Re: [PATCH v4 0/4] blk-cgroup: fix blkg list and policy data races

[Nilay Shroff]

On 8/3/26 1:50 PM, yu kuai wrote:
> Hi,
>
> 在 2026/8/3 14:51, Nilay Shroff 写道:
> > On 8/2/26 4:55 PM, Yu Kuai wrote:
> > > From: Yu Kuai <yukuai@xxxxxxx>
> > >
> > > This set fix some problems that are reported long time ago with
> > > minimal changes,
> > > the blkcg_mutex refactor I'm working on can fix these problems as
> > > well, but it's
> > > complicated and may not land in this merge window. So I think this
> > > set should land
> > > in this merge window first.
> > >
> > > Patch 1 protects blkg_destroy_all()'s q->blkg_list walk with
> > > blkcg_mutex.
> > >
> > > Patches 2-3 fix races between blkcg_activate_policy() and concurrent
> > > blkg destruction.
> > >
> > > Patch 4 factors the policy data teardown loop into a helper after the
> > > race fixes.
> >
> > This series looks good to me, however as I recall, we discussed about
> > protecting blkg_create() as well using ->blkcg_mutex. I remember the
> > blkg_create() is not protected with ->blkcg_mutex under each call path,
> > so would you to also cover that change in this patchset?
>
> I can't do this for now without a big refactor, because it's possible that
> blkg_create() can be called from bio_set_dev(), and bio_set_dev() can be
> called from many atomic contexts, examples are patch 1,2,3,5,8,9,10 from the
> following RFC v1 set:
>
> [RFC PATCH v1 00/17] blk-cgroup: protect blkgs with blkcg_mutex - Yu Kuai <https://lore.kernel.org/all/20260704195124.1375075-1-yukuai@xxxxxxxxxx/>
Okay understood. With that, for this entire patchset:

Reviewed-by: Nilay Shroff <nilay@xxxxxxxxxxxxx>