linux-kernel - Re: [PATCH] mm: kmem: fix split_page

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Message-Id: <D5816457-E0F4-4571-A81F-DE46C27F8C3D@linux.dev>
Date: Tue, 20 Aug 2024 10:37:12 +0800
From: Muchun Song <muchun.song@...ux.dev>
To: Shakeel Butt <shakeel.butt@...ux.dev>
Cc: Muchun Song <songmuchun@...edance.com>,
 Johannes Weiner <hannes@...xchg.org>,
 Michal Hocko <mhocko@...nel.org>,
 Roman Gushchin <roman.gushchin@...ux.dev>,
 Andrew Morton <akpm@...ux-foundation.org>,
 cgroups@...r.kernel.org,
 Linux Memory Management List <linux-mm@...ck.org>,
 Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
 syzbot <syzbot+ef4ecf7b6bdc4157bfa4@...kaller.appspotmail.com>
Subject: Re: [PATCH] mm: kmem: fix split_page_memcg()



> On Aug 19, 2024, at 23:37, Shakeel Butt <shakeel.butt@...ux.dev> wrote:
> 
> On Mon, Aug 19, 2024 at 04:04:15PM GMT, Muchun Song wrote:
>> split_page_memcg() does not care about the returned memcg for kmem
>> pages, so folio_memcg_charged() should be used, otherwise obj_cgroup_memcg
>> will complain about this.
> 
> Basically avoid calling folio_memcg() for folio_memcg_kmem(folio),
> correct?

Yes. Unless you hold rcu lock.

> 
>> 
>> Reported-by: syzbot+ef4ecf7b6bdc4157bfa4@...kaller.appspotmail.com
>> Signed-off-by: Muchun Song <songmuchun@...edance.com>
> 
> Acked-by: Shakeel Butt <shakeel.butt@...ux.dev>
> 

Thanks.