Re: [PATCH 2/6] SCSI: use blk_mq_run_hw_queues() in scsi_kick_queue()

On Tue, Jul 11, 2017 at 07:57:53PM +0000, Bart Van Assche wrote:

On Wed, 2017-07-12 at 02:20 +0800, Ming Lei wrote:

quoted

Now SCSI won't stop queue, and not necessary to use
blk_mq_start_hw_queues(), so switch to blk_mq_run_hw_queues()
instead.

Cc: "James E.J. Bottomley" <redacted>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: linux-scsi@vger.kernel.org
Signed-off-by: Ming Lei <redacted>
---
 drivers/scsi/scsi_lib.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index f6097b89d5d3..91d890356b78 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c

@@ -333,7 +333,7 @@ void scsi_device_unbusy(struct scsi_device *sdev)
 static void scsi_kick_queue(struct request_queue *q)
 {
 	if (q->mq_ops)
-		blk_mq_start_hw_queues(q);
+		blk_mq_run_hw_queues(q, false);
 	else
 		blk_run_queue(q);
 }

Hello Ming,

Now that we have separate flags to represent the "stopped" and "quiesced"
states, wouldn't it be better not to modify scsi_kick_queue() but instead to
stop a SCSI hardware queue again if scsi_queue_rq() returns BLK_STS_RESOURCE?
See also commits 36e3cf273977 ("scsi: Avoid that SCSI queues get stuck") and
commit 52d7f1b5c2f3 ("blk-mq: Avoid that requeueing starts stopped queues").

As you can see in the following patches, all stop/start queue APIs will
be removed, and the 'stopped' state will become a internal state.

It doesn't make sense to clear 'stopped' for scsi anymore, since the
queue won't be stopped actually. So we need this change.

-- 
Ming