[PATCH v3 0/8] correct quiescing in several block drivers

[PATCH v3 0/8] correct quiescing in several block drivers

[Sagi Grimberg]

Before we either iterate on tags we must guarantee that the
hw queues are stopped and no inflight .queue_rq is active.
Thats what blk_mq_quiesce_queue is for, so use it where appropriate.

Note that before we cleanup the request queue, we must unquiesce in
order to guarantee to not block on requests queued during quiescing.

Changes from v2:
- removed admin_q requeue list kick altogether (suggested by Ming)

Changes from v1:
- dropped the xen_blockfront patch, not sure if it was helpful at all
- removed the requeue kick in nvme drivers while making nvme unconditionally
  kick the requeue list when requeuing a request instead of doing so when
  unquiescing the queues. Note that this change was a two step change to
  keep bisection possible.
- fixed possible hangs with unquiescing before cleanup of the request queue
  in mtip32xx and nvme drivers.
- added check that the request started in mtip32xx itration callouts.
- collected review tags.

*** SUBJECT HERE ***

*** BLURB HERE ***

Sagi Grimberg (8):
  nvme-rdma: quiesce/unquiesce admin_q instead of start/stop its hw
    queues
  nvme-fc: quiesce/unquiesce admin_q instead of start/stop its hw queues
  nvme-loop: quiesce/unquiesce admin_q instead of start/stop its hw
    queues
  nvme-pci: quiesce/unquiesce admin_q instead of start/stop its hw
    queues
  nvme: kick requeue list when requeueing a request instead of when
    starting the queues
  nbd: quiesce request queues to make sure no submissions are inflight
  mtip32xx: quiesce request queues to make sure no submissions are
    inflight
  virtio_blk: quiesce/unquiesce live IO when entering PM states

 drivers/block/mtip32xx/mtip32xx.c | 19 +++++++++++++++----
 drivers/block/nbd.c               |  4 ++--
 drivers/block/virtio_blk.c        |  4 ++--
 drivers/nvme/host/core.c          | 19 ++-----------------
 drivers/nvme/host/fc.c            |  5 +++--
 drivers/nvme/host/pci.c           |  6 +++---
 drivers/nvme/host/rdma.c          |  7 ++++---
 drivers/nvme/target/loop.c        |  3 ++-
 8 files changed, 33 insertions(+), 34 deletions(-)

-- 
2.7.4

[PATCH v3 1/8] nvme-rdma: quiesce/unquiesce admin_q instead of start/stop its hw queues

[Sagi Grimberg]

unlike blk_mq_stop_hw_queues and blk_mq_start_stopped_hw_queues
quiescing/unquiescing respects the submission path rcu grace.
Also make sure to kick the requeue list when appropriate.

Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
---
 drivers/nvme/host/rdma.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/nvme/host/rdma.c b/drivers/nvme/host/rdma.c
index cfb22531fc16..f2cf9638b4d2 100644
--- a/drivers/nvme/host/rdma.c
+++ b/drivers/nvme/host/rdma.c
@@ -778,7 +778,7 @@ static void nvme_rdma_error_recovery_work(struct work_struct *work)
 
 	if (ctrl->ctrl.queue_count > 1)
 		nvme_stop_queues(&ctrl->ctrl);
-	blk_mq_stop_hw_queues(ctrl->ctrl.admin_q);
+	blk_mq_quiesce_queue(ctrl->ctrl.admin_q);
 
 	/* We must take care of fastfail/requeue all our inflight requests */
 	if (ctrl->ctrl.queue_count > 1)
@@ -791,7 +791,7 @@ static void nvme_rdma_error_recovery_work(struct work_struct *work)
 	 * queues are not a live anymore, so restart the queues to fail fast
 	 * new IO
 	 */
-	blk_mq_start_stopped_hw_queues(ctrl->ctrl.admin_q, true);
+	blk_mq_unquiesce_queue(ctrl->ctrl.admin_q);
 	nvme_start_queues(&ctrl->ctrl);
 
 	nvme_rdma_reconnect_or_remove(ctrl);
@@ -1636,9 +1636,10 @@ static void nvme_rdma_shutdown_ctrl(struct nvme_rdma_ctrl *ctrl)
 	if (test_bit(NVME_RDMA_Q_LIVE, &ctrl->queues[0].flags))
 		nvme_shutdown_ctrl(&ctrl->ctrl);
 
-	blk_mq_stop_hw_queues(ctrl->ctrl.admin_q);
+	blk_mq_quiesce_queue(ctrl->ctrl.admin_q);
 	blk_mq_tagset_busy_iter(&ctrl->admin_tag_set,
 				nvme_cancel_request, &ctrl->ctrl);
+	blk_mq_unquiesce_queue(ctrl->ctrl.admin_q);
 	nvme_rdma_destroy_admin_queue(ctrl);
 }
 
-- 
2.7.4

Re: [PATCH v3 1/8] nvme-rdma: quiesce/unquiesce admin_q instead of start/stop its hw queues

[Ming Lei]

On Wed, Jul 05, 2017 at 08:00:30PM +0300, Sagi Grimberg wrote:
> unlike blk_mq_stop_hw_queues and blk_mq_start_stopped_hw_queues
> quiescing/unquiescing respects the submission path rcu grace.
> Also make sure to kick the requeue list when appropriate.
> 
> Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
> ---
>  drivers/nvme/host/rdma.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/nvme/host/rdma.c b/drivers/nvme/host/rdma.c
> index cfb22531fc16..f2cf9638b4d2 100644
> --- a/drivers/nvme/host/rdma.c
> +++ b/drivers/nvme/host/rdma.c
> @@ -778,7 +778,7 @@ static void nvme_rdma_error_recovery_work(struct work_struct *work)
>  
>  	if (ctrl->ctrl.queue_count > 1)
>  		nvme_stop_queues(&ctrl->ctrl);
> -	blk_mq_stop_hw_queues(ctrl->ctrl.admin_q);
> +	blk_mq_quiesce_queue(ctrl->ctrl.admin_q);
>  
>  	/* We must take care of fastfail/requeue all our inflight requests */
>  	if (ctrl->ctrl.queue_count > 1)
> @@ -791,7 +791,7 @@ static void nvme_rdma_error_recovery_work(struct work_struct *work)
>  	 * queues are not a live anymore, so restart the queues to fail fast
>  	 * new IO
>  	 */
> -	blk_mq_start_stopped_hw_queues(ctrl->ctrl.admin_q, true);
> +	blk_mq_unquiesce_queue(ctrl->ctrl.admin_q);
>  	nvme_start_queues(&ctrl->ctrl);
>  
>  	nvme_rdma_reconnect_or_remove(ctrl);
> @@ -1636,9 +1636,10 @@ static void nvme_rdma_shutdown_ctrl(struct nvme_rdma_ctrl *ctrl)
>  	if (test_bit(NVME_RDMA_Q_LIVE, &ctrl->queues[0].flags))
>  		nvme_shutdown_ctrl(&ctrl->ctrl);
>  
> -	blk_mq_stop_hw_queues(ctrl->ctrl.admin_q);
> +	blk_mq_quiesce_queue(ctrl->ctrl.admin_q);
>  	blk_mq_tagset_busy_iter(&ctrl->admin_tag_set,
>  				nvme_cancel_request, &ctrl->ctrl);
> +	blk_mq_unquiesce_queue(ctrl->ctrl.admin_q);
>  	nvme_rdma_destroy_admin_queue(ctrl);
>  }
>  
> -- 
> 2.7.4
> 

Reviewed-by: Ming Lei <ming.lei@redhat.com>

-- 
Ming

[PATCH v3 2/8] nvme-fc: quiesce/unquiesce admin_q instead of start/stop its hw queues

[Sagi Grimberg]

unlike blk_mq_stop_hw_queues and blk_mq_start_stopped_hw_queues
quiescing/unquiescing respects the submission path rcu grace.

Also, make sure to unquiesce before cleanup the admin queue.

Reviewed-By: James Smart <james.smart@broadcom.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
---
 drivers/nvme/host/fc.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/host/fc.c b/drivers/nvme/host/fc.c
index 50cc3b2b0e11..8d55e7827932 100644
--- a/drivers/nvme/host/fc.c
+++ b/drivers/nvme/host/fc.c
@@ -1703,6 +1703,7 @@ nvme_fc_ctrl_free(struct kref *ref)
 	list_del(&ctrl->ctrl_list);
 	spin_unlock_irqrestore(&ctrl->rport->lock, flags);
 
+	blk_mq_unquiesce_queue(ctrl->ctrl.admin_q);
 	blk_cleanup_queue(ctrl->ctrl.admin_q);
 	blk_mq_free_tag_set(&ctrl->admin_tag_set);
 
@@ -2321,7 +2322,7 @@ nvme_fc_create_association(struct nvme_fc_ctrl *ctrl)
 		goto out_delete_hw_queue;
 
 	if (ctrl->ctrl.state != NVME_CTRL_NEW)
-		blk_mq_start_stopped_hw_queues(ctrl->ctrl.admin_q, true);
+		blk_mq_unquiesce_queue(ctrl->ctrl.admin_q);
 
 	ret = nvmf_connect_admin_queue(&ctrl->ctrl);
 	if (ret)
@@ -2475,7 +2476,7 @@ nvme_fc_delete_association(struct nvme_fc_ctrl *ctrl)
 	 * use blk_mq_tagset_busy_itr() and the transport routine to
 	 * terminate the exchanges.
 	 */
-	blk_mq_stop_hw_queues(ctrl->ctrl.admin_q);
+	blk_mq_quiesce_queue(ctrl->ctrl.admin_q);
 	blk_mq_tagset_busy_iter(&ctrl->admin_tag_set,
 				nvme_fc_terminate_exchange, &ctrl->ctrl);
 
-- 
2.7.4

Re: [PATCH v3 2/8] nvme-fc: quiesce/unquiesce admin_q instead of start/stop its hw queues

[Ming Lei]

On Wed, Jul 05, 2017 at 08:00:31PM +0300, Sagi Grimberg wrote:
> unlike blk_mq_stop_hw_queues and blk_mq_start_stopped_hw_queues
> quiescing/unquiescing respects the submission path rcu grace.
> 
> Also, make sure to unquiesce before cleanup the admin queue.
> 
> Reviewed-By: James Smart <james.smart@broadcom.com>
> Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
> ---
>  drivers/nvme/host/fc.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/nvme/host/fc.c b/drivers/nvme/host/fc.c
> index 50cc3b2b0e11..8d55e7827932 100644
> --- a/drivers/nvme/host/fc.c
> +++ b/drivers/nvme/host/fc.c
> @@ -1703,6 +1703,7 @@ nvme_fc_ctrl_free(struct kref *ref)
>  	list_del(&ctrl->ctrl_list);
>  	spin_unlock_irqrestore(&ctrl->rport->lock, flags);
>  
> +	blk_mq_unquiesce_queue(ctrl->ctrl.admin_q);
>  	blk_cleanup_queue(ctrl->ctrl.admin_q);
>  	blk_mq_free_tag_set(&ctrl->admin_tag_set);
>  
> @@ -2321,7 +2322,7 @@ nvme_fc_create_association(struct nvme_fc_ctrl *ctrl)
>  		goto out_delete_hw_queue;
>  
>  	if (ctrl->ctrl.state != NVME_CTRL_NEW)
> -		blk_mq_start_stopped_hw_queues(ctrl->ctrl.admin_q, true);
> +		blk_mq_unquiesce_queue(ctrl->ctrl.admin_q);
>  
>  	ret = nvmf_connect_admin_queue(&ctrl->ctrl);
>  	if (ret)
> @@ -2475,7 +2476,7 @@ nvme_fc_delete_association(struct nvme_fc_ctrl *ctrl)
>  	 * use blk_mq_tagset_busy_itr() and the transport routine to
>  	 * terminate the exchanges.
>  	 */
> -	blk_mq_stop_hw_queues(ctrl->ctrl.admin_q);
> +	blk_mq_quiesce_queue(ctrl->ctrl.admin_q);
>  	blk_mq_tagset_busy_iter(&ctrl->admin_tag_set,
>  				nvme_fc_terminate_exchange, &ctrl->ctrl);
>  
> -- 
> 2.7.4
> 

Maybe it is a little better to the blk_mq_unquiesce_queue() before
blk_cleanup_queue() after blk_mq_tagset_busy_iter() in
nvme_fc_delete_association(). But it shouldn't be a big deal.

So looks fine,

	Reviewed-by: Ming Lei <ming.lei@redhat.com>


-- 
Ming

[PATCH v3 3/8] nvme-loop: quiesce/unquiesce admin_q instead of start/stop its hw queues

[Sagi Grimberg]

unlike blk_mq_stop_hw_queues and blk_mq_start_stopped_hw_queues
quiescing/unquiescing respects the submission path rcu grace.

Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
---
 drivers/nvme/target/loop.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/target/loop.c b/drivers/nvme/target/loop.c
index 3d51341e62ee..6a0b70685e77 100644
--- a/drivers/nvme/target/loop.c
+++ b/drivers/nvme/target/loop.c
@@ -434,9 +434,10 @@ static void nvme_loop_shutdown_ctrl(struct nvme_loop_ctrl *ctrl)
 	if (ctrl->ctrl.state == NVME_CTRL_LIVE)
 		nvme_shutdown_ctrl(&ctrl->ctrl);
 
-	blk_mq_stop_hw_queues(ctrl->ctrl.admin_q);
+	blk_mq_quiesce_queue(ctrl->ctrl.admin_q);
 	blk_mq_tagset_busy_iter(&ctrl->admin_tag_set,
 				nvme_cancel_request, &ctrl->ctrl);
+	blk_mq_unquiesce_queue(ctrl->ctrl.admin_q);
 	nvme_loop_destroy_admin_queue(ctrl);
 }
 
-- 
2.7.4

[PATCH v3 4/8] nvme-pci: quiesce/unquiesce admin_q instead of start/stop its hw queues

[Sagi Grimberg]

unlike blk_mq_stop_hw_queues and blk_mq_start_stopped_hw_queues
quiescing/unquiescing respects the submission path rcu grace.

Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
---
 drivers/nvme/host/pci.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index eb729ff70e7d..d9c0010a9bbc 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -1125,7 +1125,7 @@ static int nvme_suspend_queue(struct nvme_queue *nvmeq)
 	spin_unlock_irq(&nvmeq->q_lock);
 
 	if (!nvmeq->qid && nvmeq->dev->ctrl.admin_q)
-		blk_mq_stop_hw_queues(nvmeq->dev->ctrl.admin_q);
+		blk_mq_quiesce_queue(nvmeq->dev->ctrl.admin_q);
 
 	pci_free_irq(to_pci_dev(nvmeq->dev->dev), vector, nvmeq);
 
@@ -1315,7 +1315,7 @@ static void nvme_dev_remove_admin(struct nvme_dev *dev)
 		 * user requests may be waiting on a stopped queue. Start the
 		 * queue to flush these to completion.
 		 */
-		blk_mq_start_stopped_hw_queues(dev->ctrl.admin_q, true);
+		blk_mq_unquiesce_queue(dev->ctrl.admin_q);
 		blk_cleanup_queue(dev->ctrl.admin_q);
 		blk_mq_free_tag_set(&dev->admin_tagset);
 	}
@@ -1352,7 +1352,7 @@ static int nvme_alloc_admin_tags(struct nvme_dev *dev)
 			return -ENODEV;
 		}
 	} else
-		blk_mq_start_stopped_hw_queues(dev->ctrl.admin_q, true);
+		blk_mq_unquiesce_queue(dev->ctrl.admin_q);
 
 	return 0;
 }
-- 
2.7.4

Re: [PATCH v3 4/8] nvme-pci: quiesce/unquiesce admin_q instead of start/stop its hw queues

[Ming Lei]

On Wed, Jul 05, 2017 at 08:00:33PM +0300, Sagi Grimberg wrote:
> unlike blk_mq_stop_hw_queues and blk_mq_start_stopped_hw_queues
> quiescing/unquiescing respects the submission path rcu grace.
> 
> Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
> ---
>  drivers/nvme/host/pci.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
> index eb729ff70e7d..d9c0010a9bbc 100644
> --- a/drivers/nvme/host/pci.c
> +++ b/drivers/nvme/host/pci.c
> @@ -1125,7 +1125,7 @@ static int nvme_suspend_queue(struct nvme_queue *nvmeq)
>  	spin_unlock_irq(&nvmeq->q_lock);
>  
>  	if (!nvmeq->qid && nvmeq->dev->ctrl.admin_q)
> -		blk_mq_stop_hw_queues(nvmeq->dev->ctrl.admin_q);
> +		blk_mq_quiesce_queue(nvmeq->dev->ctrl.admin_q);
>  
>  	pci_free_irq(to_pci_dev(nvmeq->dev->dev), vector, nvmeq);
>  
> @@ -1315,7 +1315,7 @@ static void nvme_dev_remove_admin(struct nvme_dev *dev)
>  		 * user requests may be waiting on a stopped queue. Start the
>  		 * queue to flush these to completion.
>  		 */
> -		blk_mq_start_stopped_hw_queues(dev->ctrl.admin_q, true);
> +		blk_mq_unquiesce_queue(dev->ctrl.admin_q);
>  		blk_cleanup_queue(dev->ctrl.admin_q);
>  		blk_mq_free_tag_set(&dev->admin_tagset);
>  	}
> @@ -1352,7 +1352,7 @@ static int nvme_alloc_admin_tags(struct nvme_dev *dev)
>  			return -ENODEV;
>  		}
>  	} else
> -		blk_mq_start_stopped_hw_queues(dev->ctrl.admin_q, true);
> +		blk_mq_unquiesce_queue(dev->ctrl.admin_q);
>  
>  	return 0;
>  }
> -- 
> 2.7.4
> 

Reviewed-by: Ming Lei <ming.lei@redhat.com>


-- 
Ming

[PATCH v3 5/8] nvme: kick requeue list when requeueing a request instead of when starting the queues

[Sagi Grimberg]

When we requeue a request, we can always insert the request
back to the scheduler instead of doing it when restarting
the queues and kicking the requeue work, so get rid of
the requeue kick in nvme (core and drivers).

Also, now there is no need start hw queues in nvme_kill_queues
We don't stop the hw queues anymore, so no need to
start them.

Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
---
 drivers/nvme/host/core.c | 19 ++-----------------
 1 file changed, 2 insertions(+), 17 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index d70df1d0072d..48cafaa6fbc5 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -131,7 +131,7 @@ void nvme_complete_rq(struct request *req)
 {
 	if (unlikely(nvme_req(req)->status && nvme_req_needs_retry(req))) {
 		nvme_req(req)->retries++;
-		blk_mq_requeue_request(req, !blk_mq_queue_stopped(req->q));
+		blk_mq_requeue_request(req, true);
 		return;
 	}
 
@@ -2694,9 +2694,6 @@ void nvme_kill_queues(struct nvme_ctrl *ctrl)
 	/* Forcibly unquiesce queues to avoid blocking dispatch */
 	blk_mq_unquiesce_queue(ctrl->admin_q);
 
-	/* Forcibly start all queues to avoid having stuck requests */
-	blk_mq_start_hw_queues(ctrl->admin_q);
-
 	list_for_each_entry(ns, &ctrl->namespaces, list) {
 		/*
 		 * Revalidating a dead namespace sets capacity to 0. This will
@@ -2709,16 +2706,6 @@ void nvme_kill_queues(struct nvme_ctrl *ctrl)
 
 		/* Forcibly unquiesce queues to avoid blocking dispatch */
 		blk_mq_unquiesce_queue(ns->queue);
-
-		/*
-		 * Forcibly start all queues to avoid having stuck requests.
-		 * Note that we must ensure the queues are not stopped
-		 * when the final removal happens.
-		 */
-		blk_mq_start_hw_queues(ns->queue);
-
-		/* draining requests in requeue list */
-		blk_mq_kick_requeue_list(ns->queue);
 	}
 	mutex_unlock(&ctrl->namespaces_mutex);
 }
@@ -2787,10 +2774,8 @@ void nvme_start_queues(struct nvme_ctrl *ctrl)
 	struct nvme_ns *ns;
 
 	mutex_lock(&ctrl->namespaces_mutex);
-	list_for_each_entry(ns, &ctrl->namespaces, list) {
+	list_for_each_entry(ns, &ctrl->namespaces, list)
 		blk_mq_unquiesce_queue(ns->queue);
-		blk_mq_kick_requeue_list(ns->queue);
-	}
 	mutex_unlock(&ctrl->namespaces_mutex);
 }
 EXPORT_SYMBOL_GPL(nvme_start_queues);
-- 
2.7.4

Re: [PATCH v3 5/8] nvme: kick requeue list when requeueing a request instead of when starting the queues

[Ming Lei]

On Wed, Jul 05, 2017 at 08:00:34PM +0300, Sagi Grimberg wrote:
> When we requeue a request, we can always insert the request
> back to the scheduler instead of doing it when restarting
> the queues and kicking the requeue work, so get rid of
> the requeue kick in nvme (core and drivers).
> 
> Also, now there is no need start hw queues in nvme_kill_queues
> We don't stop the hw queues anymore, so no need to
> start them.
> 
> Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
> ---
>  drivers/nvme/host/core.c | 19 ++-----------------
>  1 file changed, 2 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index d70df1d0072d..48cafaa6fbc5 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -131,7 +131,7 @@ void nvme_complete_rq(struct request *req)
>  {
>  	if (unlikely(nvme_req(req)->status && nvme_req_needs_retry(req))) {
>  		nvme_req(req)->retries++;
> -		blk_mq_requeue_request(req, !blk_mq_queue_stopped(req->q));
> +		blk_mq_requeue_request(req, true);
>  		return;
>  	}
>  
> @@ -2694,9 +2694,6 @@ void nvme_kill_queues(struct nvme_ctrl *ctrl)
>  	/* Forcibly unquiesce queues to avoid blocking dispatch */
>  	blk_mq_unquiesce_queue(ctrl->admin_q);
>  
> -	/* Forcibly start all queues to avoid having stuck requests */
> -	blk_mq_start_hw_queues(ctrl->admin_q);
> -
>  	list_for_each_entry(ns, &ctrl->namespaces, list) {
>  		/*
>  		 * Revalidating a dead namespace sets capacity to 0. This will
> @@ -2709,16 +2706,6 @@ void nvme_kill_queues(struct nvme_ctrl *ctrl)
>  
>  		/* Forcibly unquiesce queues to avoid blocking dispatch */
>  		blk_mq_unquiesce_queue(ns->queue);
> -
> -		/*
> -		 * Forcibly start all queues to avoid having stuck requests.
> -		 * Note that we must ensure the queues are not stopped
> -		 * when the final removal happens.
> -		 */
> -		blk_mq_start_hw_queues(ns->queue);
> -
> -		/* draining requests in requeue list */
> -		blk_mq_kick_requeue_list(ns->queue);
>  	}
>  	mutex_unlock(&ctrl->namespaces_mutex);
>  }
> @@ -2787,10 +2774,8 @@ void nvme_start_queues(struct nvme_ctrl *ctrl)
>  	struct nvme_ns *ns;
>  
>  	mutex_lock(&ctrl->namespaces_mutex);
> -	list_for_each_entry(ns, &ctrl->namespaces, list) {
> +	list_for_each_entry(ns, &ctrl->namespaces, list)
>  		blk_mq_unquiesce_queue(ns->queue);
> -		blk_mq_kick_requeue_list(ns->queue);
> -	}
>  	mutex_unlock(&ctrl->namespaces_mutex);
>  }
>  EXPORT_SYMBOL_GPL(nvme_start_queues);
> -- 
> 2.7.4
> 

Yeah, this is a good cleanup, and be one of my motivation of
the quiesce improvement, and I believe we can do more this kind of
cleanup to remove racy stop/start queue in other drivers.

Reviewed-by: Ming Lei <ming.lei@redhat.com>

-- 
Ming

Re: [PATCH v3 5/8] nvme: kick requeue list when requeueing a request instead of when starting the queues

[Christoph Hellwig]

I wonder if we should simply always kick the list and remove the
parameter and blk_mq_kick_requeue_list.  It seems like this split
has caused a lot more harm then good, and the other drivers using
it that way are probably having issues as well.

Re: [PATCH v3 5/8] nvme: kick requeue list when requeueing a request instead of when starting the queues

[Ming Lei]

On Thu, Jul 06, 2017 at 01:06:21AM +0200, Christoph Hellwig wrote:
> I wonder if we should simply always kick the list and remove the
> parameter and blk_mq_kick_requeue_list.  It seems like this split
> has caused a lot more harm then good, and the other drivers using
> it that way are probably having issues as well.

It is only NVMe and DM which use blk_mq_kick_requeue_list() in this way,
other drivers passes either ture or false to blk_mq_kick_requeue_list().

Yeah, looks DM need to switch to this way too.

Drivers may want to schedule at batch especially in fast path, so maybe
they should be allowed to use in splitting way.

-- 
Ming

[PATCH v3 6/8] nbd: quiesce request queues to make sure no submissions are inflight

[Sagi Grimberg]

Unlike blk_mq_stop_hw_queues, blk_mq_quiesce_queue respects the
submission path rcu grace. quiesce the queue before iterating
on live tags.

Reviewed-by: Ming Lei <ming.lei@redhat.com>
Cc: Josef Bacik <jbacik@fb.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
---
 drivers/block/nbd.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 977ec960dd2f..dea7d85134ee 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -661,9 +661,9 @@ static void nbd_clear_req(struct request *req, void *data, bool reserved)
 
 static void nbd_clear_que(struct nbd_device *nbd)
 {
-	blk_mq_stop_hw_queues(nbd->disk->queue);
+	blk_mq_quiesce_queue(nbd->disk->queue);
 	blk_mq_tagset_busy_iter(&nbd->tag_set, nbd_clear_req, NULL);
-	blk_mq_start_hw_queues(nbd->disk->queue);
+	blk_mq_unquiesce_queue(nbd->disk->queue);
 	dev_dbg(disk_to_dev(nbd->disk), "queue cleared\n");
 }
 
-- 
2.7.4

Re: [PATCH v3 6/8] nbd: quiesce request queues to make sure no submissions are inflight

[Josef Bacik]

On Wed, Jul 05, 2017 at 08:00:35PM +0300, Sagi Grimberg wrote:
> Unlike blk_mq_stop_hw_queues, blk_mq_quiesce_queue respects the
> submission path rcu grace. quiesce the queue before iterating
> on live tags.
> 
> Reviewed-by: Ming Lei <ming.lei@redhat.com>
> Cc: Josef Bacik <jbacik@fb.com>
> Signed-off-by: Sagi Grimberg <sagi@grimberg.me>

Sounds fine by me, you can add

Acked-by: Josef Bacik <jbacik@fb.com>

Thanks,

Josef

[PATCH v3 7/8] mtip32xx: quiesce request queues to make sure no submissions are inflight

[Sagi Grimberg]

Unlike blk_mq_stop_hw_queues, blk_mq_quiesce_queue respects the
submission path rcu grace. quiesce the queue before iterating
on live tags, or performing device io quiescing.

While were at it, verify that the request started in mtip_abort_cmd
amd mtip_queue_cmd tag iteration calls.

Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
---
 drivers/block/mtip32xx/mtip32xx.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/drivers/block/mtip32xx/mtip32xx.c b/drivers/block/mtip32xx/mtip32xx.c
index 61b046f256ca..87717a1a5c89 100644
--- a/drivers/block/mtip32xx/mtip32xx.c
+++ b/drivers/block/mtip32xx/mtip32xx.c
@@ -950,7 +950,7 @@ static int mtip_quiesce_io(struct mtip_port *port, unsigned long timeout)
 	unsigned long to;
 	bool active = true;
 
-	blk_mq_stop_hw_queues(port->dd->queue);
+	blk_mq_quiesce_queue(port->dd->queue);
 
 	to = jiffies + msecs_to_jiffies(timeout);
 	do {
@@ -970,10 +970,10 @@ static int mtip_quiesce_io(struct mtip_port *port, unsigned long timeout)
 			break;
 	} while (time_before(jiffies, to));
 
-	blk_mq_start_stopped_hw_queues(port->dd->queue, true);
+	blk_mq_unquiesce_queue(port->dd->queue);
 	return active ? -EBUSY : 0;
 err_fault:
-	blk_mq_start_stopped_hw_queues(port->dd->queue, true);
+	blk_mq_unquiesce_queue(port->dd->queue);
 	return -EFAULT;
 }
 
@@ -2737,6 +2737,9 @@ static void mtip_abort_cmd(struct request *req, void *data,
 	struct mtip_cmd *cmd = blk_mq_rq_to_pdu(req);
 	struct driver_data *dd = data;
 
+	if (!blk_mq_request_started(req))
+		return;
+
 	dbg_printk(MTIP_DRV_NAME " Aborting request, tag = %d\n", req->tag);
 
 	clear_bit(req->tag, dd->port->cmds_to_issue);
@@ -2749,6 +2752,9 @@ static void mtip_queue_cmd(struct request *req, void *data,
 {
 	struct driver_data *dd = data;
 
+	if (!blk_mq_request_started(req))
+		return;
+
 	set_bit(req->tag, dd->port->cmds_to_issue);
 	blk_abort_request(req);
 }
@@ -2814,6 +2820,8 @@ static int mtip_service_thread(void *data)
 				dev_warn(&dd->pdev->dev,
 					"Completion workers still active!");
 
+			blk_mq_quiesce_queue(dd->queue);
+
 			spin_lock(dd->queue->queue_lock);
 			blk_mq_tagset_busy_iter(&dd->tags,
 							mtip_queue_cmd, dd);
@@ -2826,6 +2834,8 @@ static int mtip_service_thread(void *data)
 							mtip_abort_cmd, dd);
 
 			clear_bit(MTIP_PF_TO_ACTIVE_BIT, &dd->port->flags);
+
+			blk_mq_unquiesce_queue(dd->queue);
 		}
 
 		if (test_bit(MTIP_PF_ISSUE_CMDS_BIT, &port->flags)) {
@@ -3995,8 +4005,9 @@ static int mtip_block_remove(struct driver_data *dd)
 						dd->disk->disk_name);
 
 	blk_freeze_queue_start(dd->queue);
-	blk_mq_stop_hw_queues(dd->queue);
+	blk_mq_quiesce_queue(dd->queue);
 	blk_mq_tagset_busy_iter(&dd->tags, mtip_no_dev_cleanup, dd);
+	blk_mq_unquiesce_queue(dd->queue);
 
 	/*
 	 * Delete our gendisk structure. This also removes the device
-- 
2.7.4

[PATCH v3 8/8] virtio_blk: quiesce/unquiesce live IO when entering PM states

[Sagi Grimberg]

Without it its not guaranteed that no .queue_rq is inflight.

Reviewed-by: Ming Lei <ming.lei@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Cc: virtio-dev@lists.oasis-open.org
Cc: Jason Wang <jasowang@redhat.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
---
 drivers/block/virtio_blk.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 0297ad7c1452..4e02aa5fdac0 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -840,7 +840,7 @@ static int virtblk_freeze(struct virtio_device *vdev)
 	/* Make sure no work handler is accessing the device. */
 	flush_work(&vblk->config_work);
 
-	blk_mq_stop_hw_queues(vblk->disk->queue);
+	blk_mq_quiesce_queue(vblk->disk->queue);
 
 	vdev->config->del_vqs(vdev);
 	return 0;
@@ -857,7 +857,7 @@ static int virtblk_restore(struct virtio_device *vdev)
 
 	virtio_device_ready(vdev);
 
-	blk_mq_start_stopped_hw_queues(vblk->disk->queue, true);
+	blk_mq_unquiesce_queue(vblk->disk->queue);
 	return 0;
 }
 #endif
-- 
2.7.4