From: Christoph Hellwig <hch@lst.de>
To: yu kuai <yukuai@fygo.io>
Cc: axboe@kernel.dk, tj@kernel.org, hch@lst.de,
dongsheng.yang@linux.dev, cengku@gmail.com, josef@toxicpanda.com,
nilay@linux.ibm.com, ming.lei@redhat.com,
linux-block@vger.kernel.org, cgroups@vger.kernel.org
Subject: Re: [RFC PATCH v2 1/8] block: associate blkg in submit_bio instead of bio_set_dev
Date: Tue, 28 Jul 2026 06:23:13 +0200 [thread overview]
Message-ID: <20260728042313.GA19817@lst.de> (raw)
In-Reply-To: <933b4285-1c85-4076-831a-0501d5c38e16@fygo.io>
On Mon, Jul 27, 2026 at 04:16:29PM +0800, yu kuai wrote:
> > open-coded blkg_put().
>
> Turns out bio will be submitted by kworker for some drivers and for
> blkcg_punt_bio_submit(). Is it possible to record blkcg during bio initialization,
> as blkcg must exist, and then covert it to blkg during submission? I can use union
> for blkcg and blkg to avoid new field in struct bio.
Mixing the two up sounds like a receipt for a lot of problems
unfortunately. I wonder if we could switch to only store the blkcg in
the bio and look up the blkg as needed. This assumes we can get away
with a relatively small numbers of lookups for typical setups. I'm not
really sure how much the different users are combined - if not much this
might actually be a big net benefit, if on the other hand we'd have to
do a lot of separate lookups it might not work very well.
This could be combined with a way to do more efficient blkg lookups
using e.g. a rhashtable.
next prev parent reply other threads:[~2026-07-28 4:23 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-24 12:30 [RFC PATCH v2 0/8] blk-cgroup: protect blkgs with blkcg_mutex Yu Kuai
2026-07-24 12:30 ` [RFC PATCH v2 1/8] block: associate blkg in submit_bio instead of bio_set_dev Yu Kuai
2026-07-27 8:16 ` yu kuai
2026-07-28 4:23 ` Christoph Hellwig [this message]
2026-07-24 12:30 ` [RFC PATCH v2 2/8] blk-throttle: protect throttle state with td lock Yu Kuai
2026-07-24 12:30 ` [RFC PATCH v2 3/8] blk-cgroup: protect blkgs with blkcg_mutex Yu Kuai
2026-07-24 12:30 ` [RFC PATCH v2 4/8] blk-cgroup: remove blkg radix tree preloading Yu Kuai
2026-07-24 12:30 ` [RFC PATCH v2 5/8] blk-cgroup: allocate blkgs in blkg_create Yu Kuai
2026-07-24 12:30 ` [RFC PATCH v2 6/8] blk-cgroup: share blkg creation between lookup and config prep Yu Kuai
2026-07-24 12:30 ` [RFC PATCH v2 7/8] bfq: avoid blkg lookup from locked cgroup update Yu Kuai
2026-07-24 12:30 ` [RFC PATCH v2 8/8] block: fail nowait bio submit if blkg allocation can't sleep Yu Kuai
2026-07-26 7:08 ` [syzbot ci] Re: blk-cgroup: protect blkgs with blkcg_mutex syzbot ci
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