From: Waiman Long <longman@redhat.com>
To: "Michal Koutný" <mkoutny@suse.com>, "Ming Lei" <ming.lei@redhat.com>
Cc: Yosry Ahmed <yosryahmed@google.com>,
Linux-MM <linux-mm@kvack.org>, Michal Hocko <mhocko@kernel.org>,
Shakeel Butt <shakeelb@google.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Roman Gushchin <roman.gushchin@linux.dev>,
Muchun Song <muchun.song@linux.dev>, Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org, cgroups@vger.kernel.org,
Tejun Heo <tj@kernel.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@redhat.com> 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: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20230524011935.719659-1-ming.lei@redhat.com>
2023-05-24 2:06 ` Yosry Ahmed
2023-05-24 2:37 ` Ming Lei
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]
2023-05-26 21:11 ` Michal Koutný
2023-05-24 4:04 ` Waiman Long
2023-05-24 4:13 ` Yosry Ahmed
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