Re: [PATCH v2 3/8] mm: move anon-exclusive batch helper to mm.h

[Barry Song]

On Tue, Sep 1, 2026 at 1:44 PM Dev Jain <dev.jain@xxxxxxx> wrote:
>
> In preparation for optimizing large folio unmapping, we need to reuse
> the page_anon_exclusive_batch helper in rmap.c and rmap.h and obey the
> existing use in mprotect.c .
>
> Therefore, move it from mprotect.c to mm.h. Gate with CONFIG_MMU since
> both rmap and mprotect users are built only for CONFIG_MMU.
>
> While at it, change start_idx and max_len to unsigned long type for
> future proofing against THP support at >= PUD level. Also shorten
> expected_anon_exclusive -> anon_exclusive.
>
> Signed-off-by: Dev Jain <dev.jain@xxxxxxx>
> ---
>  include/linux/mm.h | 19 +++++++++++++++++++
>  mm/mprotect.c      | 17 -----------------
>  2 files changed, 19 insertions(+), 17 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index dd09c438fa23e..63da8813bc5df 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -244,6 +244,25 @@ static inline unsigned long folio_page_idx(const struct folio *folio,
>         return page - &folio->page;
>  }
>
> +#ifdef CONFIG_MMU
> +/*
> + * Get max length of consecutive PTEs pointing to PageAnonExclusive() pages or
> + * !PageAnonExclusive() pages, starting from start_idx. Caller must enforce
> + * that the PTEs point to consecutive pages of the same anon large folio.
> + */
> +static __always_inline int page_anon_exclusive_batch(unsigned long start_idx,
> +               unsigned long max_len, struct page *first_page, bool anon_exclusive)
> +{
> +       int idx;
> +
> +       for (idx = start_idx + 1; idx < start_idx + max_len; ++idx) {
> +               if (anon_exclusive != PageAnonExclusive(first_page + idx))
> +                       break;
> +       }
> +       return idx - start_idx;
> +}
> +#endif
> +

Hi Dev,

I really don't want everything to become a top-level header
file. If these are only mm-internal things, could we move them
to mm/internal.h or another more appropriate header?

Best Regards
Barry