On 10 Jun 2020, at 16:12, Matthew Wilcox wrote:

> From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
>
> Introduce the new page policy of PF_SECOND which lets us use the
> normal pageflags generation machinery to create the various DoubleMap
> manipulation functions.
>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> ---
>  include/linux/page-flags.h | 40 ++++++++++----------------------------
>  1 file changed, 10 insertions(+), 30 deletions(-)
>
> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
> index de6e0696f55c..979460df4768 100644
> --- a/include/linux/page-flags.h
> +++ b/include/linux/page-flags.h
> @@ -232,6 +232,9 @@ static inline void page_init_poison(struct page *page, size_t size)
>   *
>   * PF_NO_COMPOUND:
>   *     the page flag is not relevant for compound pages.
> + *
> + * PF_SECOND:
> + *     the page flag is stored in the first tail page.
>   */

Would PF_FIRST_TAIL or PF_SECOND_IN_COMPOUND be more informative?

—
Best Regards,
Yan Zi