From: John Fastabend <john.fastabend@gmail.com>
To: "Roman Gushchin" <guro@fb.com>, "Michal Koutný" <mkoutny@suse.com>
Cc: quanyang.wang@windriver.com, Tejun Heo <tj@kernel.org>,
Li Zefan <lizefan@huawei.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>, Jens Axboe <axboe@kernel.dk>,
Ming Lei <ming.lei@redhat.com>,
cgroups@vger.kernel.org, linux-kernel@vger.kernel.org,
netdev@vger.kernel.org, bpf@vger.kernel.org
Subject: Re: [PATCH] cgroup: fix memory leak caused by missing cgroup_bpf_offline
Date: Fri, 22 Oct 2021 08:50:48 -0700 [thread overview]
Message-ID: <6172ddd8c3f59_82a7f208e4@john-XPS-13-9370.notmuch> (raw)
In-Reply-To: <YWRmYk4hHhPf602i@carbon.dhcp.thefacebook.com>
Roman Gushchin wrote:
> On Mon, Oct 11, 2021 at 06:21:28PM +0200, Michal Koutny wrote:
> > Hello.
> >
> > On Thu, Oct 07, 2021 at 08:16:03PM +0800, quanyang.wang@windriver.com wrote:
> > > This is because that root_cgrp->bpf.refcnt.data is allocated by the
> > > function percpu_ref_init in cgroup_bpf_inherit which is called by
> > > cgroup_setup_root when mounting, but not freed along with root_cgrp
> > > when umounting.
> >
> > Good catch!
>
> +1
>
> >
> > > Adding cgroup_bpf_offline which calls percpu_ref_kill to
> > > cgroup_kill_sb can free root_cgrp->bpf.refcnt.data in umount path.
> >
> > That is sensible.
> >
> > > Fixes: 2b0d3d3e4fcfb ("percpu_ref: reduce memory footprint of percpu_ref in fast path")
> >
> > Why this Fixes:? Is the leak absent before the percpu_ref refactoring?
>
> I agree, the "fixes" tag looks dubious to me.
>
> > I guess the embedded data are free'd together with cgroup. Makes me
> > wonder why struct cgroup_bpf has a separate percpu_ref counter from
> > struct cgroup...
>
> This is because a cgroup can stay a long time (sometimes effectively forever)
> in a dying state, so we want to release bpf structures earlier.
>
> Thanks!
Other than whitespace LGTM.
Acked-by: John Fastabend <john.fastabend@gmail.com>
next prev parent reply other threads:[~2021-10-22 15:51 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-07 12:16 [PATCH] cgroup: fix memory leak caused by missing cgroup_bpf_offline quanyang.wang
2021-10-11 16:21 ` Michal Koutný
2021-10-11 16:29 ` Roman Gushchin
2021-10-11 16:29 ` Roman Gushchin
2021-10-22 15:50 ` John Fastabend [this message]
2021-10-12 6:22 ` Quanyang Wang
2021-10-12 6:22 ` Quanyang Wang
2021-10-12 9:32 ` Michal Koutný
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