From: Roman Gushchin <guro@fb.com>
To: "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: Mon, 11 Oct 2021 09:29:22 -0700 [thread overview]
Message-ID: <YWRmYk4hHhPf602i@carbon.dhcp.thefacebook.com> (raw)
In-Reply-To: <20211011162128.GC61605@blackbody.suse.cz>
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!
next prev parent reply other threads:[~2021-10-11 16:30 UTC|newest]
Thread overview: 6+ 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 [this message]
2021-10-22 15:50 ` John Fastabend
2021-10-12 6:22 ` Quanyang Wang
2021-10-12 9:32 ` Michal Koutný
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=YWRmYk4hHhPf602i@carbon.dhcp.thefacebook.com \
--to=guro@fb.com \
--cc=andrii@kernel.org \
--cc=ast@kernel.org \
--cc=axboe@kernel.dk \
--cc=bpf@vger.kernel.org \
--cc=cgroups@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=hannes@cmpxchg.org \
--cc=linux-kernel@vger.kernel.org \
--cc=lizefan@huawei.com \
--cc=ming.lei@redhat.com \
--cc=mkoutny@suse.com \
--cc=netdev@vger.kernel.org \
--cc=quanyang.wang@windriver.com \
--cc=tj@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).