linux-kernel - Re: [PATCH v1 16/26] mm: thp: prevent memory cgroup release in folio_split_queue_lock{

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Message-ID: <aR7XAJn11ubk_om2@hyeyoo>
Date: Thu, 20 Nov 2025 17:53:20 +0900
From: Harry Yoo <harry.yoo@...cle.com>
To: Qi Zheng <qi.zheng@...ux.dev>
Cc: hannes@...xchg.org, hughd@...gle.com, mhocko@...e.com,
        roman.gushchin@...ux.dev, shakeel.butt@...ux.dev,
        muchun.song@...ux.dev, david@...hat.com, lorenzo.stoakes@...cle.com,
        ziy@...dia.com, imran.f.khan@...cle.com, kamalesh.babulal@...cle.com,
        axelrasmussen@...gle.com, yuanchu@...gle.com, weixugc@...gle.com,
        akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
        Qi Zheng <zhengqi.arch@...edance.com>
Subject: Re: [PATCH v1 16/26] mm: thp: prevent memory cgroup release in
 folio_split_queue_lock{_irqsave}()

On Tue, Oct 28, 2025 at 09:58:29PM +0800, Qi Zheng wrote:
> From: Qi Zheng <zhengqi.arch@...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_split_queue_lock{_irqsave}().
> 
> Signed-off-by: Qi Zheng <zhengqi.arch@...edance.com>
> ---

Looks good to me,
Reviewed-by: Harry Yoo <harry.yoo@...cle.com>

Yeah, once we acquire the split-queue lock, the split queue won't
disappear under us because the reparenting logic also takes the same
lock before reparenting.

-- 
Cheers,
Harry / Hyeonggon