Re: [PATCH v2 7/7] [RFC] nvme: Fix a race condition

[Bart Van Assche]

On 10/11/16 09:46, Christoph Hellwig wrote:

On Wed, Sep 28, 2016 at 05:01:45PM -0700, Bart Van Assche wrote:

Avoid that nvme_queue_rq() is still running when nvme_stop_queues()
returns. Untested.

Signed-off-by: Bart Van Assche 
Cc: Keith Busch 
Cc: Christoph Hellwig 
Cc: Sagi Grimberg 
---
 drivers/nvme/host/core.c | 20 
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index d791fba..98f1f29 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -201,13 +201,9 @@ fail:

 void nvme_requeue_req(struct request *req)
 {
-   unsigned long flags;
-
blk_mq_requeue_request(req);
-   spin_lock_irqsave(req->q->queue_lock, flags);
-   if (!blk_mq_queue_stopped(req->q))
-   blk_mq_kick_requeue_list(req->q);
-   spin_unlock_irqrestore(req->q->queue_lock, flags);
+   WARN_ON_ONCE(blk_mq_queue_stopped(req->q));
+   blk_mq_kick_requeue_list(req->q);
 }
 EXPORT_SYMBOL_GPL(nvme_requeue_req);


Can we just add a 'bool kick' argument to blk_mq_requeue_request and
move all this handling to the core?


Hello Christoph,

That sounds like a good idea to me. Thanks also for the other review 
comments you posted on this patch series. I will rework patch 6/7 such 
that the code for waiting is moved into the SCSI core.


Bart.
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Re: [PATCH v2 7/7] [RFC] nvme: Fix a race condition

[Christoph Hellwig]

On Wed, Sep 28, 2016 at 05:01:45PM -0700, Bart Van Assche wrote:
> Avoid that nvme_queue_rq() is still running when nvme_stop_queues()
> returns. Untested.
> 
> Signed-off-by: Bart Van Assche 
> Cc: Keith Busch 
> Cc: Christoph Hellwig 
> Cc: Sagi Grimberg 
> ---
>  drivers/nvme/host/core.c | 20 
>  1 file changed, 12 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index d791fba..98f1f29 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -201,13 +201,9 @@ fail:
>  
>  void nvme_requeue_req(struct request *req)
>  {
> - unsigned long flags;
> -
>   blk_mq_requeue_request(req);
> - spin_lock_irqsave(req->q->queue_lock, flags);
> - if (!blk_mq_queue_stopped(req->q))
> - blk_mq_kick_requeue_list(req->q);
> - spin_unlock_irqrestore(req->q->queue_lock, flags);
> + WARN_ON_ONCE(blk_mq_queue_stopped(req->q));
> + blk_mq_kick_requeue_list(req->q);
>  }
>  EXPORT_SYMBOL_GPL(nvme_requeue_req);

Can we just add a 'bool kick' argument to blk_mq_requeue_request and
move all this handling to the core?
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Re: [PATCH v2 7/7] [RFC] nvme: Fix a race condition

[Sagi Grimberg]

Avoid that nvme_queue_rq() is still running when nvme_stop_queues()
returns. Untested.

Signed-off-by: Bart Van Assche 
Cc: Keith Busch 
Cc: Christoph Hellwig 
Cc: Sagi Grimberg 


Bart this looks really good! and possibly fixes an issue
I've been chasing with fabrics a while ago. I'll take it
for testing but you can add my:

Reviewed-by: Sagi Grimberg 
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