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From: Muchun Song <muchun.song@linux.dev>
To: "Oscar Salvador (SUSE)" <osalvador@kernel.org>
Cc: Joshua Hahn <joshua.hahnjy@gmail.com>,
	Hongfu Li <hongfu.li@linux.dev>,
	Oscar Salvador <osalvador@suse.de>,
	David Hildenbrand <david@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Shakeel Butt <shakeel.butt@linux.dev>,
	Michal Hocko <mhocko@suse.com>,
	Roman Gushchin <roman.gushchin@linux.dev>,
	Nhat Pham <nphamcs@gmail.com>, Chris Down <chris@chrisdown.name>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Michal Hocko <mhocko@kernel.org>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	cgroups@vger.kernel.org, Hongfu Li <lihongfu@kylinos.cn>,
	stable@vger.kernel.org
Subject: Re: [PATCH 2/2] mm/memcg: migrate per-node hugetlb lruvec stat together with hugetlb folio
Date: Tue, 22 Sep 2026 14:31:14 +0800	[thread overview]
Message-ID: <D086B92E-13A8-48A7-97B6-CD671EE22033@linux.dev> (raw)
In-Reply-To: <arIEfJXYpspgX4-G@localhost.localdomain>



> On Sep 22, 2026, at 12:30, Oscar Salvador (SUSE) <osalvador@kernel.org> wrote:
> 
> On Mon, Sep 21, 2026 at 09:20:53PM -0700, Joshua Hahn wrote:
>> On Tue, 22 Sep 2026 06:15:07 +0200 "Oscar Salvador (SUSE)" <osalvador@kernel.org> wrote:
> 
>>> Why do we need the whole thing to be embraced by rcu?
>> 
>> Hi Oscar,
> 
> Hi Joshua,
> 
>> 
>> I believe it's because now getting the memcg from the objcg requires
>> an RCU lock to make sure it doesn't get removed while we work on the
>> memcg. I think this is since Qi Zheng's "Eliminate Dying Memory
>> Cgroup" series.
> 
> Yes, I understood that obj_cgroup_memcg might need the rcu-dance, but I was
> unsure about the mod_memcg_lruvec_state() calls.

The caller needs to make sure the liveness of lruvec, in which case,
lruvec is from memcg, so rcu lock is needed here.

Thanks,
Muchun

> 
> 
> -- 
> Oscar Salvador
> SUSE Labs


  reply	other threads:[~2026-09-22  6:31 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-09-21  9:12 [PATCH 0/2] mm: fix hugetlb NR_HUGETLB accounting on folio migration Hongfu Li
2026-09-21  9:12 ` [PATCH 1/2] mm/hugetlb: account migration target folio in per-node NR_HUGETLB vmstat Hongfu Li
2026-09-21 22:35   ` Joshua Hahn
2026-09-22  3:34     ` Muchun Song
2026-09-22  3:33   ` Muchun Song
2026-09-22  4:04   ` Oscar Salvador (SUSE)
2026-09-21  9:12 ` [PATCH 2/2] mm/memcg: migrate per-node hugetlb lruvec stat together with hugetlb folio Hongfu Li
2026-09-21 23:03   ` Joshua Hahn
2026-09-22  4:15   ` Oscar Salvador (SUSE)
2026-09-22  4:20     ` Joshua Hahn
2026-09-22  4:30       ` Oscar Salvador (SUSE)
2026-09-22  6:31         ` Muchun Song [this message]
2026-09-22  6:18   ` Muchun Song
2026-09-22  9:38     ` Hongfu Li

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