lkml.org 
[lkml]   [2021]   [Oct]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] cgroup: fix memory leak caused by missing cgroup_bpf_offline
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!

\
 
 \ /
  Last update: 2021-10-11 18:30    [W:0.085 / U:0.456 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site