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    Subject[PATCH AUTOSEL 5.9 103/147] block: Consider only dispatched requests for inflight statistic
    Date
    From: Gabriel Krisman Bertazi <krisman@collabora.com>

    [ Upstream commit a926c7afffcc0f2e35e6acbccb16921bacf34617 ]

    According to Documentation/block/stat.rst, inflight should not include
    I/O requests that are in the queue but not yet dispatched to the device,
    but blk-mq identifies as inflight any request that has a tag allocated,
    which, for queues without elevator, happens at request allocation time
    and before it is queued in the ctx (default case in blk_mq_submit_bio).

    In addition, current behavior is different for queues with elevator from
    queues without it, since for the former the driver tag is allocated at
    dispatch time. A more precise approach would be to only consider
    requests with state MQ_RQ_IN_FLIGHT.

    This effectively reverts commit 6131837b1de6 ("blk-mq: count allocated
    but not started requests in iostats inflight") to consolidate blk-mq
    behavior with itself (elevator case) and with original documentation,
    but it differs from the behavior used by the legacy path.

    This version differs from v1 by using blk_mq_rq_state to access the
    state attribute. Avoid using blk_mq_request_started, which was
    suggested, since we don't want to include MQ_RQ_COMPLETE.

    Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
    Cc: Omar Sandoval <osandov@fb.com>
    Signed-off-by: Jens Axboe <axboe@kernel.dk>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    block/blk-mq.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/block/blk-mq.c b/block/blk-mq.c
    index cdced4aca2e81..fd578a0ea67dc 100644
    --- a/block/blk-mq.c
    +++ b/block/blk-mq.c
    @@ -105,7 +105,7 @@ static bool blk_mq_check_inflight(struct blk_mq_hw_ctx *hctx,
    {
    struct mq_inflight *mi = priv;

    - if (rq->part == mi->part)
    + if (rq->part == mi->part && blk_mq_rq_state(rq) == MQ_RQ_IN_FLIGHT)
    mi->inflight[rq_data_dir(rq)]++;

    return true;
    --
    2.25.1
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