[patch 15/48] lockd: fix regression in lockds handling of blocked locks

Greg KH
2009-02-14T01:34:20Z

[-- Attachment #1: lockd-fix-regression-in-lockd-s-handling-of-blocked-locks.patch --]
[-- Type: text/plain, Size: 1698 bytes --]

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

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

From: J. Bruce Fields <bfields@citi.umich.edu>

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@frankvm.com>
Reported-by: Frank van Maarseveen <frankvm@frankvm.com>
Cc: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

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

--- a/fs/lockd/svclock.c
+++ b/fs/lockd/svclock.c
@@ -427,7 +427,7 @@ 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;
@@ -443,6 +443,10 @@ 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 */