Re: [RFC] mm/migrate: make sure folio_unlock() before folio_wait_writeback()

Yunseong Kim
2025-10-07T06:32:32Z

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@kzalloc.com
>
>>
>> Byungchul
>

Thank you!

Yunseong