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    Subject[PATCH 5.7 160/166] blk-mq: consider non-idle request as "inflight" in blk_mq_rq_inflight()
    Date
    From: Ming Lei <ming.lei@redhat.com>

    commit 05a4fed69ff00a8bd83538684cb602a4636b07a7 upstream.

    dm-multipath is the only user of blk_mq_queue_inflight(). When
    dm-multipath calls blk_mq_queue_inflight() to check if it has
    outstanding IO it can get a false negative. The reason for this is
    blk_mq_rq_inflight() doesn't consider requests that are no longer
    MQ_RQ_IN_FLIGHT but that are now MQ_RQ_COMPLETE (->complete isn't
    called or finished yet) as "inflight".

    This causes request-based dm-multipath's dm_wait_for_completion() to
    return before all outstanding dm-multipath requests have actually
    completed. This breaks DM multipath's suspend functionality because
    blk-mq requests complete after DM's suspend has finished -- which
    shouldn't happen.

    Fix this by considering any request not in the MQ_RQ_IDLE state
    (so either MQ_RQ_COMPLETE or MQ_RQ_IN_FLIGHT) as "inflight" in
    blk_mq_rq_inflight().

    Fixes: 3c94d83cb3526 ("blk-mq: change blk_mq_queue_busy() to blk_mq_queue_inflight()")
    Signed-off-by: Ming Lei <ming.lei@redhat.com>
    Signed-off-by: Mike Snitzer <snitzer@redhat.com>
    Cc: stable@vger.kernel.org
    Signed-off-by: Jens Axboe <axboe@kernel.dk>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    block/blk-mq.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    --- a/block/blk-mq.c
    +++ b/block/blk-mq.c
    @@ -803,10 +803,10 @@ static bool blk_mq_rq_inflight(struct bl
    void *priv, bool reserved)
    {
    /*
    - * If we find a request that is inflight and the queue matches,
    + * If we find a request that isn't idle and the queue matches,
    * we know the queue is busy. Return false to stop the iteration.
    */
    - if (rq->state == MQ_RQ_IN_FLIGHT && rq->q == hctx->queue) {
    + if (blk_mq_request_started(rq) && rq->q == hctx->queue) {
    bool *busy = priv;

    *busy = true;

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