* [PATCH AUTOSEL 5.14 05/34] blk-mq: avoid to iterate over stale request
[not found] <20210923033823.1420814-1-sashal@kernel.org>
@ 2021-09-23 3:37 ` Sasha Levin
0 siblings, 0 replies; only message in thread
From: Sasha Levin @ 2021-09-23 3:37 UTC (permalink / raw)
To: linux-kernel, stable
Cc: Ming Lei, linux-scsi, Martin K. Petersen, luojiaxing, Jens Axboe,
Sasha Levin, linux-block
From: Ming Lei <ming.lei@redhat.com>
[ Upstream commit 67f3b2f822b7e71cfc9b42dbd9f3144fa2933e0b ]
blk-mq can't run allocating driver tag and updating ->rqs[tag]
atomically, meantime blk-mq doesn't clear ->rqs[tag] after the driver
tag is released.
So there is chance to iterating over one stale request just after the
tag is allocated and before updating ->rqs[tag].
scsi_host_busy_iter() calls scsi_host_check_in_flight() to count scsi
in-flight requests after scsi host is blocked, so no new scsi command can
be marked as SCMD_STATE_INFLIGHT. However, driver tag allocation still can
be run by blk-mq core. One request is marked as SCMD_STATE_INFLIGHT,
but this request may have been kept in another slot of ->rqs[], meantime
the slot can be allocated out but ->rqs[] isn't updated yet. Then this
in-flight request is counted twice as SCMD_STATE_INFLIGHT. This way causes
trouble in handling scsi error.
Fixes the issue by not iterating over stale request.
Cc: linux-scsi@vger.kernel.org
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Reported-by: luojiaxing <luojiaxing@huawei.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20210906065003.439019-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
block/blk-mq-tag.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 86f87346232a..ff5caeb82542 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -208,7 +208,7 @@ static struct request *blk_mq_find_and_get_req(struct blk_mq_tags *tags,
spin_lock_irqsave(&tags->lock, flags);
rq = tags->rqs[bitnr];
- if (!rq || !refcount_inc_not_zero(&rq->ref))
+ if (!rq || rq->tag != bitnr || !refcount_inc_not_zero(&rq->ref))
rq = NULL;
spin_unlock_irqrestore(&tags->lock, flags);
return rq;
--
2.30.2
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2021-09-23 3:37 ` [PATCH AUTOSEL 5.14 05/34] blk-mq: avoid to iterate over stale request Sasha Levin
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