lockd: fix regression in lockd's handling of blocked locks

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>

diff --git a/fs/lockd/svclock.c b/fs/lockd/svclock.c
index 6063a8e..763b78a 100644 (file)
--- a/fs/lockd/svclock.c
+++ b/fs/lockd/svclock.c
@@ -427,7 +427,7 @@ nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
                        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, struct nlm_file *file,
                        goto out;
        }
 
+       ret = nlm_lck_denied;
+       if (!wait)
+               goto out;
+
        ret = nlm_lck_blocked;
 
        /* Append to list of blocked */