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

Ming Lei
2017-07-12T03:15:13Z

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:
> > 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" <jejb@linux.vnet.ibm.com>
> > Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
> > Cc: linux-scsi@vger.kernel.org
> > Signed-off-by: Ming Lei <ming.lei@redhat.com>
> > ---
> > 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