linux-kernel - Re: [RFC] mm/migrate: make sure folio_unlock() before folio_wait

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Message-ID: <3b66d603-543d-4616-92a5-9e6e32f116be@kzalloc.com>
Date: Tue, 7 Oct 2025 15:32:27 +0900
From: Yunseong Kim <ysk@...lloc.com>
To: Byungchul Park <byungchul@...com>, Hillf Danton <hdanton@...a.com>
Cc: David Hildenbrand <david@...hat.com>, akpm@...ux-foundation.org,
 linux-mm@...ck.org, linux-kernel@...r.kernel.org, kernel_team@...ynix.com,
 Yeoreum Yun <yeoreum.yun@....com>
Subject: Re: [RFC] mm/migrate: make sure folio_unlock() before
 folio_wait_writeback()

Hi Hillf,

Here are the syzlang and kernel log, and you can also find the gist snippet
in the body of the first RFC mail:

 https://gist.github.com/kzall0c/a6091bb2fd536865ca9aabfd017a1fc5

I am reviewing this issue again on the v6.17, The issue is always reproducible,
usually occurring within about 10k attempts with the 8 procs.

On 10/3/25 9:52 AM, Byungchul Park wrote:
> On Fri, Oct 03, 2025 at 09:48:28AM +0900, Byungchul Park wrote:
>> On Fri, Oct 03, 2025 at 06:02:10AM +0800, Hillf Danton wrote:
>>> On Thu, 2 Oct 2025 13:38:59 +0200 David Hildenbrand wrote:
>>>>
>>>> If it's a real issue, I wonder if a trylock on the writeback path could
>>>> be an option.
>>>>
>>> Given Thanks to Yunseong for reporting the issue, testing, and confirming if
>>> this patch can resolve the issue, could you share your reproducer with
>>> reviewers Byungchul?
>>
>> Sure.  Yunseong told me it's 100% reproducable.  Yunseong, can you help
>> him reproduce the issue, please?
> 
> +to ysk@...lloc.com
> 
>>
>> 	Byungchul
> 

Thank you!

Yunseong