[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 <bart.vanassche at sandisk.com>
> Cc: Keith Busch <keith.busch at intel.com>
> Cc: Christoph Hellwig <hch at lst.de>
> Cc: Sagi Grimberg <sagi at grimberg.me>
> ---
>  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?