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Subject: Re: [PATCH] mm: kfence: fix PG_slab and memcg_data clearing
From:   Muchun Song <muchun.song@linux.dev>
In-Reply-To: <20230320142954.fd314c5e46c1d18887ccf8cc@linux-foundation.org>
Date:   Tue, 21 Mar 2023 11:03:41 +0800
Cc:     Muchun Song <songmuchun@bytedance.com>, glider@google.com,
        elver@google.com, dvyukov@google.com, sjpark@amazon.de,
        jannh@google.com, Roman Gushchin <roman.gushchin@linux.dev>,
        kasan-dev@googlegroups.com,
        Linux Memory Management List <linux-mm@kvack.org>,
        linux-kernel@vger.kernel.org
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Message-Id: <962CB717-DF8B-490A-86A0-2ACE90209012@linux.dev>
References: <20230320030059.20189-1-songmuchun@bytedance.com>
 <20230320142954.fd314c5e46c1d18887ccf8cc@linux-foundation.org>
To:     Andrew Morton <akpm@linux-foundation.org>
Precedence: bulk


> On Mar 21, 2023, at 05:29, Andrew Morton <akpm@linux-foundation.org> =
wrote:
>=20
> On Mon, 20 Mar 2023 11:00:59 +0800 Muchun Song =
<songmuchun@bytedance.com> wrote:
>=20
>> 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.
>>=20
>> Fixes: 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure")
>> Fixes: 8f0b36497303 ("mm: kfence: fix objcgs vector allocation")
>> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
>=20
> 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?
>=20

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.