NFSv4.1: Fix bug only first CB_NOTIFY_LOCK is handled

When a waiter is waked by CB_NOTIFY_LOCK, it will retry
nfs4_proc_setlk(). The waiter may fail to nfs4_proc_setlk() and sleep
again. However, the waiter is already removed from clp->cl_lock_waitq
when handling CB_NOTIFY_LOCK in nfs4_wake_lock_waiter(). So any
subsequent CB_NOTIFY_LOCK won't wake this waiter anymore. We should
put the waiter back to clp->cl_lock_waitq before retrying.

Cc: stable@vger.kernel.org #4.9+
Signed-off-by: Yihao Wu <wuyihao@linux.alibaba.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

fs/nfs/nfs4proc.c

@@ -6987,20 +6987,22 @@ nfs4_retry_setlk(struct nfs4_state *state, int cmd, struct file_lock *request)
 	init_wait(&wait);
 	wait.private = &waiter;
 	wait.func = nfs4_wake_lock_waiter;
-	add_wait_queue(q, &wait);
 
 	while(!signalled()) {
+		add_wait_queue(q, &wait);
 		status = nfs4_proc_setlk(state, cmd, request);
-		if ((status != -EAGAIN) || IS_SETLK(cmd))
+		if ((status != -EAGAIN) || IS_SETLK(cmd)) {
+			finish_wait(q, &wait);
 			break;
+		}
 
 		status = -ERESTARTSYS;
 		freezer_do_not_count();
 		wait_woken(&wait, TASK_INTERRUPTIBLE, NFS4_LOCK_MAXTIMEOUT);
 		freezer_count();
+		finish_wait(q, &wait);
 	}
 
-	finish_wait(q, &wait);
 	return status;
 }
 #else /* !CONFIG_NFS_V4_1 */