Re: [PATCH v2 2/3] nvme: avoid to use blk_mq_abort_requeue_list()

[Ming Lei <ming.lei@redhat.com>]

On Sat, May 20, 2017 at 11:56:04AM +0800, Ming Lei wrote:
> NVMe may add request into requeue list simply and not kick off the
> requeue if hw queues are stopped. Then blk_mq_abort_requeue_list()
> is called in both nvme_kill_queues() and nvme_ns_remove() for
> dealing with this issue.
> 
> Unfortunately blk_mq_abort_requeue_list() is absolutely a
> race maker, for example, one request may be requeued during
> the aborting. So this patch just calls blk_mq_kick_requeue_list() in
> nvme_kill_queues() to handle this issue like what nvme_start_queues()
> does. Now all requests in requeue list when queues are stopped will be
> handled by blk_mq_kick_requeue_list() when queues are restarted, either
> in nvme_start_queues() or in nvme_kill_queues().
> 
> Cc: stable@vger.kernel.org
> Reported-by: Zhang Yi <yizhan@redhat.com>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>  drivers/nvme/host/core.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index ce0d96913ee6..9ce0a0a16984 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -2098,7 +2098,6 @@ static void nvme_ns_remove(struct nvme_ns *ns)
>  		if (ns->ndev)
>  			nvme_nvm_unregister_sysfs(ns);
>  		del_gendisk(ns->disk);
> -		blk_mq_abort_requeue_list(ns->queue);
>  		blk_cleanup_queue(ns->queue);
>  	}
>  
> @@ -2436,7 +2435,6 @@ void nvme_kill_queues(struct nvme_ctrl *ctrl)
>  			continue;
>  		revalidate_disk(ns->disk);
>  		blk_set_queue_dying(ns->queue);
> -		blk_mq_abort_requeue_list(ns->queue);
>  
>  		/*
>  		 * We have to force to start queues for avoiding hang
> @@ -2444,6 +2442,9 @@ void nvme_kill_queues(struct nvme_ctrl *ctrl)
>  		 * be stopped forever from now on.
>  		 */
>  		blk_mq_start_hw_queues(ns->queue);
> +
> +		/* draining requests in requeue list */
> +		blk_mq_kick_requeue_list(q);

oops, the above line causes build failure, please
take the following one.

---

>From e70cfe2edacf278e3e6605f8c08e01ebf65bff01 Mon Sep 17 00:00:00 2001
From: Ming Lei <ming.lei@redhat.com>
Date: Wed, 17 May 2017 09:02:07 +0800
Subject: [PATCH v2 2/3] nvme: avoid to use blk_mq_abort_requeue_list()

NVMe may add request into requeue list simply and not kick off the
requeue if hw queues are stopped. Then blk_mq_abort_requeue_list()
is called in both nvme_kill_queues() and nvme_ns_remove() for
dealing with this issue.

Unfortunately blk_mq_abort_requeue_list() is absolutely a
race maker, for example, one request may be requeued during
the aborting. So this patch just calls blk_mq_kick_requeue_list() in
nvme_kill_queues() to handle this issue like what nvme_start_queues()
does. Now all requests in requeue list when queues are stopped will be
handled by blk_mq_kick_requeue_list() when queues are restarted, either
in nvme_start_queues() or in nvme_kill_queues().

Cc: stable@vger.kernel.org
Reported-by: Zhang Yi <yizhan@redhat.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 drivers/nvme/host/core.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index ce0d96913ee6..e344f5d7c1bc 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -2098,7 +2098,6 @@ static void nvme_ns_remove(struct nvme_ns *ns)
 		if (ns->ndev)
 			nvme_nvm_unregister_sysfs(ns);
 		del_gendisk(ns->disk);
-		blk_mq_abort_requeue_list(ns->queue);
 		blk_cleanup_queue(ns->queue);
 	}
 
@@ -2436,7 +2435,6 @@ void nvme_kill_queues(struct nvme_ctrl *ctrl)
 			continue;
 		revalidate_disk(ns->disk);
 		blk_set_queue_dying(ns->queue);
-		blk_mq_abort_requeue_list(ns->queue);
 
 		/*
 		 * We have to force to start queues for avoiding hang
@@ -2444,6 +2442,9 @@ void nvme_kill_queues(struct nvme_ctrl *ctrl)
 		 * be stopped forever from now on.
 		 */
 		blk_mq_start_hw_queues(ns->queue);
+
+		/* draining requests in requeue list */
+		blk_mq_kick_requeue_list(ns->queue);
 	}
 	mutex_unlock(&ctrl->namespaces_mutex);
 }
-- 
2.9.4