Commit 632bfb63 authored by yangerkun's avatar yangerkun Committed by Jens Axboe
Browse files

blk-mq: call commit_rqs while list empty but error happen 



Blk-mq should call commit_rqs once 'bd.last != true' and no more
request will come(so virtscsi can kick the virtqueue, e.g.). We already
do that in 'blk_mq_dispatch_rq_list/blk_mq_try_issue_list_directly' while
list not empty and 'queued > 0'. However, we can seen the same scene
once the last request in list call queue_rq and return error like
BLK_STS_IOERR which will not requeue the request, and lead that list
empty but need call commit_rqs too(Or the request for virtscsi will stay
timeout until other request kick virtqueue).

We found this problem by do fsstress test with offline/online virtscsi
device repeat quickly.

Fixes: d666ba98 ("blk-mq: add mq_ops->commit_rqs()")
Reported-by: default avatarzhangyi (F) <yi.zhang@huawei.com>
Signed-off-by: default avataryangerkun <yangerkun@huawei.com>
Reviewed-by: default avatarMing Lei <ming.lei@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 3aab9177

block/blk-mq.c

+9 −9
Original line number Diff line number Diff line
@@ -1412,6 +1412,11 @@ out: 


	hctx->dispatched[queued_to_index(queued)]++;



	/* If we didn't flush the entire list, we could have told the driver

	 * there was more coming, but that turned out to be a lie.

	 */

	if ((!list_empty(list) || errors) && q->mq_ops->commit_rqs && queued)

		q->mq_ops->commit_rqs(hctx);

	/*

	 * Any items that need requeuing? Stuff them into hctx->dispatch,

	 * that is where we will continue on next queue run.
@@ -1425,14 +1430,6 @@ out: 


		blk_mq_release_budgets(q, nr_budgets);



		/*

		 * If we didn't flush the entire list, we could have told

		 * the driver there was more coming, but that turned out to

		 * be a lie.

		 */

		if (q->mq_ops->commit_rqs && queued)

			q->mq_ops->commit_rqs(hctx);



		spin_lock(&hctx->lock);

		list_splice_tail_init(list, &hctx->dispatch);

		spin_unlock(&hctx->lock);
@@ -2079,6 +2076,7 @@ void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx, 
		struct list_head *list)

{

	int queued = 0;

	int errors = 0;



	while (!list_empty(list)) {

		blk_status_t ret;
@@ -2095,6 +2093,7 @@ void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx, 
				break;

			}

			blk_mq_end_request(rq, ret);

			errors++;

		} else

			queued++;

	}
@@ -2104,7 +2103,8 @@ void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx, 
	 * the driver there was more coming, but that turned out to

	 * be a lie.

	 */

	if (!list_empty(list) && hctx->queue->mq_ops->commit_rqs && queued)

	if ((!list_empty(list) || errors) &&

	     hctx->queue->mq_ops->commit_rqs && queued)

		hctx->queue->mq_ops->commit_rqs(hctx);

}

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