Re: [PATCH 2/2] madvise: don't use mapcount() against large folio for sharing check

Yin, Fengwei
2023-07-29T13:53:31Z

Hi Andrew,

On 7/29/2023 1:41 AM, Andrew Morton wrote:
> On Sat, 29 Jul 2023 00:13:56 +0800 Yin Fengwei <fengwei.yin@intel.com> wrote:
>
>> Fixes: 98b211d6415f ("madvise: convert madvise_free_pte_range() to use a folio")
>> Fixes: fc986a38b670 ("mm: huge_memory: convert madvise_free_huge_pmd to use a folio")
>
> Having two Fixes: for one patch presumably makes backporting more
> complicated and adds risk of making mistakes.
>
> So I have split this into a three-patch series and I've fixed up the patch naming:
>
> Subject: madvise:madvise_cold_or_pageout_pte_range(): don't use mapcount() against large folio for sharing check
> Subject: madvise:madvise_free_huge_pmd(): don't use mapcount() against large folio for sharing check
> Subject: madvise:madvise_free_pte_range(): don't use mapcount() against large folio for sharing check
Thanks a lot for your kind help. Will be careful for the future patches.

>
> I haven't added cc:stable at this time - that awaits the description of
> user-visible effects.
The impact of the patch:
Without the patch, when user calls madvise() with MADV_COLD, MADV_PAGEOUT
and MADV_FREE, it's likely THP pages will be skipped. With the patch,
It's likely the THP pages will be split to pages which will be made code,
reclaimed and freed.

Regards
Yin, Fengwei