) {
+			struct rds_ext_header_rdma ext_hdr = {};
+			struct rds_ext_header_rdma_bytes
+				rdma_bytes_ext_hdr = {};
+
+			ext_hdr.h_rdma_rkey = cpu_to_be32(rm->rdma.op_rkey);
+			if (rds_message_add_extension(&rm->m_inc.i_hdr,
+						      RDS_EXTHDR_RDMA,
+						      &ext_hdr)) {
+				/* prepare the rdma bytes ext header */
+				rdma_bytes_ext_hdr.h_rflags =
+					rm->rdma.op_write ?
+					RDS_FLAG_RDMA_WR_BYTES :
+					RDS_FLAG_RDMA_RD_BYTES;
+				rdma_bytes_ext_hdr.h_rdma_bytes =
+					cpu_to_be32(rm->rdma.op_bytes);
+			} else {
+				rdsdebug("RDS_EXTHDR_RDMA dropped");
+			}
+
+			if (rds_message_add_extension(&rm->m_inc.i_hdr,
+						      RDS_EXTHDR_RDMA_BYTES,
+						      &rdma_bytes_ext_hdr)) {
+				/* rdma bytes ext header was added successfully,
+				 * notify the remote side via flag in header
+				 */
+				rm->m_inc.i_hdr.h_flags |=
+					RDS_FLAG_EXTHDR_EXTENSION;
+			} else {
+				rdsdebug("RDS_EXTHDR_RDMA_BYTES dropped");
+			}
+		}
+		if (rm->m_rdma_cookie &&
+		    !rds_message_add_rdma_dest_extension(&rm->m_inc.i_hdr,
+				rds_rdma_cookie_key(rm->m_rdma_cookie),
+				rds_rdma_cookie_offset(rm->m_rdma_cookie))) {
+			rdsdebug("RDS_EXTHDR_RDMA_DEST dropped\n");
+		}
+
+		/* Note - rds_ib_piggyb_ack clears the ACK_REQUIRED bit, so
+		 * we should not do this unless we have a chance of at least
+		 * sticking the header into the send ring. Which is why we
+		 * should call rds_ib_ring_alloc first. */
+		rm->m_inc.i_hdr.h_ack = cpu_to_be64(rds_ib_piggyb_ack(ic));
+		rds_message_make_checksum(&rm->m_inc.i_hdr);
+
+		/*
+		 * Update adv_credits since we reset the ACK_REQUIRED bit.
+		 */
+		if (ic->i_flowctl) {
+			rds_ib_send_grab_credits(ic, 0, &posted, 1, RDS_MAX_ADV_CREDIT - adv_credits);
+			adv_credits += posted;
+			BUG_ON(adv_credits > 255);
+		}
+	}
+
+	/* Sometimes you want to put a fence between an RDMA
+	 * READ and the following SEND.
+	 * We could either do this all the time
+	 * or when requested by the user. Right now, we let
+	 * the application choose.
+	 */
+	if (rm->rdma.op_active && rm->rdma.op_fence)
+		send_flags = IB_SEND_FENCE;
+
+	/* Each frag gets a header. Msgs may be 0 bytes */
+	send = &ic->i_sends[pos];
+	first = send;
+	prev = NULL;
+	scat = &ic->i_data_op->op_sg[rm->data.op_dmasg];
+	i = 0;
+	do {
+		unsigned int len = 0;
+
+		/* Set up the header */
+		send->s_wr.send_flags = send_flags;
+		send->s_wr.opcode = IB_WR_SEND;
+		send->s_wr.num_sge = 1;
+		send->s_wr.next = NULL;
+		send->s_queued = jiffies;
+		send->s_op = NULL;
+
+		send->s_sge[0].addr = ic->i_send_hdrs_dma[pos];
+
+		send->s_sge[0].length = sizeof(struct rds_header);
+		send->s_sge[0].lkey = ic->i_pd->local_dma_lkey;
+
+		ib_dma_sync_single_for_cpu(ic->rds_ibdev->dev,
+					   ic->i_send_hdrs_dma[pos],
+					   sizeof(struct rds_header),
+					   DMA_TO_DEVICE);
+		memcpy(ic->i_send_hdrs[pos], &rm->m_inc.i_hdr,
+		       sizeof(struct rds_header));
+
+
+		/* Set up the data, if present */
+		if (i < work_alloc
+		    && scat != &rm->data.op_sg[rm->data.op_count]) {
+			len = min(RDS_FRAG_SIZE,
+				  sg_dma_len(scat) - rm->data.op_dmaoff);
+			send->s_wr.num_sge = 2;
+
+			send->s_sge[1].addr = sg_dma_address(scat);
+			send->s_sge[1].addr += rm->data.op_dmaoff;
+			send->s_sge[1].length = len;
+			send->s_sge[1].lkey = ic->i_pd->local_dma_lkey;
+
+			bytes_sent += len;
+			rm->data.op_dmaoff += len;
+			if (rm->data.op_dmaoff == sg_dma_len(scat)) {
+				scat++;
+				rm->data.op_dmasg++;
+				rm->data.op_dmaoff = 0;
+			}
+		}
+
+		rds_ib_set_wr_signal_state(ic, send, false);
+
+		/*
+		 * Always signal the last one if we're stopping due to flow control.
+		 */
+		if (ic->i_flowctl && flow_controlled && i == (work_alloc - 1)) {
+			rds_ib_set_wr_signal_state(ic, send, true);
+			send->s_wr.send_flags |= IB_SEND_SOLICITED;
+		}
+
+		if (send->s_wr.send_flags & IB_SEND_SIGNALED)
+			nr_sig++;
+
+		rdsdebug("send %p wr %p num_sge %u next %p\n", send,
+			 &send->s_wr, send->s_wr.num_sge, send->s_wr.next);
+
+		if (ic->i_flowctl && adv_credits) {
+			struct rds_header *hdr = ic->i_send_hdrs[pos];
+
+			/* add credit and redo the header checksum */
+			hdr->h_credit = adv_credits;
+			rds_message_make_checksum(hdr);
+			adv_credits = 0;
+			rds_ib_stats_inc(s_ib_tx_credit_updates);
+		}
+		ib_dma_sync_single_for_device(ic->rds_ibdev->dev,
+					      ic->i_send_hdrs_dma[pos],
+					      sizeof(struct rds_header),
+					      DMA_TO_DEVICE);
+
+		if (prev)
+			prev->s_wr.next = &send->s_wr;
+		prev = send;
+
+		pos = (pos + 1) % ic->i_send_ring.w_nr;
+		send = &ic->i_sends[pos];
+		i++;
+
+	} while (i < work_alloc
+		 && scat != &rm->data.op_sg[rm->data.op_count]);
+
+	/* Account the RDS header in the number of bytes we sent, but just once.
+	 * The caller has no concept of fragmentation. */
+	if (hdr_off == 0)
+		bytes_sent += sizeof(struct rds_header);
+
+	/* if we finished the message then send completion owns it */
+	if (scat == &rm->data.op_sg[rm->data.op_count]) {
+		prev->s_op = ic->i_data_op;
+		prev->s_wr.send_flags |= IB_SEND_SOLICITED;
+		if (!(prev->s_wr.send_flags & IB_SEND_SIGNALED))
+			nr_sig += rds_ib_set_wr_signal_state(ic, prev, true);
+		ic->i_data_op = NULL;
+	}
+
+	/* Put back wrs & credits we didn't use */
+	if (i < work_alloc) {
+		rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc - i);
+		work_alloc = i;
+	}
+	if (ic->i_flowctl && i < credit_alloc)
+		rds_ib_send_add_credits(conn, credit_alloc - i);
+
+	if (nr_sig)
+		atomic_add(nr_sig, &ic->i_signaled_sends);
+
+	/* XXX need to worry about failed_wr and partial sends. */
+	failed_wr = &first->s_wr;
+	ret = ib_post_send(ic->i_cm_id->qp, &first->s_wr, &failed_wr);
+	rdsdebug("ic %p first %p (wr %p) ret %d wr %p\n", ic,
+		 first, &first->s_wr, ret, failed_wr);
+	BUG_ON(failed_wr != &first->s_wr);
+	if (ret) {
+		printk(KERN_WARNING "RDS/IB: ib_post_send to %pI6c "
+		       "returned %d\n", &conn->c_faddr, ret);
+		rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc);
+		rds_ib_sub_signaled(ic, nr_sig);
+		if (prev->s_op) {
+			ic->i_data_op = prev->s_op;
+			prev->s_op = NULL;
+		}
+
+		rds_ib_conn_error(ic->conn, "ib_post_send failed\n");
+		goto out;
+	}
+
+	ret = bytes_sent;
+out:
+	BUG_ON(adv_credits);
+	return ret;
+}
+
+/*
+ * Issue atomic operation.
+ * A simplified version of the rdma case, we always map 1 SG, and
+ * only 8 bytes, for the return value from the atomic operation.
+ */
+int rds_ib_xmit_atomic(struct rds_connection *conn, struct rm_atomic_op *op)
+{
+	struct rds_ib_connection *ic = conn->c_transport_data;
+	struct rds_ib_send_work *send = NULL;
+	const struct ib_send_wr *failed_wr;
+	u32 pos;
+	u32 work_alloc;
+	int ret;
+	int nr_sig = 0;
+
+	work_alloc = rds_ib_ring_alloc(&ic->i_send_ring, 1, &pos);
+	if (work_alloc != 1) {
+		rds_ib_stats_inc(s_ib_tx_ring_full);
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	/* address of send request in ring */
+	send = &ic->i_sends[pos];
+	send->s_queued = jiffies;
+
+	if (op->op_type == RDS_ATOMIC_TYPE_CSWP) {
+		send->s_atomic_wr.wr.opcode = IB_WR_MASKED_ATOMIC_CMP_AND_SWP;
+		send->s_atomic_wr.compare_add = op->op_m_cswp.compare;
+		send->s_atomic_wr.swap = op->op_m_cswp.swap;
+		send->s_atomic_wr.compare_add_mask = op->op_m_cswp.compare_mask;
+		send->s_atomic_wr.swap_mask = op->op_m_cswp.swap_mask;
+	} else { /* FADD */
+		send->s_atomic_wr.wr.opcode = IB_WR_MASKED_ATOMIC_FETCH_AND_ADD;
+		send->s_atomic_wr.compare_add = op->op_m_fadd.add;
+		send->s_atomic_wr.swap = 0;
+		send->s_atomic_wr.compare_add_mask = op->op_m_fadd.nocarry_mask;
+		send->s_atomic_wr.swap_mask = 0;
+	}
+	send->s_wr.send_flags = 0;
+	nr_sig = rds_ib_set_wr_signal_state(ic, send, op->op_notify);
+	send->s_atomic_wr.wr.num_sge = 1;
+	send->s_atomic_wr.wr.next = NULL;
+	send->s_atomic_wr.remote_addr = op->op_remote_addr;
+	send->s_atomic_wr.rkey = op->op_rkey;
+	send->s_op = op;
+	rds_message_addref(container_of(send->s_op, struct rds_message, atomic));
+
+	/* map 8 byte retval buffer to the device */
+	ret = ib_dma_map_sg(ic->i_cm_id->device, op->op_sg, 1, DMA_FROM_DEVICE);
+	rdsdebug("ic %p mapping atomic op %p. mapped %d pg\n", ic, op, ret);
+	if (ret != 1) {
+		rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc);
+		rds_ib_stats_inc(s_ib_tx_sg_mapping_failure);
+		ret = -ENOMEM; /* XXX ? */
+		goto out;
+	}
+
+	/* Convert our struct scatterlist to struct ib_sge */
+	send->s_sge[0].addr = sg_dma_address(op->op_sg);
+	send->s_sge[0].length = sg_dma_len(op->op_sg);
+	send->s_sge[0].lkey = ic->i_pd->local_dma_lkey;
+
+	rdsdebug("rva %Lx rpa %Lx len %u\n", op->op_remote_addr,
+		 send->s_sge[0].addr, send->s_sge[0].length);
+
+	if (nr_sig)
+		atomic_add(nr_sig, &ic->i_signaled_sends);
+
+	failed_wr = &send->s_atomic_wr.wr;
+	ret = ib_post_send(ic->i_cm_id->qp, &send->s_atomic_wr.wr, &failed_wr);
+	rdsdebug("ic %p send %p (wr %p) ret %d wr %p\n", ic,
+		 send, &send->s_atomic_wr, ret, failed_wr);
+	BUG_ON(failed_wr != &send->s_atomic_wr.wr);
+	if (ret) {
+		printk(KERN_WARNING "RDS/IB: atomic ib_post_send to %pI6c "
+		       "returned %d\n", &conn->c_faddr, ret);
+		rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc);
+		rds_ib_sub_signaled(ic, nr_sig);
+		goto out;
+	}
+
+	if (unlikely(failed_wr != &send->s_atomic_wr.wr)) {
+		printk(KERN_WARNING "RDS/IB: atomic ib_post_send() rc=%d, but failed_wqe updated!\n", ret);
+		BUG_ON(failed_wr != &send->s_atomic_wr.wr);
+	}
+
+out:
+	return ret;
+}
+
+int rds_ib_xmit_rdma(struct rds_connection *conn, struct rm_rdma_op *op)
+{
+	struct rds_ib_connection *ic = conn->c_transport_data;
+	struct rds_ib_send_work *send = NULL;
+	struct rds_ib_send_work *first;
+	struct rds_ib_send_work *prev;
+	const struct ib_send_wr *failed_wr;
+	struct scatterlist *scat;
+	unsigned long len;
+	u64 remote_addr = op->op_remote_addr;
+	u32 max_sge = ic->rds_ibdev->max_sge;
+	u32 pos;
+	u32 work_alloc;
+	u32 i;
+	u32 j;
+	int sent;
+	int ret;
+	int num_sge;
+	int nr_sig = 0;
+	u64 odp_addr = op->op_odp_addr;
+	u32 odp_lkey = 0;
+
+	/* map the op the first time we see it */
+	if (!op->op_odp_mr) {
+		if (!op->op_mapped) {
+			op->op_count =
+				ib_dma_map_sg(ic->i_cm_id->device, op->op_sg,
+					      op->op_nents,
+					      (op->op_write) ? DMA_TO_DEVICE :
+							       DMA_FROM_DEVICE);
+			rdsdebug("ic %p mapping op %p: %d\n", ic, op,
+				 op->op_count);
+			if (op->op_count == 0) {
+				rds_ib_stats_inc(s_ib_tx_sg_mapping_failure);
+				ret = -ENOMEM; /* XXX ? */
+				goto out;
+			}
+			op->op_mapped = 1;
+		}
+	} else {
+		op->op_count = op->op_nents;
+		odp_lkey = rds_ib_get_lkey(op->op_odp_mr->r_trans_private);
+	}
+
+	/*
+	 * Instead of knowing how to return a partial rdma read/write we insist that there
+	 * be enough work requests to send the entire message.
+	 */
+	i = DIV_ROUND_UP(op->op_count, max_sge);
+
+	work_alloc = rds_ib_ring_alloc(&ic->i_send_ring, i, &pos);
+	if (work_alloc != i) {
+		rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc);
+		rds_ib_stats_inc(s_ib_tx_ring_full);
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	send = &ic->i_sends[pos];
+	first = send;
+	prev = NULL;
+	scat = &op->op_sg[0];
+	sent = 0;
+	num_sge = op->op_count;
+
+	for (i = 0; i < work_alloc && scat != &op->op_sg[op->op_count]; i++) {
+		send->s_wr.send_flags = 0;
+		send->s_queued = jiffies;
+		send->s_op = NULL;
+
+		if (!op->op_notify)
+			nr_sig += rds_ib_set_wr_signal_state(ic, send,
+							     op->op_notify);
+
+		send->s_wr.opcode = op->op_write ? IB_WR_RDMA_WRITE : IB_WR_RDMA_READ;
+		send->s_rdma_wr.remote_addr = remote_addr;
+		send->s_rdma_wr.rkey = op->op_rkey;
+
+		if (num_sge > max_sge) {
+			send->s_rdma_wr.wr.num_sge = max_sge;
+			num_sge -= max_sge;
+		} else {
+			send->s_rdma_wr.wr.num_sge = num_sge;
+		}
+
+		send->s_rdma_wr.wr.next = NULL;
+
+		if (prev)
+			prev->s_rdma_wr.wr.next = &send->s_rdma_wr.wr;
+
+		for (j = 0; j < send->s_rdma_wr.wr.num_sge &&
+		     scat != &op->op_sg[op->op_count]; j++) {
+			len = sg_dma_len(scat);
+			if (!op->op_odp_mr) {
+				send->s_sge[j].addr = sg_dma_address(scat);
+				send->s_sge[j].lkey = ic->i_pd->local_dma_lkey;
+			} else {
+				send->s_sge[j].addr = odp_addr;
+				send->s_sge[j].lkey = odp_lkey;
+			}
+			send->s_sge[j].length = len;
+
+			sent += len;
+			rdsdebug("ic %p sent %d remote_addr %llu\n", ic, sent, remote_addr);
+
+			remote_addr += len;
+			odp_addr += len;
+			scat++;
+		}
+
+		rdsdebug("send %p wr %p num_sge %u next %p\n", send,
+			&send->s_rdma_wr.wr,
+			send->s_rdma_wr.wr.num_sge,
+			send->s_rdma_wr.wr.next);
+
+		prev = send;
+		if (++send == &ic->i_sends[ic->i_send_ring.w_nr])
+			send = ic->i_sends;
+	}
+
+	/* give a reference to the last op */
+	if (scat == &op->op_sg[op->op_count]) {
+		prev->s_op = op;
+		rds_message_addref(container_of(op, struct rds_message, rdma));
+	}
+
+	if (i < work_alloc) {
+		rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc - i);
+		work_alloc = i;
+	}
+
+	if (nr_sig)
+		atomic_add(nr_sig, &ic->i_signaled_sends);
+
+	failed_wr = &first->s_rdma_wr.wr;
+	ret = ib_post_send(ic->i_cm_id->qp, &first->s_rdma_wr.wr, &failed_wr);
+	rdsdebug("ic %p first %p (wr %p) ret %d wr %p\n", ic,
+		 first, &first->s_rdma_wr.wr, ret, failed_wr);
+	BUG_ON(failed_wr != &first->s_rdma_wr.wr);
+	if (ret) {
+		printk(KERN_WARNING "RDS/IB: rdma ib_post_send to %pI6c "
+		       "returned %d\n", &conn->c_faddr, ret);
+		rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc);
+		rds_ib_sub_signaled(ic, nr_sig);
+		goto out;
+	}
+
+	if (unlikely(failed_wr != &first->s_rdma_wr.wr)) {
+		printk(KERN_WARNING "RDS/IB: ib_post_send() rc=%d, but failed_wqe updated!\n", ret);
+		BUG_ON(failed_wr != &first->s_rdma_wr.wr);
+	}
+
+
+out:
+	return ret;
+}
+
+void rds_ib_xmit_path_complete(struct rds_conn_path *cp)
+{
+	struct rds_connection *conn = cp->cp_conn;
+	struct rds_ib_connection *ic = conn->c_transport_data;
+
+	/* We may have a pending ACK or window update we were unable
+	 * to send previously (due to flow control). Try again. */
+	rds_ib_attempt_ack(ic);
+}
diff --git a/net/rds/ib_stats.c b/net/rds/ib_stats.c
new file mode 100644
index 000000000..ac46d8961
--- /dev/null
+++ b/net/rds/ib_stats.c
@@ -0,0 +1,107 @@
+/*
+ * Copyright (c) 2006 Oracle.  All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+#include <linux/percpu.h>
+#include <linux/seq_file.h>
+#include <linux/proc_fs.h>
+
+#include "rds.h"
+#include "ib.h"
+
+DEFINE_PER_CPU_SHARED_ALIGNED(struct rds_ib_statistics, rds_ib_stats);
+
+static const char *const rds_ib_stat_names[] = {
+	"ib_connect_raced",
+	"ib_listen_closed_stale",
+	"ib_evt_handler_call",
+	"ib_tasklet_call",
+	"ib_tx_cq_event",
+	"ib_tx_ring_full",
+	"ib_tx_throttle",
+	"ib_tx_sg_mapping_failure",
+	"ib_tx_stalled",
+	"ib_tx_credit_updates",
+	"ib_rx_cq_event",
+	"ib_rx_ring_empty",
+	"ib_rx_refill_from_cq",
+	"ib_rx_refill_from_thread",
+	"ib_rx_alloc_limit",
+	"ib_rx_total_frags",
+	"ib_rx_total_incs",
+	"ib_rx_credit_updates",
+	"ib_ack_sent",
+	"ib_ack_send_failure",
+	"ib_ack_send_delayed",
+	"ib_ack_send_piggybacked",
+	"ib_ack_received",
+	"ib_rdma_mr_8k_alloc",
+	"ib_rdma_mr_8k_free",
+	"ib_rdma_mr_8k_used",
+	"ib_rdma_mr_8k_pool_flush",
+	"ib_rdma_mr_8k_pool_wait",
+	"ib_rdma_mr_8k_pool_depleted",
+	"ib_rdma_mr_1m_alloc",
+	"ib_rdma_mr_1m_free",
+	"ib_rdma_mr_1m_used",
+	"ib_rdma_mr_1m_pool_flush",
+	"ib_rdma_mr_1m_pool_wait",
+	"ib_rdma_mr_1m_pool_depleted",
+	"ib_rdma_mr_8k_reused",
+	"ib_rdma_mr_1m_reused",
+	"ib_atomic_cswp",
+	"ib_atomic_fadd",
+};
+
+unsigned int rds_ib_stats_info_copy(struct rds_info_iterator *iter,
+				    unsigned int avail)
+{
+	struct rds_ib_statistics stats = {0, };
+	uint64_t *src;
+	uint64_t *sum;
+	size_t i;
+	int cpu;
+
+	if (avail < ARRAY_SIZE(rds_ib_stat_names))
+		goto out;
+
+	for_each_online_cpu(cpu) {
+		src = (uint64_t *)&(per_cpu(rds_ib_stats, cpu));
+		sum = (uint64_t *)&stats;
+		for (i = 0; i < sizeof(stats) / sizeof(uint64_t); i++)
+			*(sum++) += *(src++);
+	}
+
+	rds_stats_info_copy(iter, (uint64_t *)&stats, rds_ib_stat_names,
+			    ARRAY_SIZE(rds_ib_stat_names));
+out:
+	return ARRAY_SIZE(rds_ib_stat_names);
+}
diff --git a/net/rds/ib_sysctl.c b/net/rds/ib_sysctl.c
new file mode 100644
index 000000000..2af678e71
--- /dev/null
+++ b/net/rds/ib_sysctl.c
@@ -0,0 +1,120 @@
+/*
+ * Copyright (c) 2006 Oracle.  All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+#include <linux/kernel.h>
+#include <linux/sysctl.h>
+#include <linux/proc_fs.h>
+
+#include "ib.h"
+
+static struct ctl_table_header *rds_ib_sysctl_hdr;
+
+unsigned long rds_ib_sysctl_max_send_wr = RDS_IB_DEFAULT_SEND_WR;
+unsigned long rds_ib_sysctl_max_recv_wr = RDS_IB_DEFAULT_RECV_WR;
+unsigned long rds_ib_sysctl_max_recv_allocation = (128 * 1024 * 1024) / RDS_FRAG_SIZE;
+static unsigned long rds_ib_sysctl_max_wr_min = 1;
+/* hardware will fail CQ creation long before this */
+static unsigned long rds_ib_sysctl_max_wr_max = (u32)~0;
+
+unsigned long rds_ib_sysctl_max_unsig_wrs = 16;
+static unsigned long rds_ib_sysctl_max_unsig_wr_min = 1;
+static unsigned long rds_ib_sysctl_max_unsig_wr_max = 64;
+
+/*
+ * This sysctl does nothing.
+ *
+ * Backwards compatibility with RDS 3.0 wire protocol
+ * disables initial FC credit exchange.
+ * If it's ever possible to drop 3.0 support,
+ * setting this to 1 and moving init/refill of send/recv
+ * rings from ib_cm_connect_complete() back into ib_setup_qp()
+ * will cause credits to be added before protocol negotiation.
+ */
+unsigned int rds_ib_sysctl_flow_control = 0;
+
+static struct ctl_table rds_ib_sysctl_table[] = {
+	{
+		.procname       = "max_send_wr",
+		.data		= &rds_ib_sysctl_max_send_wr,
+		.maxlen         = sizeof(unsigned long),
+		.mode           = 0644,
+		.proc_handler   = proc_doulongvec_minmax,
+		.extra1		= &rds_ib_sysctl_max_wr_min,
+		.extra2		= &rds_ib_sysctl_max_wr_max,
+	},
+	{
+		.procname       = "max_recv_wr",
+		.data		= &rds_ib_sysctl_max_recv_wr,
+		.maxlen         = sizeof(unsigned long),
+		.mode           = 0644,
+		.proc_handler   = proc_doulongvec_minmax,
+		.extra1		= &rds_ib_sysctl_max_wr_min,
+		.extra2		= &rds_ib_sysctl_max_wr_max,
+	},
+	{
+		.procname       = "max_unsignaled_wr",
+		.data		= &rds_ib_sysctl_max_unsig_wrs,
+		.maxlen         = sizeof(unsigned long),
+		.mode           = 0644,
+		.proc_handler   = proc_doulongvec_minmax,
+		.extra1		= &rds_ib_sysctl_max_unsig_wr_min,
+		.extra2		= &rds_ib_sysctl_max_unsig_wr_max,
+	},
+	{
+		.procname       = "max_recv_allocation",
+		.data		= &rds_ib_sysctl_max_recv_allocation,
+		.maxlen         = sizeof(unsigned long),
+		.mode           = 0644,
+		.proc_handler   = proc_doulongvec_minmax,
+	},
+	{
+		.procname	= "flow_control",
+		.data		= &rds_ib_sysctl_flow_control,
+		.maxlen		= sizeof(rds_ib_sysctl_flow_control),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
+};
+
+void rds_ib_sysctl_exit(void)
+{
+	if (rds_ib_sysctl_hdr)
+		unregister_net_sysctl_table(rds_ib_sysctl_hdr);
+}
+
+int rds_ib_sysctl_init(void)
+{
+	rds_ib_sysctl_hdr = register_net_sysctl(&init_net, "net/rds/ib", rds_ib_sysctl_table);
+	if (!rds_ib_sysctl_hdr)
+		return -ENOMEM;
+	return 0;
+}
diff --git a/net/rds/info.c b/net/rds/info.c
new file mode 100644
index 000000000..31e7ad108
--- /dev/null
+++ b/net/rds/info.c
@@ -0,0 +1,267 @@
+/*
+ * Copyright (c) 2006 Oracle.  All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+#include <linux/percpu.h>
+#include <linux/seq_file.h>
+#include <linux/srcu.h>
+#include <linux/slab.h>
+#include <linux/proc_fs.h>
+#include <linux/export.h>
+#include <linux/uio.h>
+
+#include "rds.h"
+
+/*
+ * This file implements a getsockopt() call which copies a set of fixed
+ * sized structs into a user-specified buffer as a means of providing
+ * read-only information about RDS.
+ *
+ * For a given information source there are a given number of fixed sized
+ * structs at a given time.  The structs are only copied if the user-specified
+ * buffer is big enough.  The destination pages that make up the buffer
+ * are pinned for the duration of the copy.
+ *
+ * This gives us the following benefits:
+ *
+ * - simple implementation, no copy "position" across multiple calls
+ * - consistent snapshot of an info source
+ * - atomic copy works well with whatever locking info source has
+ * - one portable tool to get rds info across implementations
+ * - long-lived tool can get info without allocating
+ *
+ * at the following costs:
+ *
+ * - info source copy must be pinned, may be "large"
+ */
+
+struct rds_info_iterator {
+	struct page **pages;
+	void *addr;
+	unsigned long offset;
+};
+
+DEFINE_STATIC_SRCU(rds_info_srcu);
+static DEFINE_SPINLOCK(rds_info_lock);
+static rds_info_func rds_info_funcs[RDS_INFO_LAST - RDS_INFO_FIRST + 1];
+
+void rds_info_register_func(int optname, rds_info_func func)
+{
+	int offset = optname - RDS_INFO_FIRST;
+
+	BUG_ON(optname < RDS_INFO_FIRST || optname > RDS_INFO_LAST);
+
+	spin_lock(&rds_info_lock);
+	if (WARN_ON_ONCE(rds_info_funcs[offset])) {
+		spin_unlock(&rds_info_lock);
+		return;
+	}
+	WRITE_ONCE(rds_info_funcs[offset], func);
+	spin_unlock(&rds_info_lock);
+}
+EXPORT_SYMBOL_GPL(rds_info_register_func);
+
+void rds_info_deregister_func(int optname, rds_info_func func)
+{
+	int offset = optname - RDS_INFO_FIRST;
+
+	BUG_ON(optname < RDS_INFO_FIRST || optname > RDS_INFO_LAST);
+
+	spin_lock(&rds_info_lock);
+	if (WARN_ON_ONCE(rds_info_funcs[offset] != func)) {
+		spin_unlock(&rds_info_lock);
+		return;
+	}
+	WRITE_ONCE(rds_info_funcs[offset], NULL);
+	spin_unlock(&rds_info_lock);
+	synchronize_srcu(&rds_info_srcu);
+}
+EXPORT_SYMBOL_GPL(rds_info_deregister_func);
+
+/*
+ * Typically we hold an atomic kmap across multiple rds_info_copy() calls
+ * because the kmap is so expensive.  This must be called before using blocking
+ * operations while holding the mapping and as the iterator is torn down.
+ */
+void rds_info_iter_unmap(struct rds_info_iterator *iter)
+{
+	if (iter->addr) {
+		kunmap_atomic(iter->addr);
+		iter->addr = NULL;
+	}
+}
+
+/*
+ * get_user_pages() called flush_dcache_page() on the pages for us.
+ */
+void rds_info_copy(struct rds_info_iterator *iter, void *data,
+		   unsigned long bytes)
+{
+	unsigned long this;
+
+	while (bytes) {
+		if (!iter->addr)
+			iter->addr = kmap_atomic(*iter->pages);
+
+		this = min(bytes, PAGE_SIZE - iter->offset);
+
+		rdsdebug("page %p addr %p offset %lu this %lu data %p "
+			  "bytes %lu\n", *iter->pages, iter->addr,
+			  iter->offset, this, data, bytes);
+
+		memcpy(iter->addr + iter->offset, data, this);
+
+		data += this;
+		bytes -= this;
+		iter->offset += this;
+
+		if (iter->offset == PAGE_SIZE) {
+			kunmap_atomic(iter->addr);
+			iter->addr = NULL;
+			iter->offset = 0;
+			iter->pages++;
+		}
+	}
+}
+EXPORT_SYMBOL_GPL(rds_info_copy);
+
+/*
+ * @opt->iter_out describes the buffer that the information snapshot will be
+ * copied into, and @opt->optlen is the size of that buffer on input.  On
+ * output @opt->optlen is set to the size of the requested snapshot in bytes.
+ *
+ * This function returns -errno if there is a failure, particularly -ENOSPC
+ * if the given buffer was not large enough to fit the snapshot.  On success
+ * it returns the positive number of bytes of each array element in the
+ * snapshot.
+ */
+int rds_info_getsockopt(struct socket *sock, int optname, sockopt_t *opt)
+{
+	struct rds_info_iterator iter;
+	struct rds_info_lengths lens;
+	unsigned long nr_pages = 0;
+	rds_info_func func;
+	struct page **pages = NULL;
+	size_t offset0 = 0;
+	int srcu_idx;
+	int npages = 0;
+	int ret;
+	int len;
+	int total;
+
+	len = opt->optlen;
+
+	/* check for all kinds of wrapping and the like */
+	if (len < 0 || len > INT_MAX - PAGE_SIZE + 1) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	/* The info producers write into the pages with kmap_atomic() while
+	 * holding a spinlock, so they need a genuine page-backed user buffer.
+	 */
+	if (!user_backed_iter(&opt->iter_out)) {
+		ret = -EOPNOTSUPP;
+		goto out;
+	}
+
+	/* a 0 len call is just trying to probe its length */
+	if (len == 0)
+		goto call_func;
+
+	/*
+	 * Preallocate the page array and pass it in so that
+	 * iov_iter_extract_pages() fills it in place rather than allocating
+	 * one for us.  Handing it a non-NULL array keeps ownership of the
+	 * array with us on every return path, instead of depending on the
+	 * iterator code to allocate and hand it back.
+	 */
+	npages = iov_iter_npages(&opt->iter_out, INT_MAX);
+	pages = kvmalloc_array(npages, sizeof(*pages), GFP_KERNEL);
+	if (!pages) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	ret = iov_iter_extract_pages(&opt->iter_out, &pages, len, npages,
+				     0, &offset0);
+	if (ret < 0)
+		goto out;
+	nr_pages = DIV_ROUND_UP(offset0 + ret, PAGE_SIZE);
+	if (ret != len) {
+		ret = -EAGAIN; /* XXX ? */
+		goto out;
+	}
+
+	rdsdebug("len %d nr_pages %lu\n", len, nr_pages);
+
+call_func:
+	srcu_idx = srcu_read_lock(&rds_info_srcu);
+	func = READ_ONCE(rds_info_funcs[optname - RDS_INFO_FIRST]);
+	if (!func) {
+		srcu_read_unlock(&rds_info_srcu, srcu_idx);
+		ret = -ENOPROTOOPT;
+		goto out;
+	}
+
+	iter.pages = pages;
+	iter.addr = NULL;
+	iter.offset = offset0;
+
+	func(sock, len, &iter, &lens);
+	srcu_read_unlock(&rds_info_srcu, srcu_idx);
+	BUG_ON(lens.each == 0);
+
+	total = lens.nr * lens.each;
+
+	rds_info_iter_unmap(&iter);
+
+	if (total > len) {
+		len = total;
+		ret = -ENOSPC;
+	} else {
+		len = total;
+		ret = lens.each;
+	}
+
+	opt->optlen = len;
+
+out:
+	/*
+	 * iov_iter_extract_pages() pins only user-backed (ubuf) iters;
+	 * iov_iter_extract_will_pin() reports whether an unpin is owed here.
+	 */
+	if (pages && iov_iter_extract_will_pin(&opt->iter_out))
+		unpin_user_pages_dirty_lock(pages, nr_pages, true);
+	kvfree(pages);
+
+	return ret;
+}
diff --git a/net/rds/info.h b/net/rds/info.h
new file mode 100644
index 000000000..1aab62ab6
--- /dev/null
+++ b/net/rds/info.h
@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _RDS_INFO_H
+#define _RDS_INFO_H
+
+struct rds_info_lengths {
+	unsigned int	nr;
+	unsigned int	each;
+};
+
+struct rds_info_iterator;
+
+/*
+ * These functions must fill in the fields of @lens to reflect the size
+ * of the available info source.  If the snapshot fits in @len then it
+ * should be copied using @iter.  The caller will deduce if it was copied
+ * or not by comparing the lengths.
+ */
+typedef void (*rds_info_func)(struct socket *sock, unsigned int len,
+			      struct rds_info_iterator *iter,
+			      struct rds_info_lengths *lens);
+
+void rds_info_register_func(int optname, rds_info_func func);
+void rds_info_deregister_func(int optname, rds_info_func func);
+int rds_info_getsockopt(struct socket *sock, int optname, sockopt_t *opt);
+void rds_info_copy(struct rds_info_iterator *iter, void *data,
+		   unsigned long bytes);
+void rds_info_iter_unmap(struct rds_info_iterator *iter);
+
+
+#endif
diff --git a/net/rds/loop.c b/net/rds/loop.c
new file mode 100644
index 000000000..e6b0750bb
--- /dev/null
+++ b/net/rds/loop.c
@@ -0,0 +1,258 @@
+/*
+ * Copyright (c) 2006, 2017 Oracle and/or its affiliates. All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/in.h>
+#include <net/net_namespace.h>
+#include <net/netns/generic.h>
+#include <linux/ipv6.h>
+
+#include "rds_single_path.h"
+#include "rds.h"
+#include "loop.h"
+
+static DEFINE_SPINLOCK(loop_conns_lock);
+static LIST_HEAD(loop_conns);
+static atomic_t rds_loop_unloading = ATOMIC_INIT(0);
+
+static void rds_loop_set_unloading(void)
+{
+	atomic_set(&rds_loop_unloading, 1);
+}
+
+static bool rds_loop_is_unloading(struct rds_connection *conn)
+{
+	return atomic_read(&rds_loop_unloading) != 0;
+}
+
+/*
+ * This 'loopback' transport is a special case for flows that originate
+ * and terminate on the same machine.
+ *
+ * Connection build-up notices if the destination address is thought of
+ * as a local address by a transport.  At that time it decides to use the
+ * loopback transport instead of the bound transport of the sending socket.
+ *
+ * The loopback transport's sending path just hands the sent rds_message
+ * straight to the receiving path via an embedded rds_incoming.
+ */
+
+/*
+ * Usually a message transits both the sender and receiver's conns as it
+ * flows to the receiver.  In the loopback case, though, the receive path
+ * is handed the sending conn so the sense of the addresses is reversed.
+ */
+static int rds_loop_xmit(struct rds_connection *conn, struct rds_message *rm,
+			 unsigned int hdr_off, unsigned int sg,
+			 unsigned int off)
+{
+	struct scatterlist *sgp = &rm->data.op_sg[sg];
+	int ret = sizeof(struct rds_header) +
+			be32_to_cpu(rm->m_inc.i_hdr.h_len);
+
+	/* Do not send cong updates to loopback */
+	if (rm->m_inc.i_hdr.h_flags & RDS_FLAG_CONG_BITMAP) {
+		rds_cong_map_updated(conn->c_fcong, ~(u64) 0);
+		ret = min_t(int, ret, sgp->length - conn->c_xmit_data_off);
+		goto out;
+	}
+
+	BUG_ON(hdr_off || sg || off);
+
+	/* rds_send_queue_rm() stored the connection path in this embedded
+	 * inc; use the path init so the re-initialization keeps the field
+	 * valid instead of discarding it.
+	 */
+	rds_inc_path_init(&rm->m_inc, &conn->c_path[0], &conn->c_laddr);
+	/* For the embedded inc. Matching put is in loop_inc_free() */
+	rds_message_addref(rm);
+
+	rds_recv_incoming(conn, &conn->c_laddr, &conn->c_faddr, &rm->m_inc,
+			  GFP_KERNEL);
+
+	rds_send_drop_acked(conn, be64_to_cpu(rm->m_inc.i_hdr.h_sequence),
+			    NULL);
+
+	rds_inc_put(&rm->m_inc);
+out:
+	return ret;
+}
+
+/*
+ * See rds_loop_xmit(). Since our inc is embedded in the rm, we
+ * make sure the rm lives at least until the inc is done.
+ */
+static void rds_loop_inc_free(struct rds_incoming *inc)
+{
+	struct rds_message *rm = container_of(inc, struct rds_message, m_inc);
+
+	rds_message_put(rm);
+}
+
+/* we need to at least give the thread something to succeed */
+static int rds_loop_recv_path(struct rds_conn_path *cp)
+{
+	return 0;
+}
+
+struct rds_loop_connection {
+	struct list_head loop_node;
+	struct rds_connection *conn;
+};
+
+/*
+ * Even the loopback transport needs to keep track of its connections,
+ * so it can call rds_conn_destroy() on them on exit. N.B. there are
+ * 1+ loopback addresses (127.*.*.*) so it's not a bug to have
+ * multiple loopback conns allocated, although rather useless.
+ */
+static int rds_loop_conn_alloc(struct rds_connection *conn, gfp_t gfp)
+{
+	struct rds_loop_connection *lc;
+	unsigned long flags;
+
+	lc = kzalloc_obj(struct rds_loop_connection, gfp);
+	if (!lc)
+		return -ENOMEM;
+
+	INIT_LIST_HEAD(&lc->loop_node);
+	lc->conn = conn;
+	conn->c_transport_data = lc;
+
+	spin_lock_irqsave(&loop_conns_lock, flags);
+	list_add_tail(&lc->loop_node, &loop_conns);
+	spin_unlock_irqrestore(&loop_conns_lock, flags);
+
+	return 0;
+}
+
+static void rds_loop_conn_free(void *arg)
+{
+	struct rds_loop_connection *lc = arg;
+	unsigned long flags;
+
+	rdsdebug("lc %p\n", lc);
+	spin_lock_irqsave(&loop_conns_lock, flags);
+	list_del(&lc->loop_node);
+	spin_unlock_irqrestore(&loop_conns_lock, flags);
+	kfree(lc);
+}
+
+static int rds_loop_conn_path_connect(struct rds_conn_path *cp)
+{
+	rds_connect_complete(cp->cp_conn);
+	return 0;
+}
+
+static void rds_loop_conn_path_shutdown(struct rds_conn_path *cp)
+{
+}
+
+void rds_loop_exit(void)
+{
+	struct rds_loop_connection *lc, *_lc;
+	LIST_HEAD(tmp_list);
+
+	rds_loop_set_unloading();
+	synchronize_rcu();
+	/* avoid calling conn_destroy with irqs off */
+	spin_lock_irq(&loop_conns_lock);
+	list_splice(&loop_conns, &tmp_list);
+	INIT_LIST_HEAD(&loop_conns);
+	spin_unlock_irq(&loop_conns_lock);
+
+	list_for_each_entry_safe(lc, _lc, &tmp_list, loop_node) {
+		WARN_ON(lc->conn->c_passive);
+		rds_conn_destroy(lc->conn);
+	}
+}
+
+static void rds_loop_kill_conns(struct net *net)
+{
+	struct rds_loop_connection *lc, *_lc;
+	LIST_HEAD(tmp_list);
+
+	spin_lock_irq(&loop_conns_lock);
+	list_for_each_entry_safe(lc, _lc, &loop_conns, loop_node)  {
+		struct net *c_net = read_pnet(&lc->conn->c_net);
+
+		if (net != c_net)
+			continue;
+		list_move_tail(&lc->loop_node, &tmp_list);
+	}
+	spin_unlock_irq(&loop_conns_lock);
+
+	list_for_each_entry_safe(lc, _lc, &tmp_list, loop_node) {
+		WARN_ON(lc->conn->c_passive);
+		rds_conn_destroy(lc->conn);
+	}
+}
+
+static void __net_exit rds_loop_exit_net(struct net *net)
+{
+	rds_loop_kill_conns(net);
+}
+
+static struct pernet_operations rds_loop_net_ops = {
+	.exit = rds_loop_exit_net,
+};
+
+int rds_loop_net_init(void)
+{
+	return register_pernet_device(&rds_loop_net_ops);
+}
+
+void rds_loop_net_exit(void)
+{
+	unregister_pernet_device(&rds_loop_net_ops);
+}
+
+/*
+ * This is missing .xmit_* because loop doesn't go through generic
+ * rds_send_xmit() and doesn't call rds_recv_incoming().  .listen_stop and
+ * .laddr_check are missing because transport.c doesn't iterate over
+ * rds_loop_transport.
+ */
+struct rds_transport rds_loop_transport = {
+	.xmit			= rds_loop_xmit,
+	.recv_path		= rds_loop_recv_path,
+	.conn_alloc		= rds_loop_conn_alloc,
+	.conn_free		= rds_loop_conn_free,
+	.conn_path_connect	= rds_loop_conn_path_connect,
+	.conn_path_shutdown	= rds_loop_conn_path_shutdown,
+	.inc_copy_to_user	= rds_message_inc_copy_to_user,
+	.inc_free		= rds_loop_inc_free,
+	.t_name			= "loopback",
+	.t_type			= RDS_TRANS_LOOP,
+	.t_unloading		= rds_loop_is_unloading,
+};
diff --git a/net/rds/loop.h b/net/rds/loop.h
new file mode 100644
index 000000000..bbc8cdd03
--- /dev/null
+++ b/net/rds/loop.h
@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _RDS_LOOP_H
+#define _RDS_LOOP_H
+
+/* loop.c */
+extern struct rds_transport rds_loop_transport;
+
+int rds_loop_net_init(void);
+void rds_loop_net_exit(void);
+void rds_loop_exit(void);
+
+#endif
diff --git a/net/rds/message.c b/net/rds/message.c
new file mode 100644
index 000000000..f25f25925
--- /dev/null
+++ b/net/rds/message.c
@@ -0,0 +1,596 @@
+/*
+ * Copyright (c) 2006, 2020 Oracle and/or its affiliates.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/export.h>
+#include <linux/skbuff.h>
+#include <linux/list.h>
+#include <linux/errqueue.h>
+
+#include "rds.h"
+
+static unsigned int	rds_exthdr_size[__RDS_EXTHDR_MAX] = {
+[RDS_EXTHDR_NONE]	= 0,
+[RDS_EXTHDR_VERSION]	= sizeof(struct rds_ext_header_version),
+[RDS_EXTHDR_RDMA]	= sizeof(struct rds_ext_header_rdma),
+[RDS_EXTHDR_RDMA_DEST]	= sizeof(struct rds_ext_header_rdma_dest),
+[RDS_EXTHDR_RDMA_BYTES] = sizeof(struct rds_ext_header_rdma_bytes),
+[RDS_EXTHDR_NPATHS]	= sizeof(__be16),
+[RDS_EXTHDR_GEN_NUM]	= sizeof(__be32),
+[RDS_EXTHDR_SPORT_IDX]	= 1,
+};
+
+void rds_message_addref(struct rds_message *rm)
+{
+	rdsdebug("addref rm %p ref %d\n", rm, refcount_read(&rm->m_refcount));
+	refcount_inc(&rm->m_refcount);
+}
+EXPORT_SYMBOL_GPL(rds_message_addref);
+
+static inline bool rds_zcookie_add(struct rds_msg_zcopy_info *info, u32 cookie)
+{
+	struct rds_zcopy_cookies *ck = &info->zcookies;
+	int ncookies = ck->num;
+
+	if (ncookies == RDS_MAX_ZCOOKIES)
+		return false;
+	ck->cookies[ncookies] = cookie;
+	ck->num =  ++ncookies;
+	return true;
+}
+
+static struct rds_msg_zcopy_info *rds_info_from_znotifier(struct rds_znotifier *znotif)
+{
+	return container_of(znotif, struct rds_msg_zcopy_info, znotif);
+}
+
+void rds_notify_msg_zcopy_purge(struct rds_msg_zcopy_queue *q)
+{
+	unsigned long flags;
+	LIST_HEAD(copy);
+	struct rds_msg_zcopy_info *info, *tmp;
+
+	spin_lock_irqsave(&q->lock, flags);
+	list_splice(&q->zcookie_head, &copy);
+	INIT_LIST_HEAD(&q->zcookie_head);
+	spin_unlock_irqrestore(&q->lock, flags);
+
+	list_for_each_entry_safe(info, tmp, &copy, rs_zcookie_next) {
+		list_del(&info->rs_zcookie_next);
+		kfree(info);
+	}
+}
+
+static void rds_rm_zerocopy_callback(struct rds_sock *rs,
+				     struct rds_znotifier *znotif)
+{
+	struct rds_msg_zcopy_info *info;
+	struct rds_msg_zcopy_queue *q;
+	u32 cookie = znotif->z_cookie;
+	struct rds_zcopy_cookies *ck;
+	struct list_head *head;
+	unsigned long flags;
+
+	mm_unaccount_pinned_pages(&znotif->z_mmp);
+	q = &rs->rs_zcookie_queue;
+	spin_lock_irqsave(&q->lock, flags);
+	head = &q->zcookie_head;
+	if (!list_empty(head)) {
+		info = list_first_entry(head, struct rds_msg_zcopy_info,
+					rs_zcookie_next);
+		if (rds_zcookie_add(info, cookie)) {
+			spin_unlock_irqrestore(&q->lock, flags);
+			kfree(rds_info_from_znotifier(znotif));
+			/* caller invokes rds_wake_sk_sleep() */
+			return;
+		}
+	}
+
+	info = rds_info_from_znotifier(znotif);
+	ck = &info->zcookies;
+	memset(ck, 0, sizeof(*ck));
+	WARN_ON(!rds_zcookie_add(info, cookie));
+	list_add_tail(&info->rs_zcookie_next, &q->zcookie_head);
+
+	spin_unlock_irqrestore(&q->lock, flags);
+	/* caller invokes rds_wake_sk_sleep() */
+}
+
+/*
+ * This relies on dma_map_sg() not touching sg[].page during merging.
+ */
+static void rds_message_purge(struct rds_message *rm)
+{
+	struct rds_znotifier *znotifier;
+	unsigned long i, flags;
+	bool zcopy;
+
+	if (unlikely(test_bit(RDS_MSG_PAGEVEC, &rm->m_flags)))
+		return;
+
+	spin_lock_irqsave(&rm->m_rs_lock, flags);
+	znotifier = rm->data.op_mmp_znotifier;
+	rm->data.op_mmp_znotifier = NULL;
+	zcopy = !!znotifier;
+
+	if (rm->m_rs) {
+		struct rds_sock *rs = rm->m_rs;
+
+		if (znotifier) {
+			rds_rm_zerocopy_callback(rs, znotifier);
+			rds_wake_sk_sleep(rs);
+		}
+		sock_put(rds_rs_to_sk(rs));
+		rm->m_rs = NULL;
+	} else if (znotifier) {
+		/*
+		 * Zerocopy can fail before the message is queued on the
+		 * socket, so there is no rs to carry the notification.
+		 */
+		mm_unaccount_pinned_pages(&znotifier->z_mmp);
+		kfree(rds_info_from_znotifier(znotifier));
+	}
+	spin_unlock_irqrestore(&rm->m_rs_lock, flags);
+
+	for (i = 0; i < rm->data.op_nents; i++) {
+		/* XXX will have to put_page for page refs */
+		if (!zcopy)
+			__free_page(sg_page(&rm->data.op_sg[i]));
+		else
+			put_page(sg_page(&rm->data.op_sg[i]));
+	}
+	rm->data.op_nents = 0;
+
+	if (rm->rdma.op_active)
+		rds_rdma_free_op(&rm->rdma);
+	if (rm->rdma.op_rdma_mr)
+		kref_put(&rm->rdma.op_rdma_mr->r_kref, __rds_put_mr_final);
+
+	if (rm->atomic.op_active)
+		rds_atomic_free_op(&rm->atomic);
+	if (rm->atomic.op_rdma_mr)
+		kref_put(&rm->atomic.op_rdma_mr->r_kref, __rds_put_mr_final);
+}
+
+static void rds_message_unpin_worker(struct work_struct *work)
+{
+	struct rds_message *rm = container_of(work, struct rds_message,
+					      m_unpin_work);
+
+	if (rm->rdma.op_unpin_deferred)
+		rds_rdma_op_unpin_pages(&rm->rdma);
+	if (rm->atomic.op_unpin_deferred)
+		rds_atomic_op_unpin_page(&rm->atomic);
+
+	kfree(rm);
+}
+
+void rds_message_put(struct rds_message *rm)
+{
+	rdsdebug("put rm %p ref %d\n", rm, refcount_read(&rm->m_refcount));
+	WARN(!refcount_read(&rm->m_refcount), "danger refcount zero on %p\n", rm);
+	if (refcount_dec_and_test(&rm->m_refcount)) {
+		BUG_ON(!list_empty(&rm->m_sock_item));
+		BUG_ON(!list_empty(&rm->m_conn_item));
+
+		rds_message_purge(rm);
+
+		/* A final put in atomic context cannot dirty the ops'
+		 * user pages on unpin, so rds_rdma_free_op() and
+		 * rds_atomic_free_op() deferred it.  Finish the unpin,
+		 * and the free, from process context.
+		 */
+		if (rm->rdma.op_unpin_deferred ||
+		    rm->atomic.op_unpin_deferred) {
+			INIT_WORK(&rm->m_unpin_work, rds_message_unpin_worker);
+			queue_work(rds_wq, &rm->m_unpin_work);
+			return;
+		}
+
+		kfree(rm);
+	}
+}
+EXPORT_SYMBOL_GPL(rds_message_put);
+
+void rds_message_populate_header(struct rds_header *hdr, __be16 sport,
+				 __be16 dport, u64 seq)
+{
+	hdr->h_flags = 0;
+	hdr->h_sport = sport;
+	hdr->h_dport = dport;
+	hdr->h_sequence = cpu_to_be64(seq);
+	/* see rds_find_next_ext_space for reason why we memset the
+	 * ext header
+	 */
+	memset(hdr->h_exthdr, RDS_EXTHDR_NONE, RDS_HEADER_EXT_SPACE);
+}
+EXPORT_SYMBOL_GPL(rds_message_populate_header);
+
+/*
+ * Find the next place we can add an RDS header extension with
+ * specific length. Extension headers are pushed one after the
+ * other. In the following, the number after the colon is the number
+ * of bytes:
+ *
+ * [ type1:1 dta1:len1 [ type2:1 dta2:len2 ] ... ] RDS_EXTHDR_NONE
+ *
+ * If the extension headers fill the complete extension header space
+ * (16 bytes), the trailing RDS_EXTHDR_NONE is omitted.
+ */
+static int rds_find_next_ext_space(struct rds_header *hdr, unsigned int len,
+				   u8 **ext_start)
+{
+	unsigned int ext_len;
+	unsigned int type;
+	int ind = 0;
+
+	while ((ind + 1 + len) <= RDS_HEADER_EXT_SPACE) {
+		if (hdr->h_exthdr[ind] == RDS_EXTHDR_NONE) {
+			*ext_start = hdr->h_exthdr + ind;
+			return 0;
+		}
+
+		type = hdr->h_exthdr[ind];
+
+		ext_len = (type < __RDS_EXTHDR_MAX) ? rds_exthdr_size[type] : 0;
+		WARN_ONCE(!ext_len, "Unknown ext hdr type %d\n", type);
+		if (!ext_len)
+			return -EINVAL;
+
+		/* ind points to a valid ext hdr with known length */
+		ind += 1 + ext_len;
+	}
+
+	/* no room for extension */
+	return -ENOSPC;
+}
+
+/* The ext hdr space is prefilled with zero from the kzalloc() */
+int rds_message_add_extension(struct rds_header *hdr,
+			      unsigned int type, const void *data)
+{
+	unsigned char *dst;
+	unsigned int len;
+
+	len = (type < __RDS_EXTHDR_MAX) ? rds_exthdr_size[type] : 0;
+	if (!len)
+		return 0;
+
+	if (rds_find_next_ext_space(hdr, len, &dst))
+		return 0;
+
+	*dst++ = type;
+	memcpy(dst, data, len);
+
+	return 1;
+}
+EXPORT_SYMBOL_GPL(rds_message_add_extension);
+
+/*
+ * If a message has extension headers, retrieve them here.
+ * Call like this:
+ *
+ * unsigned int pos = 0;
+ *
+ * while (1) {
+ *	buflen = sizeof(buffer);
+ *	type = rds_message_next_extension(hdr, &pos, buffer, &buflen);
+ *	if (type == RDS_EXTHDR_NONE)
+ *		break;
+ *	...
+ * }
+ */
+int rds_message_next_extension(struct rds_header *hdr,
+		unsigned int *pos, void *buf, unsigned int *buflen)
+{
+	unsigned int offset, ext_type, ext_len;
+	u8 *src = hdr->h_exthdr;
+
+	offset = *pos;
+	if (offset >= RDS_HEADER_EXT_SPACE)
+		goto none;
+
+	/* Get the extension type and length. For now, the
+	 * length is implied by the extension type. */
+	ext_type = src[offset++];
+
+	if (ext_type == RDS_EXTHDR_NONE || ext_type >= __RDS_EXTHDR_MAX)
+		goto none;
+	ext_len = rds_exthdr_size[ext_type];
+	if (offset + ext_len > RDS_HEADER_EXT_SPACE)
+		goto none;
+
+	*pos = offset + ext_len;
+	if (ext_len < *buflen)
+		*buflen = ext_len;
+	memcpy(buf, src + offset, *buflen);
+	return ext_type;
+
+none:
+	*pos = RDS_HEADER_EXT_SPACE;
+	*buflen = 0;
+	return RDS_EXTHDR_NONE;
+}
+
+int rds_message_add_rdma_dest_extension(struct rds_header *hdr, u32 r_key, u32 offset)
+{
+	struct rds_ext_header_rdma_dest ext_hdr;
+
+	ext_hdr.h_rdma_rkey = cpu_to_be32(r_key);
+	ext_hdr.h_rdma_offset = cpu_to_be32(offset);
+	return rds_message_add_extension(hdr, RDS_EXTHDR_RDMA_DEST, &ext_hdr);
+}
+EXPORT_SYMBOL_GPL(rds_message_add_rdma_dest_extension);
+
+/*
+ * Each rds_message is allocated with extra space for the scatterlist entries
+ * rds ops will need. This is to minimize memory allocation count. Then, each rds op
+ * can grab SGs when initializing its part of the rds_message.
+ */
+struct rds_message *rds_message_alloc(unsigned int extra_len, gfp_t gfp)
+{
+	struct rds_message *rm;
+
+	if (extra_len > KMALLOC_MAX_SIZE - sizeof(struct rds_message))
+		return NULL;
+
+	rm = kzalloc(sizeof(struct rds_message) + extra_len, gfp);
+	if (!rm)
+		goto out;
+
+	rm->m_used_sgs = 0;
+	rm->m_total_sgs = extra_len / sizeof(struct scatterlist);
+
+	refcount_set(&rm->m_refcount, 1);
+	INIT_LIST_HEAD(&rm->m_sock_item);
+	INIT_LIST_HEAD(&rm->m_conn_item);
+	spin_lock_init(&rm->m_rs_lock);
+	init_waitqueue_head(&rm->m_flush_wait);
+
+out:
+	return rm;
+}
+
+/*
+ * RDS ops use this to grab SG entries from the rm's sg pool.
+ */
+struct scatterlist *rds_message_alloc_sgs(struct rds_message *rm, int nents)
+{
+	struct scatterlist *sg_first = (struct scatterlist *) &rm[1];
+	struct scatterlist *sg_ret;
+
+	if (nents <= 0) {
+		pr_warn("rds: alloc sgs failed! nents <= 0\n");
+		return ERR_PTR(-EINVAL);
+	}
+
+	if (rm->m_used_sgs + nents > rm->m_total_sgs) {
+		pr_warn("rds: alloc sgs failed! total %d used %d nents %d\n",
+			rm->m_total_sgs, rm->m_used_sgs, nents);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	sg_ret = &sg_first[rm->m_used_sgs];
+	sg_init_table(sg_ret, nents);
+	rm->m_used_sgs += nents;
+
+	return sg_ret;
+}
+
+struct rds_message *rds_message_map_pages(unsigned long *page_addrs, unsigned int total_len)
+{
+	struct rds_message *rm;
+	unsigned int i;
+	int num_sgs = DIV_ROUND_UP(total_len, PAGE_SIZE);
+	int extra_bytes = num_sgs * sizeof(struct scatterlist);
+
+	rm = rds_message_alloc(extra_bytes, GFP_NOWAIT);
+	if (!rm)
+		return ERR_PTR(-ENOMEM);
+
+	set_bit(RDS_MSG_PAGEVEC, &rm->m_flags);
+	rm->m_inc.i_hdr.h_len = cpu_to_be32(total_len);
+	rm->data.op_nents = DIV_ROUND_UP(total_len, PAGE_SIZE);
+	rm->data.op_sg = rds_message_alloc_sgs(rm, num_sgs);
+	if (IS_ERR(rm->data.op_sg)) {
+		void *err = ERR_CAST(rm->data.op_sg);
+		rds_message_put(rm);
+		return err;
+	}
+
+	for (i = 0; i < rm->data.op_nents; ++i) {
+		sg_set_page(&rm->data.op_sg[i],
+				virt_to_page((void *)page_addrs[i]),
+				PAGE_SIZE, 0);
+	}
+
+	return rm;
+}
+
+static int rds_message_zcopy_from_user(struct rds_message *rm, struct iov_iter *from)
+{
+	struct scatterlist *sg;
+	int ret = 0;
+	int length = iov_iter_count(from);
+	struct rds_msg_zcopy_info *info;
+
+	rm->m_inc.i_hdr.h_len = cpu_to_be32(iov_iter_count(from));
+
+	/*
+	 * now allocate and copy in the data payload.
+	 */
+	sg = rm->data.op_sg;
+
+	info = kzalloc_obj(*info);
+	if (!info)
+		return -ENOMEM;
+	INIT_LIST_HEAD(&info->rs_zcookie_next);
+	rm->data.op_mmp_znotifier = &info->znotif;
+	if (mm_account_pinned_pages(&rm->data.op_mmp_znotifier->z_mmp,
+				    length)) {
+		ret = -ENOMEM;
+		goto err;
+	}
+	while (iov_iter_count(from)) {
+		struct page *pages;
+		size_t start;
+		ssize_t copied;
+
+		copied = iov_iter_get_pages2(from, &pages, PAGE_SIZE,
+					    1, &start);
+		if (copied < 0) {
+			struct mmpin *mmp;
+			int i;
+
+			for (i = 0; i < rm->data.op_nents; i++)
+				put_page(sg_page(&rm->data.op_sg[i]));
+			rm->data.op_nents = 0;
+			mmp = &rm->data.op_mmp_znotifier->z_mmp;
+			mm_unaccount_pinned_pages(mmp);
+			ret = -EFAULT;
+			goto err;
+		}
+		length -= copied;
+		sg_set_page(sg, pages, copied, start);
+		rm->data.op_nents++;
+		sg++;
+	}
+	WARN_ON_ONCE(length != 0);
+	return ret;
+err:
+	kfree(info);
+	rm->data.op_mmp_znotifier = NULL;
+	return ret;
+}
+
+int rds_message_copy_from_user(struct rds_message *rm, struct iov_iter *from,
+			       bool zcopy)
+{
+	unsigned long to_copy, nbytes;
+	unsigned long sg_off;
+	struct scatterlist *sg;
+	int ret = 0;
+
+	rm->m_inc.i_hdr.h_len = cpu_to_be32(iov_iter_count(from));
+
+	/* now allocate and copy in the data payload.  */
+	sg = rm->data.op_sg;
+	sg_off = 0; /* Dear gcc, sg->page will be null from kzalloc. */
+
+	if (zcopy)
+		return rds_message_zcopy_from_user(rm, from);
+
+	while (iov_iter_count(from)) {
+		if (!sg_page(sg)) {
+			ret = rds_page_remainder_alloc(sg, iov_iter_count(from),
+						       GFP_HIGHUSER);
+			if (ret)
+				return ret;
+			rm->data.op_nents++;
+			sg_off = 0;
+		}
+
+		to_copy = min_t(unsigned long, iov_iter_count(from),
+				sg->length - sg_off);
+
+		rds_stats_add(s_copy_from_user, to_copy);
+		nbytes = copy_page_from_iter(sg_page(sg), sg->offset + sg_off,
+					     to_copy, from);
+		if (nbytes != to_copy)
+			return -EFAULT;
+
+		sg_off += to_copy;
+
+		if (sg_off == sg->length)
+			sg++;
+	}
+
+	return ret;
+}
+
+int rds_message_inc_copy_to_user(struct rds_incoming *inc, struct iov_iter *to)
+{
+	struct rds_message *rm;
+	struct scatterlist *sg;
+	unsigned long to_copy;
+	unsigned long vec_off;
+	int copied;
+	int ret;
+	u32 len;
+
+	rm = container_of(inc, struct rds_message, m_inc);
+	len = be32_to_cpu(rm->m_inc.i_hdr.h_len);
+
+	sg = rm->data.op_sg;
+	vec_off = 0;
+	copied = 0;
+
+	while (iov_iter_count(to) && copied < len) {
+		to_copy = min_t(unsigned long, iov_iter_count(to),
+				sg->length - vec_off);
+		to_copy = min_t(unsigned long, to_copy, len - copied);
+
+		rds_stats_add(s_copy_to_user, to_copy);
+		ret = copy_page_to_iter(sg_page(sg), sg->offset + vec_off,
+					to_copy, to);
+		if (ret != to_copy)
+			return -EFAULT;
+
+		vec_off += to_copy;
+		copied += to_copy;
+
+		if (vec_off == sg->length) {
+			vec_off = 0;
+			sg++;
+		}
+	}
+
+	return copied;
+}
+
+/*
+ * If the message is still on the send queue, wait until the transport
+ * is done with it. This is particularly important for RDMA operations.
+ */
+void rds_message_wait(struct rds_message *rm)
+{
+	wait_event_interruptible(rm->m_flush_wait,
+			!test_bit(RDS_MSG_MAPPED, &rm->m_flags));
+}
+
+void rds_message_unmapped(struct rds_message *rm)
+{
+	clear_bit(RDS_MSG_MAPPED, &rm->m_flags);
+	wake_up_interruptible(&rm->m_flush_wait);
+}
+EXPORT_SYMBOL_GPL(rds_message_unmapped);
diff --git a/net/rds/page.c b/net/rds/page.c
new file mode 100644
index 000000000..afb151eac
--- /dev/null
+++ b/net/rds/page.c
@@ -0,0 +1,170 @@
+/*
+ * Copyright (c) 2006 Oracle.  All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+#include <linux/highmem.h>
+#include <linux/gfp.h>
+#include <linux/cpu.h>
+#include <linux/export.h>
+
+#include "rds.h"
+
+struct rds_page_remainder {
+	struct page	*r_page;
+	unsigned long	r_offset;
+	local_lock_t	bh_lock;
+};
+
+static DEFINE_PER_CPU_SHARED_ALIGNED(struct rds_page_remainder, rds_page_remainders) = {
+	.bh_lock = INIT_LOCAL_LOCK(bh_lock),
+};
+
+/**
+ * rds_page_remainder_alloc - build up regions of a message.
+ *
+ * @scat: Scatter list for message
+ * @bytes: the number of bytes needed.
+ * @gfp: the waiting behaviour of the allocation
+ *
+ * @gfp is always ored with __GFP_HIGHMEM.  Callers must be prepared to
+ * kmap the pages, etc.
+ *
+ * If @bytes is at least a full page then this just returns a page from
+ * alloc_page().
+ *
+ * If @bytes is a partial page then this stores the unused region of the
+ * page in a per-cpu structure.  Future partial-page allocations may be
+ * satisfied from that cached region.  This lets us waste less memory on
+ * small allocations with minimal complexity.  It works because the transmit
+ * path passes read-only page regions down to devices.  They hold a page
+ * reference until they are done with the region.
+ */
+int rds_page_remainder_alloc(struct scatterlist *scat, unsigned long bytes,
+			     gfp_t gfp)
+{
+	struct rds_page_remainder *rem;
+	struct page *page;
+	int ret;
+
+	gfp |= __GFP_HIGHMEM;
+
+	/* jump straight to allocation if we're trying for a huge page */
+	if (bytes >= PAGE_SIZE) {
+		page = alloc_page(gfp);
+		if (!page) {
+			ret = -ENOMEM;
+		} else {
+			sg_set_page(scat, page, PAGE_SIZE, 0);
+			ret = 0;
+		}
+		goto out;
+	}
+
+	local_bh_disable();
+	local_lock_nested_bh(&rds_page_remainders.bh_lock);
+	rem = this_cpu_ptr(&rds_page_remainders);
+
+	while (1) {
+		/* avoid a tiny region getting stuck by tossing it */
+		if (rem->r_page && bytes > (PAGE_SIZE - rem->r_offset)) {
+			rds_stats_inc(s_page_remainder_miss);
+			__free_page(rem->r_page);
+			rem->r_page = NULL;
+		}
+
+		/* hand out a fragment from the cached page */
+		if (rem->r_page && bytes <= (PAGE_SIZE - rem->r_offset)) {
+			sg_set_page(scat, rem->r_page, bytes, rem->r_offset);
+			get_page(sg_page(scat));
+
+			if (rem->r_offset != 0)
+				rds_stats_inc(s_page_remainder_hit);
+
+			rem->r_offset += ALIGN(bytes, 8);
+			if (rem->r_offset >= PAGE_SIZE) {
+				__free_page(rem->r_page);
+				rem->r_page = NULL;
+			}
+			ret = 0;
+			break;
+		}
+
+		/* alloc if there is nothing for us to use */
+		local_unlock_nested_bh(&rds_page_remainders.bh_lock);
+		local_bh_enable();
+
+		page = alloc_page(gfp);
+
+		local_bh_disable();
+		local_lock_nested_bh(&rds_page_remainders.bh_lock);
+		rem = this_cpu_ptr(&rds_page_remainders);
+
+		if (!page) {
+			ret = -ENOMEM;
+			break;
+		}
+
+		/* did someone race to fill the remainder before us? */
+		if (rem->r_page) {
+			__free_page(page);
+			continue;
+		}
+
+		/* otherwise install our page and loop around to alloc */
+		rem->r_page = page;
+		rem->r_offset = 0;
+	}
+
+	local_unlock_nested_bh(&rds_page_remainders.bh_lock);
+	local_bh_enable();
+out:
+	rdsdebug("bytes %lu ret %d %p %u %u\n", bytes, ret,
+		 ret ? NULL : sg_page(scat), ret ? 0 : scat->offset,
+		 ret ? 0 : scat->length);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(rds_page_remainder_alloc);
+
+void rds_page_exit(void)
+{
+	unsigned int cpu;
+
+	for_each_possible_cpu(cpu) {
+		struct rds_page_remainder *rem;
+
+		rem = &per_cpu(rds_page_remainders, cpu);
+		rdsdebug("cpu %u\n", cpu);
+
+		if (rem->r_page)
+			__free_page(rem->r_page);
+		rem->r_page = NULL;
+	}
+}
diff --git a/net/rds/rdma.c b/net/rds/rdma.c
new file mode 100644
index 000000000..078090d29
--- /dev/null
+++ b/net/rds/rdma.c
@@ -0,0 +1,993 @@
+/*
+ * Copyright (c) 2007, 2020 Oracle and/or its affiliates.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+#include <linux/pagemap.h>
+#include <linux/slab.h>
+#include <linux/rbtree.h>
+#include <linux/dma-mapping.h> /* for DMA_*_DEVICE */
+
+#include "rds.h"
+
+/*
+ * XXX
+ *  - build with sparse
+ *  - should we detect duplicate keys on a socket?  hmm.
+ *  - an rdma is an mlock, apply rlimit?
+ */
+
+/*
+ * get the number of pages by looking at the page indices that the start and
+ * end addresses fall in.
+ *
+ * Returns 0 if the vec is invalid.  It is invalid if the number of bytes
+ * causes the address to wrap or overflows an unsigned int.  This comes
+ * from being stored in the 'length' member of 'struct scatterlist'.
+ */
+static unsigned int rds_pages_in_vec(struct rds_iovec *vec)
+{
+	if ((vec->addr + vec->bytes <= vec->addr) ||
+	    (vec->bytes > (u64)UINT_MAX))
+		return 0;
+
+	return ((vec->addr + vec->bytes + PAGE_SIZE - 1) >> PAGE_SHIFT) -
+		(vec->addr >> PAGE_SHIFT);
+}
+
+static struct rds_mr *rds_mr_tree_walk(struct rb_root *root, u64 key,
+				       struct rds_mr *insert)
+{
+	struct rb_node **p = &root->rb_node;
+	struct rb_node *parent = NULL;
+	struct rds_mr *mr;
+
+	while (*p) {
+		parent = *p;
+		mr = rb_entry(parent, struct rds_mr, r_rb_node);
+
+		if (key < mr->r_key)
+			p = &(*p)->rb_left;
+		else if (key > mr->r_key)
+			p = &(*p)->rb_right;
+		else
+			return mr;
+	}
+
+	if (insert) {
+		rb_link_node(&insert->r_rb_node, parent, p);
+		rb_insert_color(&insert->r_rb_node, root);
+		kref_get(&insert->r_kref);
+	}
+	return NULL;
+}
+
+/*
+ * Destroy the transport-specific part of a MR.
+ */
+static void rds_destroy_mr(struct rds_mr *mr)
+{
+	struct rds_sock *rs = mr->r_sock;
+	void *trans_private = NULL;
+	unsigned long flags;
+
+	rdsdebug("RDS: destroy mr key is %x refcnt %u\n",
+		 mr->r_key, kref_read(&mr->r_kref));
+
+	spin_lock_irqsave(&rs->rs_rdma_lock, flags);
+	if (!RB_EMPTY_NODE(&mr->r_rb_node))
+		rb_erase(&mr->r_rb_node, &rs->rs_rdma_keys);
+	trans_private = mr->r_trans_private;
+	mr->r_trans_private = NULL;
+	spin_unlock_irqrestore(&rs->rs_rdma_lock, flags);
+
+	if (trans_private)
+		mr->r_trans->free_mr(trans_private, mr->r_invalidate);
+}
+
+void __rds_put_mr_final(struct kref *kref)
+{
+	struct rds_mr *mr = container_of(kref, struct rds_mr, r_kref);
+
+	rds_destroy_mr(mr);
+	sock_put(rds_rs_to_sk(mr->r_sock));
+	kfree(mr);
+}
+
+/*
+ * By the time this is called we can't have any more ioctls called on
+ * the socket so we don't need to worry about racing with others.
+ */
+void rds_rdma_drop_keys(struct rds_sock *rs)
+{
+	struct rds_mr *mr;
+	struct rb_node *node;
+	unsigned long flags;
+
+	/* Release any MRs associated with this socket */
+	spin_lock_irqsave(&rs->rs_rdma_lock, flags);
+	while ((node = rb_first(&rs->rs_rdma_keys))) {
+		mr = rb_entry(node, struct rds_mr, r_rb_node);
+		if (mr->r_trans == rs->rs_transport)
+			mr->r_invalidate = 0;
+		rb_erase(&mr->r_rb_node, &rs->rs_rdma_keys);
+		RB_CLEAR_NODE(&mr->r_rb_node);
+		spin_unlock_irqrestore(&rs->rs_rdma_lock, flags);
+		kref_put(&mr->r_kref, __rds_put_mr_final);
+		spin_lock_irqsave(&rs->rs_rdma_lock, flags);
+	}
+	spin_unlock_irqrestore(&rs->rs_rdma_lock, flags);
+
+	if (rs->rs_transport && rs->rs_transport->flush_mrs)
+		rs->rs_transport->flush_mrs();
+}
+
+/*
+ * Helper function to pin user pages.
+ */
+static int rds_pin_pages(unsigned long user_addr, unsigned int nr_pages,
+			struct page **pages, int write)
+{
+	unsigned int gup_flags = FOLL_LONGTERM;
+	int ret;
+
+	if (write)
+		gup_flags |= FOLL_WRITE;
+
+	ret = pin_user_pages_fast(user_addr, nr_pages, gup_flags, pages);
+	if (ret >= 0 && ret < nr_pages) {
+		unpin_user_pages(pages, ret);
+		ret = -EFAULT;
+	}
+
+	return ret;
+}
+
+static int __rds_rdma_map(struct rds_sock *rs, struct rds_get_mr_args *args,
+			  u64 *cookie_ret, struct rds_mr **mr_ret,
+			  struct rds_conn_path *cp)
+{
+	struct rds_mr *mr = NULL, *found;
+	struct scatterlist *sg = NULL;
+	unsigned int nr_pages;
+	struct page **pages = NULL;
+	void *trans_private;
+	unsigned long flags;
+	rds_rdma_cookie_t cookie;
+	unsigned int nents = 0;
+	int need_odp = 0;
+	long i;
+	int ret;
+
+	if (ipv6_addr_any(&rs->rs_bound_addr) || !rs->rs_transport) {
+		ret = -ENOTCONN; /* XXX not a great errno */
+		goto out;
+	}
+
+	if (!rs->rs_transport->get_mr) {
+		ret = -EOPNOTSUPP;
+		goto out;
+	}
+
+	/* If the combination of the addr and size requested for this memory
+	 * region causes an integer overflow, return error.
+	 */
+	if (((args->vec.addr + args->vec.bytes) < args->vec.addr) ||
+	    PAGE_ALIGN(args->vec.addr + args->vec.bytes) <
+		    (args->vec.addr + args->vec.bytes)) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	if (!can_do_mlock()) {
+		ret = -EPERM;
+		goto out;
+	}
+
+	nr_pages = rds_pages_in_vec(&args->vec);
+	if (nr_pages == 0) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	/* Restrict the size of mr irrespective of underlying transport
+	 * To account for unaligned mr regions, subtract one from nr_pages
+	 */
+	if ((nr_pages - 1) > (RDS_MAX_MSG_SIZE >> PAGE_SHIFT)) {
+		ret = -EMSGSIZE;
+		goto out;
+	}
+
+	rdsdebug("RDS: get_mr addr %llx len %llu nr_pages %u\n",
+		args->vec.addr, args->vec.bytes, nr_pages);
+
+	/* XXX clamp nr_pages to limit the size of this alloc? */
+	pages = kzalloc_objs(struct page *, nr_pages);
+	if (!pages) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	mr = kzalloc_obj(struct rds_mr);
+	if (!mr) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	kref_init(&mr->r_kref);
+	RB_CLEAR_NODE(&mr->r_rb_node);
+	mr->r_trans = rs->rs_transport;
+	/* The MR can outlive its socket: a socket reference is held
+	 * until the final kref is dropped in __rds_put_mr_final().
+	 */
+	mr->r_sock = rs;
+	sock_hold(rds_rs_to_sk(rs));
+
+	if (args->flags & RDS_RDMA_USE_ONCE)
+		mr->r_use_once = 1;
+	if (args->flags & RDS_RDMA_INVALIDATE)
+		mr->r_invalidate = 1;
+	if (args->flags & RDS_RDMA_READWRITE)
+		mr->r_write = 1;
+
+	/*
+	 * Pin the pages that make up the user buffer and transfer the page
+	 * pointers to the mr's sg array.  We check to see if we've mapped
+	 * the whole region after transferring the partial page references
+	 * to the sg array so that we can have one page ref cleanup path.
+	 *
+	 * For now we have no flag that tells us whether the mapping is
+	 * r/o or r/w. We need to assume r/w, or we'll do a lot of RDMA to
+	 * the zero page.
+	 */
+	ret = rds_pin_pages(args->vec.addr, nr_pages, pages, 1);
+	if (ret == -EOPNOTSUPP) {
+		need_odp = 1;
+	} else if (ret <= 0) {
+		goto out;
+	} else {
+		nents = ret;
+		sg = kmalloc_objs(*sg, nents);
+		if (!sg) {
+			ret = -ENOMEM;
+			goto out;
+		}
+		WARN_ON(!nents);
+		sg_init_table(sg, nents);
+
+		/* Stick all pages into the scatterlist */
+		for (i = 0 ; i < nents; i++)
+			sg_set_page(&sg[i], pages[i], PAGE_SIZE, 0);
+
+		rdsdebug("RDS: trans_private nents is %u\n", nents);
+	}
+	/* Obtain a transport specific MR. If this succeeds, the
+	 * s/g list is now owned by the MR.
+	 * Note that dma_map() implies that pending writes are
+	 * flushed to RAM, so no dma_sync is needed here. */
+	trans_private = rs->rs_transport->get_mr(
+		sg, nents, rs, &mr->r_key, cp ? cp->cp_conn : NULL,
+		args->vec.addr, args->vec.bytes,
+		need_odp ? ODP_ZEROBASED : ODP_NOT_NEEDED);
+
+	if (IS_ERR(trans_private)) {
+		/* In ODP case, we don't GUP pages, so don't need
+		 * to release anything.
+		 */
+		if (!need_odp) {
+			unpin_user_pages(pages, nr_pages);
+			kfree(sg);
+		}
+		ret = PTR_ERR(trans_private);
+		/* Trigger connection so that its ready for the next retry */
+		if (ret == -ENODEV && cp)
+			rds_conn_connect_if_down(cp->cp_conn);
+		goto out;
+	}
+
+	mr->r_trans_private = trans_private;
+
+	rdsdebug("RDS: get_mr put_user key is %x cookie_addr %p\n",
+	       mr->r_key, (void *)(unsigned long) args->cookie_addr);
+
+	/* The user may pass us an unaligned address, but we can only
+	 * map page aligned regions. So we keep the offset, and build
+	 * a 64bit cookie containing <R_Key, offset> and pass that
+	 * around. */
+	if (need_odp)
+		cookie = rds_rdma_make_cookie(mr->r_key, 0);
+	else
+		cookie = rds_rdma_make_cookie(mr->r_key,
+					      args->vec.addr & ~PAGE_MASK);
+	if (cookie_ret)
+		*cookie_ret = cookie;
+
+	if (args->cookie_addr &&
+	    put_user(cookie, (u64 __user *)(unsigned long)args->cookie_addr)) {
+		ret = -EFAULT;
+		goto out;
+	}
+
+	/* Inserting the new MR into the rbtree bumps its
+	 * reference count. */
+	spin_lock_irqsave(&rs->rs_rdma_lock, flags);
+	found = rds_mr_tree_walk(&rs->rs_rdma_keys, mr->r_key, mr);
+	spin_unlock_irqrestore(&rs->rs_rdma_lock, flags);
+
+	BUG_ON(found && found != mr);
+
+	rdsdebug("RDS: get_mr key is %x\n", mr->r_key);
+	if (mr_ret) {
+		kref_get(&mr->r_kref);
+		*mr_ret = mr;
+	}
+
+	ret = 0;
+out:
+	kfree(pages);
+	if (mr)
+		kref_put(&mr->r_kref, __rds_put_mr_final);
+	return ret;
+}
+
+int rds_get_mr(struct rds_sock *rs, sockptr_t optval, int optlen)
+{
+	struct rds_get_mr_args args;
+
+	if (optlen != sizeof(struct rds_get_mr_args))
+		return -EINVAL;
+
+	if (copy_from_sockptr(&args, optval, sizeof(struct rds_get_mr_args)))
+		return -EFAULT;
+
+	return __rds_rdma_map(rs, &args, NULL, NULL, NULL);
+}
+
+int rds_get_mr_for_dest(struct rds_sock *rs, sockptr_t optval, int optlen)
+{
+	struct rds_get_mr_for_dest_args args;
+	struct rds_get_mr_args new_args;
+
+	if (optlen != sizeof(struct rds_get_mr_for_dest_args))
+		return -EINVAL;
+
+	if (copy_from_sockptr(&args, optval,
+			   sizeof(struct rds_get_mr_for_dest_args)))
+		return -EFAULT;
+
+	/*
+	 * Initially, just behave like get_mr().
+	 * TODO: Implement get_mr as wrapper around this
+	 *	 and deprecate it.
+	 */
+	new_args.vec = args.vec;
+	new_args.cookie_addr = args.cookie_addr;
+	new_args.flags = args.flags;
+
+	return __rds_rdma_map(rs, &new_args, NULL, NULL, NULL);
+}
+
+/*
+ * Free the MR indicated by the given R_Key
+ */
+int rds_free_mr(struct rds_sock *rs, sockptr_t optval, int optlen)
+{
+	struct rds_free_mr_args args;
+	struct rds_mr *mr;
+	unsigned long flags;
+
+	if (optlen != sizeof(struct rds_free_mr_args))
+		return -EINVAL;
+
+	if (copy_from_sockptr(&args, optval, sizeof(struct rds_free_mr_args)))
+		return -EFAULT;
+
+	/* Special case - a null cookie means flush all unused MRs */
+	if (args.cookie == 0) {
+		if (!rs->rs_transport || !rs->rs_transport->flush_mrs)
+			return -EINVAL;
+		rs->rs_transport->flush_mrs();
+		return 0;
+	}
+
+	/* Look up the MR given its R_key and remove it from the rbtree
+	 * so nobody else finds it.
+	 * This should also prevent races with rds_rdma_unuse.
+	 */
+	spin_lock_irqsave(&rs->rs_rdma_lock, flags);
+	mr = rds_mr_tree_walk(&rs->rs_rdma_keys, rds_rdma_cookie_key(args.cookie), NULL);
+	if (mr) {
+		rb_erase(&mr->r_rb_node, &rs->rs_rdma_keys);
+		RB_CLEAR_NODE(&mr->r_rb_node);
+		if (args.flags & RDS_RDMA_INVALIDATE)
+			mr->r_invalidate = 1;
+	}
+	spin_unlock_irqrestore(&rs->rs_rdma_lock, flags);
+
+	if (!mr)
+		return -EINVAL;
+
+	kref_put(&mr->r_kref, __rds_put_mr_final);
+	return 0;
+}
+
+/*
+ * This is called when we receive an extension header that
+ * tells us this MR was used. It allows us to implement
+ * use_once semantics
+ */
+void rds_rdma_unuse(struct rds_sock *rs, u32 r_key, int force)
+{
+	struct rds_mr *mr;
+	unsigned long flags;
+	int zot_me = 0;
+
+	spin_lock_irqsave(&rs->rs_rdma_lock, flags);
+	mr = rds_mr_tree_walk(&rs->rs_rdma_keys, r_key, NULL);
+	if (!mr) {
+		pr_debug("rds: trying to unuse MR with unknown r_key %u!\n",
+			 r_key);
+		spin_unlock_irqrestore(&rs->rs_rdma_lock, flags);
+		return;
+	}
+
+	/* Get a reference so that the MR won't go away before calling
+	 * sync_mr() below.
+	 */
+	kref_get(&mr->r_kref);
+
+	/* If it is going to be freed, remove it from the tree now so
+	 * that no other thread can find it and free it.
+	 */
+	if (mr->r_use_once || force) {
+		rb_erase(&mr->r_rb_node, &rs->rs_rdma_keys);
+		RB_CLEAR_NODE(&mr->r_rb_node);
+		zot_me = 1;
+	}
+	spin_unlock_irqrestore(&rs->rs_rdma_lock, flags);
+
+	/* May have to issue a dma_sync on this memory region.
+	 * Note we could avoid this if the operation was a RDMA READ,
+	 * but at this point we can't tell. */
+	if (mr->r_trans->sync_mr)
+		mr->r_trans->sync_mr(mr->r_trans_private, DMA_FROM_DEVICE);
+
+	/* Release the reference held above. */
+	kref_put(&mr->r_kref, __rds_put_mr_final);
+
+	/* If the MR was marked as invalidate, this will
+	 * trigger an async flush. */
+	if (zot_me)
+		kref_put(&mr->r_kref, __rds_put_mr_final);
+}
+
+void rds_rdma_op_unpin_pages(struct rm_rdma_op *ro)
+{
+	unsigned int i;
+
+	for (i = 0; i < ro->op_nents; i++) {
+		struct page *page = sg_page(&ro->op_sg[i]);
+
+		/* Mark page dirty if it was possibly modified, which
+		 * is the case for a RDMA_READ which copies from remote
+		 * to local memory
+		 */
+		unpin_user_pages_dirty_lock(&page, 1, !ro->op_write);
+	}
+}
+
+void rds_rdma_free_op(struct rm_rdma_op *ro)
+{
+	if (ro->op_odp_mr) {
+		kref_put(&ro->op_odp_mr->r_kref, __rds_put_mr_final);
+	} else if (in_task() || ro->op_write) {
+		/* An RDMA write's pages are only read by the remote
+		 * side; unpinning without dirtying does not sleep.
+		 */
+		rds_rdma_op_unpin_pages(ro);
+	} else {
+		/* Dirtying the pages on unpin can sleep; leave them
+		 * pinned and have rds_message_put() finish the unpin
+		 * from process context.
+		 */
+		ro->op_unpin_deferred = 1;
+	}
+
+	kfree(ro->op_notifier);
+	ro->op_notifier = NULL;
+	ro->op_active = 0;
+	ro->op_odp_mr = NULL;
+}
+
+void rds_atomic_op_unpin_page(struct rm_atomic_op *ao)
+{
+	struct page *page = sg_page(ao->op_sg);
+
+	/* Mark page dirty if it was possibly modified, which
+	 * is the case for a RDMA_READ which copies from remote
+	 * to local memory */
+	unpin_user_pages_dirty_lock(&page, 1, true);
+}
+
+void rds_atomic_free_op(struct rm_atomic_op *ao)
+{
+	if (in_task()) {
+		rds_atomic_op_unpin_page(ao);
+	} else {
+		/* Dirtying the page on unpin can sleep; leave it
+		 * pinned and have rds_message_put() finish the unpin
+		 * from process context.
+		 */
+		ao->op_unpin_deferred = 1;
+	}
+
+	kfree(ao->op_notifier);
+	ao->op_notifier = NULL;
+	ao->op_active = 0;
+}
+
+
+/*
+ * Count the number of pages needed to describe an incoming iovec array.
+ */
+static int rds_rdma_pages(struct rds_iovec iov[], int nr_iovecs)
+{
+	int tot_pages = 0;
+	unsigned int nr_pages;
+	unsigned int i;
+
+	/* figure out the number of pages in the vector */
+	for (i = 0; i < nr_iovecs; i++) {
+		nr_pages = rds_pages_in_vec(&iov[i]);
+		if (nr_pages == 0)
+			return -EINVAL;
+
+		tot_pages += nr_pages;
+
+		/*
+		 * nr_pages for one entry is limited to (UINT_MAX>>PAGE_SHIFT)+1,
+		 * so tot_pages cannot overflow without first going negative.
+		 */
+		if (tot_pages < 0)
+			return -EINVAL;
+	}
+
+	return tot_pages;
+}
+
+int rds_rdma_extra_size(struct rds_rdma_args *args,
+			struct rds_iov_vector *iov)
+{
+	struct rds_iovec *vec;
+	struct rds_iovec __user *local_vec;
+	int tot_pages = 0;
+	unsigned int nr_pages;
+	unsigned int i;
+
+	local_vec = (struct rds_iovec __user *)(unsigned long) args->local_vec_addr;
+
+	if (args->nr_local == 0)
+		return -EINVAL;
+
+	if (args->nr_local > UIO_MAXIOV)
+		return -EMSGSIZE;
+
+	iov->iov = kzalloc_objs(struct rds_iovec, args->nr_local);
+	if (!iov->iov)
+		return -ENOMEM;
+
+	vec = &iov->iov[0];
+
+	if (copy_from_user(vec, local_vec, args->nr_local *
+			   sizeof(struct rds_iovec)))
+		return -EFAULT;
+	iov->len = args->nr_local;
+
+	/* figure out the number of pages in the vector */
+	for (i = 0; i < args->nr_local; i++, vec++) {
+
+		nr_pages = rds_pages_in_vec(vec);
+		if (nr_pages == 0)
+			return -EINVAL;
+
+		tot_pages += nr_pages;
+
+		/*
+		 * nr_pages for one entry is limited to (UINT_MAX>>PAGE_SHIFT)+1,
+		 * so tot_pages cannot overflow without first going negative.
+		 */
+		if (tot_pages < 0)
+			return -EINVAL;
+	}
+
+	return tot_pages * sizeof(struct scatterlist);
+}
+
+/*
+ * The application asks for a RDMA transfer.
+ * Extract all arguments and set up the rdma_op
+ */
+int rds_cmsg_rdma_args(struct rds_sock *rs, struct rds_message *rm,
+		       struct cmsghdr *cmsg,
+		       struct rds_iov_vector *vec)
+{
+	struct rds_rdma_args *args;
+	struct rm_rdma_op *op = &rm->rdma;
+	int nr_pages;
+	unsigned int nr_bytes;
+	struct page **pages = NULL;
+	struct rds_iovec *iovs;
+	unsigned int i, j;
+	int ret = 0;
+	bool odp_supported = true;
+
+	if (cmsg->cmsg_len < CMSG_LEN(sizeof(struct rds_rdma_args))
+	    || rm->rdma.op_active)
+		return -EINVAL;
+
+	args = CMSG_DATA(cmsg);
+
+	if (ipv6_addr_any(&rs->rs_bound_addr)) {
+		ret = -ENOTCONN; /* XXX not a great errno */
+		goto out_ret;
+	}
+
+	if (args->nr_local > UIO_MAXIOV) {
+		ret = -EMSGSIZE;
+		goto out_ret;
+	}
+
+	if (vec->len != args->nr_local) {
+		ret = -EINVAL;
+		goto out_ret;
+	}
+	/* odp-mr is not supported for multiple requests within one message */
+	if (args->nr_local != 1)
+		odp_supported = false;
+
+	iovs = vec->iov;
+
+	nr_pages = rds_rdma_pages(iovs, args->nr_local);
+	if (nr_pages < 0) {
+		ret = -EINVAL;
+		goto out_ret;
+	}
+
+	pages = kzalloc_objs(struct page *, nr_pages);
+	if (!pages) {
+		ret = -ENOMEM;
+		goto out_ret;
+	}
+
+	op->op_write = !!(args->flags & RDS_RDMA_READWRITE);
+	op->op_fence = !!(args->flags & RDS_RDMA_FENCE);
+	op->op_notify = !!(args->flags & RDS_RDMA_NOTIFY_ME);
+	op->op_silent = !!(args->flags & RDS_RDMA_SILENT);
+	op->op_active = 1;
+	op->op_recverr = rs->rs_recverr;
+	op->op_odp_mr = NULL;
+
+	WARN_ON(!nr_pages);
+	op->op_sg = rds_message_alloc_sgs(rm, nr_pages);
+	if (IS_ERR(op->op_sg)) {
+		ret = PTR_ERR(op->op_sg);
+		goto out_pages;
+	}
+
+	if (op->op_notify || op->op_recverr) {
+		/* We allocate an uninitialized notifier here, because
+		 * we don't want to do that in the completion handler. We
+		 * would have to use GFP_ATOMIC there, and don't want to deal
+		 * with failed allocations.
+		 */
+		op->op_notifier = kmalloc_obj(struct rds_notifier);
+		if (!op->op_notifier) {
+			ret = -ENOMEM;
+			goto out_pages;
+		}
+		op->op_notifier->n_user_token = args->user_token;
+		op->op_notifier->n_status = RDS_RDMA_SUCCESS;
+	}
+
+	/* The cookie contains the R_Key of the remote memory region, and
+	 * optionally an offset into it. This is how we implement RDMA into
+	 * unaligned memory.
+	 * When setting up the RDMA, we need to add that offset to the
+	 * destination address (which is really an offset into the MR)
+	 * FIXME: We may want to move this into ib_rdma.c
+	 */
+	op->op_rkey = rds_rdma_cookie_key(args->cookie);
+	op->op_remote_addr = args->remote_vec.addr + rds_rdma_cookie_offset(args->cookie);
+
+	nr_bytes = 0;
+
+	rdsdebug("RDS: rdma prepare nr_local %llu rva %llx rkey %x\n",
+	       (unsigned long long)args->nr_local,
+	       (unsigned long long)args->remote_vec.addr,
+	       op->op_rkey);
+
+	for (i = 0; i < args->nr_local; i++) {
+		struct rds_iovec *iov = &iovs[i];
+		/* don't need to check, rds_rdma_pages() verified nr will be +nonzero */
+		unsigned int nr = rds_pages_in_vec(iov);
+
+		rs->rs_user_addr = iov->addr;
+		rs->rs_user_bytes = iov->bytes;
+
+		/* If it's a WRITE operation, we want to pin the pages for reading.
+		 * If it's a READ operation, we need to pin the pages for writing.
+		 */
+		ret = rds_pin_pages(iov->addr, nr, pages, !op->op_write);
+		if ((!odp_supported && ret <= 0) ||
+		    (odp_supported && ret <= 0 && ret != -EOPNOTSUPP))
+			goto out_pages;
+
+		if (ret == -EOPNOTSUPP) {
+			struct rds_mr *local_odp_mr;
+
+			if (!rs->rs_transport->get_mr) {
+				ret = -EOPNOTSUPP;
+				goto out_pages;
+			}
+			local_odp_mr = kzalloc_obj(*local_odp_mr);
+			if (!local_odp_mr) {
+				ret = -ENOMEM;
+				goto out_pages;
+			}
+			RB_CLEAR_NODE(&local_odp_mr->r_rb_node);
+			kref_init(&local_odp_mr->r_kref);
+			local_odp_mr->r_trans = rs->rs_transport;
+			/* The MR can outlive its socket: a socket
+			 * reference is held until the final kref is
+			 * dropped in __rds_put_mr_final().
+			 */
+			local_odp_mr->r_sock = rs;
+			sock_hold(rds_rs_to_sk(rs));
+			local_odp_mr->r_trans_private =
+				rs->rs_transport->get_mr(
+					NULL, 0, rs, &local_odp_mr->r_key, NULL,
+					iov->addr, iov->bytes, ODP_VIRTUAL);
+			if (IS_ERR(local_odp_mr->r_trans_private)) {
+				ret = PTR_ERR(local_odp_mr->r_trans_private);
+				rdsdebug("get_mr ret %d %p\"", ret,
+					 local_odp_mr->r_trans_private);
+				local_odp_mr->r_trans_private = NULL;
+				kref_put(&local_odp_mr->r_kref,
+					 __rds_put_mr_final);
+				ret = -EOPNOTSUPP;
+				goto out_pages;
+			}
+			rdsdebug("Need odp; local_odp_mr %p trans_private %p\n",
+				 local_odp_mr, local_odp_mr->r_trans_private);
+			op->op_odp_mr = local_odp_mr;
+			op->op_odp_addr = iov->addr;
+		}
+
+		rdsdebug("RDS: nr_bytes %u nr %u iov->bytes %llu iov->addr %llx\n",
+			 nr_bytes, nr, iov->bytes, iov->addr);
+
+		nr_bytes += iov->bytes;
+
+		for (j = 0; j < nr; j++) {
+			unsigned int offset = iov->addr & ~PAGE_MASK;
+			struct scatterlist *sg;
+
+			sg = &op->op_sg[op->op_nents + j];
+			sg_set_page(sg, pages[j],
+					min_t(unsigned int, iov->bytes, PAGE_SIZE - offset),
+					offset);
+
+			sg_dma_len(sg) = sg->length;
+			rdsdebug("RDS: sg->offset %x sg->len %x iov->addr %llx iov->bytes %llu\n",
+			       sg->offset, sg->length, iov->addr, iov->bytes);
+
+			iov->addr += sg->length;
+			iov->bytes -= sg->length;
+		}
+
+		op->op_nents += nr;
+	}
+
+	if (nr_bytes > args->remote_vec.bytes) {
+		rdsdebug("RDS nr_bytes %u remote_bytes %u do not match\n",
+				nr_bytes,
+				(unsigned int) args->remote_vec.bytes);
+		ret = -EINVAL;
+		goto out_pages;
+	}
+	op->op_bytes = nr_bytes;
+	ret = 0;
+
+out_pages:
+	kfree(pages);
+out_ret:
+	if (ret)
+		rds_rdma_free_op(op);
+	else
+		rds_stats_inc(s_send_rdma);
+
+	return ret;
+}
+
+/*
+ * The application wants us to pass an RDMA destination (aka MR)
+ * to the remote
+ */
+int rds_cmsg_rdma_dest(struct rds_sock *rs, struct rds_message *rm,
+			  struct cmsghdr *cmsg)
+{
+	unsigned long flags;
+	struct rds_mr *mr;
+	u32 r_key;
+	int err = 0;
+
+	if (cmsg->cmsg_len < CMSG_LEN(sizeof(rds_rdma_cookie_t)) ||
+	    rm->m_rdma_cookie != 0)
+		return -EINVAL;
+
+	memcpy(&rm->m_rdma_cookie, CMSG_DATA(cmsg), sizeof(rm->m_rdma_cookie));
+
+	/* We are reusing a previously mapped MR here. Most likely, the
+	 * application has written to the buffer, so we need to explicitly
+	 * flush those writes to RAM. Otherwise the HCA may not see them
+	 * when doing a DMA from that buffer.
+	 */
+	r_key = rds_rdma_cookie_key(rm->m_rdma_cookie);
+
+	spin_lock_irqsave(&rs->rs_rdma_lock, flags);
+	mr = rds_mr_tree_walk(&rs->rs_rdma_keys, r_key, NULL);
+	if (!mr)
+		err = -EINVAL;	/* invalid r_key */
+	else
+		kref_get(&mr->r_kref);
+	spin_unlock_irqrestore(&rs->rs_rdma_lock, flags);
+
+	if (mr) {
+		mr->r_trans->sync_mr(mr->r_trans_private,
+				     DMA_TO_DEVICE);
+		rm->rdma.op_rdma_mr = mr;
+	}
+	return err;
+}
+
+/*
+ * The application passes us an address range it wants to enable RDMA
+ * to/from. We map the area, and save the <R_Key,offset> pair
+ * in rm->m_rdma_cookie. This causes it to be sent along to the peer
+ * in an extension header.
+ */
+int rds_cmsg_rdma_map(struct rds_sock *rs, struct rds_message *rm,
+			  struct cmsghdr *cmsg)
+{
+	if (cmsg->cmsg_len < CMSG_LEN(sizeof(struct rds_get_mr_args)) ||
+	    rm->m_rdma_cookie != 0)
+		return -EINVAL;
+
+	return __rds_rdma_map(rs, CMSG_DATA(cmsg), &rm->m_rdma_cookie,
+			      &rm->rdma.op_rdma_mr, rm->m_conn_path);
+}
+
+/*
+ * Fill in rds_message for an atomic request.
+ */
+int rds_cmsg_atomic(struct rds_sock *rs, struct rds_message *rm,
+		    struct cmsghdr *cmsg)
+{
+	struct page *page = NULL;
+	struct rds_atomic_args *args;
+	int ret = 0;
+
+	if (cmsg->cmsg_len < CMSG_LEN(sizeof(struct rds_atomic_args))
+	 || rm->atomic.op_active)
+		return -EINVAL;
+
+	args = CMSG_DATA(cmsg);
+
+	/* Nonmasked & masked cmsg ops converted to masked hw ops */
+	switch (cmsg->cmsg_type) {
+	case RDS_CMSG_ATOMIC_FADD:
+		rm->atomic.op_type = RDS_ATOMIC_TYPE_FADD;
+		rm->atomic.op_m_fadd.add = args->fadd.add;
+		rm->atomic.op_m_fadd.nocarry_mask = 0;
+		break;
+	case RDS_CMSG_MASKED_ATOMIC_FADD:
+		rm->atomic.op_type = RDS_ATOMIC_TYPE_FADD;
+		rm->atomic.op_m_fadd.add = args->m_fadd.add;
+		rm->atomic.op_m_fadd.nocarry_mask = args->m_fadd.nocarry_mask;
+		break;
+	case RDS_CMSG_ATOMIC_CSWP:
+		rm->atomic.op_type = RDS_ATOMIC_TYPE_CSWP;
+		rm->atomic.op_m_cswp.compare = args->cswp.compare;
+		rm->atomic.op_m_cswp.swap = args->cswp.swap;
+		rm->atomic.op_m_cswp.compare_mask = ~0;
+		rm->atomic.op_m_cswp.swap_mask = ~0;
+		break;
+	case RDS_CMSG_MASKED_ATOMIC_CSWP:
+		rm->atomic.op_type = RDS_ATOMIC_TYPE_CSWP;
+		rm->atomic.op_m_cswp.compare = args->m_cswp.compare;
+		rm->atomic.op_m_cswp.swap = args->m_cswp.swap;
+		rm->atomic.op_m_cswp.compare_mask = args->m_cswp.compare_mask;
+		rm->atomic.op_m_cswp.swap_mask = args->m_cswp.swap_mask;
+		break;
+	default:
+		BUG(); /* should never happen */
+	}
+
+	rm->atomic.op_notify = !!(args->flags & RDS_RDMA_NOTIFY_ME);
+	rm->atomic.op_silent = !!(args->flags & RDS_RDMA_SILENT);
+	rm->atomic.op_active = 1;
+	rm->atomic.op_recverr = rs->rs_recverr;
+	rm->atomic.op_sg = rds_message_alloc_sgs(rm, 1);
+	if (IS_ERR(rm->atomic.op_sg)) {
+		ret = PTR_ERR(rm->atomic.op_sg);
+		goto err;
+	}
+
+	/* verify 8 byte-aligned */
+	if (args->local_addr & 0x7) {
+		ret = -EFAULT;
+		goto err;
+	}
+
+	ret = rds_pin_pages(args->local_addr, 1, &page, 1);
+	if (ret != 1)
+		goto err;
+	ret = 0;
+
+	sg_set_page(rm->atomic.op_sg, page, 8, offset_in_page(args->local_addr));
+
+	if (rm->atomic.op_notify || rm->atomic.op_recverr) {
+		/* We allocate an uninitialized notifier here, because
+		 * we don't want to do that in the completion handler. We
+		 * would have to use GFP_ATOMIC there, and don't want to deal
+		 * with failed allocations.
+		 */
+		rm->atomic.op_notifier = kmalloc_obj(*rm->atomic.op_notifier);
+		if (!rm->atomic.op_notifier) {
+			ret = -ENOMEM;
+			goto err;
+		}
+
+		rm->atomic.op_notifier->n_user_token = args->user_token;
+		rm->atomic.op_notifier->n_status = RDS_RDMA_SUCCESS;
+	}
+
+	rm->atomic.op_rkey = rds_rdma_cookie_key(args->cookie);
+	rm->atomic.op_remote_addr = args->remote_addr + rds_rdma_cookie_offset(args->cookie);
+
+	return ret;
+err:
+	if (page)
+		unpin_user_page(page);
+	rm->atomic.op_active = 0;
+	kfree(rm->atomic.op_notifier);
+
+	return ret;
+}
diff --git a/net/rds/rdma_transport.c b/net/rds/rdma_transport.c
new file mode 100644
index 000000000..b15cf316b
--- /dev/null
+++ b/net/rds/rdma_transport.c
@@ -0,0 +1,322 @@
+/*
+ * Copyright (c) 2009, 2018 Oracle and/or its affiliates. All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+#include <linux/module.h>
+#include <rdma/rdma_cm.h>
+
+#include "rds_single_path.h"
+#include "rdma_transport.h"
+#include "ib.h"
+
+/* Global IPv4 and IPv6 RDS RDMA listener cm_id */
+static struct rdma_cm_id *rds_rdma_listen_id;
+#if IS_ENABLED(CONFIG_IPV6)
+static struct rdma_cm_id *rds6_rdma_listen_id;
+#endif
+
+/* Per IB specification 7.7.3, service level is a 4-bit field. */
+#define TOS_TO_SL(tos)		((tos) & 0xF)
+
+static int rds_rdma_cm_event_handler_cmn(struct rdma_cm_id *cm_id,
+					 struct rdma_cm_event *event,
+					 bool isv6)
+{
+	/* this can be null in the listening path */
+	struct rds_connection *conn = cm_id->context;
+	struct rds_transport *trans;
+	int ret = 0;
+	int *err;
+	u8 len;
+
+	rdsdebug("conn %p id %p handling event %u (%s)\n", conn, cm_id,
+		 event->event, rdma_event_msg(event->event));
+
+	if (cm_id->device->node_type == RDMA_NODE_IB_CA)
+		trans = &rds_ib_transport;
+
+	/* Prevent shutdown from tearing down the connection
+	 * while we're executing. */
+	if (conn) {
+		mutex_lock(&conn->c_cm_lock);
+
+		/* If the connection is being shut down, bail out
+		 * right away. We return 0 so cm_id doesn't get
+		 * destroyed prematurely */
+		if (rds_conn_state(conn) == RDS_CONN_DISCONNECTING) {
+			/* Reject incoming connections while we're tearing
+			 * down an existing one. */
+			if (event->event == RDMA_CM_EVENT_CONNECT_REQUEST)
+				ret = 1;
+			goto out;
+		}
+	}
+
+	switch (event->event) {
+	case RDMA_CM_EVENT_CONNECT_REQUEST:
+		ret = trans->cm_handle_connect(cm_id, event, isv6);
+		break;
+
+	case RDMA_CM_EVENT_ADDR_RESOLVED:
+		if (conn) {
+			rdma_set_service_type(cm_id, conn->c_tos);
+			rdma_set_min_rnr_timer(cm_id, IB_RNR_TIMER_000_32);
+			/* XXX do we need to clean up if this fails? */
+			ret = rdma_resolve_route(cm_id,
+						 RDS_RDMA_RESOLVE_TIMEOUT_MS);
+		}
+		break;
+
+	case RDMA_CM_EVENT_ROUTE_RESOLVED:
+		/* Connection could have been dropped so make sure the
+		 * cm_id is valid before proceeding
+		 */
+		if (conn) {
+			struct rds_ib_connection *ibic;
+
+			ibic = conn->c_transport_data;
+			if (ibic && ibic->i_cm_id == cm_id) {
+				cm_id->route.path_rec[0].sl =
+					TOS_TO_SL(conn->c_tos);
+				ret = trans->cm_initiate_connect(cm_id, isv6);
+			} else {
+				rds_conn_drop(conn);
+			}
+		}
+		break;
+
+	case RDMA_CM_EVENT_ESTABLISHED:
+		if (conn)
+			trans->cm_connect_complete(conn, event);
+		break;
+
+	case RDMA_CM_EVENT_REJECTED:
+		if (!conn)
+			break;
+		err = (int *)rdma_consumer_reject_data(cm_id, event, &len);
+		if (!err ||
+		    (err && len >= sizeof(*err) &&
+		     ((*err) <= RDS_RDMA_REJ_INCOMPAT))) {
+			pr_warn("RDS/RDMA: conn <%pI6c, %pI6c> rejected, dropping connection\n",
+				&conn->c_laddr, &conn->c_faddr);
+
+			if (!conn->c_tos)
+				conn->c_proposed_version = RDS_PROTOCOL_COMPAT_VERSION;
+
+			rds_conn_drop(conn);
+		}
+		rdsdebug("Connection rejected: %s\n",
+			 rdma_reject_msg(cm_id, event->status));
+		break;
+	case RDMA_CM_EVENT_ADDR_ERROR:
+	case RDMA_CM_EVENT_ROUTE_ERROR:
+	case RDMA_CM_EVENT_CONNECT_ERROR:
+	case RDMA_CM_EVENT_UNREACHABLE:
+	case RDMA_CM_EVENT_DEVICE_REMOVAL:
+	case RDMA_CM_EVENT_ADDR_CHANGE:
+		if (conn)
+			rds_conn_drop(conn);
+		break;
+
+	case RDMA_CM_EVENT_DISCONNECTED:
+		if (!conn)
+			break;
+		rdsdebug("DISCONNECT event - dropping connection "
+			 "%pI6c->%pI6c\n", &conn->c_laddr,
+			 &conn->c_faddr);
+		rds_conn_drop(conn);
+		break;
+
+	case RDMA_CM_EVENT_TIMEWAIT_EXIT:
+		if (conn) {
+			pr_info("RDS: RDMA_CM_EVENT_TIMEWAIT_EXIT event: dropping connection %pI6c->%pI6c\n",
+				&conn->c_laddr, &conn->c_faddr);
+			rds_conn_drop(conn);
+		}
+		break;
+
+	default:
+		/* things like device disconnect? */
+		printk(KERN_ERR "RDS: unknown event %u (%s)!\n",
+		       event->event, rdma_event_msg(event->event));
+		break;
+	}
+
+out:
+	if (conn)
+		mutex_unlock(&conn->c_cm_lock);
+
+	rdsdebug("id %p event %u (%s) handling ret %d\n", cm_id, event->event,
+		 rdma_event_msg(event->event), ret);
+
+	return ret;
+}
+
+int rds_rdma_cm_event_handler(struct rdma_cm_id *cm_id,
+			      struct rdma_cm_event *event)
+{
+	return rds_rdma_cm_event_handler_cmn(cm_id, event, false);
+}
+
+#if IS_ENABLED(CONFIG_IPV6)
+int rds6_rdma_cm_event_handler(struct rdma_cm_id *cm_id,
+			       struct rdma_cm_event *event)
+{
+	return rds_rdma_cm_event_handler_cmn(cm_id, event, true);
+}
+#endif
+
+static int rds_rdma_listen_init_common(rdma_cm_event_handler handler,
+				       struct sockaddr *sa,
+				       struct rdma_cm_id **ret_cm_id)
+{
+	struct rdma_cm_id *cm_id;
+	int ret;
+
+	cm_id = rdma_create_id(&init_net, handler, NULL,
+			       RDMA_PS_TCP, IB_QPT_RC);
+	if (IS_ERR(cm_id)) {
+		ret = PTR_ERR(cm_id);
+		printk(KERN_ERR "RDS/RDMA: failed to setup listener, "
+		       "rdma_create_id() returned %d\n", ret);
+		return ret;
+	}
+
+	/*
+	 * XXX I bet this binds the cm_id to a device.  If we want to support
+	 * fail-over we'll have to take this into consideration.
+	 */
+	ret = rdma_bind_addr(cm_id, sa);
+	if (ret) {
+		printk(KERN_ERR "RDS/RDMA: failed to setup listener, "
+		       "rdma_bind_addr() returned %d\n", ret);
+		goto out;
+	}
+
+	ret = rdma_listen(cm_id, 128);
+	if (ret) {
+		printk(KERN_ERR "RDS/RDMA: failed to setup listener, "
+		       "rdma_listen() returned %d\n", ret);
+		goto out;
+	}
+
+	rdsdebug("cm %p listening on port %u\n", cm_id, RDS_PORT);
+
+	*ret_cm_id = cm_id;
+	cm_id = NULL;
+out:
+	if (cm_id)
+		rdma_destroy_id(cm_id);
+	return ret;
+}
+
+/* Initialize the RDS RDMA listeners.  We create two listeners for
+ * compatibility reason.  The one on RDS_PORT is used for IPv4
+ * requests only.  The one on RDS_CM_PORT is used for IPv6 requests
+ * only.  So only IPv6 enabled RDS module will communicate using this
+ * port.
+ */
+static int rds_rdma_listen_init(void)
+{
+	int ret;
+#if IS_ENABLED(CONFIG_IPV6)
+	struct sockaddr_in6 sin6;
+#endif
+	struct sockaddr_in sin;
+
+	sin.sin_family = PF_INET;
+	sin.sin_addr.s_addr = htonl(INADDR_ANY);
+	sin.sin_port = htons(RDS_PORT);
+	ret = rds_rdma_listen_init_common(rds_rdma_cm_event_handler,
+					  (struct sockaddr *)&sin,
+					  &rds_rdma_listen_id);
+	if (ret != 0)
+		return ret;
+
+#if IS_ENABLED(CONFIG_IPV6)
+	sin6.sin6_family = PF_INET6;
+	sin6.sin6_addr = in6addr_any;
+	sin6.sin6_port = htons(RDS_CM_PORT);
+	sin6.sin6_scope_id = 0;
+	sin6.sin6_flowinfo = 0;
+	ret = rds_rdma_listen_init_common(rds6_rdma_cm_event_handler,
+					  (struct sockaddr *)&sin6,
+					  &rds6_rdma_listen_id);
+	/* Keep going even when IPv6 is not enabled in the system. */
+	if (ret != 0)
+		rdsdebug("Cannot set up IPv6 RDMA listener\n");
+#endif
+	return 0;
+}
+
+static void rds_rdma_listen_stop(void)
+{
+	if (rds_rdma_listen_id) {
+		rdsdebug("cm %p\n", rds_rdma_listen_id);
+		rdma_destroy_id(rds_rdma_listen_id);
+		rds_rdma_listen_id = NULL;
+	}
+#if IS_ENABLED(CONFIG_IPV6)
+	if (rds6_rdma_listen_id) {
+		rdsdebug("cm %p\n", rds6_rdma_listen_id);
+		rdma_destroy_id(rds6_rdma_listen_id);
+		rds6_rdma_listen_id = NULL;
+	}
+#endif
+}
+
+static int __init rds_rdma_init(void)
+{
+	int ret;
+
+	ret = rds_ib_init();
+	if (ret)
+		goto out;
+
+	ret = rds_rdma_listen_init();
+	if (ret)
+		rds_ib_exit();
+out:
+	return ret;
+}
+module_init(rds_rdma_init);
+
+static void __exit rds_rdma_exit(void)
+{
+	/* stop listening first to ensure no new connections are attempted */
+	rds_rdma_listen_stop();
+	rds_ib_exit();
+}
+module_exit(rds_rdma_exit);
+
+MODULE_AUTHOR("Oracle Corporation <rds-devel@oss.oracle.com>");
+MODULE_DESCRIPTION("RDS: IB transport");
+MODULE_LICENSE("Dual BSD/GPL");
diff --git a/net/rds/rdma_transport.h b/net/rds/rdma_transport.h
new file mode 100644
index 000000000..d2fdb1529
--- /dev/null
+++ b/net/rds/rdma_transport.h
@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _RDMA_TRANSPORT_H
+#define _RDMA_TRANSPORT_H
+
+#include <rdma/ib_verbs.h>
+#include <rdma/rdma_cm.h>
+#include "rds.h"
+
+/* RDMA_CM also uses 16385 as the listener port. */
+#define RDS_CM_PORT	16385
+
+#define RDS_RDMA_RESOLVE_TIMEOUT_MS     5000
+
+/* Below reject reason is for legacy interoperability issue with non-linux
+ * RDS endpoints where older version incompatibility is conveyed via value 1.
+ * For future version(s), proper encoded reject reason should be used.
+ */
+#define RDS_RDMA_REJ_INCOMPAT		1
+
+int rds_rdma_cm_event_handler(struct rdma_cm_id *cm_id,
+			      struct rdma_cm_event *event);
+int rds6_rdma_cm_event_handler(struct rdma_cm_id *cm_id,
+			       struct rdma_cm_event *event);
+
+/* from ib.c */
+extern struct rds_transport rds_ib_transport;
+int rds_ib_init(void);
+void rds_ib_exit(void);
+
+#endif
diff --git a/net/rds/rds.h b/net/rds/rds.h
new file mode 100644
index 000000000..2db49573d
--- /dev/null
+++ b/net/rds/rds.h
@@ -0,0 +1,1063 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _RDS_RDS_H
+#define _RDS_RDS_H
+
+#include <net/sock.h>
+#include <linux/scatterlist.h>
+#include <linux/highmem.h>
+#include <rdma/rdma_cm.h>
+#include <linux/mutex.h>
+#include <linux/rds.h>
+#include <linux/rhashtable.h>
+#include <linux/refcount.h>
+#include <linux/in6.h>
+
+#include "info.h"
+
+/*
+ * RDS Network protocol version
+ */
+#define RDS_PROTOCOL_3_0	0x0300
+#define RDS_PROTOCOL_3_1	0x0301
+#define RDS_PROTOCOL_4_0	0x0400
+#define RDS_PROTOCOL_4_1	0x0401
+#define RDS_PROTOCOL_VERSION	RDS_PROTOCOL_3_1
+#define RDS_PROTOCOL_MAJOR(v)	((v) >> 8)
+#define RDS_PROTOCOL_MINOR(v)	((v) & 255)
+#define RDS_PROTOCOL(maj, min)	(((maj) << 8) | min)
+#define RDS_PROTOCOL_COMPAT_VERSION	RDS_PROTOCOL_3_1
+
+/* The following ports, 16385, 18634, 18635, are registered with IANA as
+ * the ports to be used for RDS over TCP and UDP.  Currently, only RDS over
+ * TCP and RDS over IB/RDMA are implemented.  18634 is the historical value
+ * used for the RDMA_CM listener port.  RDS/TCP uses port 16385.  After
+ * IPv6 work, RDMA_CM also uses 16385 as the listener port.  18634 is kept
+ * to ensure compatibility with older RDS modules.  Those ports are defined
+ * in each transport's header file.
+ */
+#define RDS_PORT	18634
+
+#ifdef ATOMIC64_INIT
+#define KERNEL_HAS_ATOMIC64
+#endif
+#ifdef RDS_DEBUG
+#define rdsdebug(fmt, args...) pr_debug("%s(): " fmt, __func__ , ##args)
+#else
+/* sigh, pr_debug() causes unused variable warnings */
+static inline __printf(1, 2)
+void rdsdebug(char *fmt, ...)
+{
+}
+#endif
+
+#define RDS_FRAG_SHIFT	12
+#define RDS_FRAG_SIZE	((unsigned int)(1 << RDS_FRAG_SHIFT))
+
+/* Used to limit both RDMA and non-RDMA RDS message to 1MB */
+#define RDS_MAX_MSG_SIZE	((unsigned int)(1 << 20))
+
+#define RDS_CONG_MAP_BYTES	(65536 / 8)
+#define RDS_CONG_MAP_PAGES	(PAGE_ALIGN(RDS_CONG_MAP_BYTES) / PAGE_SIZE)
+#define RDS_CONG_MAP_PAGE_BITS	(PAGE_SIZE * 8)
+
+struct rds_cong_map {
+	struct rb_node		m_rb_node;
+	struct in6_addr		m_addr;
+	wait_queue_head_t	m_waitq;
+	struct list_head	m_conn_list;
+	unsigned long		m_page_addrs[RDS_CONG_MAP_PAGES];
+};
+
+
+/*
+ * This is how we will track the connection state:
+ * A connection is always in one of the following
+ * states. Updates to the state are atomic and imply
+ * a memory barrier.
+ */
+enum {
+	RDS_CONN_DOWN = 0,
+	RDS_CONN_CONNECTING,
+	RDS_CONN_DISCONNECTING,
+	RDS_CONN_UP,
+	RDS_CONN_RESETTING,
+	RDS_CONN_ERROR,
+};
+
+/* Bits for c_flags */
+#define RDS_LL_SEND_FULL	0
+#define RDS_RECONNECT_PENDING	1
+#define RDS_IN_XMIT		2
+#define RDS_RECV_REFILL		3
+#define	RDS_DESTROY_PENDING	4
+
+/* Max number of multipaths per RDS connection. Must be a power of 2 */
+#define	RDS_MPATH_WORKERS	8
+#define	RDS_MPATH_HASH(rs, n) (jhash_1word(ntohs((rs)->rs_bound_port), \
+			       (rs)->rs_hash_initval) & ((n) - 1))
+
+#define IS_CANONICAL(laddr, faddr) (htonl(laddr) < htonl(faddr))
+
+/* Per mpath connection state */
+struct rds_conn_path {
+	struct rds_connection	*cp_conn;
+	struct rds_message	*cp_xmit_rm;
+	unsigned long		cp_xmit_sg;
+	unsigned int		cp_xmit_hdr_off;
+	unsigned int		cp_xmit_data_off;
+	unsigned int		cp_xmit_atomic_sent;
+	unsigned int		cp_xmit_rdma_sent;
+	unsigned int		cp_xmit_data_sent;
+
+	spinlock_t		cp_lock;		/* protect msg queues */
+	u64			cp_next_tx_seq;
+	struct list_head	cp_send_queue;
+	struct list_head	cp_retrans;
+
+	u64			cp_next_rx_seq;
+
+	void			*cp_transport_data;
+
+	struct workqueue_struct	*cp_wq;
+	atomic_t		cp_state;
+	unsigned long		cp_send_gen;
+	unsigned long		cp_flags;
+	unsigned long		cp_reconnect_jiffies;
+	struct delayed_work	cp_send_w;
+	struct delayed_work	cp_recv_w;
+	struct delayed_work	cp_conn_w;
+	struct work_struct	cp_down_w;
+	struct mutex		cp_cm_lock;	/* protect cp_state & cm */
+	wait_queue_head_t	cp_waitq;
+
+	unsigned int		cp_unacked_packets;
+	unsigned int		cp_unacked_bytes;
+	unsigned int		cp_index;
+};
+
+/* One rds_connection per RDS address pair */
+struct rds_connection {
+	struct hlist_node	c_hash_node;
+	struct in6_addr		c_laddr;
+	struct in6_addr		c_faddr;
+	int			c_dev_if; /* ifindex used for this conn */
+	int			c_bound_if; /* ifindex of c_laddr */
+	unsigned int		c_loopback:1,
+				c_isv6:1,
+				c_ping_triggered:1,
+				c_pad_to_32:29;
+	int			c_npaths;
+	bool			c_with_sport_idx;
+	struct rds_connection	*c_passive;
+	struct rds_transport	*c_trans;
+
+	struct rds_cong_map	*c_lcong;
+	struct rds_cong_map	*c_fcong;
+
+	/* Protocol version */
+	unsigned int		c_proposed_version;
+	unsigned int		c_version;
+	possible_net_t		c_net;
+
+	/* TOS */
+	u8			c_tos;
+
+	struct list_head	c_map_item;
+	unsigned long		c_map_queued;
+
+	struct rds_conn_path	*c_path;
+	wait_queue_head_t	c_hs_waitq; /* handshake waitq */
+
+	u32			c_my_gen_num;
+	u32			c_peer_gen_num;
+
+	u64			c_cp0_mprds_catchup_tx_seq;
+};
+
+static inline
+struct net *rds_conn_net(struct rds_connection *conn)
+{
+	return read_pnet(&conn->c_net);
+}
+
+static inline
+void rds_conn_net_set(struct rds_connection *conn, struct net *net)
+{
+	write_pnet(&conn->c_net, net);
+}
+
+#define RDS_FLAG_CONG_BITMAP		0x01
+#define RDS_FLAG_ACK_REQUIRED		0x02
+#define RDS_FLAG_RETRANSMITTED		0x04
+#define RDS_FLAG_EXTHDR_EXTENSION	0x20
+#define RDS_MAX_ADV_CREDIT		255
+
+/* RDS_FLAG_PROBE_PORT is the reserved sport used for sending a ping
+ * probe to exchange control information before establishing a connection.
+ * Currently the control information that is exchanged is the number of
+ * supported paths. If the peer is a legacy (older kernel revision) peer,
+ * it would return a pong message without additional control information
+ * that would then alert the sender that the peer was an older rev.
+ */
+#define RDS_FLAG_PROBE_PORT	1
+#define	RDS_HS_PROBE(sport, dport) \
+		((sport == RDS_FLAG_PROBE_PORT && dport == 0) || \
+		 (sport == 0 && dport == RDS_FLAG_PROBE_PORT))
+/*
+ * Maximum space available for extension headers.
+ */
+#define RDS_HEADER_EXT_SPACE	16
+
+struct rds_header {
+	__be64	h_sequence;
+	__be64	h_ack;
+	__be32	h_len;
+	__be16	h_sport;
+	__be16	h_dport;
+	u8	h_flags;
+	u8	h_credit;
+	u8	h_padding[4];
+	__sum16	h_csum;
+
+	u8	h_exthdr[RDS_HEADER_EXT_SPACE];
+};
+
+/*
+ * Reserved - indicates end of extensions
+ */
+#define RDS_EXTHDR_NONE		0
+
+/*
+ * This extension header is included in the very
+ * first message that is sent on a new connection,
+ * and identifies the protocol level. This will help
+ * rolling updates if a future change requires breaking
+ * the protocol.
+ * NB: This is no longer true for IB, where we do a version
+ * negotiation during the connection setup phase (protocol
+ * version information is included in the RDMA CM private data).
+ */
+#define RDS_EXTHDR_VERSION	1
+struct rds_ext_header_version {
+	__be32			h_version;
+};
+
+/*
+ * This extension header is included in the RDS message
+ * chasing an RDMA operation.
+ */
+#define RDS_EXTHDR_RDMA		2
+struct rds_ext_header_rdma {
+	__be32			h_rdma_rkey;
+};
+
+/*
+ * This extension header tells the peer about the
+ * destination <R_Key,offset> of the requested RDMA
+ * operation.
+ */
+#define RDS_EXTHDR_RDMA_DEST	3
+struct rds_ext_header_rdma_dest {
+	__be32			h_rdma_rkey;
+	__be32			h_rdma_offset;
+};
+
+/*
+ * This extension header tells the peer about delivered RDMA byte count.
+ */
+#define RDS_EXTHDR_RDMA_BYTES	4
+
+struct rds_ext_header_rdma_bytes {
+	__be32		h_rdma_bytes;	/* byte count */
+	u8		h_rflags;	/* direction of RDMA, write or read */
+	u8		h_pad[3];
+};
+
+#define RDS_FLAG_RDMA_WR_BYTES	0x01
+#define RDS_FLAG_RDMA_RD_BYTES	0x02
+
+/* Extension header announcing number of paths.
+ * Implicit length = 2 bytes.
+ */
+#define RDS_EXTHDR_NPATHS	5
+#define RDS_EXTHDR_GEN_NUM	6
+#define RDS_EXTHDR_SPORT_IDX    8
+
+#define __RDS_EXTHDR_MAX	16 /* for now */
+
+#define RDS_RX_MAX_TRACES	(RDS_MSG_RX_DGRAM_TRACE_MAX + 1)
+#define	RDS_MSG_RX_HDR		0
+#define	RDS_MSG_RX_START	1
+#define	RDS_MSG_RX_END		2
+#define	RDS_MSG_RX_CMSG		3
+
+/* The following values are whitelisted for usercopy */
+struct rds_inc_usercopy {
+	rds_rdma_cookie_t	rdma_cookie;
+	ktime_t			rx_tstamp;
+};
+
+struct rds_incoming {
+	refcount_t		i_refcount;
+	struct list_head	i_item;
+	struct rds_connection	*i_conn;
+	struct rds_conn_path	*i_conn_path;
+	struct rds_header	i_hdr;
+	unsigned long		i_rx_jiffies;
+	struct in6_addr		i_saddr;
+
+	struct rds_inc_usercopy i_usercopy;
+	u64			i_rx_lat_trace[RDS_RX_MAX_TRACES];
+};
+
+struct rds_mr {
+	struct rb_node		r_rb_node;
+	struct kref		r_kref;
+	u32			r_key;
+
+	/* A copy of the creation flags */
+	unsigned int		r_use_once:1;
+	unsigned int		r_invalidate:1;
+	unsigned int		r_write:1;
+
+	struct rds_sock		*r_sock; /* socket that owns us; counted
+					  * reference, dropped by
+					  * __rds_put_mr_final()
+					  */
+	struct rds_transport	*r_trans;
+	void			*r_trans_private;
+};
+
+static inline rds_rdma_cookie_t rds_rdma_make_cookie(u32 r_key, u32 offset)
+{
+	return r_key | (((u64) offset) << 32);
+}
+
+static inline u32 rds_rdma_cookie_key(rds_rdma_cookie_t cookie)
+{
+	return cookie;
+}
+
+static inline u32 rds_rdma_cookie_offset(rds_rdma_cookie_t cookie)
+{
+	return cookie >> 32;
+}
+
+/* atomic operation types */
+#define RDS_ATOMIC_TYPE_CSWP		0
+#define RDS_ATOMIC_TYPE_FADD		1
+
+/*
+ * m_sock_item and m_conn_item are on lists that are serialized under
+ * conn->c_lock.  m_sock_item has additional meaning in that once it is empty
+ * the message will not be put back on the retransmit list after being sent.
+ * messages that are canceled while being sent rely on this.
+ *
+ * m_inc is used by loopback so that it can pass an incoming message straight
+ * back up into the rx path.  It embeds a wire header which is also used by
+ * the send path, which is kind of awkward.
+ *
+ * m_sock_item indicates the message's presence on a socket's send or receive
+ * queue.  m_rs will point to that socket.
+ *
+ * m_daddr is used by cancellation to prune messages to a given destination.
+ *
+ * The RDS_MSG_ON_SOCK and RDS_MSG_ON_CONN flags are used to avoid lock
+ * nesting.  As paths iterate over messages on a sock, or conn, they must
+ * also lock the conn, or sock, to remove the message from those lists too.
+ * Testing the flag to determine if the message is still on the lists lets
+ * us avoid testing the list_head directly.  That means each path can use
+ * the message's list_head to keep it on a local list while juggling locks
+ * without confusing the other path.
+ *
+ * m_ack_seq is an optional field set by transports who need a different
+ * sequence number range to invalidate.  They can use this in a callback
+ * that they pass to rds_send_drop_acked() to see if each message has been
+ * acked.  The HAS_ACK_SEQ flag can be used to detect messages which haven't
+ * had ack_seq set yet.
+ */
+#define RDS_MSG_ON_SOCK		1
+#define RDS_MSG_ON_CONN		2
+#define RDS_MSG_HAS_ACK_SEQ	3
+#define RDS_MSG_ACK_REQUIRED	4
+#define RDS_MSG_RETRANSMITTED	5
+#define RDS_MSG_MAPPED		6
+#define RDS_MSG_PAGEVEC		7
+#define RDS_MSG_FLUSH		8
+
+struct rds_znotifier {
+	struct mmpin		z_mmp;
+	u32			z_cookie;
+};
+
+struct rds_msg_zcopy_info {
+	struct list_head rs_zcookie_next;
+	union {
+		struct rds_znotifier znotif;
+		struct rds_zcopy_cookies zcookies;
+	};
+};
+
+struct rds_msg_zcopy_queue {
+	struct list_head zcookie_head;
+	spinlock_t lock; /* protects zcookie_head queue */
+};
+
+static inline void rds_message_zcopy_queue_init(struct rds_msg_zcopy_queue *q)
+{
+	spin_lock_init(&q->lock);
+	INIT_LIST_HEAD(&q->zcookie_head);
+}
+
+struct rds_iov_vector {
+	struct rds_iovec *iov;
+	int               len;
+};
+
+struct rds_iov_vector_arr {
+	struct rds_iov_vector *vec;
+	int                    len;
+	int                    indx;
+	int                    incr;
+};
+
+struct rds_message {
+	refcount_t		m_refcount;
+	struct list_head	m_sock_item;
+	struct list_head	m_conn_item;
+	struct rds_incoming	m_inc;
+	u64			m_ack_seq;
+	struct in6_addr		m_daddr;
+	unsigned long		m_flags;
+
+	/* Never access m_rs without holding m_rs_lock.
+	 * Lock nesting is
+	 *  rm->m_rs_lock
+	 *   -> rs->rs_lock
+	 */
+	spinlock_t		m_rs_lock;
+	wait_queue_head_t	m_flush_wait;
+
+	struct rds_sock		*m_rs;
+
+	/* cookie to send to remote, in rds header */
+	rds_rdma_cookie_t	m_rdma_cookie;
+
+	unsigned int		m_used_sgs;
+	unsigned int		m_total_sgs;
+
+	void			*m_final_op;
+
+	/* Unpins the ops' user pages and frees the message from
+	 * process context when the final put happens in atomic
+	 * context: dirtying the pages on unpin can sleep.
+	 */
+	struct work_struct	m_unpin_work;
+
+	struct {
+		struct rm_atomic_op {
+			int			op_type;
+			union {
+				struct {
+					uint64_t	compare;
+					uint64_t	swap;
+					uint64_t	compare_mask;
+					uint64_t	swap_mask;
+				} op_m_cswp;
+				struct {
+					uint64_t	add;
+					uint64_t	nocarry_mask;
+				} op_m_fadd;
+			};
+
+			u32			op_rkey;
+			u64			op_remote_addr;
+			unsigned int		op_notify:1;
+			unsigned int		op_recverr:1;
+			unsigned int		op_mapped:1;
+			unsigned int		op_silent:1;
+			unsigned int		op_active:1;
+			unsigned int		op_unpin_deferred:1;
+			struct scatterlist	*op_sg;
+			struct rds_notifier	*op_notifier;
+
+			struct rds_mr		*op_rdma_mr;
+		} atomic;
+		struct rm_rdma_op {
+			u32			op_rkey;
+			u64			op_remote_addr;
+			unsigned int		op_write:1;
+			unsigned int		op_fence:1;
+			unsigned int		op_notify:1;
+			unsigned int		op_recverr:1;
+			unsigned int		op_mapped:1;
+			unsigned int		op_silent:1;
+			unsigned int		op_active:1;
+			unsigned int		op_unpin_deferred:1;
+			unsigned int		op_bytes;
+			unsigned int		op_nents;
+			unsigned int		op_count;
+			struct scatterlist	*op_sg;
+			struct rds_notifier	*op_notifier;
+
+			struct rds_mr		*op_rdma_mr;
+
+			u64			op_odp_addr;
+			struct rds_mr		*op_odp_mr;
+		} rdma;
+		struct rm_data_op {
+			unsigned int		op_active:1;
+			unsigned int		op_nents;
+			unsigned int		op_count;
+			unsigned int		op_dmasg;
+			unsigned int		op_dmaoff;
+			struct rds_znotifier	*op_mmp_znotifier;
+			struct scatterlist	*op_sg;
+		} data;
+	};
+
+	struct rds_conn_path *m_conn_path;
+};
+
+/*
+ * The RDS notifier is used (optionally) to tell the application about
+ * completed RDMA operations. Rather than keeping the whole rds message
+ * around on the queue, we allocate a small notifier that is put on the
+ * socket's notifier_list. Notifications are delivered to the application
+ * through control messages.
+ */
+struct rds_notifier {
+	struct list_head	n_list;
+	uint64_t		n_user_token;
+	int			n_status;
+};
+
+/* Available as part of RDS core, so doesn't need to participate
+ * in get_preferred transport etc
+ */
+#define	RDS_TRANS_LOOP	3
+
+struct rds_transport {
+	char			t_name[TRANSNAMSIZ];
+	struct list_head	t_item;
+	struct module		*t_owner;
+	unsigned int		t_prefer_loopback:1,
+				t_mp_capable:1;
+	unsigned int		t_type;
+
+	int (*laddr_check)(struct net *net, const struct in6_addr *addr,
+			   __u32 scope_id);
+	int (*conn_alloc)(struct rds_connection *conn, gfp_t gfp);
+	void (*conn_free)(void *data);
+
+	/*
+	 * conn_slots_available is invoked when a previously unavailable
+	 * connection slot becomes available again. rds_tcp_accept_one_path may
+	 * return -ENOBUFS if it cannot find an available slot, and then stashes
+	 * the new socket in "rds_tcp_accepted_sock". This function re-issues
+	 * `rds_tcp_accept_one_path`, which picks up the stashed socket and
+	 * continuing where it left with "-ENOBUFS" last time.  This ensures
+	 * messages received on the new socket are not discarded when no
+	 * connection path was available at the time.
+	 */
+	void (*conn_slots_available)(struct rds_connection *conn, bool fan_out);
+	int (*conn_path_connect)(struct rds_conn_path *cp);
+
+	/*
+	 * conn_shutdown stops traffic on the given connection.  Once
+	 * it returns the connection can not call rds_recv_incoming().
+	 * This will only be called once after conn_connect returns
+	 * non-zero success and will The caller serializes this with
+	 * the send and connecting paths (xmit_* and conn_*).  The
+	 * transport is responsible for other serialization, including
+	 * rds_recv_incoming().  This is called in process context but
+	 * should try hard not to block.
+	 */
+	void (*conn_path_shutdown)(struct rds_conn_path *conn);
+	void (*xmit_path_prepare)(struct rds_conn_path *cp);
+	void (*xmit_path_complete)(struct rds_conn_path *cp);
+
+	/*
+	 * .xmit is called by rds_send_xmit() to tell the transport to send
+	 * part of a message.  The caller serializes on the send_sem so this
+	 * doesn't need to be reentrant for a given conn.  The header must be
+	 * sent before the data payload.  .xmit must be prepared to send a
+	 * message with no data payload.  .xmit should return the number of
+	 * bytes that were sent down the connection, including header bytes.
+	 * Returning 0 tells the caller that it doesn't need to perform any
+	 * additional work now.  This is usually the case when the transport has
+	 * filled the sending queue for its connection and will handle
+	 * triggering the rds thread to continue the send when space becomes
+	 * available.  Returning -EAGAIN tells the caller to retry the send
+	 * immediately.  Returning -ENOMEM tells the caller to retry the send at
+	 * some point in the future.
+	 */
+	int (*xmit)(struct rds_connection *conn, struct rds_message *rm,
+		    unsigned int hdr_off, unsigned int sg, unsigned int off);
+	int (*xmit_rdma)(struct rds_connection *conn, struct rm_rdma_op *op);
+	int (*xmit_atomic)(struct rds_connection *conn, struct rm_atomic_op *op);
+	int (*recv_path)(struct rds_conn_path *cp);
+	int (*inc_copy_to_user)(struct rds_incoming *inc, struct iov_iter *to);
+	void (*inc_free)(struct rds_incoming *inc);
+
+	int (*cm_handle_connect)(struct rdma_cm_id *cm_id,
+				 struct rdma_cm_event *event, bool isv6);
+	int (*cm_initiate_connect)(struct rdma_cm_id *cm_id, bool isv6);
+	void (*cm_connect_complete)(struct rds_connection *conn,
+				    struct rdma_cm_event *event);
+
+	unsigned int (*stats_info_copy)(struct rds_info_iterator *iter,
+					unsigned int avail);
+	void (*exit)(void);
+	void *(*get_mr)(struct scatterlist *sg, unsigned long nr_sg,
+			struct rds_sock *rs, u32 *key_ret,
+			struct rds_connection *conn,
+			u64 start, u64 length, int need_odp);
+	void (*sync_mr)(void *trans_private, int direction);
+	void (*free_mr)(void *trans_private, int invalidate);
+	void (*flush_mrs)(void);
+	bool (*t_unloading)(struct rds_connection *conn);
+	u8 (*get_tos_map)(u8 tos);
+};
+
+/* Bind hash table key length.  It is the sum of the size of a struct
+ * in6_addr, a scope_id  and a port.
+ */
+#define RDS_BOUND_KEY_LEN \
+	(sizeof(struct in6_addr) + sizeof(__u32) + sizeof(__be16))
+
+struct rds_sock {
+	struct sock		rs_sk;
+
+	u64			rs_user_addr;
+	u64			rs_user_bytes;
+
+	/*
+	 * bound_addr used for both incoming and outgoing, no INADDR_ANY
+	 * support.
+	 */
+	struct rhash_head	rs_bound_node;
+	u8			rs_bound_key[RDS_BOUND_KEY_LEN];
+	struct sockaddr_in6	rs_bound_sin6;
+#define rs_bound_addr		rs_bound_sin6.sin6_addr
+#define rs_bound_addr_v4	rs_bound_sin6.sin6_addr.s6_addr32[3]
+#define rs_bound_port		rs_bound_sin6.sin6_port
+#define rs_bound_scope_id	rs_bound_sin6.sin6_scope_id
+	struct in6_addr		rs_conn_addr;
+#define rs_conn_addr_v4		rs_conn_addr.s6_addr32[3]
+	__be16			rs_conn_port;
+	struct rds_transport    *rs_transport;
+
+	/*
+	 * rds_sendmsg caches the conn it used the last time around.
+	 * This helps avoid costly lookups.
+	 */
+	struct rds_connection	*rs_conn;
+
+	/* flag indicating we were congested or not */
+	int			rs_congested;
+	/* seen congestion (ENOBUFS) when sending? */
+	int			rs_seen_congestion;
+
+	/* rs_lock protects all these adjacent members before the newline */
+	spinlock_t		rs_lock;
+	struct list_head	rs_send_queue;
+	u32			rs_snd_bytes;
+	int			rs_rcv_bytes;
+	struct list_head	rs_notify_queue;	/* currently used for failed RDMAs */
+
+	/* Congestion wake_up. If rs_cong_monitor is set, we use cong_mask
+	 * to decide whether the application should be woken up.
+	 * If not set, we use rs_cong_track to find out whether a cong map
+	 * update arrived.
+	 */
+	uint64_t		rs_cong_mask;
+	uint64_t		rs_cong_notify;
+	struct list_head	rs_cong_list;
+	unsigned long		rs_cong_track;
+
+	/*
+	 * rs_recv_lock protects the receive queue, and is
+	 * used to serialize with rds_release.
+	 */
+	rwlock_t		rs_recv_lock;
+	struct list_head	rs_recv_queue;
+
+	/* just for stats reporting */
+	struct list_head	rs_item;
+
+	/* these have their own lock */
+	spinlock_t		rs_rdma_lock;
+	struct rb_root		rs_rdma_keys;
+
+	/* Socket options - in case there will be more */
+	unsigned char		rs_recverr,
+				rs_cong_monitor;
+	u32			rs_hash_initval;
+
+	/* Socket receive path trace points*/
+	u8			rs_rx_traces;
+	u8			rs_rx_trace[RDS_MSG_RX_DGRAM_TRACE_MAX];
+	struct rds_msg_zcopy_queue rs_zcookie_queue;
+	u8			rs_tos;
+};
+
+static inline struct rds_sock *rds_sk_to_rs(const struct sock *sk)
+{
+	return container_of(sk, struct rds_sock, rs_sk);
+}
+static inline struct sock *rds_rs_to_sk(struct rds_sock *rs)
+{
+	return &rs->rs_sk;
+}
+
+/*
+ * The stack assigns sk_sndbuf and sk_rcvbuf to twice the specified value
+ * to account for overhead.  We don't account for overhead, we just apply
+ * the number of payload bytes to the specified value.
+ */
+static inline int rds_sk_sndbuf(struct rds_sock *rs)
+{
+	return rds_rs_to_sk(rs)->sk_sndbuf / 2;
+}
+static inline int rds_sk_rcvbuf(struct rds_sock *rs)
+{
+	return rds_rs_to_sk(rs)->sk_rcvbuf / 2;
+}
+
+struct rds_statistics {
+	u64	s_conn_reset;
+	u64	s_recv_drop_bad_checksum;
+	u64	s_recv_drop_old_seq;
+	u64	s_recv_drop_no_sock;
+	u64	s_recv_drop_dead_sock;
+	u64	s_recv_deliver_raced;
+	u64	s_recv_delivered;
+	u64	s_recv_queued;
+	u64	s_recv_immediate_retry;
+	u64	s_recv_delayed_retry;
+	u64	s_recv_ack_required;
+	u64	s_recv_rdma_bytes;
+	u64	s_recv_ping;
+	u64	s_send_queue_empty;
+	u64	s_send_queue_full;
+	u64	s_send_lock_contention;
+	u64	s_send_lock_queue_raced;
+	u64	s_send_immediate_retry;
+	u64	s_send_delayed_retry;
+	u64	s_send_drop_acked;
+	u64	s_send_ack_required;
+	u64	s_send_queued;
+	u64	s_send_rdma;
+	u64	s_send_rdma_bytes;
+	u64	s_send_pong;
+	u64	s_page_remainder_hit;
+	u64	s_page_remainder_miss;
+	u64	s_copy_to_user;
+	u64	s_copy_from_user;
+	u64	s_cong_update_queued;
+	u64	s_cong_update_received;
+	u64	s_cong_send_error;
+	u64	s_cong_send_blocked;
+	u64	s_recv_bytes_added_to_socket;
+	u64	s_recv_bytes_removed_from_socket;
+	u64	s_send_stuck_rm;
+	u64	s_mprds_catchup_tx0_retries;
+};
+
+/* af_rds.c */
+void rds_sock_addref(struct rds_sock *rs);
+void rds_sock_put(struct rds_sock *rs);
+void rds_wake_sk_sleep(struct rds_sock *rs);
+static inline void __rds_wake_sk_sleep(struct sock *sk)
+{
+	wait_queue_head_t *waitq = sk_sleep(sk);
+
+	if (!sock_flag(sk, SOCK_DEAD) && waitq)
+		wake_up(waitq);
+}
+extern wait_queue_head_t rds_poll_waitq;
+
+
+/* bind.c */
+int rds_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int addr_len);
+void rds_remove_bound(struct rds_sock *rs);
+struct rds_sock *rds_find_bound(const struct in6_addr *addr, __be16 port,
+				__u32 scope_id);
+int rds_bind_lock_init(void);
+void rds_bind_lock_destroy(void);
+
+/* cong.c */
+int rds_cong_get_maps(struct rds_connection *conn);
+void rds_cong_add_conn(struct rds_connection *conn);
+void rds_cong_remove_conn(struct rds_connection *conn);
+void rds_cong_set_bit(struct rds_cong_map *map, __be16 port);
+void rds_cong_clear_bit(struct rds_cong_map *map, __be16 port);
+int rds_cong_wait(struct rds_cong_map *map, __be16 port, int nonblock, struct rds_sock *rs);
+void rds_cong_queue_updates(struct rds_cong_map *map);
+void rds_cong_map_updated(struct rds_cong_map *map, uint64_t);
+int rds_cong_updated_since(unsigned long *recent);
+void rds_cong_add_socket(struct rds_sock *);
+void rds_cong_remove_socket(struct rds_sock *);
+void rds_cong_exit(void);
+struct rds_message *rds_cong_update_alloc(struct rds_connection *conn);
+
+/* connection.c */
+extern u32 rds_gen_num;
+int rds_conn_init(void);
+void rds_conn_exit(void);
+struct rds_connection *rds_conn_create(struct net *net,
+				       const struct in6_addr *laddr,
+				       const struct in6_addr *faddr,
+				       struct rds_transport *trans,
+				       u8 tos, gfp_t gfp,
+				       int dev_if);
+struct rds_connection *rds_conn_create_outgoing(struct net *net,
+						const struct in6_addr *laddr,
+						const struct in6_addr *faddr,
+						struct rds_transport *trans,
+						u8 tos, gfp_t gfp, int dev_if);
+void rds_conn_shutdown(struct rds_conn_path *cpath);
+void rds_conn_destroy(struct rds_connection *conn);
+void rds_conn_drop(struct rds_connection *conn);
+void rds_conn_path_drop(struct rds_conn_path *cpath, bool destroy);
+void rds_conn_connect_if_down(struct rds_connection *conn);
+void rds_conn_path_connect_if_down(struct rds_conn_path *cp);
+void rds_check_all_paths(struct rds_connection *conn);
+void rds_for_each_conn_info(struct socket *sock, unsigned int len,
+			  struct rds_info_iterator *iter,
+			  struct rds_info_lengths *lens,
+			  int (*visitor)(struct rds_connection *, void *),
+			  u64 *buffer,
+			  size_t item_len);
+
+__printf(2, 3)
+void __rds_conn_path_error(struct rds_conn_path *cp, const char *, ...);
+#define rds_conn_path_error(cp, fmt...) \
+	__rds_conn_path_error(cp, KERN_WARNING "RDS: " fmt)
+
+static inline int
+rds_conn_path_transition(struct rds_conn_path *cp, int old, int new)
+{
+	return atomic_cmpxchg(&cp->cp_state, old, new) == old;
+}
+
+static inline int
+rds_conn_transition(struct rds_connection *conn, int old, int new)
+{
+	WARN_ON(conn->c_trans->t_mp_capable);
+	return rds_conn_path_transition(&conn->c_path[0], old, new);
+}
+
+static inline int
+rds_conn_path_state(struct rds_conn_path *cp)
+{
+	return atomic_read(&cp->cp_state);
+}
+
+static inline int
+rds_conn_state(struct rds_connection *conn)
+{
+	WARN_ON(conn->c_trans->t_mp_capable);
+	return rds_conn_path_state(&conn->c_path[0]);
+}
+
+static inline int
+rds_conn_path_up(struct rds_conn_path *cp)
+{
+	return atomic_read(&cp->cp_state) == RDS_CONN_UP;
+}
+
+static inline int
+rds_conn_path_down(struct rds_conn_path *cp)
+{
+	return atomic_read(&cp->cp_state) == RDS_CONN_DOWN;
+}
+
+static inline int
+rds_conn_up(struct rds_connection *conn)
+{
+	WARN_ON(conn->c_trans->t_mp_capable);
+	return rds_conn_path_up(&conn->c_path[0]);
+}
+
+static inline int
+rds_conn_path_connecting(struct rds_conn_path *cp)
+{
+	return atomic_read(&cp->cp_state) == RDS_CONN_CONNECTING;
+}
+
+static inline int
+rds_conn_connecting(struct rds_connection *conn)
+{
+	WARN_ON(conn->c_trans->t_mp_capable);
+	return rds_conn_path_connecting(&conn->c_path[0]);
+}
+
+/* message.c */
+struct rds_message *rds_message_alloc(unsigned int nents, gfp_t gfp);
+struct scatterlist *rds_message_alloc_sgs(struct rds_message *rm, int nents);
+int rds_message_copy_from_user(struct rds_message *rm, struct iov_iter *from,
+			       bool zcopy);
+struct rds_message *rds_message_map_pages(unsigned long *page_addrs, unsigned int total_len);
+void rds_message_populate_header(struct rds_header *hdr, __be16 sport,
+				 __be16 dport, u64 seq);
+int rds_message_add_extension(struct rds_header *hdr,
+			      unsigned int type, const void *data);
+int rds_message_next_extension(struct rds_header *hdr,
+			       unsigned int *pos, void *buf, unsigned int *buflen);
+int rds_message_add_rdma_dest_extension(struct rds_header *hdr, u32 r_key, u32 offset);
+int rds_message_inc_copy_to_user(struct rds_incoming *inc, struct iov_iter *to);
+void rds_message_addref(struct rds_message *rm);
+void rds_message_put(struct rds_message *rm);
+void rds_message_wait(struct rds_message *rm);
+void rds_message_unmapped(struct rds_message *rm);
+void rds_notify_msg_zcopy_purge(struct rds_msg_zcopy_queue *info);
+
+static inline void rds_message_make_checksum(struct rds_header *hdr)
+{
+	hdr->h_csum = 0;
+	hdr->h_csum = ip_fast_csum((void *) hdr, sizeof(*hdr) >> 2);
+}
+
+static inline int rds_message_verify_checksum(const struct rds_header *hdr)
+{
+	return !hdr->h_csum || ip_fast_csum((void *) hdr, sizeof(*hdr) >> 2) == 0;
+}
+
+
+/* page.c */
+int rds_page_remainder_alloc(struct scatterlist *scat, unsigned long bytes,
+			     gfp_t gfp);
+void rds_page_exit(void);
+
+/* recv.c */
+void rds_inc_init(struct rds_incoming *inc, struct rds_connection *conn,
+		  struct in6_addr *saddr);
+void rds_inc_path_init(struct rds_incoming *inc, struct rds_conn_path *conn,
+		       struct in6_addr *saddr);
+void rds_inc_put(struct rds_incoming *inc);
+void rds_recv_incoming(struct rds_connection *conn, struct in6_addr *saddr,
+		       struct in6_addr *daddr,
+		       struct rds_incoming *inc, gfp_t gfp);
+int rds_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
+		int msg_flags);
+void rds_clear_recv_queue(struct rds_sock *rs);
+int rds_notify_queue_get(struct rds_sock *rs, struct msghdr *msg);
+void rds_inc_info_copy(struct rds_incoming *inc,
+		       struct rds_info_iterator *iter,
+		       __be32 saddr, __be32 daddr, int flip);
+void rds6_inc_info_copy(struct rds_incoming *inc,
+			struct rds_info_iterator *iter,
+			struct in6_addr *saddr, struct in6_addr *daddr,
+			int flip);
+
+/* send.c */
+int rds_sendmsg(struct socket *sock, struct msghdr *msg, size_t payload_len);
+void rds_send_path_reset(struct rds_conn_path *conn);
+int rds_send_xmit(struct rds_conn_path *cp);
+struct sockaddr_in;
+void rds_send_drop_to(struct rds_sock *rs, struct sockaddr_in6 *dest);
+typedef int (*is_acked_func)(struct rds_message *rm, uint64_t ack);
+void rds_send_drop_acked(struct rds_connection *conn, u64 ack,
+			 is_acked_func is_acked);
+void rds_send_path_drop_acked(struct rds_conn_path *cp, u64 ack,
+			      is_acked_func is_acked);
+void rds_send_ping(struct rds_connection *conn, int cp_index);
+int rds_send_pong(struct rds_conn_path *cp, __be16 dport);
+
+/* rdma.c */
+void rds_rdma_unuse(struct rds_sock *rs, u32 r_key, int force);
+int rds_get_mr(struct rds_sock *rs, sockptr_t optval, int optlen);
+int rds_get_mr_for_dest(struct rds_sock *rs, sockptr_t optval, int optlen);
+int rds_free_mr(struct rds_sock *rs, sockptr_t optval, int optlen);
+void rds_rdma_drop_keys(struct rds_sock *rs);
+int rds_rdma_extra_size(struct rds_rdma_args *args,
+			struct rds_iov_vector *iov);
+int rds_cmsg_rdma_dest(struct rds_sock *rs, struct rds_message *rm,
+			  struct cmsghdr *cmsg);
+int rds_cmsg_rdma_args(struct rds_sock *rs, struct rds_message *rm,
+			  struct cmsghdr *cmsg,
+			  struct rds_iov_vector *vec);
+int rds_cmsg_rdma_map(struct rds_sock *rs, struct rds_message *rm,
+			  struct cmsghdr *cmsg);
+void rds_rdma_free_op(struct rm_rdma_op *ro);
+void rds_atomic_free_op(struct rm_atomic_op *ao);
+void rds_rdma_op_unpin_pages(struct rm_rdma_op *ro);
+void rds_atomic_op_unpin_page(struct rm_atomic_op *ao);
+void rds_rdma_send_complete(struct rds_message *rm, int wc_status);
+void rds_atomic_send_complete(struct rds_message *rm, int wc_status);
+int rds_cmsg_atomic(struct rds_sock *rs, struct rds_message *rm,
+		    struct cmsghdr *cmsg);
+
+void __rds_put_mr_final(struct kref *kref);
+
+static inline bool rds_destroy_pending(struct rds_connection *conn)
+{
+	return !check_net(rds_conn_net(conn)) ||
+	       (conn->c_trans->t_unloading && conn->c_trans->t_unloading(conn));
+}
+
+enum {
+	ODP_NOT_NEEDED,
+	ODP_ZEROBASED,
+	ODP_VIRTUAL
+};
+
+/* stats.c */
+DECLARE_PER_CPU_SHARED_ALIGNED(struct rds_statistics, rds_stats);
+#define rds_stats_inc_which(which, member) do {		\
+	per_cpu(which, get_cpu()).member++;		\
+	put_cpu();					\
+} while (0)
+#define rds_stats_inc(member) rds_stats_inc_which(rds_stats, member)
+#define rds_stats_add_which(which, member, count) do {		\
+	per_cpu(which, get_cpu()).member += count;	\
+	put_cpu();					\
+} while (0)
+#define rds_stats_add(member, count) rds_stats_add_which(rds_stats, member, count)
+int rds_stats_init(void);
+void rds_stats_exit(void);
+void rds_stats_info_copy(struct rds_info_iterator *iter,
+			 uint64_t *values, const char *const *names,
+			 size_t nr);
+
+/* sysctl.c */
+int rds_sysctl_init(void);
+void rds_sysctl_exit(void);
+extern unsigned long rds_sysctl_sndbuf_min;
+extern unsigned long rds_sysctl_sndbuf_default;
+extern unsigned long rds_sysctl_sndbuf_max;
+extern unsigned long rds_sysctl_reconnect_min_jiffies;
+extern unsigned long rds_sysctl_reconnect_max_jiffies;
+extern unsigned int  rds_sysctl_max_unacked_packets;
+extern unsigned int  rds_sysctl_max_unacked_bytes;
+extern unsigned int  rds_sysctl_ping_enable;
+extern unsigned long rds_sysctl_trace_flags;
+extern unsigned int  rds_sysctl_trace_level;
+
+/* threads.c */
+int rds_threads_init(void);
+void rds_threads_exit(void);
+extern struct workqueue_struct *rds_wq;
+void rds_queue_reconnect(struct rds_conn_path *cp);
+void rds_connect_worker(struct work_struct *);
+void rds_shutdown_worker(struct work_struct *);
+void rds_send_worker(struct work_struct *);
+void rds_recv_worker(struct work_struct *);
+void rds_connect_path_complete(struct rds_conn_path *conn, int curr);
+void rds_connect_complete(struct rds_connection *conn);
+int rds_addr_cmp(const struct in6_addr *a1, const struct in6_addr *a2);
+
+/* transport.c */
+void rds_trans_register(struct rds_transport *trans);
+void rds_trans_unregister(struct rds_transport *trans);
+struct rds_transport *rds_trans_get_preferred(struct net *net,
+					      const struct in6_addr *addr,
+					      __u32 scope_id);
+void rds_trans_put(struct rds_transport *trans);
+unsigned int rds_trans_stats_info_copy(struct rds_info_iterator *iter,
+				       unsigned int avail);
+struct rds_transport *rds_trans_get(int t_type);
+
+#endif
diff --git a/net/rds/rds_single_path.h b/net/rds/rds_single_path.h
new file mode 100644
index 000000000..9521f6e99
--- /dev/null
+++ b/net/rds/rds_single_path.h
@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _RDS_RDS_SINGLE_H
+#define _RDS_RDS_SINGLE_H
+
+#define	c_xmit_rm		c_path[0].cp_xmit_rm
+#define	c_xmit_sg		c_path[0].cp_xmit_sg
+#define	c_xmit_hdr_off		c_path[0].cp_xmit_hdr_off
+#define	c_xmit_data_off		c_path[0].cp_xmit_data_off
+#define	c_xmit_atomic_sent	c_path[0].cp_xmit_atomic_sent
+#define	c_xmit_rdma_sent	c_path[0].cp_xmit_rdma_sent
+#define	c_xmit_data_sent	c_path[0].cp_xmit_data_sent
+#define	c_lock			c_path[0].cp_lock
+#define c_next_tx_seq		c_path[0].cp_next_tx_seq
+#define c_send_queue		c_path[0].cp_send_queue
+#define c_retrans		c_path[0].cp_retrans
+#define c_next_rx_seq		c_path[0].cp_next_rx_seq
+#define c_transport_data	c_path[0].cp_transport_data
+#define c_state			c_path[0].cp_state
+#define c_send_gen		c_path[0].cp_send_gen
+#define c_flags			c_path[0].cp_flags
+#define c_reconnect_jiffies	c_path[0].cp_reconnect_jiffies
+#define c_send_w		c_path[0].cp_send_w
+#define c_recv_w		c_path[0].cp_recv_w
+#define c_conn_w		c_path[0].cp_conn_w
+#define c_down_w		c_path[0].cp_down_w
+#define c_cm_lock		c_path[0].cp_cm_lock
+#define c_waitq			c_path[0].cp_waitq
+#define c_unacked_packets	c_path[0].cp_unacked_packets
+#define c_unacked_bytes		c_path[0].cp_unacked_bytes
+
+#endif /* _RDS_RDS_SINGLE_H */
diff --git a/net/rds/recv.c b/net/rds/recv.c
new file mode 100644
index 000000000..6204e577a
--- /dev/null
+++ b/net/rds/recv.c
@@ -0,0 +1,892 @@
+/*
+ * Copyright (c) 2006, 2019 Oracle and/or its affiliates. All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <net/sock.h>
+#include <linux/in.h>
+#include <linux/export.h>
+#include <linux/sched/clock.h>
+#include <linux/time.h>
+#include <linux/rds.h>
+
+#include "rds.h"
+
+void rds_inc_init(struct rds_incoming *inc, struct rds_connection *conn,
+		 struct in6_addr *saddr)
+{
+	refcount_set(&inc->i_refcount, 1);
+	INIT_LIST_HEAD(&inc->i_item);
+	inc->i_conn = conn;
+	inc->i_conn_path = NULL;
+	inc->i_saddr = *saddr;
+	inc->i_usercopy.rdma_cookie = 0;
+	inc->i_usercopy.rx_tstamp = ktime_set(0, 0);
+
+	memset(inc->i_rx_lat_trace, 0, sizeof(inc->i_rx_lat_trace));
+}
+EXPORT_SYMBOL_GPL(rds_inc_init);
+
+void rds_inc_path_init(struct rds_incoming *inc, struct rds_conn_path *cp,
+		       struct in6_addr  *saddr)
+{
+	refcount_set(&inc->i_refcount, 1);
+	INIT_LIST_HEAD(&inc->i_item);
+	inc->i_conn = cp->cp_conn;
+	inc->i_conn_path = cp;
+	inc->i_saddr = *saddr;
+	inc->i_usercopy.rdma_cookie = 0;
+	inc->i_usercopy.rx_tstamp = ktime_set(0, 0);
+
+	memset(inc->i_rx_lat_trace, 0, sizeof(inc->i_rx_lat_trace));
+}
+EXPORT_SYMBOL_GPL(rds_inc_path_init);
+
+static void rds_inc_addref(struct rds_incoming *inc)
+{
+	rdsdebug("addref inc %p ref %d\n", inc, refcount_read(&inc->i_refcount));
+	refcount_inc(&inc->i_refcount);
+}
+
+void rds_inc_put(struct rds_incoming *inc)
+{
+	rdsdebug("put inc %p ref %d\n", inc, refcount_read(&inc->i_refcount));
+	if (refcount_dec_and_test(&inc->i_refcount)) {
+		BUG_ON(!list_empty(&inc->i_item));
+
+		inc->i_conn->c_trans->inc_free(inc);
+	}
+}
+EXPORT_SYMBOL_GPL(rds_inc_put);
+
+static void rds_recv_rcvbuf_delta(struct rds_sock *rs, struct sock *sk,
+				  struct rds_cong_map *map,
+				  int delta, __be16 port)
+{
+	int now_congested;
+
+	if (delta == 0)
+		return;
+
+	rs->rs_rcv_bytes += delta;
+	if (delta > 0)
+		rds_stats_add(s_recv_bytes_added_to_socket, delta);
+	else
+		rds_stats_add(s_recv_bytes_removed_from_socket, -delta);
+
+	/* loop transport doesn't send/recv congestion updates */
+	if (rs->rs_transport->t_type == RDS_TRANS_LOOP)
+		return;
+
+	now_congested = rs->rs_rcv_bytes > rds_sk_rcvbuf(rs);
+
+	rdsdebug("rs %p (%pI6c:%u) recv bytes %d buf %d "
+	  "now_cong %d delta %d\n",
+	  rs, &rs->rs_bound_addr,
+	  ntohs(rs->rs_bound_port), rs->rs_rcv_bytes,
+	  rds_sk_rcvbuf(rs), now_congested, delta);
+
+	/* wasn't -> am congested */
+	if (!rs->rs_congested && now_congested) {
+		rs->rs_congested = 1;
+		rds_cong_set_bit(map, port);
+		rds_cong_queue_updates(map);
+	}
+	/* was -> aren't congested */
+	/* Require more free space before reporting uncongested to prevent
+	   bouncing cong/uncong state too often */
+	else if (rs->rs_congested && (rs->rs_rcv_bytes < (rds_sk_rcvbuf(rs)/2))) {
+		rs->rs_congested = 0;
+		rds_cong_clear_bit(map, port);
+		rds_cong_queue_updates(map);
+	}
+
+	/* do nothing if no change in cong state */
+}
+
+static void rds_conn_peer_gen_update(struct rds_connection *conn,
+				     u32 peer_gen_num)
+{
+	int i;
+	struct rds_message *rm, *tmp;
+	unsigned long flags;
+
+	WARN_ON(conn->c_trans->t_type != RDS_TRANS_TCP);
+	if (peer_gen_num != 0) {
+		if (conn->c_peer_gen_num != 0 &&
+		    peer_gen_num != conn->c_peer_gen_num) {
+			for (i = 0; i < RDS_MPATH_WORKERS; i++) {
+				struct rds_conn_path *cp;
+
+				cp = &conn->c_path[i];
+				spin_lock_irqsave(&cp->cp_lock, flags);
+				cp->cp_next_tx_seq = 1;
+				cp->cp_next_rx_seq = 0;
+				list_for_each_entry_safe(rm, tmp,
+							 &cp->cp_retrans,
+							 m_conn_item) {
+					set_bit(RDS_MSG_FLUSH, &rm->m_flags);
+				}
+				spin_unlock_irqrestore(&cp->cp_lock, flags);
+			}
+		}
+		conn->c_peer_gen_num = peer_gen_num;
+	}
+}
+
+/*
+ * Process all extension headers that come with this message.
+ */
+static void rds_recv_incoming_exthdrs(struct rds_incoming *inc, struct rds_sock *rs)
+{
+	struct rds_header *hdr = &inc->i_hdr;
+	unsigned int pos = 0, type, len;
+	union {
+		struct rds_ext_header_version version;
+		struct rds_ext_header_rdma rdma;
+		struct rds_ext_header_rdma_dest rdma_dest;
+	} buffer;
+
+	while (1) {
+		len = sizeof(buffer);
+		type = rds_message_next_extension(hdr, &pos, &buffer, &len);
+		if (type == RDS_EXTHDR_NONE)
+			break;
+		/* Process extension header here */
+		switch (type) {
+		case RDS_EXTHDR_RDMA:
+			rds_rdma_unuse(rs, be32_to_cpu(buffer.rdma.h_rdma_rkey), 0);
+			break;
+
+		case RDS_EXTHDR_RDMA_DEST:
+			/* We ignore the size for now. We could stash it
+			 * somewhere and use it for error checking. */
+			inc->i_usercopy.rdma_cookie = rds_rdma_make_cookie(
+					be32_to_cpu(buffer.rdma_dest.h_rdma_rkey),
+					be32_to_cpu(buffer.rdma_dest.h_rdma_offset));
+
+			break;
+		}
+	}
+}
+
+static void rds_recv_hs_exthdrs(struct rds_header *hdr,
+				struct rds_connection *conn)
+{
+	unsigned int pos = 0, type, len;
+	union {
+		struct rds_ext_header_version version;
+		__be16 rds_npaths;
+		__be32 rds_gen_num;
+		u8 dummy;
+	} buffer;
+	bool new_with_sport_idx = false;
+	u32 new_peer_gen_num = 0;
+	int new_npaths;
+	bool fan_out;
+
+	new_npaths = conn->c_npaths;
+
+	while (1) {
+		len = sizeof(buffer);
+		type = rds_message_next_extension(hdr, &pos, &buffer, &len);
+		if (type == RDS_EXTHDR_NONE)
+			break;
+		/* Process extension header here */
+		switch (type) {
+		case RDS_EXTHDR_NPATHS:
+			new_npaths = min_t(int, RDS_MPATH_WORKERS,
+					   be16_to_cpu(buffer.rds_npaths));
+			break;
+		case RDS_EXTHDR_GEN_NUM:
+			new_peer_gen_num = be32_to_cpu(buffer.rds_gen_num);
+			break;
+		case RDS_EXTHDR_SPORT_IDX:
+			new_with_sport_idx = true;
+			break;
+		default:
+			pr_warn_ratelimited("ignoring unknown exthdr type "
+					     "0x%x\n", type);
+		}
+	}
+
+	conn->c_with_sport_idx = new_with_sport_idx;
+
+	if (new_npaths > 1 && new_npaths != conn->c_npaths) {
+		/* We're about to fan-out.
+		 * Make sure that messages from cp_index#0
+		 * are sent prior to handling other lanes.
+		 */
+		struct rds_conn_path *cp0 = conn->c_path;
+		unsigned long flags;
+
+		spin_lock_irqsave(&cp0->cp_lock, flags);
+		conn->c_cp0_mprds_catchup_tx_seq = cp0->cp_next_tx_seq;
+		spin_unlock_irqrestore(&cp0->cp_lock, flags);
+		fan_out = true;
+	} else {
+		fan_out = false;
+	}
+
+	/* if RDS_EXTHDR_NPATHS was not found, default to a single-path */
+	conn->c_npaths = max_t(int, new_npaths, 1);
+
+	conn->c_ping_triggered = 0;
+	rds_conn_peer_gen_update(conn, new_peer_gen_num);
+
+	if (conn->c_npaths > 1 &&
+	    conn->c_trans->conn_slots_available)
+		conn->c_trans->conn_slots_available(conn, fan_out);
+}
+
+/* rds_start_mprds() will synchronously start multiple paths when appropriate.
+ * The scheme is based on the following rules:
+ *
+ * 1. rds_sendmsg on first connect attempt sends the probe ping, with the
+ *    sender's npaths (s_npaths)
+ * 2. rcvr of probe-ping knows the mprds_paths = min(s_npaths, r_npaths). It
+ *    sends back a probe-pong with r_npaths. After that, if rcvr is the
+ *    smaller ip addr, it starts rds_conn_path_connect_if_down on all
+ *    mprds_paths.
+ * 3. sender gets woken up, and can move to rds_conn_path_connect_if_down.
+ *    If it is the smaller ipaddr, rds_conn_path_connect_if_down can be
+ *    called after reception of the probe-pong on all mprds_paths.
+ *    Otherwise (sender of probe-ping is not the smaller ip addr): just call
+ *    rds_conn_path_connect_if_down on the hashed path. (see rule 4)
+ * 4. rds_connect_worker must only trigger a connection if laddr < faddr.
+ * 5. sender may end up queuing the packet on the cp. will get sent out later.
+ *    when connection is completed.
+ */
+static void rds_start_mprds(struct rds_connection *conn)
+{
+	int i;
+	struct rds_conn_path *cp;
+
+	if (conn->c_npaths > 1 &&
+	    rds_addr_cmp(&conn->c_laddr, &conn->c_faddr) < 0) {
+		for (i = 0; i < conn->c_npaths; i++) {
+			cp = &conn->c_path[i];
+			rds_conn_path_connect_if_down(cp);
+		}
+	}
+}
+
+/*
+ * The transport must make sure that this is serialized against other
+ * rx and conn reset on this specific conn.
+ *
+ * We currently assert that only one fragmented message will be sent
+ * down a connection at a time.  This lets us reassemble in the conn
+ * instead of per-flow which means that we don't have to go digging through
+ * flows to tear down partial reassembly progress on conn failure and
+ * we save flow lookup and locking for each frag arrival.  It does mean
+ * that small messages will wait behind large ones.  Fragmenting at all
+ * is only to reduce the memory consumption of pre-posted buffers.
+ *
+ * The caller passes in saddr and daddr instead of us getting it from the
+ * conn.  This lets loopback, who only has one conn for both directions,
+ * tell us which roles the addrs in the conn are playing for this message.
+ */
+void rds_recv_incoming(struct rds_connection *conn, struct in6_addr *saddr,
+		       struct in6_addr *daddr,
+		       struct rds_incoming *inc, gfp_t gfp)
+{
+	struct rds_sock *rs = NULL;
+	struct sock *sk;
+	unsigned long flags;
+	struct rds_conn_path *cp;
+
+	inc->i_conn = conn;
+	inc->i_rx_jiffies = jiffies;
+	if (conn->c_trans->t_mp_capable)
+		cp = inc->i_conn_path;
+	else
+		cp = &conn->c_path[0];
+
+	rdsdebug("conn %p next %llu inc %p seq %llu len %u sport %u dport %u "
+		 "flags 0x%x rx_jiffies %lu\n", conn,
+		 (unsigned long long)cp->cp_next_rx_seq,
+		 inc,
+		 (unsigned long long)be64_to_cpu(inc->i_hdr.h_sequence),
+		 be32_to_cpu(inc->i_hdr.h_len),
+		 be16_to_cpu(inc->i_hdr.h_sport),
+		 be16_to_cpu(inc->i_hdr.h_dport),
+		 inc->i_hdr.h_flags,
+		 inc->i_rx_jiffies);
+
+	/*
+	 * Sequence numbers should only increase.  Messages get their
+	 * sequence number as they're queued in a sending conn.  They
+	 * can be dropped, though, if the sending socket is closed before
+	 * they hit the wire.  So sequence numbers can skip forward
+	 * under normal operation.  They can also drop back in the conn
+	 * failover case as previously sent messages are resent down the
+	 * new instance of a conn.  We drop those, otherwise we have
+	 * to assume that the next valid seq does not come after a
+	 * hole in the fragment stream.
+	 *
+	 * The headers don't give us a way to realize if fragments of
+	 * a message have been dropped.  We assume that frags that arrive
+	 * to a flow are part of the current message on the flow that is
+	 * being reassembled.  This means that senders can't drop messages
+	 * from the sending conn until all their frags are sent.
+	 *
+	 * XXX we could spend more on the wire to get more robust failure
+	 * detection, arguably worth it to avoid data corruption.
+	 */
+	if (be64_to_cpu(inc->i_hdr.h_sequence) < cp->cp_next_rx_seq &&
+	    (inc->i_hdr.h_flags & RDS_FLAG_RETRANSMITTED)) {
+		rds_stats_inc(s_recv_drop_old_seq);
+		goto out;
+	}
+	cp->cp_next_rx_seq = be64_to_cpu(inc->i_hdr.h_sequence) + 1;
+
+	if (rds_sysctl_ping_enable && inc->i_hdr.h_dport == 0) {
+		if (inc->i_hdr.h_sport == 0) {
+			rdsdebug("ignore ping with 0 sport from %pI6c\n",
+				 saddr);
+			goto out;
+		}
+		rds_stats_inc(s_recv_ping);
+		rds_send_pong(cp, inc->i_hdr.h_sport);
+		/* if this is a handshake ping, start multipath if necessary */
+		if (RDS_HS_PROBE(be16_to_cpu(inc->i_hdr.h_sport),
+				 be16_to_cpu(inc->i_hdr.h_dport))) {
+			rds_recv_hs_exthdrs(&inc->i_hdr, cp->cp_conn);
+			rds_start_mprds(cp->cp_conn);
+		}
+		goto out;
+	}
+
+	if (be16_to_cpu(inc->i_hdr.h_dport) ==  RDS_FLAG_PROBE_PORT &&
+	    inc->i_hdr.h_sport == 0) {
+		rds_recv_hs_exthdrs(&inc->i_hdr, cp->cp_conn);
+		/* if this is a handshake pong, start multipath if necessary */
+		rds_start_mprds(cp->cp_conn);
+		wake_up(&cp->cp_conn->c_hs_waitq);
+		goto out;
+	}
+
+	rs = rds_find_bound(daddr, inc->i_hdr.h_dport, conn->c_bound_if);
+	if (!rs) {
+		rds_stats_inc(s_recv_drop_no_sock);
+		goto out;
+	}
+
+	/*
+	 * rds_find_bound() uses a global (netns-agnostic) hash table.
+	 * An RDS connection created in netns A can match a socket bound
+	 * in the init netns, delivering inc cross-netns with inc->i_conn
+	 * pointing into netns A.  When cleanup_net() then frees that conn,
+	 * any subsequent dereference of inc->i_conn is a use-after-free.
+	 * Drop the inc if the receiving socket lives in a different netns.
+	 */
+	if (!net_eq(sock_net(rds_rs_to_sk(rs)), rds_conn_net(conn))) {
+		rds_stats_inc(s_recv_drop_no_sock);
+		rds_sock_put(rs);
+		rs = NULL;
+		goto out;
+	}
+
+	/* Process extension headers */
+	rds_recv_incoming_exthdrs(inc, rs);
+
+	/* We can be racing with rds_release() which marks the socket dead. */
+	sk = rds_rs_to_sk(rs);
+
+	/* serialize with rds_release -> sock_orphan */
+	write_lock_irqsave(&rs->rs_recv_lock, flags);
+	if (!sock_flag(sk, SOCK_DEAD)) {
+		rdsdebug("adding inc %p to rs %p's recv queue\n", inc, rs);
+		rds_stats_inc(s_recv_queued);
+		rds_recv_rcvbuf_delta(rs, sk, inc->i_conn->c_lcong,
+				      be32_to_cpu(inc->i_hdr.h_len),
+				      inc->i_hdr.h_dport);
+		if (sock_flag(sk, SOCK_RCVTSTAMP))
+			inc->i_usercopy.rx_tstamp = ktime_get_real();
+		rds_inc_addref(inc);
+		inc->i_rx_lat_trace[RDS_MSG_RX_END] = local_clock();
+		list_add_tail(&inc->i_item, &rs->rs_recv_queue);
+		__rds_wake_sk_sleep(sk);
+	} else {
+		rds_stats_inc(s_recv_drop_dead_sock);
+	}
+	write_unlock_irqrestore(&rs->rs_recv_lock, flags);
+
+out:
+	if (rs)
+		rds_sock_put(rs);
+}
+EXPORT_SYMBOL_GPL(rds_recv_incoming);
+
+/*
+ * be very careful here.  This is being called as the condition in
+ * wait_event_*() needs to cope with being called many times.
+ */
+static int rds_next_incoming(struct rds_sock *rs, struct rds_incoming **inc)
+{
+	unsigned long flags;
+
+	if (!*inc) {
+		read_lock_irqsave(&rs->rs_recv_lock, flags);
+		if (!list_empty(&rs->rs_recv_queue)) {
+			*inc = list_entry(rs->rs_recv_queue.next,
+					  struct rds_incoming,
+					  i_item);
+			rds_inc_addref(*inc);
+		}
+		read_unlock_irqrestore(&rs->rs_recv_lock, flags);
+	}
+
+	return *inc != NULL;
+}
+
+static int rds_still_queued(struct rds_sock *rs, struct rds_incoming *inc,
+			    int drop)
+{
+	struct sock *sk = rds_rs_to_sk(rs);
+	int ret = 0;
+	unsigned long flags;
+	struct rds_incoming *to_drop = NULL;
+
+	write_lock_irqsave(&rs->rs_recv_lock, flags);
+	if (!list_empty(&inc->i_item)) {
+		ret = 1;
+		if (drop) {
+			/* XXX make sure this i_conn is reliable */
+			rds_recv_rcvbuf_delta(rs, sk, inc->i_conn->c_lcong,
+					      -be32_to_cpu(inc->i_hdr.h_len),
+					      inc->i_hdr.h_dport);
+			list_del_init(&inc->i_item);
+			to_drop = inc;
+		}
+	}
+	write_unlock_irqrestore(&rs->rs_recv_lock, flags);
+
+	if (to_drop)
+		rds_inc_put(to_drop);
+
+	rdsdebug("inc %p rs %p still %d dropped %d\n", inc, rs, ret, drop);
+	return ret;
+}
+
+/*
+ * Pull errors off the error queue.
+ * If msghdr is NULL, we will just purge the error queue.
+ */
+int rds_notify_queue_get(struct rds_sock *rs, struct msghdr *msghdr)
+{
+	struct rds_notifier *notifier;
+	struct rds_rdma_notify cmsg;
+	unsigned int count = 0, max_messages = ~0U;
+	unsigned long flags;
+	LIST_HEAD(copy);
+	int err = 0;
+
+	memset(&cmsg, 0, sizeof(cmsg));	/* fill holes with zero */
+
+	/* put_cmsg copies to user space and thus may sleep. We can't do this
+	 * with rs_lock held, so first grab as many notifications as we can stuff
+	 * in the user provided cmsg buffer. We don't try to copy more, to avoid
+	 * losing notifications - except when the buffer is so small that it wouldn't
+	 * even hold a single notification. Then we give him as much of this single
+	 * msg as we can squeeze in, and set MSG_CTRUNC.
+	 */
+	if (msghdr) {
+		max_messages = msghdr->msg_controllen / CMSG_SPACE(sizeof(cmsg));
+		if (!max_messages)
+			max_messages = 1;
+	}
+
+	spin_lock_irqsave(&rs->rs_lock, flags);
+	while (!list_empty(&rs->rs_notify_queue) && count < max_messages) {
+		notifier = list_entry(rs->rs_notify_queue.next,
+				struct rds_notifier, n_list);
+		list_move(&notifier->n_list, &copy);
+		count++;
+	}
+	spin_unlock_irqrestore(&rs->rs_lock, flags);
+
+	if (!count)
+		return 0;
+
+	while (!list_empty(&copy)) {
+		notifier = list_entry(copy.next, struct rds_notifier, n_list);
+
+		if (msghdr) {
+			cmsg.user_token = notifier->n_user_token;
+			cmsg.status = notifier->n_status;
+
+			err = put_cmsg(msghdr, SOL_RDS, RDS_CMSG_RDMA_STATUS,
+				       sizeof(cmsg), &cmsg);
+			if (err)
+				break;
+		}
+
+		list_del_init(&notifier->n_list);
+		kfree(notifier);
+	}
+
+	/* If we bailed out because of an error in put_cmsg,
+	 * we may be left with one or more notifications that we
+	 * didn't process. Return them to the head of the list. */
+	if (!list_empty(&copy)) {
+		spin_lock_irqsave(&rs->rs_lock, flags);
+		list_splice(&copy, &rs->rs_notify_queue);
+		spin_unlock_irqrestore(&rs->rs_lock, flags);
+	}
+
+	return err;
+}
+
+/*
+ * Queue a congestion notification
+ */
+static int rds_notify_cong(struct rds_sock *rs, struct msghdr *msghdr)
+{
+	uint64_t notify = rs->rs_cong_notify;
+	unsigned long flags;
+	int err;
+
+	err = put_cmsg(msghdr, SOL_RDS, RDS_CMSG_CONG_UPDATE,
+			sizeof(notify), &notify);
+	if (err)
+		return err;
+
+	spin_lock_irqsave(&rs->rs_lock, flags);
+	rs->rs_cong_notify &= ~notify;
+	spin_unlock_irqrestore(&rs->rs_lock, flags);
+
+	return 0;
+}
+
+/*
+ * Receive any control messages.
+ */
+static int rds_cmsg_recv(struct rds_incoming *inc, struct msghdr *msg,
+			 struct rds_sock *rs)
+{
+	int ret = 0;
+
+	if (inc->i_usercopy.rdma_cookie) {
+		ret = put_cmsg(msg, SOL_RDS, RDS_CMSG_RDMA_DEST,
+				sizeof(inc->i_usercopy.rdma_cookie),
+				&inc->i_usercopy.rdma_cookie);
+		if (ret)
+			goto out;
+	}
+
+	if ((inc->i_usercopy.rx_tstamp != 0) &&
+	    sock_flag(rds_rs_to_sk(rs), SOCK_RCVTSTAMP)) {
+		struct __kernel_old_timeval tv =
+			ns_to_kernel_old_timeval(inc->i_usercopy.rx_tstamp);
+
+		if (!sock_flag(rds_rs_to_sk(rs), SOCK_TSTAMP_NEW)) {
+			ret = put_cmsg(msg, SOL_SOCKET, SO_TIMESTAMP_OLD,
+				       sizeof(tv), &tv);
+		} else {
+			struct __kernel_sock_timeval sk_tv;
+
+			sk_tv.tv_sec = tv.tv_sec;
+			sk_tv.tv_usec = tv.tv_usec;
+
+			ret = put_cmsg(msg, SOL_SOCKET, SO_TIMESTAMP_NEW,
+				       sizeof(sk_tv), &sk_tv);
+		}
+
+		if (ret)
+			goto out;
+	}
+
+	if (rs->rs_rx_traces) {
+		struct rds_cmsg_rx_trace t;
+		int i, j;
+
+		memset(&t, 0, sizeof(t));
+		inc->i_rx_lat_trace[RDS_MSG_RX_CMSG] = local_clock();
+		t.rx_traces =  rs->rs_rx_traces;
+		for (i = 0; i < rs->rs_rx_traces; i++) {
+			j = rs->rs_rx_trace[i];
+			t.rx_trace_pos[i] = j;
+			t.rx_trace[i] = inc->i_rx_lat_trace[j + 1] -
+					  inc->i_rx_lat_trace[j];
+		}
+
+		ret = put_cmsg(msg, SOL_RDS, RDS_CMSG_RXPATH_LATENCY,
+			       sizeof(t), &t);
+		if (ret)
+			goto out;
+	}
+
+out:
+	return ret;
+}
+
+static bool rds_recvmsg_zcookie(struct rds_sock *rs, struct msghdr *msg)
+{
+	struct rds_msg_zcopy_queue *q = &rs->rs_zcookie_queue;
+	struct rds_msg_zcopy_info *info = NULL;
+	struct rds_zcopy_cookies *done;
+	unsigned long flags;
+
+	if (!msg->msg_control)
+		return false;
+
+	if (!sock_flag(rds_rs_to_sk(rs), SOCK_ZEROCOPY) ||
+	    msg->msg_controllen < CMSG_SPACE(sizeof(*done)))
+		return false;
+
+	spin_lock_irqsave(&q->lock, flags);
+	if (!list_empty(&q->zcookie_head)) {
+		info = list_entry(q->zcookie_head.next,
+				  struct rds_msg_zcopy_info, rs_zcookie_next);
+		list_del(&info->rs_zcookie_next);
+	}
+	spin_unlock_irqrestore(&q->lock, flags);
+	if (!info)
+		return false;
+	done = &info->zcookies;
+	if (put_cmsg(msg, SOL_RDS, RDS_CMSG_ZCOPY_COMPLETION, sizeof(*done),
+		     done)) {
+		spin_lock_irqsave(&q->lock, flags);
+		list_add(&info->rs_zcookie_next, &q->zcookie_head);
+		spin_unlock_irqrestore(&q->lock, flags);
+		return false;
+	}
+	kfree(info);
+	return true;
+}
+
+int rds_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
+		int msg_flags)
+{
+	struct sock *sk = sock->sk;
+	struct rds_sock *rs = rds_sk_to_rs(sk);
+	long timeo;
+	int ret = 0, nonblock = msg_flags & MSG_DONTWAIT;
+	DECLARE_SOCKADDR(struct sockaddr_in6 *, sin6, msg->msg_name);
+	DECLARE_SOCKADDR(struct sockaddr_in *, sin, msg->msg_name);
+	struct rds_incoming *inc = NULL;
+
+	/* udp_recvmsg()->sock_recvtimeo() gets away without locking too.. */
+	timeo = sock_rcvtimeo(sk, nonblock);
+
+	rdsdebug("size %zu flags 0x%x timeo %ld\n", size, msg_flags, timeo);
+
+	if (msg_flags & MSG_OOB)
+		goto out;
+	if (msg_flags & MSG_ERRQUEUE)
+		return sock_recv_errqueue(sk, msg, size, SOL_IP, IP_RECVERR);
+
+	while (1) {
+		/* If there are pending notifications, do those - and nothing else */
+		if (!list_empty(&rs->rs_notify_queue)) {
+			ret = rds_notify_queue_get(rs, msg);
+			break;
+		}
+
+		if (rs->rs_cong_notify) {
+			ret = rds_notify_cong(rs, msg);
+			break;
+		}
+
+		if (!rds_next_incoming(rs, &inc)) {
+			if (nonblock) {
+				bool reaped = rds_recvmsg_zcookie(rs, msg);
+
+				ret = reaped ?  0 : -EAGAIN;
+				break;
+			}
+
+			timeo = wait_event_interruptible_timeout(*sk_sleep(sk),
+					(!list_empty(&rs->rs_notify_queue) ||
+					 rs->rs_cong_notify ||
+					 rds_next_incoming(rs, &inc)), timeo);
+			rdsdebug("recvmsg woke inc %p timeo %ld\n", inc,
+				 timeo);
+			if (timeo > 0 || timeo == MAX_SCHEDULE_TIMEOUT)
+				continue;
+
+			ret = timeo;
+			if (ret == 0)
+				ret = -ETIMEDOUT;
+			break;
+		}
+
+		rdsdebug("copying inc %p from %pI6c:%u to user\n", inc,
+			 &inc->i_conn->c_faddr,
+			 ntohs(inc->i_hdr.h_sport));
+		ret = inc->i_conn->c_trans->inc_copy_to_user(inc, &msg->msg_iter);
+		if (ret < 0)
+			break;
+
+		/*
+		 * if the message we just copied isn't at the head of the
+		 * recv queue then someone else raced us to return it, try
+		 * to get the next message.
+		 */
+		if (!rds_still_queued(rs, inc, !(msg_flags & MSG_PEEK))) {
+			rds_inc_put(inc);
+			inc = NULL;
+			rds_stats_inc(s_recv_deliver_raced);
+			iov_iter_revert(&msg->msg_iter, ret);
+			continue;
+		}
+
+		if (ret < be32_to_cpu(inc->i_hdr.h_len)) {
+			if (msg_flags & MSG_TRUNC)
+				ret = be32_to_cpu(inc->i_hdr.h_len);
+			msg->msg_flags |= MSG_TRUNC;
+		}
+
+		if (rds_cmsg_recv(inc, msg, rs)) {
+			ret = -EFAULT;
+			break;
+		}
+		rds_recvmsg_zcookie(rs, msg);
+
+		rds_stats_inc(s_recv_delivered);
+
+		if (msg->msg_name) {
+			if (ipv6_addr_v4mapped(&inc->i_saddr)) {
+				sin->sin_family = AF_INET;
+				sin->sin_port = inc->i_hdr.h_sport;
+				sin->sin_addr.s_addr =
+				    inc->i_saddr.s6_addr32[3];
+				memset(sin->sin_zero, 0, sizeof(sin->sin_zero));
+				msg->msg_namelen = sizeof(*sin);
+			} else {
+				sin6->sin6_family = AF_INET6;
+				sin6->sin6_port = inc->i_hdr.h_sport;
+				sin6->sin6_addr = inc->i_saddr;
+				sin6->sin6_flowinfo = 0;
+				sin6->sin6_scope_id = rs->rs_bound_scope_id;
+				msg->msg_namelen = sizeof(*sin6);
+			}
+		}
+		break;
+	}
+
+	if (inc)
+		rds_inc_put(inc);
+
+out:
+	return ret;
+}
+
+/*
+ * The socket is being shut down and we're asked to drop messages that were
+ * queued for recvmsg.  The caller has unbound the socket so the receive path
+ * won't queue any more incoming fragments or messages on the socket.
+ */
+void rds_clear_recv_queue(struct rds_sock *rs)
+{
+	struct sock *sk = rds_rs_to_sk(rs);
+	struct rds_incoming *inc, *tmp;
+	unsigned long flags;
+	LIST_HEAD(to_drop);
+
+	write_lock_irqsave(&rs->rs_recv_lock, flags);
+	list_for_each_entry_safe(inc, tmp, &rs->rs_recv_queue, i_item) {
+		rds_recv_rcvbuf_delta(rs, sk, inc->i_conn->c_lcong,
+				      -be32_to_cpu(inc->i_hdr.h_len),
+				      inc->i_hdr.h_dport);
+		list_move(&inc->i_item, &to_drop);
+	}
+	write_unlock_irqrestore(&rs->rs_recv_lock, flags);
+
+	list_for_each_entry_safe(inc, tmp, &to_drop, i_item) {
+		list_del_init(&inc->i_item);
+		rds_inc_put(inc);
+	}
+}
+
+/*
+ * inc->i_saddr isn't used here because it is only set in the receive
+ * path.
+ */
+void rds_inc_info_copy(struct rds_incoming *inc,
+		       struct rds_info_iterator *iter,
+		       __be32 saddr, __be32 daddr, int flip)
+{
+	struct rds_info_message minfo;
+
+	minfo.seq = be64_to_cpu(inc->i_hdr.h_sequence);
+	minfo.len = be32_to_cpu(inc->i_hdr.h_len);
+	minfo.tos = inc->i_conn->c_tos;
+
+	if (flip) {
+		minfo.laddr = daddr;
+		minfo.faddr = saddr;
+		minfo.lport = inc->i_hdr.h_dport;
+		minfo.fport = inc->i_hdr.h_sport;
+	} else {
+		minfo.laddr = saddr;
+		minfo.faddr = daddr;
+		minfo.lport = inc->i_hdr.h_sport;
+		minfo.fport = inc->i_hdr.h_dport;
+	}
+
+	minfo.flags = 0;
+
+	rds_info_copy(iter, &minfo, sizeof(minfo));
+}
+
+#if IS_ENABLED(CONFIG_IPV6)
+void rds6_inc_info_copy(struct rds_incoming *inc,
+			struct rds_info_iterator *iter,
+			struct in6_addr *saddr, struct in6_addr *daddr,
+			int flip)
+{
+	struct rds6_info_message minfo6;
+
+	minfo6.seq = be64_to_cpu(inc->i_hdr.h_sequence);
+	minfo6.len = be32_to_cpu(inc->i_hdr.h_len);
+	minfo6.tos = inc->i_conn->c_tos;
+
+	if (flip) {
+		minfo6.laddr = *daddr;
+		minfo6.faddr = *saddr;
+		minfo6.lport = inc->i_hdr.h_dport;
+		minfo6.fport = inc->i_hdr.h_sport;
+	} else {
+		minfo6.laddr = *saddr;
+		minfo6.faddr = *daddr;
+		minfo6.lport = inc->i_hdr.h_sport;
+		minfo6.fport = inc->i_hdr.h_dport;
+	}
+
+	minfo6.flags = 0;
+
+	rds_info_copy(iter, &minfo6, sizeof(minfo6));
+}
+#endif
diff --git a/net/rds/send.c b/net/rds/send.c
new file mode 100644
index 000000000..15a1b97f1
--- /dev/null
+++ b/net/rds/send.c
@@ -0,0 +1,1581 @@
+/*
+ * Copyright (c) 2006, 2018 Oracle and/or its affiliates. All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+#include <linux/kernel.h>
+#include <linux/moduleparam.h>
+#include <linux/gfp.h>
+#include <net/sock.h>
+#include <linux/in.h>
+#include <linux/list.h>
+#include <linux/ratelimit.h>
+#include <linux/export.h>
+#include <linux/sizes.h>
+
+#include "rds.h"
+
+/* When transmitting messages in rds_send_xmit, we need to emerge from
+ * time to time and briefly release the CPU. Otherwise the softlock watchdog
+ * will kick our shin.
+ * Also, it seems fairer to not let one busy connection stall all the
+ * others.
+ *
+ * send_batch_count is the number of times we'll loop in send_xmit. Setting
+ * it to 0 will restore the old behavior (where we looped until we had
+ * drained the queue).
+ */
+static int send_batch_count = SZ_1K;
+module_param(send_batch_count, int, 0444);
+MODULE_PARM_DESC(send_batch_count, " batch factor when working the send queue");
+
+static void rds_send_remove_from_sock(struct list_head *messages, int status);
+
+/*
+ * Reset the send state.  Callers must ensure that this doesn't race with
+ * rds_send_xmit().
+ */
+void rds_send_path_reset(struct rds_conn_path *cp)
+{
+	struct rds_message *rm, *tmp;
+	unsigned long flags;
+
+	if (cp->cp_xmit_rm) {
+		rm = cp->cp_xmit_rm;
+		cp->cp_xmit_rm = NULL;
+		/* Tell the user the RDMA op is no longer mapped by the
+		 * transport. This isn't entirely true (it's flushed out
+		 * independently) but as the connection is down, there's
+		 * no ongoing RDMA to/from that memory */
+		rds_message_unmapped(rm);
+		rds_message_put(rm);
+	}
+
+	cp->cp_xmit_sg = 0;
+	cp->cp_xmit_hdr_off = 0;
+	cp->cp_xmit_data_off = 0;
+	cp->cp_xmit_atomic_sent = 0;
+	cp->cp_xmit_rdma_sent = 0;
+	cp->cp_xmit_data_sent = 0;
+
+	cp->cp_conn->c_map_queued = 0;
+
+	cp->cp_unacked_packets = rds_sysctl_max_unacked_packets;
+	cp->cp_unacked_bytes = rds_sysctl_max_unacked_bytes;
+
+	/* Mark messages as retransmissions, and move them to the send q */
+	spin_lock_irqsave(&cp->cp_lock, flags);
+	list_for_each_entry_safe(rm, tmp, &cp->cp_retrans, m_conn_item) {
+		set_bit(RDS_MSG_ACK_REQUIRED, &rm->m_flags);
+		set_bit(RDS_MSG_RETRANSMITTED, &rm->m_flags);
+	}
+	list_splice_init(&cp->cp_retrans, &cp->cp_send_queue);
+	spin_unlock_irqrestore(&cp->cp_lock, flags);
+}
+EXPORT_SYMBOL_GPL(rds_send_path_reset);
+
+static int acquire_in_xmit(struct rds_conn_path *cp)
+{
+	return test_and_set_bit_lock(RDS_IN_XMIT, &cp->cp_flags) == 0;
+}
+
+static void release_in_xmit(struct rds_conn_path *cp)
+{
+	clear_bit_unlock(RDS_IN_XMIT, &cp->cp_flags);
+	/*
+	 * We don't use wait_on_bit()/wake_up_bit() because our waking is in a
+	 * hot path and finding waiters is very rare.  We don't want to walk
+	 * the system-wide hashed waitqueue buckets in the fast path only to
+	 * almost never find waiters.
+	 */
+	if (waitqueue_active(&cp->cp_waitq))
+		wake_up_all(&cp->cp_waitq);
+}
+
+/*
+ * Helper function for multipath fanout to ensure lane 0 transmits queued
+ * messages before other lanes to prevent out-of-order delivery.
+ *
+ * Returns true if lane 0 still has messages or false otherwise
+ */
+static bool rds_mprds_cp0_catchup(struct rds_connection *conn)
+{
+	struct rds_conn_path *cp0 = conn->c_path;
+	struct rds_message *rm0;
+	unsigned long flags;
+	bool ret = false;
+
+	spin_lock_irqsave(&cp0->cp_lock, flags);
+
+	/* the oldest / first message in the retransmit queue
+	 * has to be at or beyond c_cp0_mprds_catchup_tx_seq
+	 */
+	if (!list_empty(&cp0->cp_retrans)) {
+		rm0 = list_entry(cp0->cp_retrans.next, struct rds_message,
+				 m_conn_item);
+		if (be64_to_cpu(rm0->m_inc.i_hdr.h_sequence) <
+		    conn->c_cp0_mprds_catchup_tx_seq) {
+			/* the retransmit queue of cp_index#0 has not
+			 * quite caught up yet
+			 */
+			ret = true;
+			goto unlock;
+		}
+	}
+
+	/* the oldest / first message of the send queue
+	 * has to be at or beyond c_cp0_mprds_catchup_tx_seq
+	 */
+	rm0 = cp0->cp_xmit_rm;
+	if (!rm0 && !list_empty(&cp0->cp_send_queue))
+		rm0 = list_entry(cp0->cp_send_queue.next, struct rds_message,
+				 m_conn_item);
+	if (rm0 && be64_to_cpu(rm0->m_inc.i_hdr.h_sequence) <
+	    conn->c_cp0_mprds_catchup_tx_seq) {
+		/* the send queue of cp_index#0 has not quite
+		 * caught up yet
+		 */
+		ret = true;
+	}
+
+unlock:
+	spin_unlock_irqrestore(&cp0->cp_lock, flags);
+	return ret;
+}
+
+/*
+ * We're making the conscious trade-off here to only send one message
+ * down the connection at a time.
+ *   Pro:
+ *      - tx queueing is a simple fifo list
+ *   	- reassembly is optional and easily done by transports per conn
+ *      - no per flow rx lookup at all, straight to the socket
+ *   	- less per-frag memory and wire overhead
+ *   Con:
+ *      - queued acks can be delayed behind large messages
+ *   Depends:
+ *      - small message latency is higher behind queued large messages
+ *      - large message latency isn't starved by intervening small sends
+ */
+int rds_send_xmit(struct rds_conn_path *cp)
+{
+	struct rds_connection *conn = cp->cp_conn;
+	struct rds_message *rm;
+	unsigned long flags;
+	unsigned int tmp;
+	struct scatterlist *sg;
+	int ret = 0;
+	LIST_HEAD(to_be_dropped);
+	int batch_count;
+	unsigned long send_gen = 0;
+	int same_rm = 0;
+
+restart:
+	batch_count = 0;
+
+	/* The drop processing after over_batch relies on
+	 * rds_send_remove_from_sock() emptying to_be_dropped entry by
+	 * entry; warn if that post-condition ever stops holding, and
+	 * re-initialize the list head.
+	 */
+	WARN_ON_ONCE(!list_empty(&to_be_dropped));
+	INIT_LIST_HEAD(&to_be_dropped);
+
+	/*
+	 * sendmsg calls here after having queued its message on the send
+	 * queue.  We only have one task feeding the connection at a time.  If
+	 * another thread is already feeding the queue then we back off.  This
+	 * avoids blocking the caller and trading per-connection data between
+	 * caches per message.
+	 */
+	if (!acquire_in_xmit(cp)) {
+		rds_stats_inc(s_send_lock_contention);
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	if (rds_destroy_pending(cp->cp_conn)) {
+		release_in_xmit(cp);
+		ret = -ENETUNREACH; /* dont requeue send work */
+		goto out;
+	}
+
+	/*
+	 * we record the send generation after doing the xmit acquire.
+	 * if someone else manages to jump in and do some work, we'll use
+	 * this to avoid a goto restart farther down.
+	 *
+	 * The acquire_in_xmit() check above ensures that only one
+	 * caller can increment c_send_gen at any time.
+	 */
+	send_gen = READ_ONCE(cp->cp_send_gen) + 1;
+	WRITE_ONCE(cp->cp_send_gen, send_gen);
+
+	/*
+	 * rds_conn_shutdown() sets the conn state and then tests RDS_IN_XMIT,
+	 * we do the opposite to avoid races.
+	 */
+	if (!rds_conn_path_up(cp)) {
+		release_in_xmit(cp);
+		ret = 0;
+		goto out;
+	}
+
+	if (conn->c_trans->xmit_path_prepare)
+		conn->c_trans->xmit_path_prepare(cp);
+
+	/*
+	 * spin trying to push headers and data down the connection until
+	 * the connection doesn't make forward progress.
+	 */
+	while (1) {
+
+		rm = cp->cp_xmit_rm;
+
+		if (!rm) {
+			same_rm = 0;
+		} else {
+			same_rm++;
+			if (same_rm >= 4096) {
+				rds_stats_inc(s_send_stuck_rm);
+				ret = -EAGAIN;
+				break;
+			}
+		}
+
+		/*
+		 * If between sending messages, we can send a pending congestion
+		 * map update.
+		 */
+		if (!rm && test_and_clear_bit(0, &conn->c_map_queued)) {
+			rm = rds_cong_update_alloc(conn);
+			if (IS_ERR(rm)) {
+				ret = PTR_ERR(rm);
+				break;
+			}
+			rm->data.op_active = 1;
+			rm->m_inc.i_conn_path = cp;
+			rm->m_inc.i_conn = cp->cp_conn;
+
+			cp->cp_xmit_rm = rm;
+		}
+
+		/*
+		 * If not already working on one, grab the next message.
+		 *
+		 * cp_xmit_rm holds a ref while we're sending this message down
+		 * the connection.  We can use this ref while holding the
+		 * send_sem.. rds_send_path_reset() is serialized with it.
+		 */
+		if (!rm) {
+			unsigned int len;
+
+			batch_count++;
+
+			/* we want to process as big a batch as we can, but
+			 * we also want to avoid softlockups.  If we've been
+			 * through a lot of messages, lets back off and see
+			 * if anyone else jumps in
+			 */
+			if (batch_count >= send_batch_count)
+				goto over_batch;
+
+			/* make sure cp_index#0 caught up during fan-out in
+			 * order to avoid lane races
+			 */
+			if (cp->cp_index > 0 && rds_mprds_cp0_catchup(conn)) {
+				rds_stats_inc(s_mprds_catchup_tx0_retries);
+				goto over_batch;
+			}
+
+			spin_lock_irqsave(&cp->cp_lock, flags);
+
+			if (!list_empty(&cp->cp_send_queue)) {
+				rm = list_entry(cp->cp_send_queue.next,
+						struct rds_message,
+						m_conn_item);
+				rds_message_addref(rm);
+
+				/*
+				 * Move the message from the send queue to the retransmit
+				 * list right away.
+				 */
+				list_move_tail(&rm->m_conn_item,
+					       &cp->cp_retrans);
+			}
+
+			spin_unlock_irqrestore(&cp->cp_lock, flags);
+
+			if (!rm)
+				break;
+
+			/* Unfortunately, the way Infiniband deals with
+			 * RDMA to a bad MR key is by moving the entire
+			 * queue pair to error state. We could possibly
+			 * recover from that, but right now we drop the
+			 * connection.
+			 * Therefore, we never retransmit messages with RDMA ops.
+			 */
+			if (test_bit(RDS_MSG_FLUSH, &rm->m_flags) ||
+			    (rm->rdma.op_active &&
+			    test_bit(RDS_MSG_RETRANSMITTED, &rm->m_flags))) {
+				spin_lock_irqsave(&cp->cp_lock, flags);
+				if (test_and_clear_bit(RDS_MSG_ON_CONN,
+						       &rm->m_flags)) {
+					/* our ref is put after the batch */
+					list_move(&rm->m_conn_item,
+						  &to_be_dropped);
+					spin_unlock_irqrestore(&cp->cp_lock,
+							       flags);
+				} else {
+					/* already off the conn list; drop
+					 * the ref taken above ourselves
+					 */
+					spin_unlock_irqrestore(&cp->cp_lock,
+							       flags);
+					rds_message_put(rm);
+				}
+				continue;
+			}
+
+			/* Require an ACK every once in a while */
+			len = ntohl(rm->m_inc.i_hdr.h_len);
+			if (cp->cp_unacked_packets == 0 ||
+			    cp->cp_unacked_bytes < len) {
+				set_bit(RDS_MSG_ACK_REQUIRED, &rm->m_flags);
+
+				cp->cp_unacked_packets =
+					rds_sysctl_max_unacked_packets;
+				cp->cp_unacked_bytes =
+					rds_sysctl_max_unacked_bytes;
+				rds_stats_inc(s_send_ack_required);
+			} else {
+				cp->cp_unacked_bytes -= len;
+				cp->cp_unacked_packets--;
+			}
+
+			cp->cp_xmit_rm = rm;
+		}
+
+		/* The transport either sends the whole rdma or none of it */
+		if (rm->rdma.op_active && !cp->cp_xmit_rdma_sent) {
+			rm->m_final_op = &rm->rdma;
+			/* The transport owns the mapped memory for now.
+			 * You can't unmap it while it's on the send queue
+			 */
+			set_bit(RDS_MSG_MAPPED, &rm->m_flags);
+			ret = conn->c_trans->xmit_rdma(conn, &rm->rdma);
+			if (ret) {
+				clear_bit(RDS_MSG_MAPPED, &rm->m_flags);
+				wake_up_interruptible(&rm->m_flush_wait);
+				break;
+			}
+			cp->cp_xmit_rdma_sent = 1;
+
+		}
+
+		if (rm->atomic.op_active && !cp->cp_xmit_atomic_sent) {
+			rm->m_final_op = &rm->atomic;
+			/* The transport owns the mapped memory for now.
+			 * You can't unmap it while it's on the send queue
+			 */
+			set_bit(RDS_MSG_MAPPED, &rm->m_flags);
+			ret = conn->c_trans->xmit_atomic(conn, &rm->atomic);
+			if (ret) {
+				clear_bit(RDS_MSG_MAPPED, &rm->m_flags);
+				wake_up_interruptible(&rm->m_flush_wait);
+				break;
+			}
+			cp->cp_xmit_atomic_sent = 1;
+
+		}
+
+		/*
+		 * A number of cases require an RDS header to be sent
+		 * even if there is no data.
+		 * We permit 0-byte sends; rds-ping depends on this.
+		 * However, if there are exclusively attached silent ops,
+		 * we skip the hdr/data send, to enable silent operation.
+		 */
+		if (rm->data.op_nents == 0) {
+			int ops_present;
+			int all_ops_are_silent = 1;
+
+			ops_present = (rm->atomic.op_active || rm->rdma.op_active);
+			if (rm->atomic.op_active && !rm->atomic.op_silent)
+				all_ops_are_silent = 0;
+			if (rm->rdma.op_active && !rm->rdma.op_silent)
+				all_ops_are_silent = 0;
+
+			if (ops_present && all_ops_are_silent
+			    && !rm->m_rdma_cookie)
+				rm->data.op_active = 0;
+		}
+
+		if (rm->data.op_active && !cp->cp_xmit_data_sent) {
+			rm->m_final_op = &rm->data;
+
+			ret = conn->c_trans->xmit(conn, rm,
+						  cp->cp_xmit_hdr_off,
+						  cp->cp_xmit_sg,
+						  cp->cp_xmit_data_off);
+			if (ret <= 0)
+				break;
+
+			if (cp->cp_xmit_hdr_off < sizeof(struct rds_header)) {
+				tmp = min_t(int, ret,
+					    sizeof(struct rds_header) -
+					    cp->cp_xmit_hdr_off);
+				cp->cp_xmit_hdr_off += tmp;
+				ret -= tmp;
+			}
+
+			sg = &rm->data.op_sg[cp->cp_xmit_sg];
+			while (ret) {
+				tmp = min_t(int, ret, sg->length -
+						      cp->cp_xmit_data_off);
+				cp->cp_xmit_data_off += tmp;
+				ret -= tmp;
+				if (cp->cp_xmit_data_off == sg->length) {
+					cp->cp_xmit_data_off = 0;
+					sg++;
+					cp->cp_xmit_sg++;
+					BUG_ON(ret != 0 && cp->cp_xmit_sg ==
+					       rm->data.op_nents);
+				}
+			}
+
+			if (cp->cp_xmit_hdr_off == sizeof(struct rds_header) &&
+			    (cp->cp_xmit_sg == rm->data.op_nents))
+				cp->cp_xmit_data_sent = 1;
+		}
+
+		/*
+		 * A rm will only take multiple times through this loop
+		 * if there is a data op. Thus, if the data is sent (or there was
+		 * none), then we're done with the rm.
+		 */
+		if (!rm->data.op_active || cp->cp_xmit_data_sent) {
+			cp->cp_xmit_rm = NULL;
+			cp->cp_xmit_sg = 0;
+			cp->cp_xmit_hdr_off = 0;
+			cp->cp_xmit_data_off = 0;
+			cp->cp_xmit_rdma_sent = 0;
+			cp->cp_xmit_atomic_sent = 0;
+			cp->cp_xmit_data_sent = 0;
+
+			rds_message_put(rm);
+		}
+	}
+
+over_batch:
+	if (conn->c_trans->xmit_path_complete)
+		conn->c_trans->xmit_path_complete(cp);
+	release_in_xmit(cp);
+
+	/* Nuke any messages we decided not to retransmit. */
+	if (!list_empty(&to_be_dropped)) {
+		/* irqs on here, so we can put(), unlike above */
+		list_for_each_entry(rm, &to_be_dropped, m_conn_item)
+			rds_message_put(rm);
+		rds_send_remove_from_sock(&to_be_dropped, RDS_RDMA_DROPPED);
+	}
+
+	/*
+	 * Other senders can queue a message after we last test the send queue
+	 * but before we clear RDS_IN_XMIT.  In that case they'd back off and
+	 * not try and send their newly queued message.  We need to check the
+	 * send queue after having cleared RDS_IN_XMIT so that their message
+	 * doesn't get stuck on the send queue.
+	 *
+	 * If the transport cannot continue (i.e ret != 0), then it must
+	 * call us when more room is available, such as from the tx
+	 * completion handler.
+	 *
+	 * We have an extra generation check here so that if someone manages
+	 * to jump in after our release_in_xmit, we'll see that they have done
+	 * some work and we will skip our goto
+	 */
+	if (ret == 0) {
+		bool raced;
+
+		smp_mb();
+		raced = send_gen != READ_ONCE(cp->cp_send_gen);
+
+		if ((test_bit(0, &conn->c_map_queued) ||
+		    !list_empty(&cp->cp_send_queue)) && !raced) {
+			if (batch_count < send_batch_count)
+				goto restart;
+			rcu_read_lock();
+			if (rds_destroy_pending(cp->cp_conn))
+				ret = -ENETUNREACH;
+			else
+				queue_delayed_work(cp->cp_wq,
+						   &cp->cp_send_w, 1);
+			rcu_read_unlock();
+		} else if (raced) {
+			rds_stats_inc(s_send_lock_queue_raced);
+		}
+	}
+out:
+	return ret;
+}
+EXPORT_SYMBOL_GPL(rds_send_xmit);
+
+static void rds_send_sndbuf_remove(struct rds_sock *rs, struct rds_message *rm)
+{
+	u32 len = be32_to_cpu(rm->m_inc.i_hdr.h_len);
+
+	assert_spin_locked(&rs->rs_lock);
+
+	BUG_ON(rs->rs_snd_bytes < len);
+	rs->rs_snd_bytes -= len;
+
+	if (rs->rs_snd_bytes == 0)
+		rds_stats_inc(s_send_queue_empty);
+}
+
+static inline int rds_send_is_acked(struct rds_message *rm, u64 ack,
+				    is_acked_func is_acked)
+{
+	if (is_acked)
+		return is_acked(rm, ack);
+	return be64_to_cpu(rm->m_inc.i_hdr.h_sequence) <= ack;
+}
+
+/*
+ * This is pretty similar to what happens below in the ACK
+ * handling code - except that we call here as soon as we get
+ * the IB send completion on the RDMA op and the accompanying
+ * message.
+ */
+void rds_rdma_send_complete(struct rds_message *rm, int status)
+{
+	struct rds_sock *rs = NULL;
+	struct rm_rdma_op *ro;
+	struct rds_notifier *notifier;
+	unsigned long flags;
+
+	spin_lock_irqsave(&rm->m_rs_lock, flags);
+
+	ro = &rm->rdma;
+	if (test_bit(RDS_MSG_ON_SOCK, &rm->m_flags) &&
+	    ro->op_active && ro->op_notify && ro->op_notifier) {
+		notifier = ro->op_notifier;
+		rs = rm->m_rs;
+		sock_hold(rds_rs_to_sk(rs));
+
+		notifier->n_status = status;
+		spin_lock(&rs->rs_lock);
+		list_add_tail(&notifier->n_list, &rs->rs_notify_queue);
+		spin_unlock(&rs->rs_lock);
+
+		ro->op_notifier = NULL;
+	}
+
+	spin_unlock_irqrestore(&rm->m_rs_lock, flags);
+
+	if (rs) {
+		rds_wake_sk_sleep(rs);
+		sock_put(rds_rs_to_sk(rs));
+	}
+}
+EXPORT_SYMBOL_GPL(rds_rdma_send_complete);
+
+/*
+ * Just like above, except looks at atomic op
+ */
+void rds_atomic_send_complete(struct rds_message *rm, int status)
+{
+	struct rds_sock *rs = NULL;
+	struct rm_atomic_op *ao;
+	struct rds_notifier *notifier;
+	unsigned long flags;
+
+	spin_lock_irqsave(&rm->m_rs_lock, flags);
+
+	ao = &rm->atomic;
+	if (test_bit(RDS_MSG_ON_SOCK, &rm->m_flags)
+	    && ao->op_active && ao->op_notify && ao->op_notifier) {
+		notifier = ao->op_notifier;
+		rs = rm->m_rs;
+		sock_hold(rds_rs_to_sk(rs));
+
+		notifier->n_status = status;
+		spin_lock(&rs->rs_lock);
+		list_add_tail(&notifier->n_list, &rs->rs_notify_queue);
+		spin_unlock(&rs->rs_lock);
+
+		ao->op_notifier = NULL;
+	}
+
+	spin_unlock_irqrestore(&rm->m_rs_lock, flags);
+
+	if (rs) {
+		rds_wake_sk_sleep(rs);
+		sock_put(rds_rs_to_sk(rs));
+	}
+}
+EXPORT_SYMBOL_GPL(rds_atomic_send_complete);
+
+/*
+ * This is the same as rds_rdma_send_complete except we
+ * don't do any locking - we have all the ingredients (message,
+ * socket, socket lock) and can just move the notifier.
+ */
+static inline void
+__rds_send_complete(struct rds_sock *rs, struct rds_message *rm, int status)
+{
+	struct rm_rdma_op *ro;
+	struct rm_atomic_op *ao;
+
+	ro = &rm->rdma;
+	if (ro->op_active && ro->op_notify && ro->op_notifier) {
+		ro->op_notifier->n_status = status;
+		list_add_tail(&ro->op_notifier->n_list, &rs->rs_notify_queue);
+		ro->op_notifier = NULL;
+	}
+
+	ao = &rm->atomic;
+	if (ao->op_active && ao->op_notify && ao->op_notifier) {
+		ao->op_notifier->n_status = status;
+		list_add_tail(&ao->op_notifier->n_list, &rs->rs_notify_queue);
+		ao->op_notifier = NULL;
+	}
+
+	/* No need to wake the app - caller does this */
+}
+
+/*
+ * This removes messages from the socket's list if they're on it.  The list
+ * argument must be private to the caller, we must be able to modify it
+ * without locks.  The messages must have a reference held for their
+ * position on the list.  This function will drop that reference after
+ * removing the messages from the 'messages' list regardless of if it found
+ * the messages on the socket list or not.
+ */
+static void rds_send_remove_from_sock(struct list_head *messages, int status)
+{
+	unsigned long flags;
+	struct rds_sock *rs = NULL;
+	struct rds_message *rm;
+
+	while (!list_empty(messages)) {
+		int was_on_sock = 0;
+
+		rm = list_entry(messages->next, struct rds_message,
+				m_conn_item);
+		list_del_init(&rm->m_conn_item);
+
+		/*
+		 * If we see this flag cleared then we're *sure* that someone
+		 * else beat us to removing it from the sock.  If we race
+		 * with their flag update we'll get the lock and then really
+		 * see that the flag has been cleared.
+		 *
+		 * The message spinlock makes sure nobody clears rm->m_rs
+		 * while we're messing with it. It does not prevent the
+		 * message from being removed from the socket, though.
+		 */
+		spin_lock_irqsave(&rm->m_rs_lock, flags);
+		if (!test_bit(RDS_MSG_ON_SOCK, &rm->m_flags))
+			goto unlock_and_drop;
+
+		if (rs != rm->m_rs) {
+			if (rs) {
+				rds_wake_sk_sleep(rs);
+				sock_put(rds_rs_to_sk(rs));
+			}
+			rs = rm->m_rs;
+			if (rs)
+				sock_hold(rds_rs_to_sk(rs));
+		}
+		if (!rs)
+			goto unlock_and_drop;
+		spin_lock(&rs->rs_lock);
+
+		if (test_and_clear_bit(RDS_MSG_ON_SOCK, &rm->m_flags)) {
+			struct rm_rdma_op *ro = &rm->rdma;
+			struct rds_notifier *notifier;
+
+			list_del_init(&rm->m_sock_item);
+			rds_send_sndbuf_remove(rs, rm);
+
+			if (ro->op_active && ro->op_notifier &&
+			       (ro->op_notify || (ro->op_recverr && status))) {
+				notifier = ro->op_notifier;
+				list_add_tail(&notifier->n_list,
+						&rs->rs_notify_queue);
+				if (!notifier->n_status)
+					notifier->n_status = status;
+				rm->rdma.op_notifier = NULL;
+			}
+			was_on_sock = 1;
+		}
+		spin_unlock(&rs->rs_lock);
+
+unlock_and_drop:
+		spin_unlock_irqrestore(&rm->m_rs_lock, flags);
+		rds_message_put(rm);
+		if (was_on_sock)
+			rds_message_put(rm);
+	}
+
+	if (rs) {
+		rds_wake_sk_sleep(rs);
+		sock_put(rds_rs_to_sk(rs));
+	}
+}
+
+/*
+ * Transports call here when they've determined that the receiver queued
+ * messages up to, and including, the given sequence number.  Messages are
+ * moved to the retrans queue when rds_send_xmit picks them off the send
+ * queue. This means that in the TCP case, the message may not have been
+ * assigned the m_ack_seq yet - but that's fine as long as tcp_is_acked
+ * checks the RDS_MSG_HAS_ACK_SEQ bit.
+ */
+void rds_send_path_drop_acked(struct rds_conn_path *cp, u64 ack,
+			      is_acked_func is_acked)
+{
+	struct rds_message *rm, *tmp;
+	unsigned long flags;
+	LIST_HEAD(list);
+
+	spin_lock_irqsave(&cp->cp_lock, flags);
+
+	list_for_each_entry_safe(rm, tmp, &cp->cp_retrans, m_conn_item) {
+		if (!rds_send_is_acked(rm, ack, is_acked))
+			break;
+
+		list_move(&rm->m_conn_item, &list);
+		clear_bit(RDS_MSG_ON_CONN, &rm->m_flags);
+	}
+
+	/* order flag updates with spin locks */
+	if (!list_empty(&list))
+		smp_mb__after_atomic();
+
+	spin_unlock_irqrestore(&cp->cp_lock, flags);
+
+	/* now remove the messages from the sock list as needed */
+	rds_send_remove_from_sock(&list, RDS_RDMA_SUCCESS);
+}
+EXPORT_SYMBOL_GPL(rds_send_path_drop_acked);
+
+void rds_send_drop_acked(struct rds_connection *conn, u64 ack,
+			 is_acked_func is_acked)
+{
+	WARN_ON(conn->c_trans->t_mp_capable);
+	rds_send_path_drop_acked(&conn->c_path[0], ack, is_acked);
+}
+EXPORT_SYMBOL_GPL(rds_send_drop_acked);
+
+void rds_send_drop_to(struct rds_sock *rs, struct sockaddr_in6 *dest)
+{
+	struct rds_message *rm, *tmp;
+	struct rds_connection *conn;
+	struct rds_conn_path *cp;
+	unsigned long flags;
+	LIST_HEAD(list);
+
+	/* get all the messages we're dropping under the rs lock */
+	spin_lock_irqsave(&rs->rs_lock, flags);
+
+	list_for_each_entry_safe(rm, tmp, &rs->rs_send_queue, m_sock_item) {
+		if (dest &&
+		    (!ipv6_addr_equal(&dest->sin6_addr, &rm->m_daddr) ||
+		     dest->sin6_port != rm->m_inc.i_hdr.h_dport))
+			continue;
+
+		list_move(&rm->m_sock_item, &list);
+		rds_send_sndbuf_remove(rs, rm);
+		clear_bit(RDS_MSG_ON_SOCK, &rm->m_flags);
+	}
+
+	/* order flag updates with the rs lock */
+	smp_mb__after_atomic();
+
+	spin_unlock_irqrestore(&rs->rs_lock, flags);
+
+	if (list_empty(&list))
+		return;
+
+	/* Remove the messages from the conn */
+	list_for_each_entry(rm, &list, m_sock_item) {
+
+		conn = rm->m_inc.i_conn;
+		if (conn->c_trans->t_mp_capable)
+			cp = rm->m_inc.i_conn_path;
+		else
+			cp = &conn->c_path[0];
+
+		spin_lock_irqsave(&cp->cp_lock, flags);
+		/*
+		 * Maybe someone else beat us to removing rm from the conn.
+		 * If we race with their flag update we'll get the lock and
+		 * then really see that the flag has been cleared.
+		 */
+		if (!test_and_clear_bit(RDS_MSG_ON_CONN, &rm->m_flags)) {
+			spin_unlock_irqrestore(&cp->cp_lock, flags);
+			continue;
+		}
+		list_del_init(&rm->m_conn_item);
+		spin_unlock_irqrestore(&cp->cp_lock, flags);
+
+		/*
+		 * Couldn't grab m_rs_lock in top loop (lock ordering),
+		 * but we can now.
+		 */
+		spin_lock_irqsave(&rm->m_rs_lock, flags);
+
+		spin_lock(&rs->rs_lock);
+		__rds_send_complete(rs, rm, RDS_RDMA_CANCELED);
+		spin_unlock(&rs->rs_lock);
+
+		spin_unlock_irqrestore(&rm->m_rs_lock, flags);
+
+		rds_message_put(rm);
+	}
+
+	rds_wake_sk_sleep(rs);
+
+	while (!list_empty(&list)) {
+		rm = list_entry(list.next, struct rds_message, m_sock_item);
+		list_del_init(&rm->m_sock_item);
+		rds_message_wait(rm);
+
+		/* just in case the code above skipped this message
+		 * because RDS_MSG_ON_CONN wasn't set, run it again here
+		 * taking m_rs_lock is the only thing that keeps us
+		 * from racing with ack processing.
+		 */
+		spin_lock_irqsave(&rm->m_rs_lock, flags);
+
+		spin_lock(&rs->rs_lock);
+		__rds_send_complete(rs, rm, RDS_RDMA_CANCELED);
+		spin_unlock(&rs->rs_lock);
+
+		spin_unlock_irqrestore(&rm->m_rs_lock, flags);
+
+		rds_message_put(rm);
+	}
+}
+
+/*
+ * we only want this to fire once so we use the callers 'queued'.  It's
+ * possible that another thread can race with us and remove the
+ * message from the flow with RDS_CANCEL_SENT_TO.
+ */
+static int rds_send_queue_rm(struct rds_sock *rs, struct rds_connection *conn,
+			     struct rds_conn_path *cp,
+			     struct rds_message *rm, __be16 sport,
+			     __be16 dport, int *queued)
+{
+	unsigned long flags;
+	u32 len;
+
+	if (*queued)
+		goto out;
+
+	len = be32_to_cpu(rm->m_inc.i_hdr.h_len);
+
+	/* this is the only place which holds both the socket's rs_lock
+	 * and the connection's c_lock */
+	spin_lock_irqsave(&rs->rs_lock, flags);
+
+	/*
+	 * If there is a little space in sndbuf, we don't queue anything,
+	 * and userspace gets -EAGAIN. But poll() indicates there's send
+	 * room. This can lead to bad behavior (spinning) if snd_bytes isn't
+	 * freed up by incoming acks. So we check the *old* value of
+	 * rs_snd_bytes here to allow the last msg to exceed the buffer,
+	 * and poll() now knows no more data can be sent.
+	 */
+	if (rs->rs_snd_bytes < rds_sk_sndbuf(rs)) {
+		rs->rs_snd_bytes += len;
+
+		/* let recv side know we are close to send space exhaustion.
+		 * This is probably not the optimal way to do it, as this
+		 * means we set the flag on *all* messages as soon as our
+		 * throughput hits a certain threshold.
+		 */
+		if (rs->rs_snd_bytes >= rds_sk_sndbuf(rs) / 2)
+			set_bit(RDS_MSG_ACK_REQUIRED, &rm->m_flags);
+
+		list_add_tail(&rm->m_sock_item, &rs->rs_send_queue);
+		set_bit(RDS_MSG_ON_SOCK, &rm->m_flags);
+		rds_message_addref(rm);
+		sock_hold(rds_rs_to_sk(rs));
+		rm->m_rs = rs;
+
+		/* The code ordering is a little weird, but we're
+		   trying to minimize the time we hold c_lock */
+		rds_message_populate_header(&rm->m_inc.i_hdr, sport, dport, 0);
+		rm->m_inc.i_conn = conn;
+		rm->m_inc.i_conn_path = cp;
+		rds_message_addref(rm);
+
+		spin_lock(&cp->cp_lock);
+		rm->m_inc.i_hdr.h_sequence = cpu_to_be64(cp->cp_next_tx_seq++);
+		list_add_tail(&rm->m_conn_item, &cp->cp_send_queue);
+		set_bit(RDS_MSG_ON_CONN, &rm->m_flags);
+		spin_unlock(&cp->cp_lock);
+
+		rdsdebug("queued msg %p len %d, rs %p bytes %d seq %llu\n",
+			 rm, len, rs, rs->rs_snd_bytes,
+			 (unsigned long long)be64_to_cpu(rm->m_inc.i_hdr.h_sequence));
+
+		*queued = 1;
+	}
+
+	spin_unlock_irqrestore(&rs->rs_lock, flags);
+out:
+	return *queued;
+}
+
+/*
+ * rds_message is getting to be quite complicated, and we'd like to allocate
+ * it all in one go. This figures out how big it needs to be up front.
+ */
+static int rds_rm_size(struct msghdr *msg, int num_sgs,
+		       struct rds_iov_vector_arr *vct)
+{
+	struct cmsghdr *cmsg;
+	int size = 0;
+	int cmsg_groups = 0;
+	int retval;
+	bool zcopy_cookie = false;
+	struct rds_iov_vector *iov, *tmp_iov;
+
+	if (num_sgs < 0)
+		return -EINVAL;
+
+	for_each_cmsghdr(cmsg, msg) {
+		if (!CMSG_OK(msg, cmsg))
+			return -EINVAL;
+
+		if (cmsg->cmsg_level != SOL_RDS)
+			continue;
+
+		switch (cmsg->cmsg_type) {
+		case RDS_CMSG_RDMA_ARGS:
+			if (cmsg->cmsg_len < CMSG_LEN(sizeof(struct rds_rdma_args)))
+				return -EINVAL;
+			if (vct->indx >= vct->len) {
+				vct->len += vct->incr;
+				tmp_iov = krealloc_array(vct->vec, vct->len,
+							 sizeof(*vct->vec), GFP_KERNEL);
+				if (!tmp_iov) {
+					vct->len -= vct->incr;
+					return -ENOMEM;
+				}
+				vct->vec = tmp_iov;
+			}
+			iov = &vct->vec[vct->indx];
+			memset(iov, 0, sizeof(struct rds_iov_vector));
+			vct->indx++;
+			cmsg_groups |= 1;
+			retval = rds_rdma_extra_size(CMSG_DATA(cmsg), iov);
+			if (retval < 0)
+				return retval;
+			size += retval;
+
+			break;
+
+		case RDS_CMSG_ZCOPY_COOKIE:
+			zcopy_cookie = true;
+			fallthrough;
+
+		case RDS_CMSG_RDMA_DEST:
+		case RDS_CMSG_RDMA_MAP:
+			cmsg_groups |= 2;
+			/* these are valid but do no add any size */
+			break;
+
+		case RDS_CMSG_ATOMIC_CSWP:
+		case RDS_CMSG_ATOMIC_FADD:
+		case RDS_CMSG_MASKED_ATOMIC_CSWP:
+		case RDS_CMSG_MASKED_ATOMIC_FADD:
+			cmsg_groups |= 1;
+			size += sizeof(struct scatterlist);
+			break;
+
+		default:
+			return -EINVAL;
+		}
+
+	}
+
+	if ((msg->msg_flags & MSG_ZEROCOPY) && !zcopy_cookie)
+		return -EINVAL;
+
+	size += num_sgs * sizeof(struct scatterlist);
+
+	/* Ensure (DEST, MAP) are never used with (ARGS, ATOMIC) */
+	if (cmsg_groups == 3)
+		return -EINVAL;
+
+	return size;
+}
+
+static int rds_cmsg_zcopy(struct rds_sock *rs, struct rds_message *rm,
+			  struct cmsghdr *cmsg)
+{
+	u32 *cookie;
+
+	if (cmsg->cmsg_len < CMSG_LEN(sizeof(*cookie)) ||
+	    !rm->data.op_mmp_znotifier)
+		return -EINVAL;
+	cookie = CMSG_DATA(cmsg);
+	rm->data.op_mmp_znotifier->z_cookie = *cookie;
+	return 0;
+}
+
+static int rds_cmsg_send(struct rds_sock *rs, struct rds_message *rm,
+			 struct msghdr *msg, int *allocated_mr,
+			 struct rds_iov_vector_arr *vct)
+{
+	struct cmsghdr *cmsg;
+	int ret = 0, ind = 0;
+
+	for_each_cmsghdr(cmsg, msg) {
+		if (!CMSG_OK(msg, cmsg))
+			return -EINVAL;
+
+		if (cmsg->cmsg_level != SOL_RDS)
+			continue;
+
+		/* As a side effect, RDMA_DEST and RDMA_MAP will set
+		 * rm->rdma.m_rdma_cookie and rm->rdma.m_rdma_mr.
+		 */
+		switch (cmsg->cmsg_type) {
+		case RDS_CMSG_RDMA_ARGS:
+			if (ind >= vct->indx)
+				return -ENOMEM;
+			ret = rds_cmsg_rdma_args(rs, rm, cmsg, &vct->vec[ind]);
+			ind++;
+			break;
+
+		case RDS_CMSG_RDMA_DEST:
+			ret = rds_cmsg_rdma_dest(rs, rm, cmsg);
+			break;
+
+		case RDS_CMSG_RDMA_MAP:
+			ret = rds_cmsg_rdma_map(rs, rm, cmsg);
+			if (!ret)
+				*allocated_mr = 1;
+			else if (ret == -ENODEV)
+				/* Accommodate the get_mr() case which can fail
+				 * if connection isn't established yet.
+				 */
+				ret = -EAGAIN;
+			break;
+		case RDS_CMSG_ATOMIC_CSWP:
+		case RDS_CMSG_ATOMIC_FADD:
+		case RDS_CMSG_MASKED_ATOMIC_CSWP:
+		case RDS_CMSG_MASKED_ATOMIC_FADD:
+			ret = rds_cmsg_atomic(rs, rm, cmsg);
+			break;
+
+		case RDS_CMSG_ZCOPY_COOKIE:
+			ret = rds_cmsg_zcopy(rs, rm, cmsg);
+			break;
+
+		default:
+			return -EINVAL;
+		}
+
+		if (ret)
+			break;
+	}
+
+	return ret;
+}
+
+static int rds_rdma_bytes(struct msghdr *msg, size_t *rdma_bytes)
+{
+	struct rds_rdma_args *args;
+	struct cmsghdr *cmsg;
+
+	for_each_cmsghdr(cmsg, msg) {
+		if (!CMSG_OK(msg, cmsg))
+			return -EINVAL;
+
+		if (cmsg->cmsg_level != SOL_RDS)
+			continue;
+
+		if (cmsg->cmsg_type == RDS_CMSG_RDMA_ARGS) {
+			if (cmsg->cmsg_len <
+			    CMSG_LEN(sizeof(struct rds_rdma_args)))
+				return -EINVAL;
+			args = CMSG_DATA(cmsg);
+			*rdma_bytes += args->remote_vec.bytes;
+		}
+	}
+	return 0;
+}
+
+int rds_sendmsg(struct socket *sock, struct msghdr *msg, size_t payload_len)
+{
+	struct sock *sk = sock->sk;
+	struct rds_sock *rs = rds_sk_to_rs(sk);
+	DECLARE_SOCKADDR(struct sockaddr_in6 *, sin6, msg->msg_name);
+	DECLARE_SOCKADDR(struct sockaddr_in *, usin, msg->msg_name);
+	__be16 dport;
+	struct rds_message *rm = NULL;
+	struct rds_connection *conn;
+	int ret = 0;
+	int queued = 0, allocated_mr = 0;
+	int nonblock = msg->msg_flags & MSG_DONTWAIT;
+	long timeo = sock_sndtimeo(sk, nonblock);
+	struct rds_conn_path *cpath;
+	struct in6_addr daddr;
+	__u32 scope_id = 0;
+	size_t rdma_payload_len = 0;
+	bool zcopy = ((msg->msg_flags & MSG_ZEROCOPY) &&
+		      sock_flag(rds_rs_to_sk(rs), SOCK_ZEROCOPY));
+	int num_sgs = DIV_ROUND_UP(payload_len, PAGE_SIZE);
+	int namelen;
+	struct rds_iov_vector_arr vct;
+	int ind;
+
+	memset(&vct, 0, sizeof(vct));
+
+	/* expect 1 RDMA CMSG per rds_sendmsg. can still grow if more needed. */
+	vct.incr = 1;
+
+	/* Mirror Linux UDP mirror of BSD error message compatibility */
+	/* XXX: Perhaps MSG_MORE someday */
+	if (msg->msg_flags & ~(MSG_DONTWAIT | MSG_CMSG_COMPAT | MSG_ZEROCOPY)) {
+		ret = -EOPNOTSUPP;
+		goto out;
+	}
+
+	namelen = msg->msg_namelen;
+	if (namelen != 0) {
+		if (namelen < sizeof(*usin)) {
+			ret = -EINVAL;
+			goto out;
+		}
+		switch (usin->sin_family) {
+		case AF_INET:
+			if (usin->sin_addr.s_addr == htonl(INADDR_ANY) ||
+			    usin->sin_addr.s_addr == htonl(INADDR_BROADCAST) ||
+			    ipv4_is_multicast(usin->sin_addr.s_addr)) {
+				ret = -EINVAL;
+				goto out;
+			}
+			ipv6_addr_set_v4mapped(usin->sin_addr.s_addr, &daddr);
+			dport = usin->sin_port;
+			break;
+
+#if IS_ENABLED(CONFIG_IPV6)
+		case AF_INET6: {
+			int addr_type;
+
+			if (namelen < sizeof(*sin6)) {
+				ret = -EINVAL;
+				goto out;
+			}
+			addr_type = ipv6_addr_type(&sin6->sin6_addr);
+			if (!(addr_type & IPV6_ADDR_UNICAST)) {
+				__be32 addr4;
+
+				if (!(addr_type & IPV6_ADDR_MAPPED)) {
+					ret = -EINVAL;
+					goto out;
+				}
+
+				/* It is a mapped address.  Need to do some
+				 * sanity checks.
+				 */
+				addr4 = sin6->sin6_addr.s6_addr32[3];
+				if (addr4 == htonl(INADDR_ANY) ||
+				    addr4 == htonl(INADDR_BROADCAST) ||
+				    ipv4_is_multicast(addr4)) {
+					ret = -EINVAL;
+					goto out;
+				}
+			}
+			if (addr_type & IPV6_ADDR_LINKLOCAL) {
+				if (sin6->sin6_scope_id == 0) {
+					ret = -EINVAL;
+					goto out;
+				}
+				scope_id = sin6->sin6_scope_id;
+			}
+
+			daddr = sin6->sin6_addr;
+			dport = sin6->sin6_port;
+			break;
+		}
+#endif
+
+		default:
+			ret = -EINVAL;
+			goto out;
+		}
+	} else {
+		/* We only care about consistency with ->connect() */
+		lock_sock(sk);
+		daddr = rs->rs_conn_addr;
+		dport = rs->rs_conn_port;
+		scope_id = rs->rs_bound_scope_id;
+		release_sock(sk);
+	}
+
+	lock_sock(sk);
+	if (ipv6_addr_any(&rs->rs_bound_addr) || ipv6_addr_any(&daddr)) {
+		release_sock(sk);
+		ret = -ENOTCONN;
+		goto out;
+	} else if (namelen != 0) {
+		/* Cannot send to an IPv4 address using an IPv6 source
+		 * address and cannot send to an IPv6 address using an
+		 * IPv4 source address.
+		 */
+		if (ipv6_addr_v4mapped(&daddr) ^
+		    ipv6_addr_v4mapped(&rs->rs_bound_addr)) {
+			release_sock(sk);
+			ret = -EOPNOTSUPP;
+			goto out;
+		}
+		/* If the socket is already bound to a link local address,
+		 * it can only send to peers on the same link.  But allow
+		 * communicating between link local and non-link local address.
+		 */
+		if (scope_id != rs->rs_bound_scope_id) {
+			if (!scope_id) {
+				scope_id = rs->rs_bound_scope_id;
+			} else if (rs->rs_bound_scope_id) {
+				release_sock(sk);
+				ret = -EINVAL;
+				goto out;
+			}
+		}
+	}
+	release_sock(sk);
+
+	ret = rds_rdma_bytes(msg, &rdma_payload_len);
+	if (ret)
+		goto out;
+
+	if (max_t(size_t, payload_len, rdma_payload_len) > RDS_MAX_MSG_SIZE) {
+		ret = -EMSGSIZE;
+		goto out;
+	}
+
+	if (payload_len > rds_sk_sndbuf(rs)) {
+		ret = -EMSGSIZE;
+		goto out;
+	}
+
+	if (zcopy) {
+		if (rs->rs_transport->t_type != RDS_TRANS_TCP) {
+			ret = -EOPNOTSUPP;
+			goto out;
+		}
+		num_sgs = iov_iter_npages(&msg->msg_iter, INT_MAX);
+	}
+	/* size of rm including all sgs */
+	ret = rds_rm_size(msg, num_sgs, &vct);
+	if (ret < 0)
+		goto out;
+
+	rm = rds_message_alloc(ret, GFP_KERNEL);
+	if (!rm) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	/* Attach data to the rm */
+	if (payload_len) {
+		rm->data.op_sg = rds_message_alloc_sgs(rm, num_sgs);
+		if (IS_ERR(rm->data.op_sg)) {
+			ret = PTR_ERR(rm->data.op_sg);
+			goto out;
+		}
+		ret = rds_message_copy_from_user(rm, &msg->msg_iter, zcopy);
+		if (ret)
+			goto out;
+	}
+	rm->data.op_active = 1;
+
+	rm->m_daddr = daddr;
+
+	/* rds_conn_create has a spinlock that runs with IRQ off.
+	 * Caching the conn in the socket helps a lot. */
+	if (rs->rs_conn && ipv6_addr_equal(&rs->rs_conn->c_faddr, &daddr) &&
+	    rs->rs_tos == rs->rs_conn->c_tos) {
+		conn = rs->rs_conn;
+	} else {
+		conn = rds_conn_create_outgoing(sock_net(sock->sk),
+						&rs->rs_bound_addr, &daddr,
+						rs->rs_transport, rs->rs_tos,
+						sock->sk->sk_allocation,
+						scope_id);
+		if (IS_ERR(conn)) {
+			ret = PTR_ERR(conn);
+			goto out;
+		}
+		rs->rs_conn = conn;
+	}
+
+	if (conn->c_trans->t_mp_capable) {
+		/* Use c_path[0] until we learn that
+		 * the peer supports more (c_npaths > 1)
+		 */
+		cpath = &conn->c_path[RDS_MPATH_HASH(rs, conn->c_npaths ? : 1)];
+	} else {
+		cpath = &conn->c_path[0];
+	}
+
+	 /* If we're multipath capable and path 0 is down, queue reconnect
+	  * and send a ping. This initiates the multipath handshake through
+	  * rds_send_probe(), which sends RDS_EXTHDR_NPATHS to the peer,
+	  * starting multipath capability negotiation.
+	  */
+	if (conn->c_trans->t_mp_capable &&
+	    !rds_conn_path_up(&conn->c_path[0])) {
+		/* Ensures that only one request is queued.  And
+		 * rds_send_ping() ensures that only one ping is
+		 * outstanding.
+		 */
+		if (!test_and_set_bit(RDS_RECONNECT_PENDING,
+				      &conn->c_path[0].cp_flags))
+			queue_delayed_work(conn->c_path[0].cp_wq,
+					   &conn->c_path[0].cp_conn_w, 0);
+		rds_send_ping(conn, 0);
+	}
+
+	rm->m_conn_path = cpath;
+
+	/* Parse any control messages the user may have included. */
+	ret = rds_cmsg_send(rs, rm, msg, &allocated_mr, &vct);
+	if (ret)
+		goto out;
+
+	if (rm->rdma.op_active && !conn->c_trans->xmit_rdma) {
+		printk_ratelimited(KERN_NOTICE "rdma_op %p conn xmit_rdma %p\n",
+			       &rm->rdma, conn->c_trans->xmit_rdma);
+		ret = -EOPNOTSUPP;
+		goto out;
+	}
+
+	if (rm->atomic.op_active && !conn->c_trans->xmit_atomic) {
+		printk_ratelimited(KERN_NOTICE "atomic_op %p conn xmit_atomic %p\n",
+			       &rm->atomic, conn->c_trans->xmit_atomic);
+		ret = -EOPNOTSUPP;
+		goto out;
+	}
+
+	if (rds_destroy_pending(conn)) {
+		ret = -EAGAIN;
+		goto out;
+	}
+
+	if (rds_conn_path_down(cpath))
+		rds_check_all_paths(conn);
+
+	ret = rds_cong_wait(conn->c_fcong, dport, nonblock, rs);
+	if (ret) {
+		WRITE_ONCE(rs->rs_seen_congestion, 1);
+		goto out;
+	}
+	while (!rds_send_queue_rm(rs, conn, cpath, rm, rs->rs_bound_port,
+				  dport, &queued)) {
+		rds_stats_inc(s_send_queue_full);
+
+		if (nonblock) {
+			ret = -EAGAIN;
+			goto out;
+		}
+
+		timeo = wait_event_interruptible_timeout(*sk_sleep(sk),
+					rds_send_queue_rm(rs, conn, cpath, rm,
+							  rs->rs_bound_port,
+							  dport,
+							  &queued),
+					timeo);
+		rdsdebug("sendmsg woke queued %d timeo %ld\n", queued, timeo);
+		if (timeo > 0 || timeo == MAX_SCHEDULE_TIMEOUT)
+			continue;
+
+		ret = timeo;
+		if (ret == 0)
+			ret = -ETIMEDOUT;
+		goto out;
+	}
+
+	/*
+	 * By now we've committed to the send.  We reuse rds_send_worker()
+	 * to retry sends in the rds thread if the transport asks us to.
+	 */
+	rds_stats_inc(s_send_queued);
+
+	ret = rds_send_xmit(cpath);
+	if (ret == -ENOMEM || ret == -EAGAIN) {
+		ret = 0;
+		rcu_read_lock();
+		if (rds_destroy_pending(cpath->cp_conn))
+			ret = -ENETUNREACH;
+		else
+			queue_delayed_work(cpath->cp_wq, &cpath->cp_send_w, 1);
+		rcu_read_unlock();
+
+		if (ret)
+			goto out;
+	}
+
+	rds_message_put(rm);
+
+	for (ind = 0; ind < vct.indx; ind++)
+		kfree(vct.vec[ind].iov);
+	kfree(vct.vec);
+
+	return payload_len;
+
+out:
+	for (ind = 0; ind < vct.indx; ind++)
+		kfree(vct.vec[ind].iov);
+	kfree(vct.vec);
+
+	/* If the user included a RDMA_MAP cmsg, we allocated a MR on the fly.
+	 * If the sendmsg goes through, we keep the MR. If it fails with EAGAIN
+	 * or in any other way, we need to destroy the MR again */
+	if (allocated_mr)
+		rds_rdma_unuse(rs, rds_rdma_cookie_key(rm->m_rdma_cookie), 1);
+
+	if (rm)
+		rds_message_put(rm);
+	return ret;
+}
+
+/*
+ * send out a probe. Can be shared by rds_send_ping,
+ * rds_send_pong, rds_send_hb.
+ * rds_send_hb should use h_flags
+ *   RDS_FLAG_HB_PING|RDS_FLAG_ACK_REQUIRED
+ * or
+ *   RDS_FLAG_HB_PONG|RDS_FLAG_ACK_REQUIRED
+ */
+static int
+rds_send_probe(struct rds_conn_path *cp, __be16 sport,
+	       __be16 dport, u8 h_flags)
+{
+	struct rds_message *rm;
+	unsigned long flags;
+	int ret = 0;
+
+	rm = rds_message_alloc(0, GFP_ATOMIC);
+	if (!rm) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	rm->m_daddr = cp->cp_conn->c_faddr;
+	rm->data.op_active = 1;
+
+	rds_conn_path_connect_if_down(cp);
+
+	ret = rds_cong_wait(cp->cp_conn->c_fcong, dport, 1, NULL);
+	if (ret)
+		goto out;
+
+	spin_lock_irqsave(&cp->cp_lock, flags);
+	list_add_tail(&rm->m_conn_item, &cp->cp_send_queue);
+	set_bit(RDS_MSG_ON_CONN, &rm->m_flags);
+	rds_message_addref(rm);
+	rm->m_inc.i_conn = cp->cp_conn;
+	rm->m_inc.i_conn_path = cp;
+
+	rds_message_populate_header(&rm->m_inc.i_hdr, sport, dport,
+				    cp->cp_next_tx_seq);
+	rm->m_inc.i_hdr.h_flags |= h_flags;
+	cp->cp_next_tx_seq++;
+
+	if (RDS_HS_PROBE(be16_to_cpu(sport), be16_to_cpu(dport)) &&
+	    cp->cp_conn->c_trans->t_mp_capable) {
+		__be16 npaths = cpu_to_be16(RDS_MPATH_WORKERS);
+		__be32 my_gen_num = cpu_to_be32(cp->cp_conn->c_my_gen_num);
+		u8 dummy = 0;
+
+		rds_message_add_extension(&rm->m_inc.i_hdr,
+					  RDS_EXTHDR_NPATHS, &npaths);
+		rds_message_add_extension(&rm->m_inc.i_hdr,
+					  RDS_EXTHDR_GEN_NUM,
+					  &my_gen_num);
+		rds_message_add_extension(&rm->m_inc.i_hdr,
+					  RDS_EXTHDR_SPORT_IDX,
+					  &dummy);
+	}
+	spin_unlock_irqrestore(&cp->cp_lock, flags);
+
+	rds_stats_inc(s_send_queued);
+	rds_stats_inc(s_send_pong);
+
+	/* schedule the send work on cp_wq */
+	rcu_read_lock();
+	if (!rds_destroy_pending(cp->cp_conn))
+		queue_delayed_work(cp->cp_wq, &cp->cp_send_w, 1);
+	rcu_read_unlock();
+
+	rds_message_put(rm);
+	return 0;
+
+out:
+	if (rm)
+		rds_message_put(rm);
+	return ret;
+}
+
+int
+rds_send_pong(struct rds_conn_path *cp, __be16 dport)
+{
+	return rds_send_probe(cp, 0, dport, 0);
+}
+
+void
+rds_send_ping(struct rds_connection *conn, int cp_index)
+{
+	unsigned long flags;
+	struct rds_conn_path *cp = &conn->c_path[cp_index];
+
+	spin_lock_irqsave(&cp->cp_lock, flags);
+	if (conn->c_ping_triggered) {
+		spin_unlock_irqrestore(&cp->cp_lock, flags);
+		return;
+	}
+	conn->c_ping_triggered = 1;
+	spin_unlock_irqrestore(&cp->cp_lock, flags);
+	rds_send_probe(cp, cpu_to_be16(RDS_FLAG_PROBE_PORT), 0, 0);
+}
+EXPORT_SYMBOL_GPL(rds_send_ping);
diff --git a/net/rds/stats.c b/net/rds/stats.c
new file mode 100644
index 000000000..24ee22d09
--- /dev/null
+++ b/net/rds/stats.c
@@ -0,0 +1,155 @@
+/*
+ * Copyright (c) 2006 Oracle.  All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+#include <linux/percpu.h>
+#include <linux/seq_file.h>
+#include <linux/proc_fs.h>
+#include <linux/export.h>
+
+#include "rds.h"
+
+DEFINE_PER_CPU_SHARED_ALIGNED(struct rds_statistics, rds_stats);
+EXPORT_PER_CPU_SYMBOL_GPL(rds_stats);
+
+/* :.,$s/unsigned long\>.*\<s_\(.*\);/"\1",/g */
+
+static const char *const rds_stat_names[] = {
+	"conn_reset",
+	"recv_drop_bad_checksum",
+	"recv_drop_old_seq",
+	"recv_drop_no_sock",
+	"recv_drop_dead_sock",
+	"recv_deliver_raced",
+	"recv_delivered",
+	"recv_queued",
+	"recv_immediate_retry",
+	"recv_delayed_retry",
+	"recv_ack_required",
+	"recv_rdma_bytes",
+	"recv_ping",
+	"send_queue_empty",
+	"send_queue_full",
+	"send_lock_contention",
+	"send_lock_queue_raced",
+	"send_immediate_retry",
+	"send_delayed_retry",
+	"send_drop_acked",
+	"send_ack_required",
+	"send_queued",
+	"send_rdma",
+	"send_rdma_bytes",
+	"send_pong",
+	"page_remainder_hit",
+	"page_remainder_miss",
+	"copy_to_user",
+	"copy_from_user",
+	"cong_update_queued",
+	"cong_update_received",
+	"cong_send_error",
+	"cong_send_blocked",
+	"recv_bytes_added_to_sock",
+	"recv_bytes_freed_fromsock",
+	"send_stuck_rm",
+	"mprds_catchup_tx0_retries",
+};
+
+void rds_stats_info_copy(struct rds_info_iterator *iter,
+			 uint64_t *values, const char *const *names, size_t nr)
+{
+	struct rds_info_counter ctr;
+	size_t i;
+
+	for (i = 0; i < nr; i++) {
+		BUG_ON(strlen(names[i]) >= sizeof(ctr.name));
+		strscpy_pad(ctr.name, names[i]);
+		ctr.value = values[i];
+
+		rds_info_copy(iter, &ctr, sizeof(ctr));
+	}
+}
+EXPORT_SYMBOL_GPL(rds_stats_info_copy);
+
+/*
+ * This gives global counters across all the transports.  The strings
+ * are copied in so that the tool doesn't need knowledge of the specific
+ * stats that we're exporting.  Some are pretty implementation dependent
+ * and may change over time.  That doesn't stop them from being useful.
+ *
+ * This is the only function in the chain that knows about the byte granular
+ * length in userspace.  It converts it to number of stat entries that the
+ * rest of the functions operate in.
+ */
+static void rds_stats_info(struct socket *sock, unsigned int len,
+			   struct rds_info_iterator *iter,
+			   struct rds_info_lengths *lens)
+{
+	struct rds_statistics stats = {0, };
+	uint64_t *src;
+	uint64_t *sum;
+	size_t i;
+	int cpu;
+	unsigned int avail;
+
+	avail = len / sizeof(struct rds_info_counter);
+
+	if (avail < ARRAY_SIZE(rds_stat_names)) {
+		avail = 0;
+		goto trans;
+	}
+
+	for_each_online_cpu(cpu) {
+		src = (uint64_t *)&(per_cpu(rds_stats, cpu));
+		sum = (uint64_t *)&stats;
+		for (i = 0; i < sizeof(stats) / sizeof(uint64_t); i++)
+			*(sum++) += *(src++);
+	}
+
+	rds_stats_info_copy(iter, (uint64_t *)&stats, rds_stat_names,
+			    ARRAY_SIZE(rds_stat_names));
+	avail -= ARRAY_SIZE(rds_stat_names);
+
+trans:
+	lens->each = sizeof(struct rds_info_counter);
+	lens->nr = rds_trans_stats_info_copy(iter, avail) +
+		   ARRAY_SIZE(rds_stat_names);
+}
+
+void rds_stats_exit(void)
+{
+	rds_info_deregister_func(RDS_INFO_COUNTERS, rds_stats_info);
+}
+
+int rds_stats_init(void)
+{
+	rds_info_register_func(RDS_INFO_COUNTERS, rds_stats_info);
+	return 0;
+}
diff --git a/net/rds/sysctl.c b/net/rds/sysctl.c
new file mode 100644
index 000000000..025f518a4
--- /dev/null
+++ b/net/rds/sysctl.c
@@ -0,0 +1,109 @@
+/*
+ * Copyright (c) 2006 Oracle.  All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+#include <linux/kernel.h>
+#include <linux/sysctl.h>
+#include <linux/proc_fs.h>
+
+#include "rds.h"
+
+static struct ctl_table_header *rds_sysctl_reg_table;
+
+static unsigned long rds_sysctl_reconnect_min = 1;
+static unsigned long rds_sysctl_reconnect_max = ~0UL;
+
+unsigned long rds_sysctl_reconnect_min_jiffies;
+unsigned long rds_sysctl_reconnect_max_jiffies = HZ;
+
+unsigned int  rds_sysctl_max_unacked_packets = 8;
+unsigned int  rds_sysctl_max_unacked_bytes = (16 << 20);
+
+unsigned int rds_sysctl_ping_enable = 1;
+
+static struct ctl_table rds_sysctl_rds_table[] = {
+	{
+		.procname       = "reconnect_min_delay_ms",
+		.data		= &rds_sysctl_reconnect_min_jiffies,
+		.maxlen         = sizeof(unsigned long),
+		.mode           = 0644,
+		.proc_handler   = proc_doulongvec_ms_jiffies_minmax,
+		.extra1		= &rds_sysctl_reconnect_min,
+		.extra2		= &rds_sysctl_reconnect_max_jiffies,
+	},
+	{
+		.procname       = "reconnect_max_delay_ms",
+		.data		= &rds_sysctl_reconnect_max_jiffies,
+		.maxlen         = sizeof(unsigned long),
+		.mode           = 0644,
+		.proc_handler   = proc_doulongvec_ms_jiffies_minmax,
+		.extra1		= &rds_sysctl_reconnect_min_jiffies,
+		.extra2		= &rds_sysctl_reconnect_max,
+	},
+	{
+		.procname	= "max_unacked_packets",
+		.data		= &rds_sysctl_max_unacked_packets,
+		.maxlen         = sizeof(int),
+		.mode           = 0644,
+		.proc_handler   = proc_dointvec,
+	},
+	{
+		.procname	= "max_unacked_bytes",
+		.data		= &rds_sysctl_max_unacked_bytes,
+		.maxlen         = sizeof(int),
+		.mode           = 0644,
+		.proc_handler   = proc_dointvec,
+	},
+	{
+		.procname	= "ping_enable",
+		.data		= &rds_sysctl_ping_enable,
+		.maxlen         = sizeof(int),
+		.mode           = 0644,
+		.proc_handler   = proc_dointvec,
+	},
+};
+
+void rds_sysctl_exit(void)
+{
+	unregister_net_sysctl_table(rds_sysctl_reg_table);
+}
+
+int rds_sysctl_init(void)
+{
+	rds_sysctl_reconnect_min = msecs_to_jiffies(1);
+	rds_sysctl_reconnect_min_jiffies = rds_sysctl_reconnect_min;
+
+	rds_sysctl_reg_table =
+		register_net_sysctl(&init_net, "net/rds", rds_sysctl_rds_table);
+	if (!rds_sysctl_reg_table)
+		return -ENOMEM;
+	return 0;
+}
diff --git a/net/rds/tcp.c b/net/rds/tcp.c
new file mode 100644
index 000000000..b263634ac
--- /dev/null
+++ b/net/rds/tcp.c
@@ -0,0 +1,804 @@
+/*
+ * Copyright (c) 2006, 2018 Oracle and/or its affiliates. All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/in.h>
+#include <linux/module.h>
+#include <net/tcp.h>
+#include <net/net_namespace.h>
+#include <net/netns/generic.h>
+#include <net/addrconf.h>
+
+#include "rds.h"
+#include "tcp.h"
+
+/* only for info exporting */
+static DEFINE_SPINLOCK(rds_tcp_tc_list_lock);
+static LIST_HEAD(rds_tcp_tc_list);
+
+/* Track rds_tcp_connection structs so they can be cleaned up */
+static DEFINE_SPINLOCK(rds_tcp_conn_lock);
+static LIST_HEAD(rds_tcp_conn_list);
+static atomic_t rds_tcp_unloading = ATOMIC_INIT(0);
+
+static struct kmem_cache *rds_tcp_conn_slab;
+
+static int rds_tcp_sndbuf_handler(const struct ctl_table *ctl, int write,
+				  void *buffer, size_t *lenp, loff_t *fpos);
+static int rds_tcp_rcvbuf_handler(const struct ctl_table *ctl, int write,
+				  void *buffer, size_t *lenp, loff_t *fpos);
+
+static int rds_tcp_min_sndbuf = SOCK_MIN_SNDBUF;
+static int rds_tcp_min_rcvbuf = SOCK_MIN_RCVBUF;
+
+static struct ctl_table rds_tcp_sysctl_table[] = {
+#define	RDS_TCP_SNDBUF	0
+	{
+		.procname       = "rds_tcp_sndbuf",
+		/* data is per-net pointer */
+		.maxlen         = sizeof(int),
+		.mode           = 0644,
+		.proc_handler   = rds_tcp_sndbuf_handler,
+		.extra1		= &rds_tcp_min_sndbuf,
+	},
+#define	RDS_TCP_RCVBUF	1
+	{
+		.procname       = "rds_tcp_rcvbuf",
+		/* data is per-net pointer */
+		.maxlen         = sizeof(int),
+		.mode           = 0644,
+		.proc_handler   = rds_tcp_rcvbuf_handler,
+		.extra1		= &rds_tcp_min_rcvbuf,
+	},
+};
+
+u32 rds_tcp_write_seq(struct rds_tcp_connection *tc)
+{
+	/* seq# of the last byte of data in tcp send buffer */
+	return tcp_sk(tc->t_sock->sk)->write_seq;
+}
+
+u32 rds_tcp_snd_una(struct rds_tcp_connection *tc)
+{
+	return tcp_sk(tc->t_sock->sk)->snd_una;
+}
+
+void rds_tcp_restore_callbacks(struct socket *sock,
+			       struct rds_tcp_connection *tc)
+{
+	rdsdebug("restoring sock %p callbacks from tc %p\n", sock, tc);
+	write_lock_bh(&sock->sk->sk_callback_lock);
+
+	/* done under the callback_lock to serialize with write_space */
+	spin_lock(&rds_tcp_tc_list_lock);
+	list_del_init(&tc->t_list_item);
+	spin_unlock(&rds_tcp_tc_list_lock);
+
+	tc->t_sock = NULL;
+
+	sock->sk->sk_write_space = tc->t_orig_write_space;
+	sock->sk->sk_data_ready = tc->t_orig_data_ready;
+	sock->sk->sk_state_change = tc->t_orig_state_change;
+	sock->sk->sk_user_data = NULL;
+
+	write_unlock_bh(&sock->sk->sk_callback_lock);
+}
+
+/*
+ * rds_tcp_reset_callbacks() switches the to the new sock and
+ * returns the existing tc->t_sock.
+ *
+ * The only functions that set tc->t_sock are rds_tcp_set_callbacks
+ * and rds_tcp_reset_callbacks.  Send and receive trust that
+ * it is set.  The absence of RDS_CONN_UP bit protects those paths
+ * from being called while it isn't set.
+ */
+void rds_tcp_reset_callbacks(struct socket *sock,
+			     struct rds_conn_path *cp)
+{
+	struct rds_tcp_connection *tc = cp->cp_transport_data;
+	struct socket *osock = tc->t_sock;
+
+	if (!osock)
+		goto newsock;
+
+	/* Need to resolve a duelling SYN between peers.
+	 * We have an outstanding SYN to this peer, which may
+	 * potentially have transitioned to the RDS_CONN_UP state,
+	 * so we must quiesce any send threads before resetting
+	 * cp_transport_data. We quiesce these threads by setting
+	 * cp_state to something other than RDS_CONN_UP, and then
+	 * waiting for any existing threads in rds_send_xmit to
+	 * complete release_in_xmit(). (Subsequent threads entering
+	 * rds_send_xmit() will bail on !rds_conn_up().
+	 *
+	 * However an incoming syn-ack at this point would end up
+	 * marking the conn as RDS_CONN_UP, and would again permit
+	 * rds_send_xmi() threads through, so ideally we would
+	 * synchronize on RDS_CONN_UP after lock_sock(), but cannot
+	 * do that: waiting on !RDS_IN_XMIT after lock_sock() may
+	 * end up deadlocking with tcp_sendmsg(), and the RDS_IN_XMIT
+	 * would not get set. As a result, we set c_state to
+	 * RDS_CONN_RESETTTING, to ensure that rds_tcp_state_change
+	 * cannot mark rds_conn_path_up() in the window before lock_sock()
+	 */
+	atomic_set(&cp->cp_state, RDS_CONN_RESETTING);
+	wait_event(cp->cp_waitq, !test_bit(RDS_IN_XMIT, &cp->cp_flags));
+	/* reset receive side state for rds_tcp_data_recv() for osock  */
+	cancel_delayed_work_sync(&cp->cp_send_w);
+	cancel_delayed_work_sync(&cp->cp_recv_w);
+	lock_sock(osock->sk);
+	if (tc->t_tinc) {
+		rds_inc_put(&tc->t_tinc->ti_inc);
+		tc->t_tinc = NULL;
+	}
+	tc->t_tinc_hdr_rem = sizeof(struct rds_header);
+	tc->t_tinc_data_rem = 0;
+	rds_tcp_restore_callbacks(osock, tc);
+	release_sock(osock->sk);
+	sock_release(osock);
+newsock:
+	rds_send_path_reset(cp);
+	lock_sock(sock->sk);
+	rds_tcp_set_callbacks(sock, cp);
+	release_sock(sock->sk);
+}
+
+/* Add tc to rds_tcp_tc_list and set tc->t_sock. See comments
+ * above rds_tcp_reset_callbacks for notes about synchronization
+ * with data path
+ */
+void rds_tcp_set_callbacks(struct socket *sock, struct rds_conn_path *cp)
+{
+	struct rds_tcp_connection *tc = cp->cp_transport_data;
+
+	rdsdebug("setting sock %p callbacks to tc %p\n", sock, tc);
+	write_lock_bh(&sock->sk->sk_callback_lock);
+
+	/* done under the callback_lock to serialize with write_space.
+	 * Set t_sock inside rds_tcp_tc_list_lock so readers walking
+	 * rds_tcp_tc_list under the same lock cannot observe an
+	 * entry whose t_sock is NULL.
+	 */
+	spin_lock(&rds_tcp_tc_list_lock);
+	tc->t_sock = sock;
+	list_add_tail(&tc->t_list_item, &rds_tcp_tc_list);
+	spin_unlock(&rds_tcp_tc_list_lock);
+
+	/* accepted sockets need our listen data ready undone */
+	if (sock->sk->sk_data_ready == rds_tcp_listen_data_ready)
+		sock->sk->sk_data_ready = sock->sk->sk_user_data;
+	if (!tc->t_rtn)
+		tc->t_rtn = net_generic(sock_net(sock->sk), rds_tcp_netid);
+	tc->t_cpath = cp;
+	tc->t_orig_data_ready = sock->sk->sk_data_ready;
+	tc->t_orig_write_space = sock->sk->sk_write_space;
+	tc->t_orig_state_change = sock->sk->sk_state_change;
+
+	sock->sk->sk_user_data = cp;
+	sock->sk->sk_data_ready = rds_tcp_data_ready;
+	sock->sk->sk_write_space = rds_tcp_write_space;
+	sock->sk->sk_state_change = rds_tcp_state_change;
+
+	write_unlock_bh(&sock->sk->sk_callback_lock);
+}
+
+/* Handle RDS_INFO_TCP_SOCKETS socket option.  It only returns IPv4
+ * connections for backward compatibility.
+ */
+static void rds_tcp_tc_info(struct socket *rds_sock, unsigned int len,
+			    struct rds_info_iterator *iter,
+			    struct rds_info_lengths *lens)
+{
+	struct net *net = sock_net(rds_sock->sk);
+	struct rds_info_tcp_socket tsinfo;
+	struct rds_tcp_connection *tc;
+	unsigned int copied = 0;
+	unsigned int cnt = 0;
+	unsigned long flags;
+
+	spin_lock_irqsave(&rds_tcp_tc_list_lock, flags);
+
+	/* First pass: count entries visible in the caller's netns. */
+	list_for_each_entry(tc, &rds_tcp_tc_list, t_list_item) {
+		if (tc->t_cpath->cp_conn->c_isv6)
+			continue;
+		if (!net_eq(rds_conn_net(tc->t_cpath->cp_conn), net))
+			continue;
+		cnt++;
+	}
+
+	if (len / sizeof(tsinfo) < cnt)
+		goto out;
+
+	list_for_each_entry(tc, &rds_tcp_tc_list, t_list_item) {
+		struct inet_sock *inet = inet_sk(tc->t_sock->sk);
+
+		if (copied >= cnt)
+			break;
+		if (tc->t_cpath->cp_conn->c_isv6)
+			continue;
+		/* Only show connections in the caller's netns. */
+		if (!net_eq(rds_conn_net(tc->t_cpath->cp_conn), net))
+			continue;
+
+		tsinfo.local_addr = inet->inet_saddr;
+		tsinfo.local_port = inet->inet_sport;
+		tsinfo.peer_addr = inet->inet_daddr;
+		tsinfo.peer_port = inet->inet_dport;
+
+		tsinfo.hdr_rem = tc->t_tinc_hdr_rem;
+		tsinfo.data_rem = tc->t_tinc_data_rem;
+		tsinfo.last_sent_nxt = tc->t_last_sent_nxt;
+		tsinfo.last_expected_una = tc->t_last_expected_una;
+		tsinfo.last_seen_una = tc->t_last_seen_una;
+		tsinfo.tos = tc->t_cpath->cp_conn->c_tos;
+
+		rds_info_copy(iter, &tsinfo, sizeof(tsinfo));
+		copied++;
+	}
+	cnt = copied;
+
+out:
+	lens->nr = cnt;
+	lens->each = sizeof(tsinfo);
+
+	spin_unlock_irqrestore(&rds_tcp_tc_list_lock, flags);
+}
+
+#if IS_ENABLED(CONFIG_IPV6)
+/* Handle RDS6_INFO_TCP_SOCKETS socket option. It returns both IPv4 and
+ * IPv6 connections. IPv4 connection address is returned in an IPv4 mapped
+ * address.
+ */
+static void rds6_tcp_tc_info(struct socket *sock, unsigned int len,
+			     struct rds_info_iterator *iter,
+			     struct rds_info_lengths *lens)
+{
+	struct net *net = sock_net(sock->sk);
+	struct rds6_info_tcp_socket tsinfo6;
+	struct rds_tcp_connection *tc;
+	unsigned int copied = 0;
+	unsigned int cnt = 0;
+	unsigned long flags;
+
+	spin_lock_irqsave(&rds_tcp_tc_list_lock, flags);
+
+	/* First pass: count entries visible in the caller's netns. */
+	list_for_each_entry(tc, &rds_tcp_tc_list, t_list_item) {
+		if (!net_eq(rds_conn_net(tc->t_cpath->cp_conn), net))
+			continue;
+		cnt++;
+	}
+
+	if (len / sizeof(tsinfo6) < cnt)
+		goto out;
+
+	list_for_each_entry(tc, &rds_tcp_tc_list, t_list_item) {
+		struct sock *sk = tc->t_sock->sk;
+		struct inet_sock *inet = inet_sk(sk);
+
+		if (copied >= cnt)
+			break;
+		/* Only show connections in the caller's netns. */
+		if (!net_eq(rds_conn_net(tc->t_cpath->cp_conn), net))
+			continue;
+
+		tsinfo6.local_addr = sk->sk_v6_rcv_saddr;
+		tsinfo6.local_port = inet->inet_sport;
+		tsinfo6.peer_addr = sk->sk_v6_daddr;
+		tsinfo6.peer_port = inet->inet_dport;
+
+		tsinfo6.hdr_rem = tc->t_tinc_hdr_rem;
+		tsinfo6.data_rem = tc->t_tinc_data_rem;
+		tsinfo6.last_sent_nxt = tc->t_last_sent_nxt;
+		tsinfo6.last_expected_una = tc->t_last_expected_una;
+		tsinfo6.last_seen_una = tc->t_last_seen_una;
+
+		rds_info_copy(iter, &tsinfo6, sizeof(tsinfo6));
+		copied++;
+	}
+	cnt = copied;
+
+out:
+	lens->nr = cnt;
+	lens->each = sizeof(tsinfo6);
+
+	spin_unlock_irqrestore(&rds_tcp_tc_list_lock, flags);
+}
+#endif
+
+int rds_tcp_laddr_check(struct net *net, const struct in6_addr *addr,
+			__u32 scope_id)
+{
+	struct net_device *dev = NULL;
+#if IS_ENABLED(CONFIG_IPV6)
+	int ret;
+#endif
+
+	if (ipv6_addr_v4mapped(addr)) {
+		if (inet_addr_type(net, addr->s6_addr32[3]) == RTN_LOCAL)
+			return 0;
+		return -EADDRNOTAVAIL;
+	}
+
+	/* If the scope_id is specified, check only those addresses
+	 * hosted on the specified interface.
+	 */
+	rcu_read_lock();
+	if (scope_id != 0) {
+		dev = dev_get_by_index_rcu(net, scope_id);
+		/* scope_id is not valid... */
+		if (!dev) {
+			rcu_read_unlock();
+			return -EADDRNOTAVAIL;
+		}
+	}
+#if IS_ENABLED(CONFIG_IPV6)
+	if (ipv6_mod_enabled()) {
+		ret = ipv6_chk_addr(net, addr, dev, 0);
+		if (ret) {
+			rcu_read_unlock();
+			return 0;
+		}
+	}
+#endif
+	rcu_read_unlock();
+	return -EADDRNOTAVAIL;
+}
+
+static void rds_tcp_conn_free(void *arg)
+{
+	struct rds_tcp_connection *tc = arg;
+	unsigned long flags;
+
+	rdsdebug("freeing tc %p\n", tc);
+
+	spin_lock_irqsave(&rds_tcp_conn_lock, flags);
+	if (!tc->t_tcp_node_detached)
+		list_del(&tc->t_tcp_node);
+	spin_unlock_irqrestore(&rds_tcp_conn_lock, flags);
+
+	kmem_cache_free(rds_tcp_conn_slab, tc);
+}
+
+static int rds_tcp_conn_alloc(struct rds_connection *conn, gfp_t gfp)
+{
+	struct rds_tcp_connection *tc;
+	int i, j;
+	int ret = 0;
+
+	for (i = 0; i < RDS_MPATH_WORKERS; i++) {
+		tc = kmem_cache_zalloc(rds_tcp_conn_slab, gfp);
+		if (!tc) {
+			ret = -ENOMEM;
+			goto fail;
+		}
+		mutex_init(&tc->t_conn_path_lock);
+		tc->t_sock = NULL;
+		tc->t_rtn = NULL;
+		tc->t_tinc = NULL;
+		tc->t_tinc_hdr_rem = sizeof(struct rds_header);
+		tc->t_tinc_data_rem = 0;
+		init_waitqueue_head(&tc->t_recv_done_waitq);
+
+		conn->c_path[i].cp_transport_data = tc;
+		tc->t_cpath = &conn->c_path[i];
+		tc->t_tcp_node_detached = true;
+
+		rdsdebug("rds_conn_path [%d] tc %p\n", i,
+			 conn->c_path[i].cp_transport_data);
+	}
+	spin_lock_irq(&rds_tcp_conn_lock);
+	for (i = 0; i < RDS_MPATH_WORKERS; i++) {
+		tc = conn->c_path[i].cp_transport_data;
+		tc->t_tcp_node_detached = false;
+		list_add_tail(&tc->t_tcp_node, &rds_tcp_conn_list);
+	}
+	spin_unlock_irq(&rds_tcp_conn_lock);
+fail:
+	if (ret) {
+		for (j = 0; j < i; j++)
+			rds_tcp_conn_free(conn->c_path[j].cp_transport_data);
+	}
+	return ret;
+}
+
+static bool list_has_conn(struct list_head *list, struct rds_connection *conn)
+{
+	struct rds_tcp_connection *tc, *_tc;
+
+	list_for_each_entry_safe(tc, _tc, list, t_tcp_node) {
+		if (tc->t_cpath->cp_conn == conn)
+			return true;
+	}
+	return false;
+}
+
+static void rds_tcp_set_unloading(void)
+{
+	atomic_set(&rds_tcp_unloading, 1);
+}
+
+static bool rds_tcp_is_unloading(struct rds_connection *conn)
+{
+	return atomic_read(&rds_tcp_unloading) != 0;
+}
+
+static void rds_tcp_destroy_conns(void)
+{
+	struct rds_tcp_connection *tc, *_tc;
+	LIST_HEAD(tmp_list);
+
+	/* avoid calling conn_destroy with irqs off */
+	spin_lock_irq(&rds_tcp_conn_lock);
+	list_for_each_entry_safe(tc, _tc, &rds_tcp_conn_list, t_tcp_node) {
+		if (!list_has_conn(&tmp_list, tc->t_cpath->cp_conn))
+			list_move_tail(&tc->t_tcp_node, &tmp_list);
+	}
+	spin_unlock_irq(&rds_tcp_conn_lock);
+
+	list_for_each_entry_safe(tc, _tc, &tmp_list, t_tcp_node)
+		rds_conn_destroy(tc->t_cpath->cp_conn);
+}
+
+static void rds_tcp_exit(void);
+
+static u8 rds_tcp_get_tos_map(u8 tos)
+{
+	/* all user tos mapped to default 0 for TCP transport */
+	return 0;
+}
+
+struct rds_transport rds_tcp_transport = {
+	.laddr_check		= rds_tcp_laddr_check,
+	.xmit_path_prepare	= rds_tcp_xmit_path_prepare,
+	.xmit_path_complete	= rds_tcp_xmit_path_complete,
+	.xmit			= rds_tcp_xmit,
+	.recv_path		= rds_tcp_recv_path,
+	.conn_alloc		= rds_tcp_conn_alloc,
+	.conn_free		= rds_tcp_conn_free,
+	.conn_slots_available	= rds_tcp_conn_slots_available,
+	.conn_path_connect	= rds_tcp_conn_path_connect,
+	.conn_path_shutdown	= rds_tcp_conn_path_shutdown,
+	.inc_copy_to_user	= rds_tcp_inc_copy_to_user,
+	.inc_free		= rds_tcp_inc_free,
+	.stats_info_copy	= rds_tcp_stats_info_copy,
+	.exit			= rds_tcp_exit,
+	.get_tos_map		= rds_tcp_get_tos_map,
+	.t_owner		= THIS_MODULE,
+	.t_name			= "tcp",
+	.t_type			= RDS_TRANS_TCP,
+	.t_prefer_loopback	= 1,
+	.t_mp_capable		= 1,
+	.t_unloading		= rds_tcp_is_unloading,
+};
+
+int rds_tcp_netid;
+
+/* All module specific customizations to the RDS-TCP socket should be done in
+ * rds_tcp_tune() and applied after socket creation.
+ */
+bool rds_tcp_tune(struct socket *sock)
+{
+	struct sock *sk = sock->sk;
+	struct net *net = sock_net(sk);
+	struct rds_tcp_net *rtn;
+
+	tcp_sock_set_nodelay(sock->sk);
+	/* TCP timer functions might access net namespace even after
+	 * a process which created this net namespace terminated.
+	 */
+	if (!sk->sk_net_refcnt) {
+		if (!maybe_get_net(net))
+			return false;
+		/*
+		 * sk_net_refcnt_upgrade() must be called before lock_sock()
+		 * because it does a GFP_KERNEL allocation, which can trigger
+		 * fs_reclaim and create a circular lock dependency with the
+		 * socket lock.  The fields it modifies (sk_net_refcnt,
+		 * ns_tracker) are not accessed by any concurrent code path
+		 * at this point.
+		 */
+		sk_net_refcnt_upgrade(sk);
+		put_net(net);
+	}
+	lock_sock(sk);
+	rtn = net_generic(net, rds_tcp_netid);
+	if (rtn->sndbuf_size > 0) {
+		sk->sk_sndbuf = rtn->sndbuf_size;
+		sk->sk_userlocks |= SOCK_SNDBUF_LOCK;
+	}
+	if (rtn->rcvbuf_size > 0) {
+		sk->sk_rcvbuf = rtn->rcvbuf_size;
+		sk->sk_userlocks |= SOCK_RCVBUF_LOCK;
+	}
+	release_sock(sk);
+	return true;
+}
+
+static void rds_tcp_accept_worker(struct work_struct *work)
+{
+	struct rds_tcp_net *rtn = container_of(work,
+					       struct rds_tcp_net,
+					       rds_tcp_accept_w);
+
+	while (rds_tcp_accept_one(rtn) == 0)
+		cond_resched();
+}
+
+void rds_tcp_accept_work(struct rds_tcp_net *rtn)
+{
+	queue_work(rds_wq, &rtn->rds_tcp_accept_w);
+}
+
+static __net_init int rds_tcp_init_net(struct net *net)
+{
+	struct rds_tcp_net *rtn = net_generic(net, rds_tcp_netid);
+	struct ctl_table *tbl;
+	int err = 0;
+
+	memset(rtn, 0, sizeof(*rtn));
+
+	mutex_init(&rtn->rds_tcp_accept_lock);
+
+	/* {snd, rcv}buf_size default to 0, which implies we let the
+	 * stack pick the value, and permit auto-tuning of buffer size.
+	 */
+	if (net == &init_net) {
+		tbl = rds_tcp_sysctl_table;
+	} else {
+		tbl = kmemdup(rds_tcp_sysctl_table,
+			      sizeof(rds_tcp_sysctl_table), GFP_KERNEL);
+		if (!tbl) {
+			pr_warn("could not set allocate sysctl table\n");
+			return -ENOMEM;
+		}
+		rtn->ctl_table = tbl;
+	}
+	tbl[RDS_TCP_SNDBUF].data = &rtn->sndbuf_size;
+	tbl[RDS_TCP_RCVBUF].data = &rtn->rcvbuf_size;
+	rtn->rds_tcp_sysctl = register_net_sysctl_sz(net, "net/rds/tcp", tbl,
+						     ARRAY_SIZE(rds_tcp_sysctl_table));
+	if (!rtn->rds_tcp_sysctl) {
+		pr_warn("could not register sysctl\n");
+		err = -ENOMEM;
+		goto fail;
+	}
+
+#if IS_ENABLED(CONFIG_IPV6)
+	rtn->rds_tcp_listen_sock = rds_tcp_listen_init(net, true);
+#else
+	rtn->rds_tcp_listen_sock = rds_tcp_listen_init(net, false);
+#endif
+	if (!rtn->rds_tcp_listen_sock) {
+		pr_warn("could not set up IPv6 listen sock\n");
+
+#if IS_ENABLED(CONFIG_IPV6)
+		/* Try IPv4 as some systems disable IPv6 */
+		rtn->rds_tcp_listen_sock = rds_tcp_listen_init(net, false);
+		if (!rtn->rds_tcp_listen_sock) {
+#endif
+			unregister_net_sysctl_table(rtn->rds_tcp_sysctl);
+			rtn->rds_tcp_sysctl = NULL;
+			err = -EAFNOSUPPORT;
+			goto fail;
+#if IS_ENABLED(CONFIG_IPV6)
+		}
+#endif
+	}
+	INIT_WORK(&rtn->rds_tcp_accept_w, rds_tcp_accept_worker);
+	return 0;
+
+fail:
+	if (net != &init_net)
+		kfree(tbl);
+	return err;
+}
+
+static void rds_tcp_kill_sock(struct net *net)
+{
+	struct rds_tcp_connection *tc, *_tc;
+	LIST_HEAD(tmp_list);
+	struct rds_tcp_net *rtn = net_generic(net, rds_tcp_netid);
+	struct socket *lsock = rtn->rds_tcp_listen_sock;
+
+	rtn->rds_tcp_listen_sock = NULL;
+	rds_tcp_listen_stop(lsock, &rtn->rds_tcp_accept_w);
+	if (rtn->rds_tcp_accepted_sock)
+		sock_release(rtn->rds_tcp_accepted_sock);
+	spin_lock_irq(&rds_tcp_conn_lock);
+	list_for_each_entry_safe(tc, _tc, &rds_tcp_conn_list, t_tcp_node) {
+		struct net *c_net = read_pnet(&tc->t_cpath->cp_conn->c_net);
+
+		if (net != c_net)
+			continue;
+		if (!list_has_conn(&tmp_list, tc->t_cpath->cp_conn)) {
+			list_move_tail(&tc->t_tcp_node, &tmp_list);
+		} else {
+			list_del(&tc->t_tcp_node);
+			tc->t_tcp_node_detached = true;
+		}
+	}
+	spin_unlock_irq(&rds_tcp_conn_lock);
+	list_for_each_entry_safe(tc, _tc, &tmp_list, t_tcp_node)
+		rds_conn_destroy(tc->t_cpath->cp_conn);
+}
+
+static void __net_exit rds_tcp_exit_net(struct net *net)
+{
+	struct rds_tcp_net *rtn = net_generic(net, rds_tcp_netid);
+
+	if (rtn->rds_tcp_sysctl)
+		unregister_net_sysctl_table(rtn->rds_tcp_sysctl);
+
+	if (net != &init_net)
+		kfree(rtn->ctl_table);
+
+	rds_tcp_kill_sock(net);
+}
+
+static struct pernet_operations rds_tcp_net_ops = {
+	.init = rds_tcp_init_net,
+	.exit = rds_tcp_exit_net,
+	.id = &rds_tcp_netid,
+	.size = sizeof(struct rds_tcp_net),
+};
+
+void *rds_tcp_listen_sock_def_readable(struct net *net)
+{
+	struct rds_tcp_net *rtn = net_generic(net, rds_tcp_netid);
+	struct socket *lsock = rtn->rds_tcp_listen_sock;
+
+	if (!lsock)
+		return NULL;
+
+	return lsock->sk->sk_user_data;
+}
+
+/* when sysctl is used to modify some kernel socket parameters,this
+ * function  resets the RDS connections in that netns  so that we can
+ * restart with new parameters.  The assumption is that such reset
+ * events are few and far-between.
+ */
+static void rds_tcp_sysctl_reset(struct net *net)
+{
+	struct rds_tcp_connection *tc, *_tc;
+
+	spin_lock_irq(&rds_tcp_conn_lock);
+	list_for_each_entry_safe(tc, _tc, &rds_tcp_conn_list, t_tcp_node) {
+		struct net *c_net = read_pnet(&tc->t_cpath->cp_conn->c_net);
+
+		if (net != c_net || !tc->t_sock)
+			continue;
+
+		/* reconnect with new parameters */
+		rds_conn_path_drop(tc->t_cpath, false);
+	}
+	spin_unlock_irq(&rds_tcp_conn_lock);
+}
+
+static int rds_tcp_skbuf_handler(struct rds_tcp_net *rtn,
+				 const struct ctl_table *ctl, int write,
+				 void *buffer, size_t *lenp, loff_t *fpos)
+{
+	int err;
+
+	err = proc_dointvec_minmax(ctl, write, buffer, lenp, fpos);
+	if (err < 0) {
+		pr_warn("Invalid input. Must be >= %d\n",
+			*(int *)(ctl->extra1));
+		return err;
+	}
+
+	if (write && rtn->rds_tcp_listen_sock && rtn->rds_tcp_listen_sock->sk) {
+		struct net *net = sock_net(rtn->rds_tcp_listen_sock->sk);
+
+		rds_tcp_sysctl_reset(net);
+	}
+
+	return 0;
+}
+
+static int rds_tcp_sndbuf_handler(const struct ctl_table *ctl, int write,
+				  void *buffer, size_t *lenp, loff_t *fpos)
+{
+	struct rds_tcp_net *rtn = container_of(ctl->data, struct rds_tcp_net,
+					       sndbuf_size);
+
+	return rds_tcp_skbuf_handler(rtn, ctl, write, buffer, lenp, fpos);
+}
+
+static int rds_tcp_rcvbuf_handler(const struct ctl_table *ctl, int write,
+				  void *buffer, size_t *lenp, loff_t *fpos)
+{
+	struct rds_tcp_net *rtn = container_of(ctl->data, struct rds_tcp_net,
+					       rcvbuf_size);
+
+	return rds_tcp_skbuf_handler(rtn, ctl, write, buffer, lenp, fpos);
+}
+
+static void rds_tcp_exit(void)
+{
+	rds_tcp_set_unloading();
+	synchronize_rcu();
+	rds_info_deregister_func(RDS_INFO_TCP_SOCKETS, rds_tcp_tc_info);
+#if IS_ENABLED(CONFIG_IPV6)
+	rds_info_deregister_func(RDS6_INFO_TCP_SOCKETS, rds6_tcp_tc_info);
+#endif
+	unregister_pernet_device(&rds_tcp_net_ops);
+	rds_tcp_destroy_conns();
+	rds_trans_unregister(&rds_tcp_transport);
+	rds_tcp_recv_exit();
+	kmem_cache_destroy(rds_tcp_conn_slab);
+}
+module_exit(rds_tcp_exit);
+
+static int __init rds_tcp_init(void)
+{
+	int ret;
+
+	rds_tcp_conn_slab = KMEM_CACHE(rds_tcp_connection, 0);
+	if (!rds_tcp_conn_slab) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	ret = rds_tcp_recv_init();
+	if (ret)
+		goto out_slab;
+
+	ret = register_pernet_device(&rds_tcp_net_ops);
+	if (ret)
+		goto out_recv;
+
+	rds_trans_register(&rds_tcp_transport);
+
+	rds_info_register_func(RDS_INFO_TCP_SOCKETS, rds_tcp_tc_info);
+#if IS_ENABLED(CONFIG_IPV6)
+	rds_info_register_func(RDS6_INFO_TCP_SOCKETS, rds6_tcp_tc_info);
+#endif
+
+	goto out;
+out_recv:
+	rds_tcp_recv_exit();
+out_slab:
+	kmem_cache_destroy(rds_tcp_conn_slab);
+out:
+	return ret;
+}
+module_init(rds_tcp_init);
+
+MODULE_AUTHOR("Oracle Corporation <rds-devel@oss.oracle.com>");
+MODULE_DESCRIPTION("RDS: TCP transport");
+MODULE_LICENSE("Dual BSD/GPL");
diff --git a/net/rds/tcp.h b/net/rds/tcp.h
new file mode 100644
index 000000000..39c863471
--- /dev/null
+++ b/net/rds/tcp.h
@@ -0,0 +1,120 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _RDS_TCP_H
+#define _RDS_TCP_H
+
+#define RDS_TCP_PORT	16385
+
+/* per-network namespace private data for this module */
+struct rds_tcp_net {
+	/* serialize "rds_tcp_accept_one" with "rds_tcp_accept_lock"
+	 * to protect "rds_tcp_accepted_sock"
+	 */
+	struct mutex		rds_tcp_accept_lock;
+	struct socket		*rds_tcp_listen_sock;
+	struct socket		*rds_tcp_accepted_sock;
+	struct work_struct	rds_tcp_accept_w;
+	struct ctl_table_header	*rds_tcp_sysctl;
+	const struct ctl_table	*ctl_table;
+	int			sndbuf_size;
+	int			rcvbuf_size;
+};
+
+struct rds_tcp_incoming {
+	struct rds_incoming	ti_inc;
+	struct sk_buff_head	ti_skb_list;
+};
+
+struct rds_tcp_connection {
+
+	struct list_head	t_tcp_node;
+	bool			t_tcp_node_detached;
+	struct rds_conn_path	*t_cpath;
+	/* t_conn_path_lock synchronizes the connection establishment between
+	 * rds_tcp_accept_one and rds_tcp_conn_path_connect
+	 */
+	struct mutex		t_conn_path_lock;
+	struct socket		*t_sock;
+	u32			t_client_port_group;
+	struct rds_tcp_net	*t_rtn;
+	void			*t_orig_write_space;
+	void			*t_orig_data_ready;
+	void			*t_orig_state_change;
+
+	struct rds_tcp_incoming	*t_tinc;
+	size_t			t_tinc_hdr_rem;
+	size_t			t_tinc_data_rem;
+
+	/* XXX error report? */
+	struct work_struct	t_conn_w;
+	struct work_struct	t_send_w;
+	struct work_struct	t_down_w;
+	struct work_struct	t_recv_w;
+
+	/* for info exporting only */
+	struct list_head	t_list_item;
+	u32			t_last_sent_nxt;
+	u32			t_last_expected_una;
+	u32			t_last_seen_una;
+
+	/* for rds_tcp_conn_path_shutdown */
+	wait_queue_head_t	t_recv_done_waitq;
+};
+
+struct rds_tcp_statistics {
+	uint64_t	s_tcp_data_ready_calls;
+	uint64_t	s_tcp_write_space_calls;
+	uint64_t	s_tcp_sndbuf_full;
+	uint64_t	s_tcp_connect_raced;
+	uint64_t	s_tcp_listen_closed_stale;
+};
+
+/* tcp.c */
+extern int rds_tcp_netid;
+bool rds_tcp_tune(struct socket *sock);
+void rds_tcp_set_callbacks(struct socket *sock, struct rds_conn_path *cp);
+void rds_tcp_reset_callbacks(struct socket *sock, struct rds_conn_path *cp);
+void rds_tcp_restore_callbacks(struct socket *sock,
+			       struct rds_tcp_connection *tc);
+u32 rds_tcp_write_seq(struct rds_tcp_connection *tc);
+u32 rds_tcp_snd_una(struct rds_tcp_connection *tc);
+extern struct rds_transport rds_tcp_transport;
+void rds_tcp_accept_work(struct rds_tcp_net *rtn);
+int rds_tcp_laddr_check(struct net *net, const struct in6_addr *addr,
+			__u32 scope_id);
+/* tcp_connect.c */
+int rds_tcp_conn_path_connect(struct rds_conn_path *cp);
+void rds_tcp_conn_path_shutdown(struct rds_conn_path *conn);
+void rds_tcp_state_change(struct sock *sk);
+
+/* tcp_listen.c */
+struct socket *rds_tcp_listen_init(struct net *net, bool isv6);
+void rds_tcp_listen_stop(struct socket *sock, struct work_struct *acceptor);
+void rds_tcp_listen_data_ready(struct sock *sk);
+void rds_tcp_conn_slots_available(struct rds_connection *conn, bool fan_out);
+int rds_tcp_accept_one(struct rds_tcp_net *rtn);
+void rds_tcp_keepalive(struct socket *sock);
+void *rds_tcp_listen_sock_def_readable(struct net *net);
+
+/* tcp_recv.c */
+int rds_tcp_recv_init(void);
+void rds_tcp_recv_exit(void);
+void rds_tcp_data_ready(struct sock *sk);
+int rds_tcp_recv_path(struct rds_conn_path *cp);
+void rds_tcp_inc_free(struct rds_incoming *inc);
+int rds_tcp_inc_copy_to_user(struct rds_incoming *inc, struct iov_iter *to);
+
+/* tcp_send.c */
+void rds_tcp_xmit_path_prepare(struct rds_conn_path *cp);
+void rds_tcp_xmit_path_complete(struct rds_conn_path *cp);
+int rds_tcp_xmit(struct rds_connection *conn, struct rds_message *rm,
+		 unsigned int hdr_off, unsigned int sg, unsigned int off);
+int rds_tcp_is_acked(struct rds_message *rm, uint64_t ack);
+void rds_tcp_write_space(struct sock *sk);
+
+/* tcp_stats.c */
+DECLARE_PER_CPU(struct rds_tcp_statistics, rds_tcp_stats);
+#define rds_tcp_stats_inc(member) rds_stats_inc_which(rds_tcp_stats, member)
+unsigned int rds_tcp_stats_info_copy(struct rds_info_iterator *iter,
+				     unsigned int avail);
+
+#endif
diff --git a/net/rds/tcp_connect.c b/net/rds/tcp_connect.c
new file mode 100644
index 000000000..b77c88ffb
--- /dev/null
+++ b/net/rds/tcp_connect.c
@@ -0,0 +1,298 @@
+/*
+ * Copyright (c) 2006, 2017 Oracle and/or its affiliates. All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+#include <linux/kernel.h>
+#include <linux/in.h>
+#include <net/tcp.h>
+
+#include "rds.h"
+#include "tcp.h"
+
+void rds_tcp_state_change(struct sock *sk)
+{
+	void (*state_change)(struct sock *sk);
+	struct rds_conn_path *cp;
+	struct rds_tcp_connection *tc;
+
+	read_lock_bh(&sk->sk_callback_lock);
+	cp = sk->sk_user_data;
+	if (!cp) {
+		state_change = sk->sk_state_change;
+		goto out;
+	}
+	tc = cp->cp_transport_data;
+	state_change = tc->t_orig_state_change;
+
+	rdsdebug("sock %p state_change to %d\n", tc->t_sock, sk->sk_state);
+
+	switch (sk->sk_state) {
+	/* ignore connecting sockets as they make progress */
+	case TCP_SYN_SENT:
+	case TCP_SYN_RECV:
+		break;
+	case TCP_ESTABLISHED:
+		/* Force the peer to reconnect so that we have the
+		 * TCP ports going from <smaller-ip>.<transient> to
+		 * <larger-ip>.<RDS_TCP_PORT>. We avoid marking the
+		 * RDS connection as RDS_CONN_UP until the reconnect,
+		 * to avoid RDS datagram loss.
+		 */
+		if (rds_addr_cmp(&cp->cp_conn->c_laddr,
+				 &cp->cp_conn->c_faddr) >= 0 &&
+		    rds_conn_path_transition(cp, RDS_CONN_CONNECTING,
+					     RDS_CONN_ERROR)) {
+			rds_conn_path_drop(cp, false);
+		} else {
+			rds_connect_path_complete(cp, RDS_CONN_CONNECTING);
+		}
+		break;
+	case TCP_CLOSING:
+	case TCP_TIME_WAIT:
+		if (wq_has_sleeper(&tc->t_recv_done_waitq))
+			wake_up(&tc->t_recv_done_waitq);
+		break;
+	case TCP_CLOSE_WAIT:
+	case TCP_LAST_ACK:
+	case TCP_CLOSE:
+		if (wq_has_sleeper(&tc->t_recv_done_waitq))
+			wake_up(&tc->t_recv_done_waitq);
+		rds_conn_path_drop(cp, false);
+		break;
+	default:
+		break;
+	}
+out:
+	read_unlock_bh(&sk->sk_callback_lock);
+	state_change(sk);
+}
+
+int rds_tcp_conn_path_connect(struct rds_conn_path *cp)
+{
+	struct socket *sock = NULL;
+	struct sockaddr_in6 sin6;
+	struct sockaddr_in sin;
+	struct sockaddr *addr;
+	int port_low, port_high, port;
+	int port_groups, groups_left;
+	int addrlen;
+	bool isv6;
+	int ret;
+	struct rds_connection *conn = cp->cp_conn;
+	struct rds_tcp_connection *tc = cp->cp_transport_data;
+
+	/* for multipath rds,we only trigger the connection after
+	 * the handshake probe has determined the number of paths.
+	 */
+	if (cp->cp_index > 0 && cp->cp_conn->c_npaths < 2)
+		return -EAGAIN;
+
+	mutex_lock(&tc->t_conn_path_lock);
+
+	if (rds_conn_path_up(cp)) {
+		mutex_unlock(&tc->t_conn_path_lock);
+		return 0;
+	}
+	if (ipv6_addr_v4mapped(&conn->c_laddr)) {
+		ret = sock_create_kern(rds_conn_net(conn), PF_INET,
+				       SOCK_STREAM, IPPROTO_TCP, &sock);
+		isv6 = false;
+	} else {
+		ret = sock_create_kern(rds_conn_net(conn), PF_INET6,
+				       SOCK_STREAM, IPPROTO_TCP, &sock);
+		isv6 = true;
+	}
+
+	if (ret < 0)
+		goto out;
+
+	if (!rds_tcp_tune(sock)) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	if (isv6) {
+		sin6.sin6_family = AF_INET6;
+		sin6.sin6_addr = conn->c_laddr;
+		sin6.sin6_port = 0;
+		sin6.sin6_flowinfo = 0;
+		sin6.sin6_scope_id = conn->c_dev_if;
+		addr = (struct sockaddr *)&sin6;
+		addrlen = sizeof(sin6);
+	} else {
+		sin.sin_family = AF_INET;
+		sin.sin_addr.s_addr = conn->c_laddr.s6_addr32[3];
+		sin.sin_port = 0;
+		addr = (struct sockaddr *)&sin;
+		addrlen = sizeof(sin);
+	}
+
+	/* encode cp->cp_index in lowest bits of source-port */
+	inet_get_local_port_range(rds_conn_net(conn), &port_low, &port_high);
+	port_low = ALIGN(port_low, RDS_MPATH_WORKERS);
+	port_groups = (port_high - port_low + 1) / RDS_MPATH_WORKERS;
+	ret = -EADDRINUSE;
+	groups_left = port_groups;
+	while (groups_left-- > 0 && ret) {
+		if (++tc->t_client_port_group >= port_groups)
+			tc->t_client_port_group = 0;
+		port =  port_low +
+			tc->t_client_port_group * RDS_MPATH_WORKERS +
+			cp->cp_index;
+
+		if (isv6)
+			sin6.sin6_port = htons(port);
+		else
+			sin.sin_port = htons(port);
+		ret = kernel_bind(sock, (struct sockaddr_unsized *)addr,
+				  addrlen);
+	}
+	if (ret) {
+		rdsdebug("bind failed with %d at address %pI6c\n",
+			 ret, &conn->c_laddr);
+		goto out;
+	}
+
+	if (isv6) {
+		sin6.sin6_family = AF_INET6;
+		sin6.sin6_addr = conn->c_faddr;
+		sin6.sin6_port = htons(RDS_TCP_PORT);
+		sin6.sin6_flowinfo = 0;
+		sin6.sin6_scope_id = conn->c_dev_if;
+		addr = (struct sockaddr *)&sin6;
+		addrlen = sizeof(sin6);
+	} else {
+		sin.sin_family = AF_INET;
+		sin.sin_addr.s_addr = conn->c_faddr.s6_addr32[3];
+		sin.sin_port = htons(RDS_TCP_PORT);
+		addr = (struct sockaddr *)&sin;
+		addrlen = sizeof(sin);
+	}
+
+	/*
+	 * once we call connect() we can start getting callbacks and they
+	 * own the socket
+	 */
+	rds_tcp_set_callbacks(sock, cp);
+	ret = kernel_connect(sock, (struct sockaddr_unsized *)addr, addrlen, O_NONBLOCK);
+
+	rdsdebug("connect to address %pI6c returned %d\n", &conn->c_faddr, ret);
+	if (ret == -EINPROGRESS)
+		ret = 0;
+	if (ret == 0) {
+		rds_tcp_keepalive(sock);
+		sock = NULL;
+	} else {
+		rds_tcp_restore_callbacks(sock, cp->cp_transport_data);
+	}
+
+out:
+	mutex_unlock(&tc->t_conn_path_lock);
+	if (sock)
+		sock_release(sock);
+	return ret;
+}
+
+/*
+ * Before killing the tcp socket this needs to serialize with callbacks.  The
+ * caller has already grabbed the sending sem so we're serialized with other
+ * senders.
+ *
+ * TCP calls the callbacks with the sock lock so we hold it while we reset the
+ * callbacks to those set by TCP.  Our callbacks won't execute again once we
+ * hold the sock lock.
+ */
+void rds_tcp_conn_path_shutdown(struct rds_conn_path *cp)
+{
+	struct rds_tcp_connection *tc = cp->cp_transport_data;
+	struct socket *sock = tc->t_sock;
+	struct sock *sk;
+	unsigned int rounds;
+
+	rdsdebug("shutting down conn %p tc %p sock %p\n",
+		 cp->cp_conn, tc, sock);
+
+	if (sock) {
+		sk = sock->sk;
+		if (rds_destroy_pending(cp->cp_conn))
+			sock_no_linger(sk);
+
+		sock->ops->shutdown(sock, SHUT_WR);
+
+		/* after sending FIN,
+		 * wait until we processed all incoming messages
+		 * and we're sure that there won't be any more:
+		 * i.e. state CLOSING, TIME_WAIT, CLOSE_WAIT,
+		 * LAST_ACK, or CLOSE (RFC 793).
+		 *
+		 * Give up waiting after 5 seconds and allow messages
+		 * to theoretically get dropped, if the TCP transition
+		 * didn't happen.
+		 */
+		rounds = 0;
+		do {
+			/* we need to ensure messages are dequeued here
+			 * since "rds_recv_worker" only dispatches messages
+			 * while the connection is still in RDS_CONN_UP
+			 * and there is no guarantee that "rds_tcp_data_ready"
+			 * was called nor that "sk_data_ready" still points to
+			 * it.
+			 */
+			rds_tcp_recv_path(cp);
+		} while (!wait_event_timeout(tc->t_recv_done_waitq,
+				(sk->sk_state == TCP_CLOSING ||
+				 sk->sk_state == TCP_TIME_WAIT ||
+				 sk->sk_state == TCP_CLOSE_WAIT ||
+				 sk->sk_state == TCP_LAST_ACK ||
+				 sk->sk_state == TCP_CLOSE) &&
+				skb_queue_empty_lockless(&sk->sk_receive_queue),
+				msecs_to_jiffies(100)) &&
+			 ++rounds < 50);
+		lock_sock(sk);
+
+		/* discard messages that the peer received already */
+		tc->t_last_seen_una = rds_tcp_snd_una(tc);
+		rds_send_path_drop_acked(cp, rds_tcp_snd_una(tc),
+					 rds_tcp_is_acked);
+
+		rds_tcp_restore_callbacks(sock, tc); /* tc->tc_sock = NULL */
+
+		release_sock(sk);
+		sock_release(sock);
+	}
+
+	if (tc->t_tinc) {
+		rds_inc_put(&tc->t_tinc->ti_inc);
+		tc->t_tinc = NULL;
+	}
+	tc->t_tinc_hdr_rem = sizeof(struct rds_header);
+	tc->t_tinc_data_rem = 0;
+}
diff --git a/net/rds/tcp_listen.c b/net/rds/tcp_listen.c
new file mode 100644
index 000000000..a3db9b057
--- /dev/null
+++ b/net/rds/tcp_listen.c
@@ -0,0 +1,464 @@
+/*
+ * Copyright (c) 2006, 2018 Oracle and/or its affiliates. All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+#include <linux/kernel.h>
+#include <linux/gfp.h>
+#include <linux/in.h>
+#include <net/tcp.h>
+#include <trace/events/sock.h>
+#include <net/net_namespace.h>
+#include <net/netns/generic.h>
+
+#include "rds.h"
+#include "tcp.h"
+
+void rds_tcp_keepalive(struct socket *sock)
+{
+	/* values below based on xs_udp_default_timeout */
+	int keepidle = 5; /* send a probe 'keepidle' secs after last data */
+	int keepcnt = 5; /* number of unack'ed probes before declaring dead */
+
+	sock_set_keepalive(sock->sk);
+	tcp_sock_set_keepcnt(sock->sk, keepcnt);
+	tcp_sock_set_keepidle(sock->sk, keepidle);
+	/* KEEPINTVL is the interval between successive probes. We follow
+	 * the model in xs_tcp_finish_connecting() and re-use keepidle.
+	 */
+	tcp_sock_set_keepintvl(sock->sk, keepidle);
+}
+
+static int
+rds_tcp_get_peer_sport(struct socket *sock)
+{
+	struct sock *sk = sock->sk;
+
+	if (!sk)
+		return -1;
+
+	return ntohs(READ_ONCE(inet_sk(sk)->inet_dport));
+}
+
+/* rds_tcp_accept_one_path(): if accepting on cp_index > 0, make sure the
+ * client's ipaddr < server's ipaddr. Otherwise, close the accepted
+ * socket and force a reconnect from smaller -> larger ip addr. The reason
+ * we special case cp_index 0 is to allow the rds probe ping itself to itself
+ * get through efficiently.
+ */
+static struct rds_tcp_connection *
+rds_tcp_accept_one_path(struct rds_connection *conn, struct socket *sock)
+{
+	int sport, npaths, i_min, i_max, i;
+
+	if (conn->c_with_sport_idx)
+		/* cp->cp_index is encoded in lowest bits of source-port */
+		sport = rds_tcp_get_peer_sport(sock);
+	else
+		sport = -1;
+
+	npaths = max_t(int, 1, conn->c_npaths);
+
+	if (sport >= 0) {
+		i_min = sport % npaths;
+		i_max = i_min;
+	} else {
+		i_min = 0;
+		i_max = npaths - 1;
+	}
+
+	for (i = i_min; i <= i_max; i++) {
+		struct rds_conn_path *cp = &conn->c_path[i];
+
+		if (rds_conn_path_transition(cp, RDS_CONN_DOWN,
+					     RDS_CONN_CONNECTING))
+			return cp->cp_transport_data;
+	}
+
+	return NULL;
+}
+
+void rds_tcp_conn_slots_available(struct rds_connection *conn, bool fan_out)
+{
+	struct rds_tcp_connection *tc;
+	struct rds_tcp_net *rtn;
+	struct socket *sock;
+	int sport, npaths;
+
+	if (rds_destroy_pending(conn))
+		return;
+
+	tc = conn->c_path->cp_transport_data;
+	rtn = tc->t_rtn;
+	if (!rtn)
+		return;
+
+	sock = tc->t_sock;
+
+	/* During fan-out, check that the connection we already
+	 * accepted in slot#0 carried the proper source port modulo.
+	 */
+	if (fan_out && conn->c_with_sport_idx && sock &&
+	    rds_addr_cmp(&conn->c_laddr, &conn->c_faddr) > 0) {
+		/* cp->cp_index is encoded in lowest bits of source-port */
+		sport = rds_tcp_get_peer_sport(sock);
+		npaths = max_t(int, 1, conn->c_npaths);
+		if (sport >= 0 && sport % npaths != 0)
+			/* peer initiated with a non-#0 lane first */
+			rds_conn_path_drop(conn->c_path, 0);
+	}
+
+	/* As soon as a connection went down,
+	 * it is safe to schedule a "rds_tcp_accept_one"
+	 * attempt even if there are no connections pending:
+	 * Function "rds_tcp_accept_one" won't block
+	 * but simply return -EAGAIN in that case.
+	 *
+	 * Doing so is necessary to address the case where an
+	 * incoming connection on "rds_tcp_listen_sock" is ready
+	 * to be accepted prior to a free slot being available:
+	 * the -ENOBUFS case in "rds_tcp_accept_one".
+	 */
+	rds_tcp_accept_work(rtn);
+}
+
+int rds_tcp_accept_one(struct rds_tcp_net *rtn)
+{
+	struct socket *listen_sock = rtn->rds_tcp_listen_sock;
+	struct socket *new_sock = NULL;
+	struct rds_connection *conn;
+	int ret;
+	struct inet_sock *inet;
+	struct rds_tcp_connection *rs_tcp = NULL;
+	int conn_state;
+	struct rds_conn_path *cp;
+	struct sock *sk;
+	struct in6_addr *my_addr, *peer_addr;
+#if !IS_ENABLED(CONFIG_IPV6)
+	struct in6_addr saddr, daddr;
+#endif
+	int dev_if = 0;
+
+	if (!listen_sock) /* module unload or netns delete in progress */
+		return -ENETUNREACH;
+
+	mutex_lock(&rtn->rds_tcp_accept_lock);
+	new_sock = rtn->rds_tcp_accepted_sock;
+	rtn->rds_tcp_accepted_sock = NULL;
+
+	if (!new_sock) {
+		ret = kernel_accept(listen_sock, &new_sock, O_NONBLOCK);
+		if (ret)
+			goto out;
+
+		rds_tcp_keepalive(new_sock);
+		if (!rds_tcp_tune(new_sock)) {
+			ret = -EINVAL;
+			goto out;
+		}
+	}
+
+	inet = inet_sk(new_sock->sk);
+
+#if IS_ENABLED(CONFIG_IPV6)
+	my_addr = &new_sock->sk->sk_v6_rcv_saddr;
+	peer_addr = &new_sock->sk->sk_v6_daddr;
+#else
+	ipv6_addr_set_v4mapped(inet->inet_saddr, &saddr);
+	ipv6_addr_set_v4mapped(inet->inet_daddr, &daddr);
+	my_addr = &saddr;
+	peer_addr = &daddr;
+#endif
+	rdsdebug("accepted family %d tcp %pI6c:%u -> %pI6c:%u\n",
+		 listen_sock->sk->sk_family,
+		 my_addr, ntohs(inet->inet_sport),
+		 peer_addr, ntohs(inet->inet_dport));
+
+#if IS_ENABLED(CONFIG_IPV6)
+	/* sk_bound_dev_if is not set if the peer address is not link local
+	 * address.  In this case, it happens that mcast_oif is set.  So
+	 * just use it.
+	 */
+	if ((ipv6_addr_type(my_addr) & IPV6_ADDR_LINKLOCAL) &&
+	    !(ipv6_addr_type(peer_addr) & IPV6_ADDR_LINKLOCAL)) {
+		struct ipv6_pinfo *inet6;
+
+		inet6 = inet6_sk(new_sock->sk);
+		dev_if = READ_ONCE(inet6->mcast_oif);
+	} else {
+		dev_if = new_sock->sk->sk_bound_dev_if;
+	}
+#endif
+
+	if (!rds_tcp_laddr_check(sock_net(listen_sock->sk), peer_addr, dev_if)) {
+		/* local address connection is only allowed via loopback */
+		ret = -EOPNOTSUPP;
+		goto out;
+	}
+
+	conn = rds_conn_create(sock_net(listen_sock->sk),
+			       my_addr, peer_addr,
+			       &rds_tcp_transport, 0, GFP_KERNEL, dev_if);
+
+	if (IS_ERR(conn)) {
+		ret = PTR_ERR(conn);
+		goto out;
+	}
+	/* An incoming SYN request came in, and TCP just accepted it.
+	 *
+	 * If the client reboots, this conn will need to be cleaned up.
+	 * rds_tcp_state_change() will do that cleanup
+	 */
+	if (rds_addr_cmp(&conn->c_faddr, &conn->c_laddr) < 0) {
+		/* Try to obtain a free connection slot.
+		 * If unsuccessful, we need to preserve "new_sock"
+		 * that we just accepted, since its "sk_receive_queue"
+		 * may contain messages already that have been acknowledged
+		 * to and discarded by the sender.
+		 * We must not throw those away!
+		 */
+		rs_tcp = rds_tcp_accept_one_path(conn, new_sock);
+		if (!rs_tcp) {
+			/* It's okay to stash "new_sock", since
+			 * "rds_tcp_conn_slots_available" triggers
+			 * "rds_tcp_accept_one" again as soon as one of the
+			 * connection slots becomes available again
+			 */
+			rtn->rds_tcp_accepted_sock = new_sock;
+			new_sock = NULL;
+			ret = -ENOBUFS;
+			goto out;
+		}
+	} else {
+		/* This connection request came from a peer with
+		 * a larger address.
+		 * Function "rds_tcp_state_change" makes sure
+		 * that the connection doesn't transition
+		 * to state "RDS_CONN_UP", and therefore
+		 * we should not have received any messages
+		 * on this socket yet.
+		 * This is the only case where it's okay to
+		 * not dequeue messages from "sk_receive_queue".
+		 */
+		if (conn->c_npaths <= 1)
+			rds_conn_path_connect_if_down(&conn->c_path[0]);
+		rs_tcp = NULL;
+		goto rst_nsk;
+	}
+
+	mutex_lock(&rs_tcp->t_conn_path_lock);
+	cp = rs_tcp->t_cpath;
+	conn_state = rds_conn_path_state(cp);
+	WARN_ON(conn_state == RDS_CONN_UP);
+	if (conn_state != RDS_CONN_CONNECTING && conn_state != RDS_CONN_ERROR) {
+		rds_conn_path_drop(cp, 0);
+		goto rst_nsk;
+	}
+	/* Save a local pointer to sk and hold a reference before setting
+	 * callbacks. Once callbacks are set, a concurrent
+	 * rds_tcp_conn_path_shutdown() may call sock_release(), which
+	 * sets new_sock->sk to NULL and drops a reference on sk.
+	 * The local pointer lets us safely access sk_state below even
+	 * if new_sock->sk has been nulled, and sock_hold() keeps sk
+	 * itself valid until we are done.
+	 */
+	sk = new_sock->sk;
+	sock_hold(sk);
+
+	if (rs_tcp->t_sock) {
+		/* Duelling SYN has been handled in rds_tcp_accept_one() */
+		rds_tcp_reset_callbacks(new_sock, cp);
+		/* rds_connect_path_complete() marks RDS_CONN_UP */
+		rds_connect_path_complete(cp, RDS_CONN_RESETTING);
+	} else {
+		rds_tcp_set_callbacks(new_sock, cp);
+		rds_connect_path_complete(cp, RDS_CONN_CONNECTING);
+	}
+
+	/* Since "rds_tcp_set_callbacks" happens this late
+	 * the connection may already have been closed without
+	 * "rds_tcp_state_change" doing its due diligence.
+	 *
+	 * If that's the case, we simply drop the path,
+	 * knowing that "rds_tcp_conn_path_shutdown" will
+	 * dequeue pending messages.
+	 */
+	if (READ_ONCE(sk->sk_state) == TCP_CLOSE_WAIT ||
+	    READ_ONCE(sk->sk_state) == TCP_LAST_ACK ||
+	    READ_ONCE(sk->sk_state) == TCP_CLOSE)
+		rds_conn_path_drop(cp, 0);
+	else
+		queue_delayed_work(cp->cp_wq, &cp->cp_recv_w, 0);
+
+	sock_put(sk);
+
+	new_sock = NULL;
+	ret = 0;
+	if (conn->c_npaths == 0)
+		rds_send_ping(cp->cp_conn, cp->cp_index);
+	goto out;
+rst_nsk:
+	/* reset the newly returned accept sock and bail.
+	 * It is safe to set linger on new_sock because the RDS connection
+	 * has not been brought up on new_sock, so no RDS-level data could
+	 * be pending on it. By setting linger, we achieve the side-effect
+	 * of avoiding TIME_WAIT state on new_sock.
+	 */
+	sock_no_linger(new_sock->sk);
+	kernel_sock_shutdown(new_sock, SHUT_RDWR);
+	ret = 0;
+out:
+	if (rs_tcp)
+		mutex_unlock(&rs_tcp->t_conn_path_lock);
+	if (new_sock)
+		sock_release(new_sock);
+
+	mutex_unlock(&rtn->rds_tcp_accept_lock);
+
+	return ret;
+}
+
+void rds_tcp_listen_data_ready(struct sock *sk)
+{
+	void (*ready)(struct sock *sk);
+
+	trace_sk_data_ready(sk);
+	rdsdebug("listen data ready sk %p\n", sk);
+
+	read_lock_bh(&sk->sk_callback_lock);
+	ready = sk->sk_user_data;
+	if (!ready) { /* check for teardown race */
+		ready = sk->sk_data_ready;
+		goto out;
+	}
+
+	/*
+	 * ->sk_data_ready is also called for a newly established child socket
+	 * before it has been accepted and the accepter has set up their
+	 * data_ready.. we only want to queue listen work for our listening
+	 * socket
+	 *
+	 * (*ready)() may be null if we are racing with netns delete, and
+	 * the listen socket is being torn down.
+	 */
+	if (sk->sk_state == TCP_LISTEN)
+		rds_tcp_accept_work(net_generic(sock_net(sk), rds_tcp_netid));
+	else
+		ready = rds_tcp_listen_sock_def_readable(sock_net(sk));
+
+out:
+	read_unlock_bh(&sk->sk_callback_lock);
+	if (ready)
+		ready(sk);
+}
+
+struct socket *rds_tcp_listen_init(struct net *net, bool isv6)
+{
+	struct socket *sock = NULL;
+	struct sockaddr_storage ss;
+	struct sockaddr_in6 *sin6;
+	struct sockaddr_in *sin;
+	int addr_len;
+	int ret;
+
+	ret = sock_create_kern(net, isv6 ? PF_INET6 : PF_INET, SOCK_STREAM,
+			       IPPROTO_TCP, &sock);
+	if (ret < 0) {
+		rdsdebug("could not create %s listener socket: %d\n",
+			 isv6 ? "IPv6" : "IPv4", ret);
+		goto out;
+	}
+
+	sock->sk->sk_reuse = SK_CAN_REUSE;
+	tcp_sock_set_nodelay(sock->sk);
+
+	write_lock_bh(&sock->sk->sk_callback_lock);
+	sock->sk->sk_user_data = sock->sk->sk_data_ready;
+	sock->sk->sk_data_ready = rds_tcp_listen_data_ready;
+	write_unlock_bh(&sock->sk->sk_callback_lock);
+
+	if (isv6) {
+		sin6 = (struct sockaddr_in6 *)&ss;
+		sin6->sin6_family = PF_INET6;
+		sin6->sin6_addr = in6addr_any;
+		sin6->sin6_port = htons(RDS_TCP_PORT);
+		sin6->sin6_scope_id = 0;
+		sin6->sin6_flowinfo = 0;
+		addr_len = sizeof(*sin6);
+	} else {
+		sin = (struct sockaddr_in *)&ss;
+		sin->sin_family = PF_INET;
+		sin->sin_addr.s_addr = htonl(INADDR_ANY);
+		sin->sin_port = htons(RDS_TCP_PORT);
+		addr_len = sizeof(*sin);
+	}
+
+	ret = kernel_bind(sock, (struct sockaddr_unsized *)&ss, addr_len);
+	if (ret < 0) {
+		rdsdebug("could not bind %s listener socket: %d\n",
+			 isv6 ? "IPv6" : "IPv4", ret);
+		goto out;
+	}
+
+	ret = sock->ops->listen(sock, 64);
+	if (ret < 0)
+		goto out;
+
+	return sock;
+out:
+	if (sock)
+		sock_release(sock);
+	return NULL;
+}
+
+void rds_tcp_listen_stop(struct socket *sock, struct work_struct *acceptor)
+{
+	struct sock *sk;
+
+	if (!sock)
+		return;
+
+	sk = sock->sk;
+
+	/* serialize with and prevent further callbacks */
+	lock_sock(sk);
+	write_lock_bh(&sk->sk_callback_lock);
+	if (sk->sk_user_data) {
+		sk->sk_data_ready = sk->sk_user_data;
+		sk->sk_user_data = NULL;
+	}
+	write_unlock_bh(&sk->sk_callback_lock);
+	release_sock(sk);
+
+	/* wait for accepts to stop and close the socket */
+	flush_workqueue(rds_wq);
+	flush_work(acceptor);
+	sock_release(sock);
+}
diff --git a/net/rds/tcp_recv.c b/net/rds/tcp_recv.c
new file mode 100644
index 000000000..ffe843ca2
--- /dev/null
+++ b/net/rds/tcp_recv.c
@@ -0,0 +1,353 @@
+/*
+ * Copyright (c) 2006, 2017 Oracle and/or its affiliates. All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <net/tcp.h>
+#include <trace/events/sock.h>
+
+#include "rds.h"
+#include "tcp.h"
+
+static struct kmem_cache *rds_tcp_incoming_slab;
+
+static void rds_tcp_inc_purge(struct rds_incoming *inc)
+{
+	struct rds_tcp_incoming *tinc;
+	tinc = container_of(inc, struct rds_tcp_incoming, ti_inc);
+	rdsdebug("purging tinc %p inc %p\n", tinc, inc);
+	skb_queue_purge(&tinc->ti_skb_list);
+}
+
+void rds_tcp_inc_free(struct rds_incoming *inc)
+{
+	struct rds_tcp_incoming *tinc;
+	tinc = container_of(inc, struct rds_tcp_incoming, ti_inc);
+	rds_tcp_inc_purge(inc);
+	rdsdebug("freeing tinc %p inc %p\n", tinc, inc);
+	kmem_cache_free(rds_tcp_incoming_slab, tinc);
+}
+
+/*
+ * this is pretty lame, but, whatever.
+ */
+int rds_tcp_inc_copy_to_user(struct rds_incoming *inc, struct iov_iter *to)
+{
+	struct rds_tcp_incoming *tinc;
+	struct sk_buff *skb;
+	int ret = 0;
+
+	if (!iov_iter_count(to))
+		goto out;
+
+	tinc = container_of(inc, struct rds_tcp_incoming, ti_inc);
+
+	skb_queue_walk(&tinc->ti_skb_list, skb) {
+		unsigned long to_copy, skb_off;
+		for (skb_off = 0; skb_off < skb->len; skb_off += to_copy) {
+			to_copy = iov_iter_count(to);
+			to_copy = min(to_copy, skb->len - skb_off);
+
+			if (skb_copy_datagram_iter(skb, skb_off, to, to_copy))
+				return -EFAULT;
+
+			rds_stats_add(s_copy_to_user, to_copy);
+			ret += to_copy;
+
+			if (!iov_iter_count(to))
+				goto out;
+		}
+	}
+out:
+	return ret;
+}
+
+/*
+ * We have a series of skbs that have fragmented pieces of the congestion
+ * bitmap.  They must add up to the exact size of the congestion bitmap.  We
+ * use the skb helpers to copy those into the pages that make up the in-memory
+ * congestion bitmap for the remote address of this connection.  We then tell
+ * the congestion core that the bitmap has been changed so that it can wake up
+ * sleepers.
+ *
+ * This is racing with sending paths which are using test_bit to see if the
+ * bitmap indicates that their recipient is congested.
+ */
+
+static void rds_tcp_cong_recv(struct rds_connection *conn,
+			      struct rds_tcp_incoming *tinc)
+{
+	struct sk_buff *skb;
+	unsigned int to_copy, skb_off;
+	unsigned int map_off;
+	unsigned int map_page;
+	struct rds_cong_map *map;
+	int ret;
+
+	/* catch completely corrupt packets */
+	if (be32_to_cpu(tinc->ti_inc.i_hdr.h_len) != RDS_CONG_MAP_BYTES)
+		return;
+
+	map_page = 0;
+	map_off = 0;
+	map = conn->c_fcong;
+
+	skb_queue_walk(&tinc->ti_skb_list, skb) {
+		skb_off = 0;
+		while (skb_off < skb->len) {
+			to_copy = min_t(unsigned int, PAGE_SIZE - map_off,
+					skb->len - skb_off);
+
+			BUG_ON(map_page >= RDS_CONG_MAP_PAGES);
+
+			/* only returns 0 or -error */
+			ret = skb_copy_bits(skb, skb_off,
+				(void *)map->m_page_addrs[map_page] + map_off,
+				to_copy);
+			BUG_ON(ret != 0);
+
+			skb_off += to_copy;
+			map_off += to_copy;
+			if (map_off == PAGE_SIZE) {
+				map_off = 0;
+				map_page++;
+			}
+		}
+	}
+
+	rds_cong_map_updated(map, ~(u64) 0);
+}
+
+struct rds_tcp_desc_arg {
+	struct rds_conn_path *conn_path;
+	gfp_t gfp;
+};
+
+static int rds_tcp_data_recv(read_descriptor_t *desc, struct sk_buff *skb,
+			     unsigned int offset, size_t len)
+{
+	struct rds_tcp_desc_arg *arg = desc->arg.data;
+	struct rds_conn_path *cp = arg->conn_path;
+	struct rds_tcp_connection *tc = cp->cp_transport_data;
+	struct rds_tcp_incoming *tinc = tc->t_tinc;
+	struct sk_buff *clone;
+	size_t left = len, to_copy;
+
+	rdsdebug("tcp data tc %p skb %p offset %u len %zu\n", tc, skb, offset,
+		 len);
+
+	/*
+	 * tcp_read_sock() interprets partial progress as an indication to stop
+	 * processing.
+	 */
+	while (left) {
+		if (!tinc) {
+			tinc = kmem_cache_alloc(rds_tcp_incoming_slab,
+						arg->gfp);
+			if (!tinc) {
+				desc->error = -ENOMEM;
+				goto out;
+			}
+			tc->t_tinc = tinc;
+			rdsdebug("allocated tinc %p\n", tinc);
+			rds_inc_path_init(&tinc->ti_inc, cp,
+					  &cp->cp_conn->c_faddr);
+			tinc->ti_inc.i_rx_lat_trace[RDS_MSG_RX_HDR] =
+					local_clock();
+
+			/*
+			 * XXX * we might be able to use the __ variants when
+			 * we've already serialized at a higher level.
+			 */
+			skb_queue_head_init(&tinc->ti_skb_list);
+		}
+
+		if (left && tc->t_tinc_hdr_rem) {
+			to_copy = min(tc->t_tinc_hdr_rem, left);
+			rdsdebug("copying %zu header from skb %p\n", to_copy,
+				 skb);
+			skb_copy_bits(skb, offset,
+				      (char *)&tinc->ti_inc.i_hdr +
+						sizeof(struct rds_header) -
+						tc->t_tinc_hdr_rem,
+				      to_copy);
+			tc->t_tinc_hdr_rem -= to_copy;
+			left -= to_copy;
+			offset += to_copy;
+
+			if (tc->t_tinc_hdr_rem == 0) {
+				/* could be 0 for a 0 len message */
+				tc->t_tinc_data_rem =
+					be32_to_cpu(tinc->ti_inc.i_hdr.h_len);
+				tinc->ti_inc.i_rx_lat_trace[RDS_MSG_RX_START] =
+					local_clock();
+			}
+		}
+
+		if (left && tc->t_tinc_data_rem) {
+			to_copy = min(tc->t_tinc_data_rem, left);
+
+			clone = pskb_extract(skb, offset, to_copy, arg->gfp);
+			if (!clone) {
+				desc->error = -ENOMEM;
+				goto out;
+			}
+
+			skb_queue_tail(&tinc->ti_skb_list, clone);
+
+			rdsdebug("skb %p data %p len %d off %u to_copy %zu -> "
+				 "clone %p data %p len %d\n",
+				 skb, skb->data, skb->len, offset, to_copy,
+				 clone, clone->data, clone->len);
+
+			tc->t_tinc_data_rem -= to_copy;
+			left -= to_copy;
+			offset += to_copy;
+		}
+
+		if (tc->t_tinc_hdr_rem == 0 && tc->t_tinc_data_rem == 0) {
+			struct rds_connection *conn = cp->cp_conn;
+
+			if (tinc->ti_inc.i_hdr.h_flags == RDS_FLAG_CONG_BITMAP)
+				rds_tcp_cong_recv(conn, tinc);
+			else
+				rds_recv_incoming(conn, &conn->c_faddr,
+						  &conn->c_laddr,
+						  &tinc->ti_inc,
+						  arg->gfp);
+
+			tc->t_tinc_hdr_rem = sizeof(struct rds_header);
+			tc->t_tinc_data_rem = 0;
+			tc->t_tinc = NULL;
+			rds_inc_put(&tinc->ti_inc);
+			tinc = NULL;
+		}
+	}
+out:
+	rdsdebug("returning len %zu left %zu skb len %d rx queue depth %d\n",
+		 len, left, skb->len,
+		 skb_queue_len(&tc->t_sock->sk->sk_receive_queue));
+	return len - left;
+}
+
+/* the caller has to hold the sock lock */
+static int rds_tcp_read_sock(struct rds_conn_path *cp, gfp_t gfp)
+{
+	struct rds_tcp_connection *tc = cp->cp_transport_data;
+	struct socket *sock = tc->t_sock;
+	read_descriptor_t desc;
+	struct rds_tcp_desc_arg arg;
+
+	/* It's like glib in the kernel! */
+	arg.conn_path = cp;
+	arg.gfp = gfp;
+	desc.arg.data = &arg;
+	desc.error = 0;
+	desc.count = 1; /* give more than one skb per call */
+
+	tcp_read_sock(sock->sk, &desc, rds_tcp_data_recv);
+	rdsdebug("tcp_read_sock for tc %p gfp %pGg returned %d\n", tc, &gfp,
+		 desc.error);
+
+	if (skb_queue_empty_lockless(&sock->sk->sk_receive_queue) &&
+	    wq_has_sleeper(&tc->t_recv_done_waitq))
+		wake_up(&tc->t_recv_done_waitq);
+
+	return desc.error;
+}
+
+/*
+ * We hold the sock lock to serialize our rds_tcp_recv->tcp_read_sock from
+ * data_ready.
+ *
+ * if we fail to allocate we're in trouble.. blindly wait some time before
+ * trying again to see if the VM can free up something for us.
+ */
+int rds_tcp_recv_path(struct rds_conn_path *cp)
+{
+	struct rds_tcp_connection *tc = cp->cp_transport_data;
+	struct socket *sock = tc->t_sock;
+	int ret = 0;
+
+	rdsdebug("recv worker path [%d] tc %p sock %p\n",
+		 cp->cp_index, tc, sock);
+
+	lock_sock(sock->sk);
+	ret = rds_tcp_read_sock(cp, GFP_KERNEL);
+	release_sock(sock->sk);
+
+	return ret;
+}
+
+void rds_tcp_data_ready(struct sock *sk)
+{
+	void (*ready)(struct sock *sk);
+	struct rds_conn_path *cp;
+	struct rds_tcp_connection *tc;
+
+	trace_sk_data_ready(sk);
+	rdsdebug("data ready sk %p\n", sk);
+
+	read_lock_bh(&sk->sk_callback_lock);
+	cp = sk->sk_user_data;
+	if (!cp) { /* check for teardown race */
+		ready = sk->sk_data_ready;
+		goto out;
+	}
+
+	tc = cp->cp_transport_data;
+	ready = tc->t_orig_data_ready;
+	rds_tcp_stats_inc(s_tcp_data_ready_calls);
+
+	if (rds_tcp_read_sock(cp, GFP_ATOMIC) == -ENOMEM) {
+		rcu_read_lock();
+		if (!rds_destroy_pending(cp->cp_conn))
+			queue_delayed_work(cp->cp_wq, &cp->cp_recv_w, 0);
+		rcu_read_unlock();
+	}
+out:
+	read_unlock_bh(&sk->sk_callback_lock);
+	ready(sk);
+}
+
+int rds_tcp_recv_init(void)
+{
+	rds_tcp_incoming_slab = KMEM_CACHE(rds_tcp_incoming, 0);
+	if (!rds_tcp_incoming_slab)
+		return -ENOMEM;
+	return 0;
+}
+
+void rds_tcp_recv_exit(void)
+{
+	kmem_cache_destroy(rds_tcp_incoming_slab);
+}
diff --git a/net/rds/tcp_send.c b/net/rds/tcp_send.c
new file mode 100644
index 000000000..7c52acc74
--- /dev/null
+++ b/net/rds/tcp_send.c
@@ -0,0 +1,226 @@
+/*
+ * Copyright (c) 2006, 2017 Oracle and/or its affiliates. All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+#include <linux/kernel.h>
+#include <linux/in.h>
+#include <net/tcp.h>
+
+#include "rds_single_path.h"
+#include "rds.h"
+#include "tcp.h"
+
+void rds_tcp_xmit_path_prepare(struct rds_conn_path *cp)
+{
+	struct rds_tcp_connection *tc = cp->cp_transport_data;
+
+	tcp_sock_set_cork(tc->t_sock->sk, true);
+}
+
+void rds_tcp_xmit_path_complete(struct rds_conn_path *cp)
+{
+	struct rds_tcp_connection *tc = cp->cp_transport_data;
+
+	tcp_sock_set_cork(tc->t_sock->sk, false);
+}
+
+/* the core send_sem serializes this with other xmit and shutdown */
+static int rds_tcp_sendmsg(struct socket *sock, void *data, unsigned int len)
+{
+	struct kvec vec = {
+		.iov_base = data,
+		.iov_len = len,
+	};
+	struct msghdr msg = {
+		.msg_flags = MSG_DONTWAIT | MSG_NOSIGNAL,
+	};
+
+	return kernel_sendmsg(sock, &msg, &vec, 1, vec.iov_len);
+}
+
+/* the core send_sem serializes this with other xmit and shutdown */
+int rds_tcp_xmit(struct rds_connection *conn, struct rds_message *rm,
+		 unsigned int hdr_off, unsigned int sg, unsigned int off)
+{
+	struct rds_conn_path *cp = rm->m_inc.i_conn_path;
+	struct rds_tcp_connection *tc = cp->cp_transport_data;
+	struct msghdr msg = {};
+	struct bio_vec bvec;
+	int done = 0;
+	int ret = 0;
+
+	if (hdr_off == 0) {
+		/*
+		 * m_ack_seq is set to the sequence number of the last byte of
+		 * header and data.  see rds_tcp_is_acked().
+		 */
+		tc->t_last_sent_nxt = rds_tcp_write_seq(tc);
+		rm->m_ack_seq = tc->t_last_sent_nxt +
+				sizeof(struct rds_header) +
+				be32_to_cpu(rm->m_inc.i_hdr.h_len) - 1;
+		smp_mb__before_atomic();
+		set_bit(RDS_MSG_HAS_ACK_SEQ, &rm->m_flags);
+		tc->t_last_expected_una = rm->m_ack_seq + 1;
+
+		if (test_bit(RDS_MSG_RETRANSMITTED, &rm->m_flags))
+			rm->m_inc.i_hdr.h_flags |= RDS_FLAG_RETRANSMITTED;
+
+		rdsdebug("rm %p tcp nxt %u ack_seq %llu\n",
+			 rm, rds_tcp_write_seq(tc),
+			 (unsigned long long)rm->m_ack_seq);
+	}
+
+	if (hdr_off < sizeof(struct rds_header)) {
+		/* see rds_tcp_write_space() */
+		set_bit(SOCK_NOSPACE, &tc->t_sock->sk->sk_socket->flags);
+
+		ret = rds_tcp_sendmsg(tc->t_sock,
+				      (void *)&rm->m_inc.i_hdr + hdr_off,
+				      sizeof(rm->m_inc.i_hdr) - hdr_off);
+		if (ret < 0)
+			goto out;
+		done += ret;
+		if (hdr_off + done != sizeof(struct rds_header))
+			goto out;
+	}
+
+	while (sg < rm->data.op_nents) {
+		msg.msg_flags = MSG_SPLICE_PAGES | MSG_DONTWAIT | MSG_NOSIGNAL;
+		if (sg + 1 < rm->data.op_nents)
+			msg.msg_flags |= MSG_MORE;
+
+		bvec_set_page(&bvec, sg_page(&rm->data.op_sg[sg]),
+			      rm->data.op_sg[sg].length - off,
+			      rm->data.op_sg[sg].offset + off);
+		iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, &bvec, 1,
+			      rm->data.op_sg[sg].length - off);
+		ret = sock_sendmsg(tc->t_sock, &msg);
+		rdsdebug("tcp sendpage %p:%u:%u ret %d\n", (void *)sg_page(&rm->data.op_sg[sg]),
+			 rm->data.op_sg[sg].offset + off, rm->data.op_sg[sg].length - off,
+			 ret);
+		if (ret <= 0)
+			break;
+
+		off += ret;
+		done += ret;
+		if (off == rm->data.op_sg[sg].length) {
+			off = 0;
+			sg++;
+		}
+	}
+
+out:
+	if (ret <= 0) {
+		/* write_space will hit after EAGAIN, all else fatal */
+		if (ret == -EAGAIN) {
+			rds_tcp_stats_inc(s_tcp_sndbuf_full);
+			ret = 0;
+		} else {
+			/* No need to disconnect/reconnect if path_drop
+			 * has already been triggered, because, e.g., of
+			 * an incoming RST.
+			 */
+			if (rds_conn_path_up(cp)) {
+				pr_warn("RDS/tcp: send to %pI6c on cp [%d]"
+					"returned %d, "
+					"disconnecting and reconnecting\n",
+					&conn->c_faddr, cp->cp_index, ret);
+				rds_conn_path_drop(cp, false);
+			}
+		}
+	}
+	if (done == 0)
+		done = ret;
+	return done;
+}
+
+/*
+ * rm->m_ack_seq is set to the tcp sequence number that corresponds to the
+ * last byte of the message, including the header.  This means that the
+ * entire message has been received if rm->m_ack_seq is "before" the next
+ * unacked byte of the TCP sequence space.  We have to do very careful
+ * wrapping 32bit comparisons here.
+ */
+int rds_tcp_is_acked(struct rds_message *rm, uint64_t ack)
+{
+	if (!test_bit(RDS_MSG_HAS_ACK_SEQ, &rm->m_flags))
+		return 0;
+	return (__s32)((u32)rm->m_ack_seq - (u32)ack) < 0;
+}
+
+void rds_tcp_write_space(struct sock *sk)
+{
+	void (*write_space)(struct sock *sk);
+	struct rds_conn_path *cp;
+	struct rds_tcp_connection *tc;
+
+	read_lock_bh(&sk->sk_callback_lock);
+	cp = sk->sk_user_data;
+	if (!cp) {
+		write_space = sk->sk_write_space;
+		goto out;
+	}
+
+	tc = cp->cp_transport_data;
+	rdsdebug("write_space for tc %p\n", tc);
+	write_space = tc->t_orig_write_space;
+	rds_tcp_stats_inc(s_tcp_write_space_calls);
+
+	rdsdebug("tcp una %u\n", rds_tcp_snd_una(tc));
+	tc->t_last_seen_una = rds_tcp_snd_una(tc);
+	rds_send_path_drop_acked(cp, rds_tcp_snd_una(tc), rds_tcp_is_acked);
+
+	rcu_read_lock();
+	if ((refcount_read(&sk->sk_wmem_alloc) << 1) <= sk->sk_sndbuf &&
+	    !rds_destroy_pending(cp->cp_conn))
+		queue_delayed_work(cp->cp_wq, &cp->cp_send_w, 0);
+	rcu_read_unlock();
+
+out:
+	read_unlock_bh(&sk->sk_callback_lock);
+
+	/*
+	 * write_space is only called when data leaves tcp's send queue if
+	 * SOCK_NOSPACE is set.  We set SOCK_NOSPACE every time we put
+	 * data in tcp's send queue because we use write_space to parse the
+	 * sequence numbers and notice that rds messages have been fully
+	 * received.
+	 *
+	 * tcp's write_space clears SOCK_NOSPACE if the send queue has more
+	 * than a certain amount of space. So we need to set it again *after*
+	 * we call tcp's write_space or else we might only get called on the
+	 * first of a series of incoming tcp acks.
+	 */
+	write_space(sk);
+
+	if (sk->sk_socket)
+		set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
+}
diff --git a/net/rds/tcp_stats.c b/net/rds/tcp_stats.c
new file mode 100644
index 000000000..f8a7954f1
--- /dev/null
+++ b/net/rds/tcp_stats.c
@@ -0,0 +1,74 @@
+/*
+ * Copyright (c) 2006 Oracle.  All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+#include <linux/percpu.h>
+#include <linux/seq_file.h>
+#include <linux/proc_fs.h>
+
+#include "rds.h"
+#include "tcp.h"
+
+DEFINE_PER_CPU(struct rds_tcp_statistics, rds_tcp_stats)
+	____cacheline_aligned;
+
+static const char * const rds_tcp_stat_names[] = {
+	"tcp_data_ready_calls",
+	"tcp_write_space_calls",
+	"tcp_sndbuf_full",
+	"tcp_connect_raced",
+	"tcp_listen_closed_stale",
+};
+
+unsigned int rds_tcp_stats_info_copy(struct rds_info_iterator *iter,
+				     unsigned int avail)
+{
+	struct rds_tcp_statistics stats = {0, };
+	uint64_t *src;
+	uint64_t *sum;
+	size_t i;
+	int cpu;
+
+	if (avail < ARRAY_SIZE(rds_tcp_stat_names))
+		goto out;
+
+	for_each_online_cpu(cpu) {
+		src = (uint64_t *)&(per_cpu(rds_tcp_stats, cpu));
+		sum = (uint64_t *)&stats;
+		for (i = 0; i < sizeof(stats) / sizeof(uint64_t); i++)
+			*(sum++) += *(src++);
+	}
+
+	rds_stats_info_copy(iter, (uint64_t *)&stats, rds_tcp_stat_names,
+			    ARRAY_SIZE(rds_tcp_stat_names));
+out:
+	return ARRAY_SIZE(rds_tcp_stat_names);
+}
diff --git a/net/rds/threads.c b/net/rds/threads.c
new file mode 100644
index 000000000..639302bab
--- /dev/null
+++ b/net/rds/threads.c
@@ -0,0 +1,311 @@
+/*
+ * Copyright (c) 2006, 2018 Oracle and/or its affiliates. All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+#include <linux/kernel.h>
+#include <linux/random.h>
+#include <linux/export.h>
+
+#include "rds.h"
+
+/*
+ * All of connection management is simplified by serializing it through
+ * work queues that execute in a connection managing thread.
+ *
+ * TCP wants to send acks through sendpage() in response to data_ready(),
+ * but it needs a process context to do so.
+ *
+ * The receive paths need to allocate but can't drop packets (!) so we have
+ * a thread around to block allocating if the receive fast path sees an
+ * allocation failure.
+ */
+
+/* Grand Unified Theory of connection life cycle:
+ * At any point in time, the connection can be in one of these states:
+ * DOWN, CONNECTING, UP, DISCONNECTING, ERROR
+ *
+ * The following transitions are possible:
+ *  ANY		  -> ERROR
+ *  UP		  -> DISCONNECTING
+ *  ERROR	  -> DISCONNECTING
+ *  DISCONNECTING -> DOWN
+ *  DOWN	  -> CONNECTING
+ *  CONNECTING	  -> UP
+ *
+ * Transition to state DISCONNECTING/DOWN:
+ *  -	Inside the shutdown worker; synchronizes with xmit path
+ *	through RDS_IN_XMIT, and with connection management callbacks
+ *	via c_cm_lock.
+ *
+ *	For receive callbacks, we rely on the underlying transport
+ *	(TCP, IB/RDMA) to provide the necessary synchronisation.
+ */
+struct workqueue_struct *rds_wq;
+EXPORT_SYMBOL_GPL(rds_wq);
+
+void rds_connect_path_complete(struct rds_conn_path *cp, int curr)
+{
+	if (!rds_conn_path_transition(cp, curr, RDS_CONN_UP)) {
+		printk(KERN_WARNING "%s: Cannot transition to state UP, "
+				"current state is %d\n",
+				__func__,
+				atomic_read(&cp->cp_state));
+		rds_conn_path_drop(cp, false);
+		return;
+	}
+
+	rdsdebug("conn %p for %pI6c to %pI6c complete\n",
+		 cp->cp_conn, &cp->cp_conn->c_laddr, &cp->cp_conn->c_faddr);
+
+	cp->cp_reconnect_jiffies = 0;
+	set_bit(0, &cp->cp_conn->c_map_queued);
+	rcu_read_lock();
+	if (!rds_destroy_pending(cp->cp_conn)) {
+		queue_delayed_work(cp->cp_wq, &cp->cp_send_w, 0);
+		queue_delayed_work(cp->cp_wq, &cp->cp_recv_w, 0);
+	}
+	rcu_read_unlock();
+	cp->cp_conn->c_proposed_version = RDS_PROTOCOL_VERSION;
+}
+EXPORT_SYMBOL_GPL(rds_connect_path_complete);
+
+void rds_connect_complete(struct rds_connection *conn)
+{
+	rds_connect_path_complete(&conn->c_path[0], RDS_CONN_CONNECTING);
+}
+EXPORT_SYMBOL_GPL(rds_connect_complete);
+
+/*
+ * This random exponential backoff is relied on to eventually resolve racing
+ * connects.
+ *
+ * If connect attempts race then both parties drop both connections and come
+ * here to wait for a random amount of time before trying again.  Eventually
+ * the backoff range will be so much greater than the time it takes to
+ * establish a connection that one of the pair will establish the connection
+ * before the other's random delay fires.
+ *
+ * Connection attempts that arrive while a connection is already established
+ * are also considered to be racing connects.  This lets a connection from
+ * a rebooted machine replace an existing stale connection before the transport
+ * notices that the connection has failed.
+ *
+ * We should *always* start with a random backoff; otherwise a broken connection
+ * will always take several iterations to be re-established.
+ */
+void rds_queue_reconnect(struct rds_conn_path *cp)
+{
+	unsigned long rand;
+	struct rds_connection *conn = cp->cp_conn;
+
+	rdsdebug("conn %p for %pI6c to %pI6c reconnect jiffies %lu\n",
+		 conn, &conn->c_laddr, &conn->c_faddr,
+		 cp->cp_reconnect_jiffies);
+
+	/* let peer with smaller addr initiate reconnect, to avoid duels */
+	if (conn->c_trans->t_type == RDS_TRANS_TCP &&
+	    rds_addr_cmp(&conn->c_laddr, &conn->c_faddr) >= 0)
+		return;
+
+	set_bit(RDS_RECONNECT_PENDING, &cp->cp_flags);
+	if (cp->cp_reconnect_jiffies == 0) {
+		cp->cp_reconnect_jiffies = rds_sysctl_reconnect_min_jiffies;
+		rcu_read_lock();
+		if (!rds_destroy_pending(cp->cp_conn))
+			queue_delayed_work(cp->cp_wq, &cp->cp_conn_w, 0);
+		rcu_read_unlock();
+		return;
+	}
+
+	get_random_bytes(&rand, sizeof(rand));
+	rdsdebug("%lu delay %lu ceil conn %p for %pI6c -> %pI6c\n",
+		 rand % cp->cp_reconnect_jiffies, cp->cp_reconnect_jiffies,
+		 conn, &conn->c_laddr, &conn->c_faddr);
+	rcu_read_lock();
+	if (!rds_destroy_pending(cp->cp_conn))
+		queue_delayed_work(cp->cp_wq, &cp->cp_conn_w,
+				   rand % cp->cp_reconnect_jiffies);
+	rcu_read_unlock();
+
+	cp->cp_reconnect_jiffies = min(cp->cp_reconnect_jiffies * 2,
+					rds_sysctl_reconnect_max_jiffies);
+}
+
+void rds_connect_worker(struct work_struct *work)
+{
+	struct rds_conn_path *cp = container_of(work,
+						struct rds_conn_path,
+						cp_conn_w.work);
+	struct rds_connection *conn = cp->cp_conn;
+	int ret;
+
+	if (cp->cp_index > 0 &&
+	    rds_addr_cmp(&cp->cp_conn->c_laddr, &cp->cp_conn->c_faddr) >= 0)
+		return;
+	clear_bit(RDS_RECONNECT_PENDING, &cp->cp_flags);
+	ret = rds_conn_path_transition(cp, RDS_CONN_DOWN, RDS_CONN_CONNECTING);
+	if (ret) {
+		ret = conn->c_trans->conn_path_connect(cp);
+		rdsdebug("conn %p for %pI6c to %pI6c dispatched, ret %d\n",
+			 conn, &conn->c_laddr, &conn->c_faddr, ret);
+
+		if (ret) {
+			if (rds_conn_path_transition(cp,
+						     RDS_CONN_CONNECTING,
+						     RDS_CONN_DOWN))
+				rds_queue_reconnect(cp);
+			else
+				rds_conn_path_error(cp, "connect failed\n");
+		}
+	}
+}
+
+void rds_send_worker(struct work_struct *work)
+{
+	struct rds_conn_path *cp = container_of(work,
+						struct rds_conn_path,
+						cp_send_w.work);
+	int ret;
+
+	if (rds_conn_path_state(cp) == RDS_CONN_UP) {
+		clear_bit(RDS_LL_SEND_FULL, &cp->cp_flags);
+		ret = rds_send_xmit(cp);
+		cond_resched();
+		rdsdebug("conn %p ret %d\n", cp->cp_conn, ret);
+		switch (ret) {
+		case -EAGAIN:
+			rds_stats_inc(s_send_immediate_retry);
+			queue_delayed_work(cp->cp_wq, &cp->cp_send_w, 0);
+			break;
+		case -ENOMEM:
+			rds_stats_inc(s_send_delayed_retry);
+			queue_delayed_work(cp->cp_wq, &cp->cp_send_w, 2);
+			break;
+		default:
+			break;
+		}
+	}
+}
+
+void rds_recv_worker(struct work_struct *work)
+{
+	struct rds_conn_path *cp = container_of(work,
+						struct rds_conn_path,
+						cp_recv_w.work);
+	int ret;
+
+	if (rds_conn_path_state(cp) == RDS_CONN_UP) {
+		ret = cp->cp_conn->c_trans->recv_path(cp);
+		rdsdebug("conn %p ret %d\n", cp->cp_conn, ret);
+		switch (ret) {
+		case -EAGAIN:
+			rds_stats_inc(s_recv_immediate_retry);
+			queue_delayed_work(cp->cp_wq, &cp->cp_recv_w, 0);
+			break;
+		case -ENOMEM:
+			rds_stats_inc(s_recv_delayed_retry);
+			queue_delayed_work(cp->cp_wq, &cp->cp_recv_w, 2);
+			break;
+		default:
+			break;
+		}
+	}
+}
+
+void rds_shutdown_worker(struct work_struct *work)
+{
+	struct rds_conn_path *cp = container_of(work,
+						struct rds_conn_path,
+						cp_down_w);
+
+	rds_conn_shutdown(cp);
+}
+
+void rds_threads_exit(void)
+{
+	destroy_workqueue(rds_wq);
+}
+
+int rds_threads_init(void)
+{
+	rds_wq = create_singlethread_workqueue("krdsd");
+	if (!rds_wq)
+		return -ENOMEM;
+
+	return 0;
+}
+
+/* Compare two IPv6 addresses.  Return 0 if the two addresses are equal.
+ * Return 1 if the first is greater.  Return -1 if the second is greater.
+ */
+int rds_addr_cmp(const struct in6_addr *addr1,
+		 const struct in6_addr *addr2)
+{
+#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && BITS_PER_LONG == 64
+	const __be64 *a1, *a2;
+	u64 x, y;
+
+	a1 = (__be64 *)addr1;
+	a2 = (__be64 *)addr2;
+
+	if (*a1 != *a2) {
+		if (be64_to_cpu(*a1) < be64_to_cpu(*a2))
+			return -1;
+		else
+			return 1;
+	} else {
+		x = be64_to_cpu(*++a1);
+		y = be64_to_cpu(*++a2);
+		if (x < y)
+			return -1;
+		else if (x > y)
+			return 1;
+		else
+			return 0;
+	}
+#else
+	u32 a, b;
+	int i;
+
+	for (i = 0; i < 4; i++) {
+		if (addr1->s6_addr32[i] != addr2->s6_addr32[i]) {
+			a = ntohl(addr1->s6_addr32[i]);
+			b = ntohl(addr2->s6_addr32[i]);
+			if (a < b)
+				return -1;
+			else if (a > b)
+				return 1;
+		}
+	}
+	return 0;
+#endif
+}
+EXPORT_SYMBOL_GPL(rds_addr_cmp);
diff --git a/net/rds/transport.c b/net/rds/transport.c
new file mode 100644
index 000000000..f8001ec80
--- /dev/null
+++ b/net/rds/transport.c
@@ -0,0 +1,169 @@
+/*
+ * Copyright (c) 2006, 2017 Oracle and/or its affiliates. All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/in.h>
+#include <linux/ipv6.h>
+
+#include "rds.h"
+#include "loop.h"
+
+static char * const rds_trans_modules[] = {
+	[RDS_TRANS_IB] = "rds_rdma",
+	[RDS_TRANS_GAP] = NULL,
+	[RDS_TRANS_TCP] = "rds_tcp",
+};
+
+static struct rds_transport *transports[RDS_TRANS_COUNT];
+static DECLARE_RWSEM(rds_trans_sem);
+
+void rds_trans_register(struct rds_transport *trans)
+{
+	BUG_ON(strlen(trans->t_name) + 1 > TRANSNAMSIZ);
+
+	down_write(&rds_trans_sem);
+
+	if (transports[trans->t_type])
+		printk(KERN_ERR "RDS Transport type %d already registered\n",
+			trans->t_type);
+	else {
+		transports[trans->t_type] = trans;
+		printk(KERN_INFO "Registered RDS/%s transport\n", trans->t_name);
+	}
+
+	up_write(&rds_trans_sem);
+}
+EXPORT_SYMBOL_GPL(rds_trans_register);
+
+void rds_trans_unregister(struct rds_transport *trans)
+{
+	down_write(&rds_trans_sem);
+
+	transports[trans->t_type] = NULL;
+	printk(KERN_INFO "Unregistered RDS/%s transport\n", trans->t_name);
+
+	up_write(&rds_trans_sem);
+}
+EXPORT_SYMBOL_GPL(rds_trans_unregister);
+
+void rds_trans_put(struct rds_transport *trans)
+{
+	if (trans)
+		module_put(trans->t_owner);
+}
+
+struct rds_transport *rds_trans_get_preferred(struct net *net,
+					      const struct in6_addr *addr,
+					      __u32 scope_id)
+{
+	struct rds_transport *ret = NULL;
+	struct rds_transport *trans;
+	unsigned int i;
+
+	if (ipv6_addr_v4mapped(addr)) {
+		if (*(u_int8_t *)&addr->s6_addr32[3] == IN_LOOPBACKNET)
+			return &rds_loop_transport;
+	} else if (ipv6_addr_loopback(addr)) {
+		return &rds_loop_transport;
+	}
+
+	down_read(&rds_trans_sem);
+	for (i = 0; i < RDS_TRANS_COUNT; i++) {
+		trans = transports[i];
+
+		if (trans && (trans->laddr_check(net, addr, scope_id) == 0) &&
+		    (!trans->t_owner || try_module_get(trans->t_owner))) {
+			ret = trans;
+			break;
+		}
+	}
+	up_read(&rds_trans_sem);
+
+	return ret;
+}
+
+struct rds_transport *rds_trans_get(int t_type)
+{
+	struct rds_transport *ret = NULL;
+	struct rds_transport *trans;
+
+	down_read(&rds_trans_sem);
+	trans = transports[t_type];
+	if (!trans) {
+		up_read(&rds_trans_sem);
+		if (rds_trans_modules[t_type])
+			request_module(rds_trans_modules[t_type]);
+		down_read(&rds_trans_sem);
+		trans = transports[t_type];
+	}
+	if (trans && trans->t_type == t_type &&
+	    (!trans->t_owner || try_module_get(trans->t_owner)))
+		ret = trans;
+
+	up_read(&rds_trans_sem);
+
+	return ret;
+}
+
+/*
+ * This returns the number of stats entries in the snapshot and only
+ * copies them using the iter if there is enough space for them.  The
+ * caller passes in the global stats so that we can size and copy while
+ * holding the lock.
+ */
+unsigned int rds_trans_stats_info_copy(struct rds_info_iterator *iter,
+				       unsigned int avail)
+
+{
+	struct rds_transport *trans;
+	unsigned int total = 0;
+	unsigned int part;
+	int i;
+
+	rds_info_iter_unmap(iter);
+	down_read(&rds_trans_sem);
+
+	for (i = 0; i < RDS_TRANS_COUNT; i++) {
+		trans = transports[i];
+		if (!trans || !trans->stats_info_copy)
+			continue;
+
+		part = trans->stats_info_copy(iter, avail);
+		avail -= min(avail, part);
+		total += part;
+	}
+
+	up_read(&rds_trans_sem);
+
+	return total;
+}