Re: [PATCH v2 3/8] blk-mq: use the introduced blk_mq_unquiesce_queue()

Ming Lei
2017-05-31T02:28:14Z

On Tue, May 30, 2017 at 12:04:02PM -0700, Eduardo Valentin wrote:
> On Sat, May 27, 2017 at 10:21:21PM +0800, Ming Lei wrote:
> > blk_mq_unquiesce_queue() is used for unquiescing the
> > queue explicitly, so replace blk_mq_start_stopped_hw_queues()
> > with it.
> >
> > Cc: linux-nvme@lists.infradead.org
> > Cc: linux-scsi@vger.kernel.org
> > Cc: dm-devel@redhat.com
> > Signed-off-by: Ming Lei <ming.lei@redhat.com>
> > ---
> > drivers/md/dm-rq.c | 2 +-
> > drivers/nvme/host/core.c | 2 +-
> > drivers/scsi/scsi_lib.c | 5 ++++-
> > 3 files changed, 6 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
> > index 2af27026aa2e..673fcf075077 100644
> > --- a/drivers/md/dm-rq.c
> > +++ b/drivers/md/dm-rq.c
> > @@ -71,7 +71,7 @@ static void dm_old_start_queue(struct request_queue *q)
> >
> > static void dm_mq_start_queue(struct request_queue *q)
> > {
> > - blk_mq_start_stopped_hw_queues(q, true);
> > + blk_mq_unquiesce_queue(q);
> > blk_mq_kick_requeue_list(q);
> > }
> >
> > diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> > index 04e115834702..231d36028afc 100644
> > --- a/drivers/nvme/host/core.c
> > +++ b/drivers/nvme/host/core.c
> > @@ -2514,7 +2514,7 @@ void nvme_start_queues(struct nvme_ctrl *ctrl)
> >
> > mutex_lock(&ctrl->namespaces_mutex);
> > list_for_each_entry(ns, &ctrl->namespaces, list) {
> > - blk_mq_start_stopped_hw_queues(ns->queue, true);
> > + blk_mq_unquiesce_queue(ns->queue);
> > blk_mq_kick_requeue_list(ns->queue);
> > }
> > mutex_unlock(&ctrl->namespaces_mutex);
> > diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> > index 814a4bd8405d..72b11f75719c 100644
> > --- a/drivers/scsi/scsi_lib.c
> > +++ b/drivers/scsi/scsi_lib.c
> > @@ -3030,7 +3030,10 @@ scsi_internal_device_unblock(struct scsi_device *sdev,
> > return -EINVAL;
> >
> > if (q->mq_ops) {
> > - blk_mq_start_stopped_hw_queues(q, false);
> > + if (blk_queue_quiesced(q))
> > + blk_mq_unquiesce_queue(q);
>
> Calling this here, at this point means:
> blk_mq_start_stopped_hw_queues(q, true);
>
> Does it make a difference, given that before the code always calling
> blk_mq_start_stopped_hw_queues(q, false);

Good catch, it should have been:

if (blk_queue_quiesced(q))
blk_mq_unquiesce_queue(q);
else
blk_mq_start_stopped_hw_queues(q, false);

Thanks,
Ming