Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 691 insertions, 0 deletions

diff --git a/fs/dlm/rcom.c b/fs/dlm/rcom.c
new file mode 100644
index 000000000..be1a71a63
--- /dev/null
+++ b/fs/dlm/rcom.c
@@ -0,0 +1,691 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/******************************************************************************
+*******************************************************************************
+**
+**  Copyright (C) Sistina Software, Inc.  1997-2003  All rights reserved.
+**  Copyright (C) 2005-2008 Red Hat, Inc.  All rights reserved.
+**
+**
+*******************************************************************************
+******************************************************************************/
+
+#include "dlm_internal.h"
+#include "lockspace.h"
+#include "member.h"
+#include "lowcomms.h"
+#include "midcomms.h"
+#include "rcom.h"
+#include "recover.h"
+#include "dir.h"
+#include "config.h"
+#include "memory.h"
+#include "lock.h"
+#include "util.h"
+
+static int rcom_response(struct dlm_ls *ls)
+{
+	return test_bit(LSFL_RCOM_READY, &ls->ls_flags);
+}
+
+static void _create_rcom(struct dlm_ls *ls, int to_nodeid, int type, int len,
+			 struct dlm_rcom **rc_ret, char *mb, int mb_len,
+			 uint64_t seq)
+{
+	struct dlm_rcom *rc;
+
+	rc = (struct dlm_rcom *) mb;
+
+	rc->rc_header.h_version = cpu_to_le32(DLM_HEADER_MAJOR | DLM_HEADER_MINOR);
+	rc->rc_header.u.h_lockspace = cpu_to_le32(ls->ls_global_id);
+	rc->rc_header.h_nodeid = cpu_to_le32(dlm_our_nodeid());
+	rc->rc_header.h_length = cpu_to_le16(mb_len);
+	rc->rc_header.h_cmd = DLM_RCOM;
+
+	rc->rc_type = cpu_to_le32(type);
+	rc->rc_seq = cpu_to_le64(seq);
+
+	*rc_ret = rc;
+}
+
+static int create_rcom(struct dlm_ls *ls, int to_nodeid, int type, int len,
+		       struct dlm_rcom **rc_ret, struct dlm_mhandle **mh_ret,
+		       uint64_t seq)
+{
+	int mb_len = sizeof(struct dlm_rcom) + len;
+	struct dlm_mhandle *mh;
+	char *mb;
+
+	mh = dlm_midcomms_get_mhandle(to_nodeid, mb_len, &mb);
+	if (!mh) {
+		log_print("%s to %d type %d len %d ENOBUFS",
+			  __func__, to_nodeid, type, len);
+		return -ENOBUFS;
+	}
+
+	_create_rcom(ls, to_nodeid, type, len, rc_ret, mb, mb_len, seq);
+	*mh_ret = mh;
+	return 0;
+}
+
+static int create_rcom_stateless(struct dlm_ls *ls, int to_nodeid, int type,
+				 int len, struct dlm_rcom **rc_ret,
+				 struct dlm_msg **msg_ret, uint64_t seq)
+{
+	int mb_len = sizeof(struct dlm_rcom) + len;
+	struct dlm_msg *msg;
+	char *mb;
+
+	msg = dlm_lowcomms_new_msg(to_nodeid, mb_len, &mb, NULL, NULL);
+	if (!msg) {
+		log_print("create_rcom to %d type %d len %d ENOBUFS",
+			  to_nodeid, type, len);
+		return -ENOBUFS;
+	}
+
+	_create_rcom(ls, to_nodeid, type, len, rc_ret, mb, mb_len, seq);
+	*msg_ret = msg;
+	return 0;
+}
+
+static void send_rcom(struct dlm_mhandle *mh, struct dlm_rcom *rc)
+{
+	dlm_midcomms_commit_mhandle(mh, NULL, 0);
+}
+
+static void send_rcom_stateless(struct dlm_msg *msg, struct dlm_rcom *rc)
+{
+	dlm_lowcomms_commit_msg(msg);
+	dlm_lowcomms_put_msg(msg);
+}
+
+static void set_rcom_status(struct dlm_ls *ls, struct rcom_status *rs,
+			    uint32_t flags)
+{
+	rs->rs_flags = cpu_to_le32(flags);
+}
+
+/* When replying to a status request, a node also sends back its
+   configuration values.  The requesting node then checks that the remote
+   node is configured the same way as itself. */
+
+static void set_rcom_config(struct dlm_ls *ls, struct rcom_config *rf,
+			    uint32_t num_slots)
+{
+	rf->rf_lvblen = cpu_to_le32(ls->ls_lvblen);
+	rf->rf_lsflags = cpu_to_le32(ls->ls_exflags);
+
+	rf->rf_our_slot = cpu_to_le16(ls->ls_slot);
+	rf->rf_num_slots = cpu_to_le16(num_slots);
+	rf->rf_generation =  cpu_to_le32(ls->ls_generation);
+}
+
+static int check_rcom_config(struct dlm_ls *ls, struct dlm_rcom *rc, int nodeid)
+{
+	struct rcom_config *rf = (struct rcom_config *) rc->rc_buf;
+
+	if ((le32_to_cpu(rc->rc_header.h_version) & 0xFFFF0000) != DLM_HEADER_MAJOR) {
+		log_error(ls, "version mismatch: %x nodeid %d: %x",
+			  DLM_HEADER_MAJOR | DLM_HEADER_MINOR, nodeid,
+			  le32_to_cpu(rc->rc_header.h_version));
+		return -EPROTO;
+	}
+
+	if (le32_to_cpu(rf->rf_lvblen) != ls->ls_lvblen ||
+	    le32_to_cpu(rf->rf_lsflags) != ls->ls_exflags) {
+		log_error(ls, "config mismatch: %d,%x nodeid %d: %d,%x",
+			  ls->ls_lvblen, ls->ls_exflags, nodeid,
+			  le32_to_cpu(rf->rf_lvblen),
+			  le32_to_cpu(rf->rf_lsflags));
+		return -EPROTO;
+	}
+	return 0;
+}
+
+static void allow_sync_reply(struct dlm_ls *ls, __le64 *new_seq)
+{
+	spin_lock_bh(&ls->ls_rcom_spin);
+	*new_seq = cpu_to_le64(++ls->ls_rcom_seq);
+	set_bit(LSFL_RCOM_WAIT, &ls->ls_flags);
+	spin_unlock_bh(&ls->ls_rcom_spin);
+}
+
+static void disallow_sync_reply(struct dlm_ls *ls)
+{
+	spin_lock_bh(&ls->ls_rcom_spin);
+	clear_bit(LSFL_RCOM_WAIT, &ls->ls_flags);
+	clear_bit(LSFL_RCOM_READY, &ls->ls_flags);
+	spin_unlock_bh(&ls->ls_rcom_spin);
+}
+
+/*
+ * low nodeid gathers one slot value at a time from each node.
+ * it sets need_slots=0, and saves rf_our_slot returned from each
+ * rcom_config.
+ *
+ * other nodes gather all slot values at once from the low nodeid.
+ * they set need_slots=1, and ignore the rf_our_slot returned from each
+ * rcom_config.  they use the rf_num_slots returned from the low
+ * node's rcom_config.
+ */
+
+int dlm_rcom_status(struct dlm_ls *ls, int nodeid, uint32_t status_flags,
+		    uint64_t seq)
+{
+	struct dlm_rcom *rc;
+	struct dlm_msg *msg;
+	int error = 0;
+
+	ls->ls_recover_nodeid = nodeid;
+
+	if (nodeid == dlm_our_nodeid()) {
+		rc = ls->ls_recover_buf;
+		rc->rc_result = cpu_to_le32(dlm_recover_status(ls));
+		goto out;
+	}
+
+retry:
+	error = create_rcom_stateless(ls, nodeid, DLM_RCOM_STATUS,
+				      sizeof(struct rcom_status), &rc, &msg,
+				      seq);
+	if (error)
+		goto out;
+
+	set_rcom_status(ls, (struct rcom_status *)rc->rc_buf, status_flags);
+
+	allow_sync_reply(ls, &rc->rc_id);
+	memset(ls->ls_recover_buf, 0, DLM_MAX_SOCKET_BUFSIZE);
+
+	send_rcom_stateless(msg, rc);
+
+	error = dlm_wait_function(ls, &rcom_response);
+	disallow_sync_reply(ls);
+	if (error == -ETIMEDOUT)
+		goto retry;
+	if (error)
+		goto out;
+
+	rc = ls->ls_recover_buf;
+
+	if (rc->rc_result == cpu_to_le32(-ESRCH)) {
+		/* we pretend the remote lockspace exists with 0 status */
+		log_debug(ls, "remote node %d not ready", nodeid);
+		rc->rc_result = 0;
+		error = 0;
+	} else {
+		error = check_rcom_config(ls, rc, nodeid);
+	}
+
+	/* the caller looks at rc_result for the remote recovery status */
+ out:
+	return error;
+}
+
+static void receive_rcom_status(struct dlm_ls *ls,
+				const struct dlm_rcom *rc_in,
+				uint64_t seq)
+{
+	struct dlm_rcom *rc;
+	struct rcom_status *rs;
+	uint32_t status;
+	int nodeid = le32_to_cpu(rc_in->rc_header.h_nodeid);
+	int len = sizeof(struct rcom_config);
+	struct dlm_msg *msg;
+	int num_slots = 0;
+	int error;
+
+	if (!dlm_slots_version(&rc_in->rc_header)) {
+		status = dlm_recover_status(ls);
+		goto do_create;
+	}
+
+	rs = (struct rcom_status *)rc_in->rc_buf;
+
+	if (!(le32_to_cpu(rs->rs_flags) & DLM_RSF_NEED_SLOTS)) {
+		status = dlm_recover_status(ls);
+		goto do_create;
+	}
+
+	spin_lock_bh(&ls->ls_recover_lock);
+	status = ls->ls_recover_status;
+	num_slots = ls->ls_num_slots;
+	spin_unlock_bh(&ls->ls_recover_lock);
+	len += num_slots * sizeof(struct rcom_slot);
+
+ do_create:
+	error = create_rcom_stateless(ls, nodeid, DLM_RCOM_STATUS_REPLY,
+				      len, &rc, &msg, seq);
+	if (error)
+		return;
+
+	rc->rc_id = rc_in->rc_id;
+	rc->rc_seq_reply = rc_in->rc_seq;
+	rc->rc_result = cpu_to_le32(status);
+
+	set_rcom_config(ls, (struct rcom_config *)rc->rc_buf, num_slots);
+
+	if (!num_slots)
+		goto do_send;
+
+	spin_lock_bh(&ls->ls_recover_lock);
+	if (ls->ls_num_slots != num_slots) {
+		spin_unlock_bh(&ls->ls_recover_lock);
+		log_debug(ls, "receive_rcom_status num_slots %d to %d",
+			  num_slots, ls->ls_num_slots);
+		rc->rc_result = 0;
+		set_rcom_config(ls, (struct rcom_config *)rc->rc_buf, 0);
+		goto do_send;
+	}
+
+	dlm_slots_copy_out(ls, rc);
+	spin_unlock_bh(&ls->ls_recover_lock);
+
+ do_send:
+	send_rcom_stateless(msg, rc);
+}
+
+static void receive_sync_reply(struct dlm_ls *ls, const struct dlm_rcom *rc_in)
+{
+	spin_lock_bh(&ls->ls_rcom_spin);
+	if (!test_bit(LSFL_RCOM_WAIT, &ls->ls_flags) ||
+	    le64_to_cpu(rc_in->rc_id) != ls->ls_rcom_seq) {
+		log_debug(ls, "reject reply %d from %d seq %llx expect %llx",
+			  le32_to_cpu(rc_in->rc_type),
+			  le32_to_cpu(rc_in->rc_header.h_nodeid),
+			  (unsigned long long)le64_to_cpu(rc_in->rc_id),
+			  (unsigned long long)ls->ls_rcom_seq);
+		goto out;
+	}
+	memcpy(ls->ls_recover_buf, rc_in,
+	       le16_to_cpu(rc_in->rc_header.h_length));
+	set_bit(LSFL_RCOM_READY, &ls->ls_flags);
+	clear_bit(LSFL_RCOM_WAIT, &ls->ls_flags);
+	wake_up(&ls->ls_wait_general);
+ out:
+	spin_unlock_bh(&ls->ls_rcom_spin);
+}
+
+int dlm_rcom_names(struct dlm_ls *ls, int nodeid, char *last_name,
+		   int last_len, uint64_t seq)
+{
+	struct dlm_mhandle *mh;
+	struct dlm_rcom *rc;
+	int error = 0;
+
+	ls->ls_recover_nodeid = nodeid;
+
+retry:
+	error = create_rcom(ls, nodeid, DLM_RCOM_NAMES, last_len,
+			    &rc, &mh, seq);
+	if (error)
+		goto out;
+	memcpy(rc->rc_buf, last_name, last_len);
+
+	allow_sync_reply(ls, &rc->rc_id);
+	memset(ls->ls_recover_buf, 0, DLM_MAX_SOCKET_BUFSIZE);
+
+	send_rcom(mh, rc);
+
+	error = dlm_wait_function(ls, &rcom_response);
+	disallow_sync_reply(ls);
+	if (error == -ETIMEDOUT)
+		goto retry;
+ out:
+	return error;
+}
+
+static void receive_rcom_names(struct dlm_ls *ls, const struct dlm_rcom *rc_in,
+			       uint64_t seq)
+{
+	struct dlm_mhandle *mh;
+	struct dlm_rcom *rc;
+	int error, inlen, outlen, nodeid;
+
+	nodeid = le32_to_cpu(rc_in->rc_header.h_nodeid);
+	inlen = le16_to_cpu(rc_in->rc_header.h_length) -
+		sizeof(struct dlm_rcom);
+	outlen = DLM_MAX_APP_BUFSIZE - sizeof(struct dlm_rcom);
+
+	error = create_rcom(ls, nodeid, DLM_RCOM_NAMES_REPLY, outlen,
+			    &rc, &mh, seq);
+	if (error)
+		return;
+	rc->rc_id = rc_in->rc_id;
+	rc->rc_seq_reply = rc_in->rc_seq;
+
+	dlm_copy_master_names(ls, rc_in->rc_buf, inlen, rc->rc_buf, outlen,
+			      nodeid);
+	send_rcom(mh, rc);
+}
+
+int dlm_send_rcom_lookup(struct dlm_rsb *r, int dir_nodeid, uint64_t seq)
+{
+	struct dlm_rcom *rc;
+	struct dlm_mhandle *mh;
+	struct dlm_ls *ls = r->res_ls;
+	int error;
+
+	error = create_rcom(ls, dir_nodeid, DLM_RCOM_LOOKUP, r->res_length,
+			    &rc, &mh, seq);
+	if (error)
+		goto out;
+	memcpy(rc->rc_buf, r->res_name, r->res_length);
+	rc->rc_id = cpu_to_le64(r->res_id);
+
+	send_rcom(mh, rc);
+ out:
+	return error;
+}
+
+static void receive_rcom_lookup(struct dlm_ls *ls,
+				const struct dlm_rcom *rc_in, uint64_t seq)
+{
+	struct dlm_rcom *rc;
+	struct dlm_mhandle *mh;
+	int error, ret_nodeid, nodeid = le32_to_cpu(rc_in->rc_header.h_nodeid);
+	int len = le16_to_cpu(rc_in->rc_header.h_length) -
+		sizeof(struct dlm_rcom);
+
+	/* Old code would send this special id to trigger a debug dump. */
+	if (rc_in->rc_id == cpu_to_le64(0xFFFFFFFF)) {
+		log_error(ls, "receive_rcom_lookup dump from %d", nodeid);
+		dlm_dump_rsb_name(ls, rc_in->rc_buf, len);
+		return;
+	}
+
+	error = create_rcom(ls, nodeid, DLM_RCOM_LOOKUP_REPLY, 0, &rc, &mh,
+			    seq);
+	if (error)
+		return;
+
+	error = dlm_master_lookup(ls, nodeid, rc_in->rc_buf, len,
+				  DLM_LU_RECOVER_MASTER, &ret_nodeid, NULL);
+	if (error)
+		ret_nodeid = error;
+	rc->rc_result = cpu_to_le32(ret_nodeid);
+	rc->rc_id = rc_in->rc_id;
+	rc->rc_seq_reply = rc_in->rc_seq;
+
+	send_rcom(mh, rc);
+}
+
+static void receive_rcom_lookup_reply(struct dlm_ls *ls,
+				      const struct dlm_rcom *rc_in)
+{
+	dlm_recover_master_reply(ls, rc_in);
+}
+
+static void pack_rcom_lock(struct dlm_rsb *r, struct dlm_lkb *lkb,
+			   struct rcom_lock *rl)
+{
+	memset(rl, 0, sizeof(*rl));
+
+	rl->rl_ownpid = cpu_to_le32(lkb->lkb_ownpid);
+	rl->rl_lkid = cpu_to_le32(lkb->lkb_id);
+	rl->rl_exflags = cpu_to_le32(lkb->lkb_exflags);
+	rl->rl_flags = cpu_to_le32(dlm_dflags_val(lkb));
+	rl->rl_lvbseq = cpu_to_le32(lkb->lkb_lvbseq);
+	rl->rl_rqmode = lkb->lkb_rqmode;
+	rl->rl_grmode = lkb->lkb_grmode;
+	rl->rl_status = lkb->lkb_status;
+	rl->rl_wait_type = cpu_to_le16(lkb->lkb_wait_type);
+
+	if (lkb->lkb_bastfn)
+		rl->rl_asts |= DLM_CB_BAST;
+	if (lkb->lkb_astfn)
+		rl->rl_asts |= DLM_CB_CAST;
+
+	rl->rl_namelen = cpu_to_le16(r->res_length);
+	memcpy(rl->rl_name, r->res_name, r->res_length);
+
+	/* FIXME: might we have an lvb without DLM_LKF_VALBLK set ?
+	   If so, receive_rcom_lock_args() won't take this copy. */
+
+	if (lkb->lkb_lvbptr)
+		memcpy(rl->rl_lvb, lkb->lkb_lvbptr, r->res_ls->ls_lvblen);
+}
+
+int dlm_send_rcom_lock(struct dlm_rsb *r, struct dlm_lkb *lkb, uint64_t seq)
+{
+	struct dlm_ls *ls = r->res_ls;
+	struct dlm_rcom *rc;
+	struct dlm_mhandle *mh;
+	struct rcom_lock *rl;
+	int error, len = sizeof(struct rcom_lock);
+
+	if (lkb->lkb_lvbptr)
+		len += ls->ls_lvblen;
+
+	error = create_rcom(ls, r->res_nodeid, DLM_RCOM_LOCK, len, &rc, &mh,
+			    seq);
+	if (error)
+		goto out;
+
+	rl = (struct rcom_lock *) rc->rc_buf;
+	pack_rcom_lock(r, lkb, rl);
+	rc->rc_id = cpu_to_le64((uintptr_t)r);
+
+	send_rcom(mh, rc);
+ out:
+	return error;
+}
+
+/* needs at least dlm_rcom + rcom_lock */
+static void receive_rcom_lock(struct dlm_ls *ls, const struct dlm_rcom *rc_in,
+			      uint64_t seq)
+{
+	__le32 rl_remid, rl_result;
+	struct rcom_lock *rl;
+	struct dlm_rcom *rc;
+	struct dlm_mhandle *mh;
+	int error, nodeid = le32_to_cpu(rc_in->rc_header.h_nodeid);
+
+	dlm_recover_master_copy(ls, rc_in, &rl_remid, &rl_result);
+
+	error = create_rcom(ls, nodeid, DLM_RCOM_LOCK_REPLY,
+			    sizeof(struct rcom_lock), &rc, &mh, seq);
+	if (error)
+		return;
+
+	memcpy(rc->rc_buf, rc_in->rc_buf, sizeof(struct rcom_lock));
+	rl = (struct rcom_lock *)rc->rc_buf;
+	/* set rl_remid and rl_result from dlm_recover_master_copy() */
+	rl->rl_remid = rl_remid;
+	rl->rl_result = rl_result;
+
+	rc->rc_id = rc_in->rc_id;
+	rc->rc_seq_reply = rc_in->rc_seq;
+
+	send_rcom(mh, rc);
+}
+
+/* If the lockspace doesn't exist then still send a status message
+   back; it's possible that it just doesn't have its global_id yet. */
+
+int dlm_send_ls_not_ready(int nodeid, const struct dlm_rcom *rc_in)
+{
+	struct dlm_rcom *rc;
+	struct rcom_config *rf;
+	struct dlm_mhandle *mh;
+	char *mb;
+	int mb_len = sizeof(struct dlm_rcom) + sizeof(struct rcom_config);
+
+	mh = dlm_midcomms_get_mhandle(nodeid, mb_len, &mb);
+	if (!mh)
+		return -ENOBUFS;
+
+	rc = (struct dlm_rcom *) mb;
+
+	rc->rc_header.h_version = cpu_to_le32(DLM_HEADER_MAJOR | DLM_HEADER_MINOR);
+	rc->rc_header.u.h_lockspace = rc_in->rc_header.u.h_lockspace;
+	rc->rc_header.h_nodeid = cpu_to_le32(dlm_our_nodeid());
+	rc->rc_header.h_length = cpu_to_le16(mb_len);
+	rc->rc_header.h_cmd = DLM_RCOM;
+
+	rc->rc_type = cpu_to_le32(DLM_RCOM_STATUS_REPLY);
+	rc->rc_id = rc_in->rc_id;
+	rc->rc_seq_reply = rc_in->rc_seq;
+	rc->rc_result = cpu_to_le32(-ESRCH);
+
+	rf = (struct rcom_config *) rc->rc_buf;
+	rf->rf_lvblen = cpu_to_le32(~0U);
+
+	dlm_midcomms_commit_mhandle(mh, NULL, 0);
+
+	return 0;
+}
+
+/*
+ * Ignore messages for stage Y before we set
+ * recover_status bit for stage X:
+ *
+ * recover_status = 0
+ *
+ * dlm_recover_members()
+ * - send nothing
+ * - recv nothing
+ * - ignore NAMES, NAMES_REPLY
+ * - ignore LOOKUP, LOOKUP_REPLY
+ * - ignore LOCK, LOCK_REPLY
+ *
+ * recover_status |= NODES
+ *
+ * dlm_recover_members_wait()
+ *
+ * dlm_recover_directory()
+ * - send NAMES
+ * - recv NAMES_REPLY
+ * - ignore LOOKUP, LOOKUP_REPLY
+ * - ignore LOCK, LOCK_REPLY
+ *
+ * recover_status |= DIR
+ *
+ * dlm_recover_directory_wait()
+ *
+ * dlm_recover_masters()
+ * - send LOOKUP
+ * - recv LOOKUP_REPLY
+ *
+ * dlm_recover_locks()
+ * - send LOCKS
+ * - recv LOCKS_REPLY
+ *
+ * recover_status |= LOCKS
+ *
+ * dlm_recover_locks_wait()
+ *
+ * recover_status |= DONE
+ */
+
+/* Called by dlm_recv; corresponds to dlm_receive_message() but special
+   recovery-only comms are sent through here. */
+
+void dlm_receive_rcom(struct dlm_ls *ls, const struct dlm_rcom *rc, int nodeid)
+{
+	int lock_size = sizeof(struct dlm_rcom) + sizeof(struct rcom_lock);
+	int stop, reply = 0, names = 0, lookup = 0, lock = 0;
+	uint32_t status;
+	uint64_t seq;
+
+	switch (rc->rc_type) {
+	case cpu_to_le32(DLM_RCOM_STATUS_REPLY):
+		reply = 1;
+		break;
+	case cpu_to_le32(DLM_RCOM_NAMES):
+		names = 1;
+		break;
+	case cpu_to_le32(DLM_RCOM_NAMES_REPLY):
+		names = 1;
+		reply = 1;
+		break;
+	case cpu_to_le32(DLM_RCOM_LOOKUP):
+		lookup = 1;
+		break;
+	case cpu_to_le32(DLM_RCOM_LOOKUP_REPLY):
+		lookup = 1;
+		reply = 1;
+		break;
+	case cpu_to_le32(DLM_RCOM_LOCK):
+		lock = 1;
+		break;
+	case cpu_to_le32(DLM_RCOM_LOCK_REPLY):
+		lock = 1;
+		reply = 1;
+		break;
+	}
+
+	spin_lock_bh(&ls->ls_recover_lock);
+	status = ls->ls_recover_status;
+	stop = dlm_recovery_stopped(ls);
+	seq = ls->ls_recover_seq;
+	spin_unlock_bh(&ls->ls_recover_lock);
+
+	if (stop && (rc->rc_type != cpu_to_le32(DLM_RCOM_STATUS)))
+		goto ignore;
+
+	if (reply && (le64_to_cpu(rc->rc_seq_reply) != seq))
+		goto ignore;
+
+	if (!(status & DLM_RS_NODES) && (names || lookup || lock))
+		goto ignore;
+
+	if (!(status & DLM_RS_DIR) && (lookup || lock))
+		goto ignore;
+
+	switch (rc->rc_type) {
+	case cpu_to_le32(DLM_RCOM_STATUS):
+		receive_rcom_status(ls, rc, seq);
+		break;
+
+	case cpu_to_le32(DLM_RCOM_NAMES):
+		receive_rcom_names(ls, rc, seq);
+		break;
+
+	case cpu_to_le32(DLM_RCOM_LOOKUP):
+		receive_rcom_lookup(ls, rc, seq);
+		break;
+
+	case cpu_to_le32(DLM_RCOM_LOCK):
+		if (le16_to_cpu(rc->rc_header.h_length) < lock_size)
+			goto Eshort;
+		receive_rcom_lock(ls, rc, seq);
+		break;
+
+	case cpu_to_le32(DLM_RCOM_STATUS_REPLY):
+		receive_sync_reply(ls, rc);
+		break;
+
+	case cpu_to_le32(DLM_RCOM_NAMES_REPLY):
+		receive_sync_reply(ls, rc);
+		break;
+
+	case cpu_to_le32(DLM_RCOM_LOOKUP_REPLY):
+		receive_rcom_lookup_reply(ls, rc);
+		break;
+
+	case cpu_to_le32(DLM_RCOM_LOCK_REPLY):
+		if (le16_to_cpu(rc->rc_header.h_length) < lock_size)
+			goto Eshort;
+		dlm_recover_process_copy(ls, rc, seq);
+		break;
+
+	default:
+		log_error(ls, "receive_rcom bad type %d",
+			  le32_to_cpu(rc->rc_type));
+	}
+	return;
+
+ignore:
+	log_limit(ls, "dlm_receive_rcom ignore msg %d "
+		  "from %d %llu %llu recover seq %llu sts %x gen %u",
+		   le32_to_cpu(rc->rc_type),
+		   nodeid,
+		   (unsigned long long)le64_to_cpu(rc->rc_seq),
+		   (unsigned long long)le64_to_cpu(rc->rc_seq_reply),
+		   (unsigned long long)seq,
+		   status, ls->ls_generation);
+	return;
+Eshort:
+	log_error(ls, "recovery message %d from %d is too short",
+		  le32_to_cpu(rc->rc_type), nodeid);
+}
+