From: "David Hildenbrand (Arm)" <david@kernel.org>
To: Zi Yan <ziy@nvidia.com>, Barry Song <baohua@kernel.org>,
Ye Liu <ye.liu@linux.dev>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Baolin Wang <baolin.wang@linux.alibaba.com>,
"Liam R. Howlett" <liam@infradead.org>,
Nico Pache <nico.pache@linux.dev>,
Ryan Roberts <ryan.roberts@arm.com>, Dev Jain <dev.jain@arm.com>,
Lance Yang <lance.yang@linux.dev>,
Usama Arif <usama.arif@linux.dev>,
Kiryl Shutsemau <kas@kernel.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Ye Liu <liuye@kylinos.cn>
Subject: Re: [PATCH] mm/huge_memory: use READ_ONCE() when cloning folio flags during split
Date: Thu, 29 Oct 2026 20:24:52 +0100 [thread overview]
Message-ID: <2c84d8ad-d189-4127-9d1d-8cf0eb40c43c@kernel.org> (raw)
In-Reply-To: <DMHKCEKNMA64.3B6O5X5918GWI@nvidia.com>
On 10/29/26 20:19, Zi Yan wrote:
> On Thu Oct 29, 2026 at 10:54 AM EDT, David Hildenbrand (Arm) wrote:
>> On 10/29/26 15:31, Zi Yan wrote:
>>>
>>> data_race() would work too.
>>>
>>>
>>> The PG_waiters on the original folio/the original head page is not lost,
>>
>> Ah, so it's not on arbitrary tail pages, just the old head.
>>
>>> but there is a chance PG_waiters is lost in the new head, because
>>> prep_compound_page() uses __SetPageHead() and can ignore the atomic set
>>> of PG_waiters.
>>
>> Fun.
>> ...>
>>> Solutions can be:
>>>
>>> 1. Use atomic SetPageHead() in prep_compound_page().
>>
>> That sounds like the right thing to do?
>
> Yes, simpler, but the atomic op can be costly at compound page init
> time. My plan is to add prep_compound_page_atomic() for
> __split_folio_to_order() and the atomic version SetPageHead().
Makes perfect sense.
--
Cheers,
David
prev parent reply other threads:[~2026-10-29 19:25 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-29 7:41 [PATCH] mm/huge_memory: use READ_ONCE() when cloning folio flags during split Ye Liu
2026-10-29 9:08 ` Barry Song
2026-10-29 10:47 ` David Hildenbrand (Arm)
2026-10-29 14:31 ` Zi Yan
2026-10-29 14:54 ` David Hildenbrand (Arm)
2026-10-29 19:19 ` Zi Yan
2026-10-29 19:24 ` David Hildenbrand (Arm) [this message]
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