Re: [PATCH 03/15] blkcg: use tryget logic when associating a blkg with a bio

Dennis Zhou
2018-08-31T20:20:40Z

Hi Josef,

On Fri, Aug 31, 2018 at 11:30:08AM -0400, Josef Bacik wrote:
> On Thu, Aug 30, 2018 at 09:53:44PM -0400, Dennis Zhou wrote:
> > diff --git a/block/blk-throttle.c b/block/blk-throttle.c
> > index a3eede00d302..c626e1f7cdcd 100644
> > --- a/block/blk-throttle.c
> > +++ b/block/blk-throttle.c
> > @@ -2129,8 +2129,9 @@ static inline void throtl_update_latency_buckets(struct throtl_data *td)
> > static void blk_throtl_assoc_bio(struct throtl_grp *tg, struct bio *bio)
> > {
> > #ifdef CONFIG_BLK_DEV_THROTTLING_LOW
> > - if (bio->bi_css)
> > - bio_associate_blkg(bio, tg_to_blkg(tg));
> > + /* fallback to root_blkg if we fail to get a blkg ref */
> > + if (bio->bi_css && bio_associate_blkg(bio, tg_to_blkg(tg)))
> > + bio_associate_blkg(bio, bio->bi_disk->queue->root_blkg);
>
> Except if we've already assocated a blkg this is just extra, can we do
>
> if (bio->bi_css && (bio_associate_blkg(bio, tg_to_blkg(tg)) == -ENODEV))
>
> to make it clear that we're only attaching it to the root if we failed to attach
> a blkg at all? Thanks,

Done in v2.

Thanks,
Dennis