[PATCH] fix queue stalling while barrier sequencing (1bc691d3) · Commits · 戴 / test

If ordered tag isn't supported, request ordering for barrier sequencing is performed by queue draining, which basically hangs the request queue until elv_completed_request() reports completion of all previous fs requests. The condition check in elv_completed_request() was only performed for fs requests. If a special request is queued between the last to-be-drained request and the barrier sequence, draining is never completed and the queue is stalled forever. This patch moves the end-of-draining condition check such that it's performed for all requests. Signed-off-by:

Tejun Heo <htejun@gmail.com> Signed-off-by:

Jens Axboe <axboe@suse.de> Signed-off-by:

Linus Torvalds <torvalds@osdl.org>

block/elevator.c

+10 −10

Original line number	Diff line number	Diff line
		@@ -610,23 +610,23 @@ void elv_completed_request(request_queue_t q, struct request rq)
		* request is released from the driver, io must be done
		*/
		if (blk_account_rq(rq)) {
		struct request *first_rq = list_entry_rq(q->queue_head.next);

		q->in_flight--;
		if (blk_sorted_rq(rq) && e->ops->elevator_completed_req_fn)
		e->ops->elevator_completed_req_fn(q, rq);
		}

		/*
		* Check if the queue is waiting for fs requests to be
		* drained for flush sequence.
		*/
		if (q->ordseq && q->in_flight == 0 &&
		if (unlikely(q->ordseq)) {
		struct request *first_rq = list_entry_rq(q->queue_head.next);
		if (q->in_flight == 0 &&
		blk_ordered_cur_seq(q) == QUEUE_ORDSEQ_DRAIN &&
		blk_ordered_req_seq(first_rq) > QUEUE_ORDSEQ_DRAIN) {
		blk_ordered_complete_seq(q, QUEUE_ORDSEQ_DRAIN, 0);
		q->request_fn(q);
		}

		if (blk_sorted_rq(rq) && e->ops->elevator_completed_req_fn)
		e->ops->elevator_completed_req_fn(q, rq);
		}
		}

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