Re: [PATCH v1 04/11] mm: thp: simlify total_mapcount()

[Yang Shi]

On Fri, Dec 17, 2021 at 3:33 AM David Hildenbrand <david@xxxxxxxxxx> wrote:
>
> Let's simplify a bit, returning for PageHuge() early and using
> head_compound_page() as we are only getting called for HEAD pages.
>
> Note the VM_BUG_ON_PAGE(PageTail(page), page) check at the beginning of
> total_mapcount().
>
> This is a preparation for further changes.
>
> Reviewed-by: Peter Xu <peterx@xxxxxxxxxx>
> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>

Reviewed-by: Yang Shi <shy828301@xxxxxxxxx>

> ---
>  mm/huge_memory.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 4751d03947da..826cabcad11a 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -2506,12 +2506,11 @@ int total_mapcount(struct page *page)
>
>         if (likely(!PageCompound(page)))
>                 return atomic_read(&page->_mapcount) + 1;
> +       if (PageHuge(page))
> +               return head_compound_mapcount(page);
>
> -       compound = compound_mapcount(page);
>         nr = compound_nr(page);
> -       if (PageHuge(page))
> -               return compound;
> -       ret = compound;
> +       ret = compound = head_compound_mapcount(page);
>         for (i = 0; i < nr; i++)
>                 ret += atomic_read(&page[i]._mapcount) + 1;
>         /* File pages has compound_mapcount included in _mapcount */
> --
> 2.31.1
>