On 18 Jun 2025, at 13:39, David Hildenbrand wrote:
> Let's allow for not clearing a page type before freeing a page to the
> buddy.
>
> We'll focus on having a type set on the first page of a larger
> allocation only.
>
> With this change, we can reliably identify typed folios even though
> they might be in the process of getting freed, which will come in handy
> in migration code (at least in the transition phase).
>
> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
> ---
> mm/page_alloc.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 858bc17653af9..44e56d31cfeb1 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1380,6 +1380,9 @@ __always_inline bool free_pages_prepare(struct page *page,
> mod_mthp_stat(order, MTHP_STAT_NR_ANON, -1);
> page->mapping = NULL;
> }
> + if (unlikely(page_has_type(page)))
> + page->page_type = UINT_MAX;
> +
> if (is_check_pages_enabled()) {
> if (free_page_is_bad(page))
> bad++;
> --
> 2.49.0
How does this preserve page type? Isn’t page->page_type = UINT_MAX clearing
page_type?
Best Regards,
Yan, Zi
