* [PATCH] blk-mq: call commit_rqs while list empty but error happen
@ 2020-09-05 11:21 yangerkun
0 siblings, 0 replies; only message in thread
From: yangerkun @ 2020-09-05 11:21 UTC (permalink / raw
To: axboe; +Cc: linux-block, ming.lei, bvanassche, hch, yi.zhang, yangerkun
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>
---
block/blk-mq.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index b3d2785eefe9..435199979545 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1412,6 +1412,11 @@ bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, 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.
@@ -1430,8 +1435,6 @@ bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *list,
* 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);
@@ -2079,6 +2082,7 @@ 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 +2099,7 @@ 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 +2109,8 @@ 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);
}
--
2.25.4
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2020-09-05 11:21 [PATCH] blk-mq: call commit_rqs while list empty but error happen yangerkun
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