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 c4f2f6c123ae..16ad9e656610 100644 --- a/block/blk-mq-tag.c +++ b/block/blk-mq-tag.c @@ -207,7 +207,7 @@ 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;