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blk-mq: don't grab rq's refcount in blk_mq_check_expired() 

Inside blk_mq_queue_tag_busy_iter() we already grabbed request's
refcount before calling ->fn(), so needn't to grab it one more time
in blk_mq_check_expired().

Meantime remove extra request expire check in blk_mq_check_expired().

Cc: Keith Busch <kbusch@kernel.org>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: John Garry <john.garry@huawei.com>
Link: https://lore.kernel.org/r/20210811155202.629575-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Ming Lei 2021-08-11 23:52:02 +08:00 committed by Jens Axboe
parent cddce01160
commit c797b40ccc
1 changed files with 5 additions and 25 deletions
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30
block/blk-mq.c
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@ -923,34 +923,14 @@ static bool blk_mq_check_expired(struct blk_mq_hw_ctx *hctx,
unsigned long *next = priv;
/*
* Just do a quick check if it is expired before locking the request in
* so we're not unnecessarilly synchronizing across CPUs.
*/
if (!blk_mq_req_expired(rq, next))
return true;
/*
* We have reason to believe the request may be expired. Take a
* reference on the request to lock this request lifetime into its
* currently allocated context to prevent it from being reallocated in
* the event the completion by-passes this timeout handler.
*
* If the reference was already released, then the driver beat the
* timeout handler to posting a natural completion.
*/
if (!refcount_inc_not_zero(&rq->ref))
return true;
/*
* The request is now locked and cannot be reallocated underneath the
* timeout handler's processing. Re-verify this exact request is truly
* expired; if it is not expired, then the request was completed and
* reallocated as a new request.
* blk_mq_queue_tag_busy_iter() has locked the request, so it cannot
* be reallocated underneath the timeout handler's processing, then
* the expire check is reliable. If the request is not expired, then
* it was completed and reallocated as a new request after returning
* from blk_mq_check_expired().
*/
if (blk_mq_req_expired(rq, next))
blk_mq_rq_timed_out(rq, reserved);
blk_mq_put_rq_ref(rq);
return true;
}