Re: [PATCH v2 3/3] mm: use PF_ONLY_HEAD for PG_active and PG_unevictable

[Matthew Wilcox]

On Fri, Feb 26, 2021 at 02:17:18AM -0700, Yu Zhao wrote:
> All places but one test, set or clear PG_active and PG_unevictable on
> small or head pages. Use compound_head() explicitly for that singleton
> so the rest can rid of redundant compound_head().

How do you know it's only one place?  I really wish you'd work with me
on folios.  They make the compiler prove that it's not a tail page.