linux-kernel - Re: [PATCH v2 13/28] mm: migrate: prevent memory cgroup release in folio_migrate

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Message-ID: <4icfifjfr77f4yle5cn4buotiscvpwxccxerwuzuj227l5kqs2@bdkeysc6xigp>
Date: Fri, 19 Dec 2025 15:51:26 -0800
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: Qi Zheng <qi.zheng@...ux.dev>
Cc: hannes@...xchg.org, hughd@...gle.com, mhocko@...e.com, 
	roman.gushchin@...ux.dev, muchun.song@...ux.dev, david@...nel.org, 
	lorenzo.stoakes@...cle.com, ziy@...dia.com, harry.yoo@...cle.com, imran.f.khan@...cle.com, 
	kamalesh.babulal@...cle.com, axelrasmussen@...gle.com, yuanchu@...gle.com, weixugc@...gle.com, 
	chenridong@...weicloud.com, mkoutny@...e.com, akpm@...ux-foundation.org, 
	hamzamahfooz@...ux.microsoft.com, apais@...ux.microsoft.com, lance.yang@...ux.dev, 
	linux-mm@...ck.org, linux-kernel@...r.kernel.org, cgroups@...r.kernel.org, 
	Muchun Song <songmuchun@...edance.com>, Qi Zheng <zhengqi.arch@...edance.com>
Subject: Re: [PATCH v2 13/28] mm: migrate: prevent memory cgroup release in
 folio_migrate_mapping()

On Wed, Dec 17, 2025 at 03:27:37PM +0800, Qi Zheng wrote:
> From: Muchun Song <songmuchun@...edance.com>
> 
> In the near future, a folio will no longer pin its corresponding
> memory cgroup. To ensure safety, it will only be appropriate to
> hold the rcu read lock or acquire a reference to the memory cgroup
> returned by folio_memcg(), thereby preventing it from being released.
> 
> In the current patch, the rcu read lock is employed to safeguard
> against the release of the memory cgroup in folio_migrate_mapping().
> 
> This serves as a preparatory measure for the reparenting of the
> LRU pages.
> 
> Signed-off-by: Muchun Song <songmuchun@...edance.com>
> Signed-off-by: Qi Zheng <zhengqi.arch@...edance.com>
> Reviewed-by: Harry Yoo <harry.yoo@...cle.com>

Acked-by: Shakeel Butt <shakeel.butt@...ux.dev>