Re: [PATCH 4/4] blk-throttle: cleanup throtl_dequeue_tg()

[Yu Kuai]

Hi, Tejun

在 2022/08/24 2:34, Tejun Heo 写道:
> On Tue, Aug 23, 2022 at 09:38:10AM +0800, Yu Kuai wrote:
> > From: Yu Kuai <yukuai3@xxxxxxxxxx>
> >
> > Now that throtl_dequeue_tg() is called when the last bio is dispatched,
> > there is no need to check the flag THROTL_TG_PENDING, since it's ensured
> > to be set when bio is throttled.
> >
> > There are no functional changes.
> >
> > Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
> > ---
> >   block/blk-throttle.c | 11 ++++-------
> >   1 file changed, 4 insertions(+), 7 deletions(-)
> >
> > diff --git a/block/blk-throttle.c b/block/blk-throttle.c
> > index 47142a1dd102..e47506a8ef47 100644
> > --- a/block/blk-throttle.c
> > +++ b/block/blk-throttle.c
> > @@ -570,14 +570,11 @@ static void throtl_enqueue_tg(struct throtl_grp *tg)
> >   
> >   static void throtl_dequeue_tg(struct throtl_grp *tg)
> >   {
> > -	if (tg->flags & THROTL_TG_PENDING) {
> > -		struct throtl_service_queue *parent_sq =
> > -			tg->service_queue.parent_sq;
> > +	struct throtl_service_queue *parent_sq = tg->service_queue.parent_sq;
> >   
> > -		throtl_rb_erase(&tg->rb_node, parent_sq);
> > -		--parent_sq->nr_pending;
> > -		tg->flags &= ~THROTL_TG_PENDING;
> > -	}
> > +	throtl_rb_erase(&tg->rb_node, parent_sq);
> > +	--parent_sq->nr_pending;
> > +	tg->flags &= ~THROTL_TG_PENDING;
>
> Yeah, I don't know about this one. This breaks the symmetry with
> throtl_enqueue_tg() and it's a bit odd that we aren't at least
> WARN_ON_ONCE() on the flag given what the flag tracks. If you want to do
> this, I think the prev approach of just removing the flag is better as that
> was symmetric at least.

Yes, you are right, thanks for the advice. Since now it's a bit
ambivalent, we might as well just remove this patch?

Thanks,
Kuai
> Thanks.