[dm-devel] [PATCH] dm rq: Avoid that request processing stalls sporadically

[Bart Van Assche]

On Fri, 2018-01-19 at 08:18 +0800, Ming Lei wrote:
> On Fri, Jan 19, 2018 at 12:14:24AM +0000, Bart Van Assche wrote:
> > On Fri, 2018-01-19 at 08:11 +0800, Ming Lei wrote:
> > > On Thu, Jan 18, 2018 at 08:37:07AM -0800, Bart Van Assche wrote:
> > > > diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
> > > > index f16096af879a..c59c59cfd2a5 100644
> > > > --- a/drivers/md/dm-rq.c
> > > > +++ b/drivers/md/dm-rq.c
> > > > @@ -761,6 +761,7 @@ static blk_status_t dm_mq_queue_rq(struct blk_mq_hw_ctx *hctx,
> > > >  		/* Undo dm_start_request() before requeuing */
> > > >  		rq_end_stats(md, rq);
> > > >  		rq_completed(md, rq_data_dir(rq), false);
> > > > +		blk_mq_delay_run_hw_queue(hctx, 100/*ms*/);
> > > >  		return BLK_STS_RESOURCE;
> > > >  	}
> > > >  
> > > 
> > > Nak.
> > 
> > This patch fixes a regression that was introduced by you. You should know
> > that regressions are not acceptable. If you don't agree with this patch,
> > please fix the root cause.
> 
> Yesterday I sent a patch, did you test that?

Yes, I did. It caused queue stalls that were so bad that sending "kick" to the
debugfs "state" attribute was not sufficient to resolve the queue stall.

Bart.