linux-kernel - Re: [PATCH] mm: memcontrol: fix forget to obtain the ref to objcg in split_page

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Date:   Fri, 2 Apr 2021 18:04:54 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Roman Gushchin <guro@...com>
Cc:     Miaohe Lin <linmiaohe@...wei.com>,
        Muchun Song <songmuchun@...edance.com>,
        <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
        <duanxiongchun@...edance.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        <hannes@...xchg.org>, <mhocko@...nel.org>, <shakeelb@...gle.com>,
        <vdavydov.dev@...il.com>
Subject: Re: [PATCH] mm: memcontrol: fix forget to obtain the ref to objcg
 in split_page_memcg

On Wed, 31 Mar 2021 20:35:02 -0700 Roman Gushchin <guro@...com> wrote:

> On Thu, Apr 01, 2021 at 11:31:16AM +0800, Miaohe Lin wrote:
> > On 2021/4/1 11:01, Muchun Song wrote:
> > > Christian Borntraeger reported a warning about "percpu ref
> > > (obj_cgroup_release) <= 0 (-1) after switching to atomic".
> > > Because we forgot to obtain the reference to the objcg and
> > > wrongly obtain the reference of memcg.
> > > 
> > > Reported-by: Christian Borntraeger <borntraeger@...ibm.com>
> > > Signed-off-by: Muchun Song <songmuchun@...edance.com>
> > 
> > Thanks for the patch.
> > Is a Fixes tag needed?
> 
> No, as the original patch hasn't been merged into the Linus's tree yet.
> So the fix can be simply squashed.

Help.  Which is "the original patch"?

> Btw, the fix looks good to me.
> 
> Acked-by: Roman Gushchin <guro@...com>