From: "Michal Koutný" <mkoutny@suse.com>
To: quanyang.wang@windriver.com
Cc: 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,
Roman Gushchin <guro@fb.com>
Subject: Re: [PATCH] cgroup: fix memory leak caused by missing cgroup_bpf_offline
Date: Mon, 11 Oct 2021 18:21:28 +0200 [thread overview]
Message-ID: <20211011162128.GC61605@blackbody.suse.cz> (raw)
In-Reply-To: <20211007121603.1484881-1-quanyang.wang@windriver.com>
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!
> 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 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...
> +++ b/kernel/cgroup/cgroup.c
> @@ -2147,8 +2147,10 @@ static void cgroup_kill_sb(struct super_block *sb)
> * And don't kill the default root.
> */
> if (list_empty(&root->cgrp.self.children) && root != &cgrp_dfl_root &&
> - !percpu_ref_is_dying(&root->cgrp.self.refcnt))
> + !percpu_ref_is_dying(&root->cgrp.self.refcnt)) {
> + cgroup_bpf_offline(&root->cgrp);
(You made some unnecessary whitespace here breaking indention :-)
> percpu_ref_kill(&root->cgrp.self.refcnt);
> + }
> cgroup_put(&root->cgrp);
> kernfs_kill_sb(sb);
> }
next prev parent reply other threads:[~2021-10-11 16:21 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 [this message]
2021-10-11 16:29 ` Roman Gushchin
2021-10-22 15:50 ` John Fastabend
2021-10-12 6:22 ` Quanyang Wang
2021-10-12 9:32 ` Michal Koutný
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