staging: lustre: ldlm: Fix a race during FLock handling

Protect against race where lock could have been just destroyed
due to overlap, in ldlm_process_flock_lock().
Easy reproducer is BULL's NFS Locktests in pthread mode.
(http://nfsv4.bullopensource.org/tools/tests/locktest.php)

Signed-off-by: Bruno Faccini <bruno.faccini@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-1126
Reviewed-on: http://review.whamcloud.com/7134
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/lustre/lustre/ldlm/ldlm_flock.c b/drivers/staging/lustre/lustre/ldlm/ldlm_flock.c
index 3f97e1c..5102d78 100644 (file)
--- a/drivers/staging/lustre/lustre/ldlm/ldlm_flock.c
+++ b/drivers/staging/lustre/lustre/ldlm/ldlm_flock.c
@@ -520,11 +520,6 @@ ldlm_flock_completion_ast(struct ldlm_lock *lock, __u64 flags, void *data)
 granted:
        OBD_FAIL_TIMEOUT(OBD_FAIL_LDLM_CP_CB_WAIT, 10);
 
-       if (lock->l_flags & LDLM_FL_DESTROYED) {
-               LDLM_DEBUG(lock, "client-side enqueue waking up: destroyed");
-               return 0;
-       }
-
        if (lock->l_flags & LDLM_FL_FAILED) {
                LDLM_DEBUG(lock, "client-side enqueue waking up: failed");
                return -EIO;
@@ -534,6 +529,16 @@ granted:
 
        lock_res_and_lock(lock);
 
+       /*
+        * Protect against race where lock could have been just destroyed
+        * due to overlap in ldlm_process_flock_lock().
+        */
+       if (lock->l_flags & LDLM_FL_DESTROYED) {
+               unlock_res_and_lock(lock);
+               LDLM_DEBUG(lock, "client-side enqueue waking up: destroyed");
+               return 0;
+       }
+
        /* ldlm_lock_enqueue() has already placed lock on the granted list. */
        list_del_init(&lock->l_res_link);