From: Jeff Layton <jlayton@redhat.com>
Date: Wed, 18 Mar 2009 13:09:26 -0400
Subject: [fs] lockd: reference count leaks in async locking case
Message-id: 1237396166-12311-1-git-send-email-jlayton@redhat.com
O-Subject: [RHEL5.4 PATCH] BZ#471254: lockd: fix reference count leaks in async locking case
Bugzilla: 471254
RH-Acked-by: Peter Staubach <staubach@redhat.com>

This patch fixes a reference count leak in lockd when async locking is
used. To reproduce this problem, I simply exported a GFS2 filesystem
via NFS and then had a client do a bunch of non-blocking locks and
unlocks in a tight loop.

After that, I unexported the filesystem and then tried to unmount it,
but it was busy. I also got the telltale printk:

    lockd: couldn't shutdown host module!

...which generally indicates reference counting problems.

The following patch from upstream fixes the above reproducer.

------------------[snip]-------------------

In a number of places where we wish only to translate nlm_drop_reply to
rpc_drop_reply errors we instead return early with rpc_drop_reply,
skipping some important end-of-function cleanup.

This results in reference count leaks when lockd is doing posix locking
on GFS2.

Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

diff --git a/fs/lockd/svc4proc.c b/fs/lockd/svc4proc.c
index 236b211..ba8e9df 100644
--- a/fs/lockd/svc4proc.c
+++ b/fs/lockd/svc4proc.c
@@ -87,6 +87,7 @@ nlm4svc_proc_test(struct svc_rqst *rqstp, struct nlm_args *argp,
 {
 	struct nlm_host	*host;
 	struct nlm_file	*file;
+	int rc = rpc_success;
 
 	dprintk("lockd: TEST4        called\n");
 	resp->cookie = argp->cookie;
@@ -94,7 +95,7 @@ nlm4svc_proc_test(struct svc_rqst *rqstp, struct nlm_args *argp,
 	/* Don't accept test requests during grace period */
 	if (nlmsvc_grace_period) {
 		resp->status = nlm_lck_denied_grace_period;
-		return rpc_success;
+		return rc;
 	}
 
 	/* Obtain client and file */
@@ -106,12 +107,13 @@ nlm4svc_proc_test(struct svc_rqst *rqstp, struct nlm_args *argp,
 	resp->status = nlmsvc_testlock(rqstp, file, host, &argp->lock,
 				       &resp->lock, &resp->cookie);
 	if (resp->status == nlm_drop_reply)
-		return rpc_drop_reply;
+		rc = rpc_drop_reply;
+	else
+		dprintk("lockd: TEST4        status %d\n", ntohl(resp->status));
 
-	dprintk("lockd: TEST4          status %d\n", ntohl(resp->status));
 	nlm_release_host(host);
 	nlm_release_file(file);
-	return rpc_success;
+	return rc;
 }
 
 static int
@@ -120,6 +122,7 @@ nlm4svc_proc_lock(struct svc_rqst *rqstp, struct nlm_args *argp,
 {
 	struct nlm_host	*host;
 	struct nlm_file	*file;
+	int rc = rpc_success;
 
 	dprintk("lockd: LOCK          called\n");
 
@@ -128,7 +131,7 @@ nlm4svc_proc_lock(struct svc_rqst *rqstp, struct nlm_args *argp,
 	/* Don't accept new lock requests during grace period */
 	if (nlmsvc_grace_period && !argp->reclaim) {
 		resp->status = nlm_lck_denied_grace_period;
-		return rpc_success;
+		return rc;
 	}
 
 	/* Obtain client and file */
@@ -152,12 +155,13 @@ nlm4svc_proc_lock(struct svc_rqst *rqstp, struct nlm_args *argp,
 	resp->status = nlmsvc_lock(rqstp, file, host, &argp->lock,
 					argp->block, &argp->cookie);
 	if (resp->status == nlm_drop_reply)
-		return rpc_drop_reply;
+		rc = rpc_drop_reply;
+	else
+		dprintk("lockd: LOCK         status %d\n", ntohl(resp->status));
 
-	dprintk("lockd: LOCK          status %d\n", ntohl(resp->status));
 	nlm_release_host(host);
 	nlm_release_file(file);
-	return rpc_success;
+	return rc;
 }
 
 static int
diff --git a/fs/lockd/svcproc.c b/fs/lockd/svcproc.c
index 46cf060..aeb8f64 100644
--- a/fs/lockd/svcproc.c
+++ b/fs/lockd/svcproc.c
@@ -116,6 +116,7 @@ nlmsvc_proc_test(struct svc_rqst *rqstp, struct nlm_args *argp,
 {
 	struct nlm_host	*host;
 	struct nlm_file	*file;
+	int rc = rpc_success;
 
 	dprintk("lockd: TEST          called\n");
 	resp->cookie = argp->cookie;
@@ -123,7 +124,7 @@ nlmsvc_proc_test(struct svc_rqst *rqstp, struct nlm_args *argp,
 	/* Don't accept test requests during grace period */
 	if (nlmsvc_grace_period) {
 		resp->status = nlm_lck_denied_grace_period;
-		return rpc_success;
+		return rc;
 	}
 
 	/* Obtain client and file */
@@ -135,13 +136,14 @@ nlmsvc_proc_test(struct svc_rqst *rqstp, struct nlm_args *argp,
 	resp->status = cast_status(nlmsvc_testlock(rqstp, file, host,
 				   &argp->lock, &resp->lock, &resp->cookie));
 	if (resp->status == nlm_drop_reply)
-		return rpc_drop_reply;
+		rc = rpc_drop_reply;
+	else
+		dprintk("lockd: TEST          status %d vers %d\n",
+			ntohl(resp->status), rqstp->rq_vers);
 
-	dprintk("lockd: TEST          status %d vers %d\n",
-		ntohl(resp->status), rqstp->rq_vers);
 	nlm_release_host(host);
 	nlm_release_file(file);
-	return rpc_success;
+	return rc;
 }
 
 static int
@@ -150,6 +152,7 @@ nlmsvc_proc_lock(struct svc_rqst *rqstp, struct nlm_args *argp,
 {
 	struct nlm_host	*host;
 	struct nlm_file	*file;
+	int rc = rpc_success;
 
 	dprintk("lockd: LOCK          called\n");
 
@@ -158,7 +161,7 @@ nlmsvc_proc_lock(struct svc_rqst *rqstp, struct nlm_args *argp,
 	/* Don't accept new lock requests during grace period */
 	if (nlmsvc_grace_period && !argp->reclaim) {
 		resp->status = nlm_lck_denied_grace_period;
-		return rpc_success;
+		return rc;
 	}
 
 	/* Obtain client and file */
@@ -182,12 +185,13 @@ nlmsvc_proc_lock(struct svc_rqst *rqstp, struct nlm_args *argp,
 	resp->status = cast_status(nlmsvc_lock(rqstp, file, host, &argp->lock,
 					       argp->block, &argp->cookie));
 	if (resp->status == nlm_drop_reply)
-		return rpc_drop_reply;
+		rc = rpc_drop_reply;
+	else
+		dprintk("lockd: LOCK         status %d\n", ntohl(resp->status));
 
-	dprintk("lockd: LOCK          status %d\n", ntohl(resp->status));
 	nlm_release_host(host);
 	nlm_release_file(file);
-	return rpc_success;
+	return rc;
 }
 
 static int