From: Waiman Long <longman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
To: "Michal Koutný" <mkoutny-IBi9RG/b67k@public.gmane.org>,
"Ming Lei" <ming.lei-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: Yosry Ahmed <yosryahmed-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>,
Linux-MM <linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org>,
Michal Hocko <mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
Shakeel Butt <shakeelb-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>,
Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>,
Roman Gushchin
<roman.gushchin-fxUVXftIFDnyG1zEObXtfA@public.gmane.org>,
Muchun Song <muchun.song-fxUVXftIFDnyG1zEObXtfA@public.gmane.org>,
Jens Axboe <axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org>,
linux-block-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Subject: Re: [PATCH] blk-cgroup: Flush stats before releasing blkcg_gq
Date: Thu, 25 May 2023 11:25:05 -0400 [thread overview]
Message-ID: <8f56f60f-8dd3-d798-3d81-6ccbb185465d@redhat.com> (raw)
In-Reply-To: <3ej42djuuzwx36yf2yeo5ggyrvogeaguos5jtve2bvuaejnwff@fak3yjwe2fbi>
On 5/25/23 10:11, Michal Koutný wrote:
> On Wed, May 24, 2023 at 10:37:10AM +0800, Ming Lei <ming.lei-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
>>> I am not at all familiar with blkcg, but does calling
>>> cgroup_rstat_flush() in offline_css() fix the problem?
>> Except for offline, this list needs to be flushed after the associated disk
>> is deleted.
> Why the second flush trigger?
> a) To break another ref-dependency cycle (like on the blkcg side)?
> b) To avoid stale data upon device removal?
>
> (Because b) should be unnecessary, a future reader would flush when
> needed.)
Since the percpu blkg_iostat_set's that are linked in the lockless list
will be freed if the corresponding blkcg_gq is freed, we need to flush
the lockless list to avoid potential use-after-free in a future
cgroup_rstat_flush*() call.
Cheers,
Longman
next prev parent reply other threads:[~2023-05-25 15:25 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-24 1:19 [PATCH] blk-cgroup: Flush stats before releasing blkcg_gq Ming Lei
[not found] ` <20230524011935.719659-1-ming.lei-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2023-05-24 2:06 ` Yosry Ahmed
[not found] ` <CAJD7tkZkbro4H-QC=RJx_dfCdGQ5c=4NJhbFrcEmQSidaaMOmg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2023-05-24 2:37 ` Ming Lei
[not found] ` <ZG14VnHl20lt9jLc-j9QsSs0H/W6P5pAslXv9rxcY2uh10dtjAL8bYrjMMd8@public.gmane.org>
2023-05-24 2:43 ` Yosry Ahmed
2023-05-24 4:10 ` Waiman Long
2023-05-24 4:21 ` Ming Lei
2023-05-25 14:11 ` Michal Koutný
2023-05-25 15:25 ` Waiman Long [this message]
[not found] ` <8f56f60f-8dd3-d798-3d81-6ccbb185465d-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2023-05-26 21:11 ` Michal Koutný
2023-05-24 4:04 ` Waiman Long
[not found] ` <11e81fc8-24db-54db-a518-b9bb67d0b504-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2023-05-24 4:13 ` Yosry Ahmed
[not found] <20230525043518.831721-1-ming.lei@redhat.com>
2023-05-25 16:01 ` Waiman Long
2023-05-25 16:06 ` Waiman Long
2023-05-26 0:34 ` Ming Lei
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