Re: [PATCH v22 1/4] mm: add MAP_DROPPABLE for designating always lazily freeable mappings

David Hildenbrand
2024-07-11T18:56:31Z

On 11.07.24 20:54, Jason A. Donenfeld wrote:
> On Thu, Jul 11, 2024 at 08:24:07PM +0200, David Hildenbrand wrote:
>>> And PG_large_rmappable seems to only be used for hugetlb branches.
>>
>> It should be set for THP/large folios.
>
> And it's tested too, apparently.
>
> Okay, well, how disappointing is this below? Because I'm running out of
> tricks for flag reuse.
>
> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
> index b9e914e1face..c1ea49a7f198 100644
> --- a/include/linux/page-flags.h
> +++ b/include/linux/page-flags.h
> @@ -110,6 +110,7 @@ enum pageflags {
> PG_workingset,
> PG_error,
> PG_owner_priv_1, /* Owner use. If pagecache, fs may use*/
> + PG_owner_priv_2,

Oh no, no new page flags please :)

Maybe just follow what Linux suggested: pass vma to pte_dirty() and
always return false for these special VMAs.

--
Cheers,

David / dhildenb