On 10/6/20 1:41 PM, Gabriel Krisman Bertazi wrote:
> 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.
Applied, thanks.
--
Jens Axboe
