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    Subject[PATCH 5.4 055/411] nbd: Fix hung on disconnect request if socket is closed before
    Date
    From: Xie Yongji <xieyongji@bytedance.com>

    [ Upstream commit 491bf8f236fdeec698fa6744993f1ecf3fafd1a5 ]

    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: Xu Jianhai <zero.xu@bytedance.com>
    Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
    Reviewed-by: Josef Bacik <josef@toxicpanda.com>
    Link: https://lore.kernel.org/r/20220322080639.142-1-xieyongji@bytedance.com
    Signed-off-by: Jens Axboe <axboe@kernel.dk>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/block/nbd.c | 13 +++++++++----
    1 file changed, 9 insertions(+), 4 deletions(-)

    diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
    index 25e81b1a59a5..510e75435c43 100644
    --- a/drivers/block/nbd.c
    +++ b/drivers/block/nbd.c
    @@ -865,11 +865,15 @@ 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)
    @@ -2014,6 +2018,7 @@ 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
    --
    2.35.1


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