linux-kernel - Re: [PATCH] mm: kfence: fix PG_slab and memcg

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Message-Id: <962CB717-DF8B-490A-86A0-2ACE90209012@linux.dev>
Date:   Tue, 21 Mar 2023 11:03:41 +0800
From:   Muchun Song <muchun.song@...ux.dev>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Muchun Song <songmuchun@...edance.com>, glider@...gle.com,
        elver@...gle.com, dvyukov@...gle.com, sjpark@...zon.de,
        jannh@...gle.com, Roman Gushchin <roman.gushchin@...ux.dev>,
        kasan-dev@...glegroups.com,
        Linux Memory Management List <linux-mm@...ck.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: kfence: fix PG_slab and memcg_data clearing



> On Mar 21, 2023, at 05:29, Andrew Morton <akpm@...ux-foundation.org> wrote:
> 
> On Mon, 20 Mar 2023 11:00:59 +0800 Muchun Song <songmuchun@...edance.com> wrote:
> 
>> It does not reset PG_slab and memcg_data when KFENCE fails to initialize
>> kfence pool at runtime. It is reporting a "Bad page state" message when
>> kfence pool is freed to buddy. The checking of whether it is a compound
>> head page seems unnecessary sicne we already guarantee this when allocating
>> kfence pool, removing the check to simplify the code.
>> 
>> Fixes: 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure")
>> Fixes: 8f0b36497303 ("mm: kfence: fix objcgs vector allocation")
>> Signed-off-by: Muchun Song <songmuchun@...edance.com>
> 
> I'm not sure how the -stable maintainers are to handle two Fixes: tags.
> Can we narrow it down to one please?  I assume 8f0b36497303 triggered
> the bad_page() warning?
> 

Actually, 0ce20dd84089 triggered the PG_slab warning and 8f0b36497303
triggered the "page still charged to cgroup" warning. This patch fixes
both warnings. Moreover, 8f0b36497303 fixes 0ce20dd84089 as well. So I think
we can narrow it down to 0ce20dd84089.

Thanks.