[patch 04/47] lockd: fix regression in lockds handling of blockedlocks

[Greg KH]

2.6.27-stable review patch.  If anyone has any objections, please let us know.

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

From: J. Bruce Fields <bfields@xxxxxxxxxxxxxx>

commit 9d9b87c1218be78ddecbc85ec3bb91c79c1d56ab upstream.

If a client requests a blocking lock, is denied, then requests it again,
then here in nlmsvc_lock() we will call vfs_lock_file() without FL_SLEEP
set, because we've already queued a block and don't need the locks code
to do it again.

But that means vfs_lock_file() will return -EAGAIN instead of
FILE_LOCK_DENIED.  So we still need to translate that -EAGAIN return
into a nlm_lck_blocked error in this case, and put ourselves back on
lockd's block list.

The bug was introduced by bde74e4bc64415b1 "locks: add special return
value for asynchronous locks".

Thanks to Frank van Maarseveen for the report; his original test
case was essentially

	for i in `seq 30`; do flock /nfsmount/foo sleep 10 & done

Tested-by: Frank van Maarseveen <frankvm@xxxxxxxxxxx>
Reported-by: Frank van Maarseveen <frankvm@xxxxxxxxxxx>
Cc: Miklos Szeredi <mszeredi@xxxxxxx>
Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 fs/lockd/svclock.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/fs/lockd/svclock.c
+++ b/fs/lockd/svclock.c
@@ -418,7 +418,7 @@ nlmsvc_lock(struct svc_rqst *rqstp, stru
 			goto out;
 		case -EAGAIN:
 			ret = nlm_lck_denied;
-			goto out;
+			break;
 		case FILE_LOCK_DEFERRED:
 			if (wait)
 				break;
@@ -434,6 +434,10 @@ nlmsvc_lock(struct svc_rqst *rqstp, stru
 			goto out;
 	}
 
+	ret = nlm_lck_denied;
+	if (!wait)
+		goto out;
+
 	ret = nlm_lck_blocked;
 
 	/* Append to list of blocked */

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