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@xxxxxxxxxx> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx> --- V2: - remove extra request expire check as suggested by Keith - modify comment a bit block/blk-mq.c | 30 +++++------------------------- 1 file changed, 5 insertions(+), 25 deletions(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index d2725f94491d..b5237211ccb7 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -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; } -- 2.31.1
