[ 10/76] lockd: create and use per-net NSM RPC clients on MON/UNMON requests

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

3.6-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Stanislav Kinsbursky <skinsbursky@parallels.com>

commit cb7323fffa85df37161f4d3be45e1f787808309c upstream.

NSM RPC client can be required on NFSv3 umount, when child reaper is dying
(and destroying it's mount namespace). It means, that current nsproxy is set
to NULL already, but creation of RPC client requires UTS namespace for gaining
hostname string.

This patch creates reference-counted per-net NSM client on first monitor
request and destroys it after last unmonitor request.

Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/lockd/mon.c |   37 ++++++++++++++++++++-----------------
 1 file changed, 20 insertions(+), 17 deletions(-)

--- a/fs/lockd/mon.c
+++ b/fs/lockd/mon.c
@@ -7,7 +7,6 @@
  */
 
 #include <linux/types.h>
-#include <linux/utsname.h>
 #include <linux/kernel.h>
 #include <linux/ktime.h>
 #include <linux/slab.h>
@@ -86,7 +85,7 @@ static struct rpc_clnt *nsm_create(struc
 	return rpc_create(&args);
 }
 
-__maybe_unused static struct rpc_clnt *nsm_client_get(struct net *net)
+static struct rpc_clnt *nsm_client_get(struct net *net)
 {
 	static DEFINE_MUTEX(nsm_create_mutex);
 	struct rpc_clnt	*clnt;
@@ -113,7 +112,7 @@ out:
 	return clnt;
 }
 
-__maybe_unused static void nsm_client_put(struct net *net)
+static void nsm_client_put(struct net *net)
 {
 	struct lockd_net *ln = net_generic(net, lockd_net_id);
 	struct rpc_clnt	*clnt = ln->nsm_clnt;
@@ -132,9 +131,8 @@ __maybe_unused static void nsm_client_pu
 }
 
 static int nsm_mon_unmon(struct nsm_handle *nsm, u32 proc, struct nsm_res *res,
-			 struct net *net)
+			 struct rpc_clnt *clnt)
 {
-	struct rpc_clnt	*clnt;
 	int		status;
 	struct nsm_args args = {
 		.priv		= &nsm->sm_priv,
@@ -142,20 +140,14 @@ static int nsm_mon_unmon(struct nsm_hand
 		.vers		= 3,
 		.proc		= NLMPROC_NSM_NOTIFY,
 		.mon_name	= nsm->sm_mon_name,
-		.nodename	= utsname()->nodename,
+		.nodename	= clnt->cl_nodename,
 	};
 	struct rpc_message msg = {
 		.rpc_argp	= &args,
 		.rpc_resp	= res,
 	};
 
-	clnt = nsm_create(net);
-	if (IS_ERR(clnt)) {
-		status = PTR_ERR(clnt);
-		dprintk("lockd: failed to create NSM upcall transport, "
-				"status=%d\n", status);
-		goto out;
-	}
+	BUG_ON(clnt == NULL);
 
 	memset(res, 0, sizeof(*res));
 
@@ -166,8 +158,6 @@ static int nsm_mon_unmon(struct nsm_hand
 				status);
 	else
 		status = 0;
-	rpc_shutdown_client(clnt);
- out:
 	return status;
 }
 
@@ -187,6 +177,7 @@ int nsm_monitor(const struct nlm_host *h
 	struct nsm_handle *nsm = host->h_nsmhandle;
 	struct nsm_res	res;
 	int		status;
+	struct rpc_clnt *clnt;
 
 	dprintk("lockd: nsm_monitor(%s)\n", nsm->sm_name);
 
@@ -199,7 +190,15 @@ int nsm_monitor(const struct nlm_host *h
 	 */
 	nsm->sm_mon_name = nsm_use_hostnames ? nsm->sm_name : nsm->sm_addrbuf;
 
-	status = nsm_mon_unmon(nsm, NSMPROC_MON, &res, host->net);
+	clnt = nsm_client_get(host->net);
+	if (IS_ERR(clnt)) {
+		status = PTR_ERR(clnt);
+		dprintk("lockd: failed to create NSM upcall transport, "
+				"status=%d, net=%p\n", status, host->net);
+		return status;
+	}
+
+	status = nsm_mon_unmon(nsm, NSMPROC_MON, &res, clnt);
 	if (unlikely(res.status != 0))
 		status = -EIO;
 	if (unlikely(status < 0)) {
@@ -231,9 +230,11 @@ void nsm_unmonitor(const struct nlm_host
 
 	if (atomic_read(&nsm->sm_count) == 1
 	 && nsm->sm_monitored && !nsm->sm_sticky) {
+		struct lockd_net *ln = net_generic(host->net, lockd_net_id);
+
 		dprintk("lockd: nsm_unmonitor(%s)\n", nsm->sm_name);
 
-		status = nsm_mon_unmon(nsm, NSMPROC_UNMON, &res, host->net);
+		status = nsm_mon_unmon(nsm, NSMPROC_UNMON, &res, ln->nsm_clnt);
 		if (res.status != 0)
 			status = -EIO;
 		if (status < 0)
@@ -241,6 +242,8 @@ void nsm_unmonitor(const struct nlm_host
 					nsm->sm_name);
 		else
 			nsm->sm_monitored = 0;
+
+		nsm_client_put(host->net);
 	}
 }