Re: [PATCH for 4.1-rc] dm: run queue on re-queue

[Mike Snitzer <snitzer@redhat.com>]

On Tue, May 26 2015 at  4:25P -0400,
Junichi Nomura <j-nomura@ce.jp.nec.com> wrote:

> Without kicking queue, requeued request may stay forever in
> the queue if there are no other I/O activities to the device.
> 
> The original error had been in v2.6.39 with commit 7eaceaccab5f
> ("block: remove per-queue plugging"), which replaced conditional
> plugging by periodic runqueue.
> 
> Commit 9d1deb83d489 in v4.1-rc1 removed the periodic runqueue
> and the problem started to manifest.
> 
> Fixes: 9d1deb83d489 ("dm: don't schedule delayed run of the queue if nothing to do")
> Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
> 
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index a930b72..0bf79a0 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -1164,6 +1164,7 @@ static void old_requeue_request(struct request *rq)
>  
>  	spin_lock_irqsave(q->queue_lock, flags);
>  	blk_requeue_request(q, rq);
> +	blk_run_queue_async(q);
>  	spin_unlock_irqrestore(q->queue_lock, flags);
>  }

Thanks Junichi.  The new blk-mq path did kick the queue, but obviously
the old request_fn path didn't.  I'll get this queued for 4.1.

Mike