dlm: reject normal unlock when lock is waiting for lookup

Non-forced unlocks should be rejected if the lock is waiting on the
rsb_lookup list for another lock to establish the master node.
Signed-off-by: David Teigland <teigland@redhat.com>

fs/dlm/lock.c

@@ -2110,18 +2110,19 @@ static int validate_unlock_args(struct dlm_lkb *lkb, struct dlm_args *args)
 	/* an lkb may be waiting for an rsb lookup to complete where the
 	   lookup was initiated by another lock */
 
-	if (args->flags & (DLM_LKF_CANCEL | DLM_LKF_FORCEUNLOCK)) {
 	if (!list_empty(&lkb->lkb_rsb_lookup)) {
+		if (args->flags & (DLM_LKF_CANCEL | DLM_LKF_FORCEUNLOCK)) {
 			log_debug(ls, "unlock on rsb_lookup %x", lkb->lkb_id);
 			list_del_init(&lkb->lkb_rsb_lookup);
 			queue_cast(lkb->lkb_resource, lkb,
 				   args->flags & DLM_LKF_CANCEL ?
 				   -DLM_ECANCEL : -DLM_EUNLOCK);
 			unhold_lkb(lkb); /* undoes create_lkb() */
+		}
+		/* caller changes -EBUSY to 0 for CANCEL and FORCEUNLOCK */
 		rv = -EBUSY;
 		goto out;
 	}
-	}
 
 	/* cancel not allowed with another cancel/unlock in progress */