kbuild: rust: keep Rust objects out of Clang LTO with inline helpersgrafted

Under `CONFIG_LTO_CLANG` + `CONFIG_RUST_INLINE_HELPERS`, one may hit
`objtool` errors such as:

    vmlinux.o: error: objtool: _R..._3Gsp4boot+0xd6a:
    can't find jump dest instruction at .text._R..._3Gsp4boot+0x1dfd

The reason is that in such builds, the Clang invocation that compiles
the combined Rust plus helpers bitcode emits LLVM bitcode (again) --
the final code generation happens in the linker's LTO step, which the
`-mllvm` trap options passed to Clang do not reach.

This, in turn, means that unreachable traps are missing, and the
impossible paths do not merely fallthrough to the next symbol, but past
the end of their own section, since LTO builds place each function in
its own section.

Thus filter `CC_FLAGS_LTO` out of the Clang invocation, so that it always
emits machine code directly, with the traps in place.

Assisted-by: LLM
Cc: Gary Guo <gary@garyguo.net>
Cc: Boqun Feng <boqun@kernel.org>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Matthew Maurer <mmaurer@google.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust")
Acked-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

1 files changed, 723 insertions, 0 deletions

diff --git a/fs/lockd/host.c b/fs/lockd/host.c
new file mode 100644
index 000000000..d572cb275
--- /dev/null
+++ b/fs/lockd/host.c
@@ -0,0 +1,723 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * linux/fs/lockd/host.c
+ *
+ * Management for NLM peer hosts. The nlm_host struct is shared
+ * between client and server implementation. The only reason to
+ * do so is to reduce code bloat.
+ *
+ * Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
+ */
+
+#include <linux/types.h>
+#include <linux/slab.h>
+#include <linux/in.h>
+#include <linux/in6.h>
+#include <linux/sunrpc/clnt.h>
+#include <linux/sunrpc/addr.h>
+#include <linux/sunrpc/svc.h>
+#include <linux/mutex.h>
+
+#include <linux/sunrpc/svc_xprt.h>
+
+#include <net/ipv6.h>
+
+#include "lockd.h"
+#include "netns.h"
+
+#define NLMDBG_FACILITY		NLMDBG_HOSTCACHE
+#define NLM_HOST_NRHASH		32
+#define NLM_HOST_REBIND		(60 * HZ)
+#define NLM_HOST_EXPIRE		(300 * HZ)
+#define NLM_HOST_COLLECT	(120 * HZ)
+
+static struct hlist_head	nlm_server_hosts[NLM_HOST_NRHASH];
+static struct hlist_head	nlm_client_hosts[NLM_HOST_NRHASH];
+
+#define for_each_host(host, chain, table) \
+	for ((chain) = (table); \
+	     (chain) < (table) + NLM_HOST_NRHASH; ++(chain)) \
+		hlist_for_each_entry((host), (chain), h_hash)
+
+#define for_each_host_safe(host, next, chain, table) \
+	for ((chain) = (table); \
+	     (chain) < (table) + NLM_HOST_NRHASH; ++(chain)) \
+		hlist_for_each_entry_safe((host), (next), \
+						(chain), h_hash)
+
+static unsigned long		nrhosts;
+static DEFINE_MUTEX(nlm_host_mutex);
+
+static void			nlm_gc_hosts(struct net *net);
+
+struct nlm_lookup_host_info {
+	const int		server;		/* search for server|client */
+	const struct sockaddr	*sap;		/* address to search for */
+	const size_t		salen;		/* it's length */
+	const unsigned short	protocol;	/* transport to search for*/
+	const u32		version;	/* NLM version to search for */
+	const char		*hostname;	/* remote's hostname */
+	const size_t		hostname_len;	/* it's length */
+	const int		noresvport;	/* use non-priv port */
+	struct net		*net;		/* network namespace to bind */
+	const struct cred	*cred;
+};
+
+/*
+ * Hash function must work well on big- and little-endian platforms
+ */
+static unsigned int __nlm_hash32(const __be32 n)
+{
+	unsigned int hash = (__force u32)n ^ ((__force u32)n >> 16);
+	return hash ^ (hash >> 8);
+}
+
+static unsigned int __nlm_hash_addr4(const struct sockaddr *sap)
+{
+	const struct sockaddr_in *sin = (struct sockaddr_in *)sap;
+	return __nlm_hash32(sin->sin_addr.s_addr);
+}
+
+static unsigned int __nlm_hash_addr6(const struct sockaddr *sap)
+{
+	const struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)sap;
+	const struct in6_addr addr = sin6->sin6_addr;
+	return __nlm_hash32(addr.s6_addr32[0]) ^
+	       __nlm_hash32(addr.s6_addr32[1]) ^
+	       __nlm_hash32(addr.s6_addr32[2]) ^
+	       __nlm_hash32(addr.s6_addr32[3]);
+}
+
+static unsigned int nlm_hash_address(const struct sockaddr *sap)
+{
+	unsigned int hash;
+
+	switch (sap->sa_family) {
+	case AF_INET:
+		hash = __nlm_hash_addr4(sap);
+		break;
+	case AF_INET6:
+		hash = __nlm_hash_addr6(sap);
+		break;
+	default:
+		hash = 0;
+	}
+	return hash & (NLM_HOST_NRHASH - 1);
+}
+
+/*
+ * Allocate and initialize an nlm_host.  Common to both client and server.
+ */
+static struct nlm_host *nlm_alloc_host(struct nlm_lookup_host_info *ni,
+				       struct nsm_handle *nsm)
+{
+	struct nlm_host *host = NULL;
+	unsigned long now = jiffies;
+
+	if (nsm != NULL)
+		refcount_inc(&nsm->sm_count);
+	else {
+		nsm = nsm_get_handle(ni->net, ni->sap, ni->salen,
+					ni->hostname, ni->hostname_len);
+		if (unlikely(nsm == NULL)) {
+			dprintk("lockd: %s failed; no nsm handle\n",
+				__func__);
+			goto out;
+		}
+	}
+
+	host = kmalloc_obj(*host);
+	if (unlikely(host == NULL)) {
+		dprintk("lockd: %s failed; no memory\n", __func__);
+		nsm_release(nsm);
+		goto out;
+	}
+
+	memcpy(nlm_addr(host), ni->sap, ni->salen);
+	host->h_addrlen    = ni->salen;
+	rpc_set_port(nlm_addr(host), 0);
+	host->h_srcaddrlen = 0;
+
+	host->h_rpcclnt    = NULL;
+	host->h_name	   = nsm->sm_name;
+	host->h_version    = ni->version;
+	host->h_proto      = ni->protocol;
+	host->h_reclaiming = 0;
+	host->h_server     = ni->server;
+	host->h_noresvport = ni->noresvport;
+	host->h_inuse      = 0;
+	init_waitqueue_head(&host->h_gracewait);
+	init_rwsem(&host->h_rwsem);
+	host->h_state      = 0;
+	host->h_nsmstate   = 0;
+	host->h_pidcount   = 0;
+	refcount_set(&host->h_count, 1);
+	mutex_init(&host->h_mutex);
+	host->h_nextrebind = now + NLM_HOST_REBIND;
+	host->h_expires    = now + NLM_HOST_EXPIRE;
+	INIT_LIST_HEAD(&host->h_lockowners);
+	spin_lock_init(&host->h_lock);
+	INIT_LIST_HEAD(&host->h_granted);
+	INIT_LIST_HEAD(&host->h_reclaim);
+	host->h_nsmhandle  = nsm;
+	host->h_addrbuf    = nsm->sm_addrbuf;
+	host->net	   = ni->net;
+	host->h_cred	   = get_cred(ni->cred);
+	strscpy(host->nodename, utsname()->nodename, sizeof(host->nodename));
+
+out:
+	return host;
+}
+
+/*
+ * Destroy an nlm_host and free associated resources
+ *
+ * Caller must hold nlm_host_mutex.
+ */
+static void nlm_destroy_host_locked(struct nlm_host *host)
+{
+	struct rpc_clnt	*clnt;
+	struct lockd_net *ln = net_generic(host->net, lockd_net_id);
+
+	dprintk("lockd: destroy host %s\n", host->h_name);
+
+	hlist_del_init(&host->h_hash);
+
+	nsm_unmonitor(host);
+	nsm_release(host->h_nsmhandle);
+
+	clnt = host->h_rpcclnt;
+	if (clnt != NULL)
+		rpc_shutdown_client(clnt);
+	put_cred(host->h_cred);
+	kfree(host);
+
+	ln->nrhosts--;
+	nrhosts--;
+}
+
+/**
+ * nlmclnt_lookup_host - Find an NLM host handle matching a remote server
+ * @sap: network address of server
+ * @salen: length of server address
+ * @protocol: transport protocol to use
+ * @version: NLM protocol version
+ * @hostname: '\0'-terminated hostname of server
+ * @noresvport: 1 if non-privileged port should be used
+ * @net: pointer to net namespace
+ * @cred: pointer to cred
+ *
+ * Returns an nlm_host structure that matches the passed-in
+ * [server address, transport protocol, NLM version, server hostname].
+ * If one doesn't already exist in the host cache, a new handle is
+ * created and returned.
+ */
+struct nlm_host *nlmclnt_lookup_host(const struct sockaddr *sap,
+				     const size_t salen,
+				     const unsigned short protocol,
+				     const u32 version,
+				     const char *hostname,
+				     int noresvport,
+				     struct net *net,
+				     const struct cred *cred)
+{
+	struct nlm_lookup_host_info ni = {
+		.server		= 0,
+		.sap		= sap,
+		.salen		= salen,
+		.protocol	= protocol,
+		.version	= version,
+		.hostname	= hostname,
+		.hostname_len	= strlen(hostname),
+		.noresvport	= noresvport,
+		.net		= net,
+		.cred		= cred,
+	};
+	struct hlist_head *chain;
+	struct nlm_host	*host;
+	struct nsm_handle *nsm = NULL;
+	struct lockd_net *ln = net_generic(net, lockd_net_id);
+
+	dprintk("lockd: %s(host='%s', vers=%u, proto=%s)\n", __func__,
+			(hostname ? hostname : "<none>"), version,
+			(protocol == IPPROTO_UDP ? "udp" : "tcp"));
+
+	mutex_lock(&nlm_host_mutex);
+
+	chain = &nlm_client_hosts[nlm_hash_address(sap)];
+	hlist_for_each_entry(host, chain, h_hash) {
+		if (host->net != net)
+			continue;
+		if (!rpc_cmp_addr(nlm_addr(host), sap))
+			continue;
+
+		/* Same address. Share an NSM handle if we already have one */
+		if (nsm == NULL)
+			nsm = host->h_nsmhandle;
+
+		if (host->h_proto != protocol)
+			continue;
+		if (host->h_version != version)
+			continue;
+
+		nlm_get_host(host);
+		dprintk("lockd: %s found host %s (%s)\n", __func__,
+			host->h_name, host->h_addrbuf);
+		goto out;
+	}
+
+	host = nlm_alloc_host(&ni, nsm);
+	if (unlikely(host == NULL))
+		goto out;
+
+	hlist_add_head(&host->h_hash, chain);
+	ln->nrhosts++;
+	nrhosts++;
+
+	dprintk("lockd: %s created host %s (%s)\n", __func__,
+		host->h_name, host->h_addrbuf);
+
+out:
+	mutex_unlock(&nlm_host_mutex);
+	return host;
+}
+
+/**
+ * nlmclnt_release_host - release client nlm_host
+ * @host: nlm_host to release
+ *
+ */
+void nlmclnt_release_host(struct nlm_host *host)
+{
+	if (host == NULL)
+		return;
+
+	dprintk("lockd: release client host %s\n", host->h_name);
+
+	WARN_ON_ONCE(host->h_server);
+
+	if (refcount_dec_and_mutex_lock(&host->h_count, &nlm_host_mutex)) {
+		WARN_ON_ONCE(!list_empty(&host->h_lockowners));
+		WARN_ON_ONCE(!list_empty(&host->h_granted));
+		WARN_ON_ONCE(!list_empty(&host->h_reclaim));
+
+		nlm_destroy_host_locked(host);
+		mutex_unlock(&nlm_host_mutex);
+	}
+}
+
+/* Callback for rpc_cancel_tasks() - matches all tasks for cancellation */
+static bool nlmclnt_match_all(const struct rpc_task *task, const void *data)
+{
+	return true;
+}
+
+/**
+ * nlmclnt_shutdown_rpc_clnt - safely shut down NLM client RPC operations
+ * @host: nlm_host to shut down
+ *
+ * Cancels outstanding RPC tasks and marks the client as shut down.
+ * Synchronizes with nlmclnt_release_host() via nlm_host_mutex to prevent
+ * races between shutdown and host destruction. Safe to call if h_rpcclnt
+ * is NULL or already shut down.
+ */
+void nlmclnt_shutdown_rpc_clnt(struct nlm_host *host)
+{
+	struct rpc_clnt *clnt;
+
+	mutex_lock(&nlm_host_mutex);
+	clnt = host->h_rpcclnt;
+	if (clnt) {
+		clnt->cl_shutdown = 1;
+		rpc_cancel_tasks(clnt, -EIO, nlmclnt_match_all, NULL);
+	}
+	mutex_unlock(&nlm_host_mutex);
+}
+EXPORT_SYMBOL_GPL(nlmclnt_shutdown_rpc_clnt);
+
+/**
+ * nlmsvc_lookup_host - Find an NLM host handle matching a remote client
+ * @rqstp: incoming NLM request
+ * @hostname: name of client host
+ * @hostname_len: length of client hostname
+ *
+ * Returns an nlm_host structure that matches the [client address,
+ * transport protocol, NLM version, client hostname] of the passed-in
+ * NLM request.  If one doesn't already exist in the host cache, a
+ * new handle is created and returned.
+ *
+ * Before possibly creating a new nlm_host, construct a sockaddr
+ * for a specific source address in case the local system has
+ * multiple network addresses.  The family of the address in
+ * rq_daddr is guaranteed to be the same as the family of the
+ * address in rq_addr, so it's safe to use the same family for
+ * the source address.
+ */
+struct nlm_host *nlmsvc_lookup_host(const struct svc_rqst *rqstp,
+				    const char *hostname,
+				    const size_t hostname_len)
+{
+	struct hlist_head *chain;
+	struct nlm_host	*host = NULL;
+	struct nsm_handle *nsm = NULL;
+	struct sockaddr *src_sap = svc_daddr(rqstp);
+	size_t src_len = rqstp->rq_daddrlen;
+	struct net *net = SVC_NET(rqstp);
+	struct nlm_lookup_host_info ni = {
+		.server		= 1,
+		.sap		= svc_addr(rqstp),
+		.salen		= rqstp->rq_addrlen,
+		.protocol	= rqstp->rq_prot,
+		.version	= rqstp->rq_vers,
+		.hostname	= hostname,
+		.hostname_len	= hostname_len,
+		.net		= net,
+	};
+	struct lockd_net *ln = net_generic(net, lockd_net_id);
+
+	dprintk("lockd: %s(host='%.*s', vers=%u, proto=%s)\n", __func__,
+			(int)hostname_len, hostname, rqstp->rq_vers,
+			(rqstp->rq_prot == IPPROTO_UDP ? "udp" : "tcp"));
+
+	mutex_lock(&nlm_host_mutex);
+
+	if (time_after_eq(jiffies, ln->next_gc))
+		nlm_gc_hosts(net);
+
+	chain = &nlm_server_hosts[nlm_hash_address(ni.sap)];
+	hlist_for_each_entry(host, chain, h_hash) {
+		if (host->net != net)
+			continue;
+		if (!rpc_cmp_addr(nlm_addr(host), ni.sap))
+			continue;
+
+		/* Same address. Share an NSM handle if we already have one */
+		if (nsm == NULL)
+			nsm = host->h_nsmhandle;
+
+		if (host->h_proto != ni.protocol)
+			continue;
+		if (host->h_version != ni.version)
+			continue;
+		if (!rpc_cmp_addr(nlm_srcaddr(host), src_sap))
+			continue;
+
+		/* Move to head of hash chain. */
+		hlist_del(&host->h_hash);
+		hlist_add_head(&host->h_hash, chain);
+
+		nlm_get_host(host);
+		dprintk("lockd: %s found host %s (%s)\n",
+			__func__, host->h_name, host->h_addrbuf);
+		goto out;
+	}
+
+	host = nlm_alloc_host(&ni, nsm);
+	if (unlikely(host == NULL))
+		goto out;
+
+	memcpy(nlm_srcaddr(host), src_sap, src_len);
+	host->h_srcaddrlen = src_len;
+	hlist_add_head(&host->h_hash, chain);
+	ln->nrhosts++;
+	nrhosts++;
+
+	refcount_inc(&host->h_count);
+
+	dprintk("lockd: %s created host %s (%s)\n",
+		__func__, host->h_name, host->h_addrbuf);
+
+out:
+	mutex_unlock(&nlm_host_mutex);
+	return host;
+}
+
+/**
+ * nlmsvc_release_host - release server nlm_host
+ * @host: nlm_host to release
+ *
+ * Host is destroyed later in nlm_gc_host().
+ */
+void nlmsvc_release_host(struct nlm_host *host)
+{
+	if (host == NULL)
+		return;
+
+	dprintk("lockd: release server host %s\n", host->h_name);
+
+	WARN_ON_ONCE(!host->h_server);
+	refcount_dec(&host->h_count);
+}
+
+/*
+ * Create the NLM RPC client for an NLM peer
+ */
+struct rpc_clnt *
+nlm_bind_host(struct nlm_host *host)
+{
+	struct rpc_clnt	*clnt;
+
+	dprintk("lockd: nlm_bind_host %s (%s)\n",
+			host->h_name, host->h_addrbuf);
+
+	/* Lock host handle */
+	mutex_lock(&host->h_mutex);
+
+	/* If we've already created an RPC client, check whether
+	 * RPC rebind is required
+	 */
+	if ((clnt = host->h_rpcclnt) != NULL) {
+		nlm_rebind_host(host);
+	} else {
+		unsigned long increment = nlm_timeout * HZ;
+		struct rpc_timeout timeparms = {
+			.to_initval	= increment,
+			.to_increment	= increment,
+			.to_maxval	= increment * 6UL,
+			.to_retries	= 5U,
+		};
+		struct rpc_create_args args = {
+			.net		= host->net,
+			.protocol	= host->h_proto,
+			.address	= nlm_addr(host),
+			.addrsize	= host->h_addrlen,
+			.timeout	= &timeparms,
+			.servername	= host->h_name,
+			.program	= &nlm_program,
+			.version	= host->h_version,
+			.authflavor	= RPC_AUTH_UNIX,
+			.flags		= (RPC_CLNT_CREATE_NOPING |
+					   RPC_CLNT_CREATE_AUTOBIND |
+					   RPC_CLNT_CREATE_REUSEPORT),
+			.cred		= host->h_cred,
+		};
+
+		/*
+		 * lockd retries server side blocks automatically so we want
+		 * those to be soft RPC calls. Client side calls need to be
+		 * hard RPC tasks.
+		 */
+		if (!host->h_server)
+			args.flags |= RPC_CLNT_CREATE_HARDRTRY;
+		if (host->h_noresvport)
+			args.flags |= RPC_CLNT_CREATE_NONPRIVPORT;
+		if (host->h_srcaddrlen)
+			args.saddress = nlm_srcaddr(host);
+
+		clnt = rpc_create(&args);
+		if (!IS_ERR(clnt))
+			host->h_rpcclnt = clnt;
+		else {
+			printk("lockd: couldn't create RPC handle for %s\n", host->h_name);
+			clnt = NULL;
+		}
+	}
+
+	mutex_unlock(&host->h_mutex);
+	return clnt;
+}
+
+/**
+ * nlm_rebind_host - If needed, force a portmap lookup of the peer's lockd port
+ * @host: NLM host handle for peer
+ *
+ * This is not needed when using a connection-oriented protocol, such as TCP.
+ * The existing autobind mechanism is sufficient to force a rebind when
+ * required, e.g. on connection state transitions.
+ */
+void
+nlm_rebind_host(struct nlm_host *host)
+{
+	if (host->h_proto != IPPROTO_UDP)
+		return;
+
+	if (host->h_rpcclnt && time_after_eq(jiffies, host->h_nextrebind)) {
+		rpc_force_rebind(host->h_rpcclnt);
+		host->h_nextrebind = jiffies + NLM_HOST_REBIND;
+	}
+}
+
+/*
+ * Increment NLM host count
+ */
+struct nlm_host * nlm_get_host(struct nlm_host *host)
+{
+	if (host) {
+		dprintk("lockd: get host %s\n", host->h_name);
+		refcount_inc(&host->h_count);
+		host->h_expires = jiffies + NLM_HOST_EXPIRE;
+	}
+	return host;
+}
+
+static struct nlm_host *next_host_state(struct hlist_head *cache,
+					struct nsm_handle *nsm,
+					const struct lockd_reboot *info)
+{
+	struct nlm_host *host;
+	struct hlist_head *chain;
+
+	mutex_lock(&nlm_host_mutex);
+	for_each_host(host, chain, cache) {
+		if (host->h_nsmhandle == nsm
+		    && host->h_nsmstate != info->state) {
+			host->h_nsmstate = info->state;
+			host->h_state++;
+
+			nlm_get_host(host);
+			mutex_unlock(&nlm_host_mutex);
+			return host;
+		}
+	}
+
+	mutex_unlock(&nlm_host_mutex);
+	return NULL;
+}
+
+/**
+ * nlm_host_rebooted - Release all resources held by rebooted host
+ * @net:  network namespace
+ * @info: pointer to decoded results of NLM_SM_NOTIFY call
+ *
+ * We were notified that the specified host has rebooted.  Release
+ * all resources held by that peer.
+ */
+void nlm_host_rebooted(const struct net *net, const struct lockd_reboot *info)
+{
+	struct nsm_handle *nsm;
+	struct nlm_host	*host;
+
+	nsm = nsm_reboot_lookup(net, info);
+	if (unlikely(nsm == NULL))
+		return;
+
+	/* Mark all hosts tied to this NSM state as having rebooted.
+	 * We run the loop repeatedly, because we drop the host table
+	 * lock for this.
+	 * To avoid processing a host several times, we match the nsmstate.
+	 */
+	while ((host = next_host_state(nlm_server_hosts, nsm, info)) != NULL) {
+		nlmsvc_free_host_resources(host);
+		nlmsvc_release_host(host);
+	}
+	while ((host = next_host_state(nlm_client_hosts, nsm, info)) != NULL) {
+		nlmclnt_recovery(host);
+		nlmclnt_release_host(host);
+	}
+
+	nsm_release(nsm);
+}
+
+static void nlm_complain_hosts(struct net *net)
+{
+	struct hlist_head *chain;
+	struct nlm_host	*host;
+
+	if (net) {
+		struct lockd_net *ln = net_generic(net, lockd_net_id);
+
+		if (ln->nrhosts == 0)
+			return;
+		pr_warn("lockd: couldn't shutdown host module for net %x!\n",
+			net->ns.inum);
+		dprintk("lockd: %lu hosts left in net %x:\n", ln->nrhosts,
+			net->ns.inum);
+	} else {
+		if (nrhosts == 0)
+			return;
+		printk(KERN_WARNING "lockd: couldn't shutdown host module!\n");
+		dprintk("lockd: %lu hosts left:\n", nrhosts);
+	}
+
+	for_each_host(host, chain, nlm_server_hosts) {
+		if (net && host->net != net)
+			continue;
+		dprintk("       %s (cnt %d use %d exp %ld net %x)\n",
+			host->h_name, refcount_read(&host->h_count),
+			host->h_inuse, host->h_expires, host->net->ns.inum);
+	}
+}
+
+void
+nlm_shutdown_hosts_net(struct net *net)
+{
+	struct hlist_head *chain;
+	struct nlm_host	*host;
+
+	mutex_lock(&nlm_host_mutex);
+
+	/* First, make all hosts eligible for gc */
+	dprintk("lockd: nuking all hosts in net %x...\n",
+		net ? net->ns.inum : 0);
+	for_each_host(host, chain, nlm_server_hosts) {
+		if (net && host->net != net)
+			continue;
+		host->h_expires = jiffies - 1;
+		if (host->h_rpcclnt) {
+			rpc_shutdown_client(host->h_rpcclnt);
+			host->h_rpcclnt = NULL;
+		}
+		nlmsvc_free_host_resources(host);
+	}
+
+	/* Then, perform a garbage collection pass */
+	nlm_gc_hosts(net);
+	nlm_complain_hosts(net);
+	mutex_unlock(&nlm_host_mutex);
+}
+
+/*
+ * Shut down the hosts module.
+ * Note that this routine is called only at server shutdown time.
+ */
+void
+nlm_shutdown_hosts(void)
+{
+	dprintk("lockd: shutting down host module\n");
+	nlm_shutdown_hosts_net(NULL);
+}
+
+/*
+ * Garbage collect any unused NLM hosts.
+ * This GC combines reference counting for async operations with
+ * mark & sweep for resources held by remote clients.
+ */
+static void
+nlm_gc_hosts(struct net *net)
+{
+	struct hlist_head *chain;
+	struct hlist_node *next;
+	struct nlm_host	*host;
+
+	dprintk("lockd: host garbage collection for net %x\n",
+		net ? net->ns.inum : 0);
+	for_each_host(host, chain, nlm_server_hosts) {
+		if (net && host->net != net)
+			continue;
+		host->h_inuse = 0;
+	}
+
+	/* Mark all hosts that hold locks, blocks or shares */
+	nlmsvc_mark_resources(net);
+
+	for_each_host_safe(host, next, chain, nlm_server_hosts) {
+		if (net && host->net != net)
+			continue;
+		if (host->h_inuse || time_before(jiffies, host->h_expires)) {
+			dprintk("nlm_gc_hosts skipping %s "
+				"(cnt %d use %d exp %ld net %x)\n",
+				host->h_name, refcount_read(&host->h_count),
+				host->h_inuse, host->h_expires,
+				host->net->ns.inum);
+			continue;
+		}
+		if (refcount_dec_if_one(&host->h_count))
+			nlm_destroy_host_locked(host);
+	}
+
+	if (net) {
+		struct lockd_net *ln = net_generic(net, lockd_net_id);
+
+		ln->next_gc = jiffies + NLM_HOST_COLLECT;
+	}
+}