nbd: Fix hung on disconnect request if socket is closed before

stable inclusion
from stable-v5.10.121
commit 8d33585ffa2ecbfebacc840a3d5b523bd0966e69
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5L6CQ

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8d33585ffa2ecbfebacc840a3d5b523bd0966e69

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

[ Upstream commit 491bf8f2 ]

When userspace closes the socket before sending a disconnect
request, the following I/O requests will be blocked in
wait_for_reconnect() until dead timeout. This will cause the
following disconnect request also hung on blk_mq_quiesce_queue().
That means we have no way to disconnect a nbd device if there
are some I/O requests waiting for reconnecting until dead timeout.
It's not expected. So let's wake up the thread waiting for
reconnecting directly when a disconnect request is sent.
Reported-by: NXu Jianhai <zero.xu@bytedance.com>
Signed-off-by: NXie Yongji <xieyongji@bytedance.com>
Reviewed-by: NJosef Bacik <josef@toxicpanda.com>
Link: https://lore.kernel.org/r/20220322080639.142-1-xieyongji@bytedance.comSigned-off-by: NJens Axboe <axboe@kernel.dk>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
Acked-by: NXie XiuQi <xiexiuqi@huawei.com>

drivers/block/nbd.c

@@ -946,11 +946,15 @@ static int wait_for_reconnect(struct nbd_device *nbd)
 	struct nbd_config *config = nbd->config;
 	if (!config->dead_conn_timeout)
 		return 0;
-	if (test_bit(NBD_RT_DISCONNECTED, &config->runtime_flags))
+
+	if (!wait_event_timeout(config->conn_wait,
+				test_bit(NBD_RT_DISCONNECTED,
+					 &config->runtime_flags) ||
+				atomic_read(&config->live_connections) > 0,
+				config->dead_conn_timeout))
 		return 0;
-	return wait_event_timeout(config->conn_wait,
-				  atomic_read(&config->live_connections) > 0,
-				  config->dead_conn_timeout) > 0;
+
+	return !test_bit(NBD_RT_DISCONNECTED, &config->runtime_flags);
 }
 
 static int nbd_handle_cmd(struct nbd_cmd *cmd, int index)
@@ -2121,6 +2125,7 @@ static void nbd_disconnect_and_put(struct nbd_device *nbd)
 	mutex_lock(&nbd->config_lock);
 	nbd_disconnect(nbd);
 	sock_shutdown(nbd);
+	wake_up(&nbd->config->conn_wait);
 	/*
 	 * Make sure recv thread has finished, so it does not drop the last
 	 * config ref and try to destroy the workqueue from inside the work