From: yangerkun yangerkun@huawei.com
[ Upstream commit 632bfb6323799c087fcb4108dfe59518609667a7 ]
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: d666ba98f849 ("blk-mq: add mq_ops->commit_rqs()") Reported-by: zhangyi (F) yi.zhang@huawei.com Signed-off-by: yangerkun yangerkun@huawei.com Reviewed-by: Ming Lei ming.lei@redhat.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- block/blk-mq.c | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c index a366726094a89..8e623e0282757 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1304,6 +1304,11 @@ bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list,
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. @@ -1311,14 +1316,6 @@ bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list, if (!list_empty(list)) { bool needs_restart;
- /* - * 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); @@ -1971,6 +1968,7 @@ 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; @@ -1987,6 +1985,7 @@ void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx, break; } blk_mq_end_request(rq, ret); + errors++; } else queued++; } @@ -1996,7 +1995,8 @@ 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); }