From: "David Hildenbrand (Arm)" <david@kernel.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>, Zi Yan <ziy@nvidia.com>,
Baolin Wang <baolin.wang@linux.alibaba.com>,
"Liam R. Howlett" <liam@infradead.org>,
Ryan Roberts <ryan.roberts@arm.com>, Dev Jain <dev.jain@arm.com>,
Barry Song <baohua@kernel.org>, Lance Yang <lance.yang@linux.dev>,
Usama Arif <usama.arif@linux.dev>,
Miaohe Lin <linmiaohe@huawei.com>,
Naoya Horiguchi <nao.horiguchi@gmail.com>,
Wei Yang <richard.weiyang@gmail.com>,
Nico Pache <nico.pache@linux.dev>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Luis Chamberlain <mcgrof@kernel.org>,
Tal Zussman <tz2294@columbia.edu>,
Li Youhong <liyouhong@kylinos.cn>,
stable@vger.kernel.org
Subject: Re: [PATCH v2] mm/memory-failure: fix folio refcount leak and min_order_for_split() locking
Date: Sat, 31 Oct 2026 10:28:59 +0100 [thread overview]
Message-ID: <895a3483-c773-4d5d-9760-c526c6cfb922@kernel.org> (raw)
In-Reply-To: <20261030163553.c5dec200dd39cec4695e545c@linux-foundation.org>
On 10/31/26 00:35, Andrew Morton wrote:
> On Fri, 30 Oct 2026 23:29:13 +0100 "David Hildenbrand (Arm)" <david@kernel.org> wrote:
>
>> hwpoison code can end up calling min_order_for_split() without holding
>> the folio lock. There isn't really something that would prevent
>> concurrent folio split. Consequently folio->mapping can get set to
>> NULL after checking for "!folio->mapping", and if the compiler
>> reloads folio->mapping, mapping_min_folio_order() would try to
>> dereference NULL.
>
> Bit confused here. Is it referring to folios which end up outside EOF
> which split effectively truncates, or did it mean to say "truncate"?
I think above should say "There isn't really something that would prevent
concurrent truncation."
>
> If the former, how is split able to folio_ref_freeze() a folio which
> hwpoison has grabbed a ref on?
>
> IOW, is the race against split, or against truncate?
It's splitting (min_order_for_split() reading ->mapping) racing with truncate
(changing ->mapping).
Want to fix up the s/folio split/truncate/ when applying or want me to resend?
Thanks¡
--
Cheers,
David
prev parent reply other threads:[~2026-10-31 9:29 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-30 22:29 David Hildenbrand (Arm)
2026-10-30 23:35 ` Andrew Morton
2026-10-31 9:28 ` David Hildenbrand (Arm) [this message]
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