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From: Michal Hocko <>
To: Muchun Song <>
Cc: Roman Gushchin <>,
	Johannes Weiner <>,
	Andrew Morton <>,
	Shakeel Butt <>,
	Vladimir Davydov <>,
	LKML <>,
	Linux Memory Management List <>
Subject: Re: [PATCH] mm: memcontrol: fix memsw uncharge for root_mem_cgroup
Date: Wed, 24 Mar 2021 09:33:14 +0100	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Wed 24-03-21 12:11:35, Muchun Song wrote:
> On Tue, Mar 23, 2021 at 11:04 PM Muchun Song <> wrote:
> >
> > The pages aren't accounted at the root level, so we cannot uncharge the
> > page to the memsw counter for the root memcg. Fix this.
> >
> > Fixes: 1f47b61fb407 ("mm: memcontrol: fix swap counter leak on swapout from offline cgroup")
> > Signed-off-by: Muchun Song <>
> I am very sorry. I should repent. I suddenly realise the fix is totally
> wrong. Because the @memcg cannot be root memcg when
> @memcg != @swap_memcg.

I am probably blind but I do not see why this would be the case.
We have memcg != swap_memcg in this branch but we do not know the
neither of the two is root_mem_cgroup, no? If we did knot that we
wouldn't have to check for swap_memcg != root_mem_cgroup. Or do I miss
Michal Hocko

  reply	other threads:[~2021-03-24  8:33 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-23 14:56 [PATCH] mm: memcontrol: fix memsw uncharge for root_mem_cgroup Muchun Song
2021-03-23 16:11 ` Michal Hocko
2021-03-24  4:11 ` Muchun Song
2021-03-24  8:33   ` Michal Hocko [this message]
2021-03-24  8:50     ` [External] " Muchun Song
2021-03-24  9:20       ` Michal Hocko

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