Re: [PATCH v1 01/10] mm: Expose clear_huge_page() unconditionally

[Yu Zhao <yuzhao@google.com>]

On Mon, Jun 26, 2023 at 11:14 AM Ryan Roberts <ryan.roberts@arm.com> wrote:
>
> In preparation for extending vma_alloc_zeroed_movable_folio() to
> allocate a arbitrary order folio, expose clear_huge_page()
> unconditionally, so that it can be used to zero the allocated folio in
> the generic implementation of vma_alloc_zeroed_movable_folio().
>
> Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
> ---
>  include/linux/mm.h | 3 ++-
>  mm/memory.c        | 2 +-
>  2 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 7f1741bd870a..7e3bf45e6491 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -3684,10 +3684,11 @@ enum mf_action_page_type {
>   */
>  extern const struct attribute_group memory_failure_attr_group;
>
> -#if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_HUGETLBFS)
>  extern void clear_huge_page(struct page *page,
>                             unsigned long addr_hint,
>                             unsigned int pages_per_huge_page);
> +
> +#if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_HUGETLBFS)

We might not want to depend on THP eventually. Right now, we still
have to, unless splitting is optional, which seems to contradict
06/10. (deferred_split_folio()  is a nop without THP.)