Re: [PATCH 06/22] slab: Reimplement page_slab()

[David Hildenbrand <david@redhat.com>]

On 29.08.25 17:47, Matthew Wilcox (Oracle) wrote:
> In order to separate slabs from folios, we need to convert from any page
> in a slab to the slab directly without going through a page to folio
> conversion first.  page_slab() is a little different from other memdesc
> converters we have in that it will return NULL if the page is not part
> of a slab.  This will be the normal style for memdesc converters in
> the future.
> 
> kfence was the only user of page_slab(), so adjust it to the new way
> of working.  It will need to be touched again when we separate slab
> from page.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> ---
>   include/linux/page-flags.h | 14 +-------------
>   mm/kfence/core.c           | 12 ++++++++----
>   mm/slab.h                  | 28 ++++++++++++++++------------
>   3 files changed, 25 insertions(+), 29 deletions(-)
> 
> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
> index 5ee6ffbdbf83..39ed2f243279 100644
> --- a/include/linux/page-flags.h
> +++ b/include/linux/page-flags.h
> @@ -1052,19 +1052,7 @@ PAGE_TYPE_OPS(Table, table, pgtable)
>    */
>   PAGE_TYPE_OPS(Guard, guard, guard)
>   
> -FOLIO_TYPE_OPS(slab, slab)
> -
> -/**
> - * PageSlab - Determine if the page belongs to the slab allocator
> - * @page: The page to test.
> - *
> - * Context: Any context.
> - * Return: True for slab pages, false for any other kind of page.
> - */
> -static inline bool PageSlab(const struct page *page)
> -{
> -	return folio_test_slab(page_folio(page));
> -}
> +PAGE_TYPE_OPS(Slab, slab, slab)
>   
>   #ifdef CONFIG_HUGETLB_PAGE
>   FOLIO_TYPE_OPS(hugetlb, hugetlb)
> diff --git a/mm/kfence/core.c b/mm/kfence/core.c
> index 0ed3be100963..5fb0f0f8f99a 100644
> --- a/mm/kfence/core.c
> +++ b/mm/kfence/core.c
> @@ -613,12 +613,14 @@ static unsigned long kfence_init_pool(void)
>   	 * enters __slab_free() slow-path.
>   	 */
>   	for (i = 0; i < KFENCE_POOL_SIZE / PAGE_SIZE; i++) {
> -		struct slab *slab = page_slab(nth_page(pages, i));
> +		struct page *page = nth_page(pages, i);
> +		struct slab *slab;
>   

There will be a slight collision with nth_page removal that should be 
easy to resolve.

Nothing jumped at me.

-- 
Cheers

David / dhildenb