Re: [PATCH] block: drain queue before waiting for q_usage_counter becoming zero

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

On Wed, Nov 22, 2017 at 04:47:48PM +0000, Bart Van Assche wrote:
> On Wed, 2017-11-22 at 13:11 +0800, Ming Lei wrote:
> > diff --git a/block/blk-mq.c b/block/blk-mq.c
> > index 11097477eeab..3d3797327491 100644
> > --- a/block/blk-mq.c
> > +++ b/block/blk-mq.c
> > @@ -161,6 +161,8 @@ void blk_freeze_queue(struct request_queue *q)
> >  	 * exported to drivers as the only user for unfreeze is blk_mq.
> >  	 */
> >  	blk_freeze_queue_start(q);
> > +	if (!q->mq_ops)
> > +		blk_drain_queue(q);
> >  	blk_mq_freeze_queue_wait(q);
> >  }
> 
> Since q_usage_counter now tracks legacy requests, is there any reason why we
> still need __blk_drain_queue()? Have you considered to eliminate
> __blk_drain_queue() and to call blk_run_queue() from inside blk_freeze_queue()
> instead of calling blk_drain_queue()? I'm asking this because

Yeah, that looks better, I am thinking of that too, will do this way
in V2.

-- 
Ming