Re: [V2][PATCH] cgroup: fix memory leak caused by missing cgroup_bpf_offline

[Quanyang Wang]

Hi Ming,

On 10/20/21 10:17 AM, Ming Lei wrote:
> On Tue, Oct 19, 2021 at 07:10:26PM +0200, Michal Koutný wrote:
> > Hi.
> >
> > On Tue, Oct 19, 2021 at 06:41:14PM +0800, Quanyang Wang <quanyang.wang@xxxxxxxxxxxxx> wrote:
> > > So I add 2 "Fixes tags" here to indicate that 2 commits introduce two
> > > different issues.
> >
> > AFAIU, both the changes are needed to cause the leak, a single patch
> > alone won't cause the issue. Is that correct? (Perhaps not as I realize,
> > see below.)
> >
> > But on second thought, the problem is the missing percpu_ref_exit() in
> > the (root) cgroup release path and percpu counter would allocate the
> > percpu_count_ptr anyway, so 4bfc0bb2c60e is only making the leak more
> > visible. Is this correct?
> >
> > I agree the commit 2b0d3d3e4fcf ("percpu_ref: reduce memory footprint of
> > percpu_ref in fast path") alone did nothing wrong.
>
> If only precpu_ref data is leaked, it is fine to add "Fixes: 2b0d3d3e4fcf",
> I thought cgroup_bpf_release() needs to release more for root cgroup, but
> looks not true.
For now, I can only observe that precpu_ref data is leaked when running 
ltp testsuite.
Thanks,
Quanyang
> Thanks,
> Ming