Re: [PATCH v4 5/6] scsi: Avoid that SCSI queues get stuck

[Christoph Hellwig]

Looks good,

Reviewed-by: Christoph Hellwig 

[PATCH v4 5/6] scsi: Avoid that SCSI queues get stuck

[Bart Van Assche]

If a .queue_rq() function returns BLK_MQ_RQ_QUEUE_BUSY then the block
driver that implements that function is responsible for rerunning the
hardware queue once requests can be queued again successfully.

commit 52d7f1b5c2f3 ("blk-mq: Avoid that requeueing starts stopped
queues") removed the blk_mq_stop_hw_queue() call from scsi_queue_rq()
for the BLK_MQ_RQ_QUEUE_BUSY case. Hence change all calls to functions
that are intended to rerun a busy queue such that these examine all
hardware queues instead of only stopped queues.

Since no other functions than scsi_internal_device_block() and
scsi_internal_device_unblock() should ever stop or restart a SCSI
queue, change the blk_mq_delay_queue() call into a
blk_mq_delay_run_hw_queue() call.

Fixes: commit 52d7f1b5c2f3 ("blk-mq: Avoid that requeueing starts stopped 
queues")
Fixes: commit 7e79dadce222 ("blk-mq: stop hardware queue in 
blk_mq_delay_queue()")
Signed-off-by: Bart Van Assche 
Cc: Martin K. Petersen 
Cc: James Bottomley 
Cc: Christoph Hellwig 
Cc: Hannes Reinecke 
Cc: Sagi Grimberg 
Cc: Long Li 
Cc: K. Y. Srinivasan 
---
 drivers/scsi/scsi_lib.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 11972d1075f1..7bc4513bf4e4 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -496,7 +496,7 @@ static void scsi_run_queue(struct request_queue *q)
scsi_starved_list_run(sdev->host);
 
if (q->mq_ops)
-   blk_mq_start_stopped_hw_queues(q, false);
+   blk_mq_run_hw_queues(q, false);
else
blk_run_queue(q);
 }
@@ -667,7 +667,7 @@ static bool scsi_end_request(struct request *req, int error,
!list_empty(>host->starved_list))
kblockd_schedule_work(>requeue_work);
else
-   blk_mq_start_stopped_hw_queues(q, true);
+   blk_mq_run_hw_queues(q, true);
} else {
unsigned long flags;
 
@@ -1974,7 +1974,7 @@ static int scsi_queue_rq(struct blk_mq_hw_ctx *hctx,
case BLK_MQ_RQ_QUEUE_BUSY:
if (atomic_read(>device_busy) == 0 &&
!scsi_device_blocked(sdev))
-   blk_mq_delay_queue(hctx, SCSI_QUEUE_DELAY);
+   blk_mq_delay_run_hw_queue(hctx, SCSI_QUEUE_DELAY);
break;
case BLK_MQ_RQ_QUEUE_ERROR:
/*
-- 
2.12.0