Re: [PATCH v2 2/4] mm/huge_memory: replace can_split_folio() with direct refcount calculation

[David Hildenbrand (Red Hat)]

On 11/25/25 10:10, Miaohe Lin wrote:
> On 2025/11/25 5:08, Zi Yan wrote:
> > On 24 Nov 2025, at 14:22, David Hildenbrand (Red Hat) wrote:
>
> <snip>
>
> > BTW, this page flag reuse is really confusing. I see PG_checked is
> > PG_owner_priv_1 too and __folio_migrate_mapping() uses folio_test_swapcache()
> > to decide the number of i_pages entries. Wouldn’t that cause any issue?
> > ext4 does not release_folio() for migration when PG_checked is set,
> > ubifs clears PG_checked in release_folio(). I have not checked all other FS
> > yet. Maybe later.
>
> folio_test_swapbacked() is also checked in folio_test_swapcache:
>
> static __always_inline bool folio_test_swapcache(struct folio *folio)
> {
> 	return folio_test_swapbacked(folio) &&
> 			test_bit(PG_swapcache, folio_flags(folio, 0));
> }
>
> So IMHO the reuse of this page flag should work fine.

Ahh, thanks for pointing that out. Confusing, as usually the 
folio_test_*() helper are straight bit tests,

All good then :)

--
Cheers

David