When I use dd test a SCSI device which use blk-mq in the following steps:
1.echo "blocked" >/sys/block/sda/device/state
2.dd if=/dev/sda of=/mnt/t.log bs=1M count=10
3.echo "running" >/sys/block/sda/device/state
dd should finish this work after step 3, unfortunately, still hung.
After step2, the key code process is like this:
blk_mq_dispatch_rq_list-->scsi_queue_rq-->prep_to_mq
-->if ret is BLK_STS_RESOURCE, delay run hw queue
prep_to_mq will return BLK_STS_RESOURCE, and scsi_queue_rq will transter
it to BLK_STS_DEV_RESOURCE. In this situtation, we should delay run hw
queue. This patch fixes that.
Fixes: 86ff7c2a80cd ("blk-mq: introduce BLK_STS_DEV_RESOURCE")
Signed-off-by: zhengbin <zhengbin13@xxxxxxxxxx>
---
block/blk-mq.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index a9c1816..556d606 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1309,15 +1309,17 @@ bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list,
* returning BLK_STS_RESOURCE. Two exceptions are scsi-mq
* and dm-rq.
*
- * If driver returns BLK_STS_RESOURCE and SCHED_RESTART
- * bit is set, run queue after a delay to avoid IO stalls
- * that could otherwise occur if the queue is idle.
+ * If driver returns BLK_STS_RESOURCE or BLK_STS_DEV_RESOURCE
+ * and SCHED_RESTART bit is set, run queue after a delay to
+ * avoid IO stalls that could otherwise occur if the queue
+ * is idle.
*/
needs_restart = blk_mq_sched_needs_restart(hctx);
if (!needs_restart ||
(no_tag && list_empty_careful(&hctx->dispatch_wait.entry)))
blk_mq_run_hw_queue(hctx, true);
- else if (needs_restart && (ret == BLK_STS_RESOURCE))
+ else if (needs_restart && ((ret == BLK_STS_RESOURCE) ||
+ (ret == BLK_STS_DEV_RESOURCE)))
blk_mq_delay_run_hw_queue(hctx, BLK_MQ_RESOURCE_DELAY);
blk_mq_update_dispatch_busy(hctx, true);
--
2.7.4
