Re: [PATCH v1 03/11] mm: simplify hugetlb and file-THP handling in __page_mapcount()

[Kirill A. Shutemov]

On Fri, Dec 17, 2021 at 12:30:41PM +0100, David Hildenbrand wrote:
> Let's return early for hugetlb, which really only relies on the compound
> mapcount so far and does not support PageDoubleMap() yet. Use the chance
> to cleanup the file-THP case to make it easier to grasp. While at it, use
> head_compound_mapcount().
> 
> This is a preparation for further changes.
> 
> Reviewed-by: Peter Xu <peterx@xxxxxxxxxx>
> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
> ---
>  mm/util.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/util.c b/mm/util.c
> index 741ba32a43ac..3239e75c148d 100644
> --- a/mm/util.c
> +++ b/mm/util.c
> @@ -732,15 +732,18 @@ int __page_mapcount(struct page *page)
>  {
>  	int ret;
>  
> -	ret = atomic_read(&page->_mapcount) + 1;
> +	if (PageHuge(page))
> +		return compound_mapcount(page);

It would be nice to make PageHuge() inlinable first. It's a shame the we
need to have to do a function call for PageHuge() check.

Otherwise, looks good:

Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>

-- 
 Kirill A. Shutemov