Re: [PATCH v3 16/17] kasan: Remove references to folio in __kasan_mempool_poison_object()

[Vlastimil Babka]

On 10/24/25 22:44, Matthew Wilcox (Oracle) wrote:
> In preparation for splitting struct slab from struct page and struct
> folio, remove mentions of struct folio from this function. We can
> discard the comment as using PageLargeKmalloc() rather than
> !folio_test_slab() makes it obvious.
>
> Signed-off-by: Matthew Wilcox (Oracle) <wi...@infradead.org>
> Acked-by: David Hildenbrand <da...@redhat.com>

+Cc KASAN folks

This too could check page_slab() first, but it's not that important. Note
that it should be fine even with not marking all tail pages as
PageLargeKmalloc(), as ptr should be pointer to the head page here.

> ---
> mm/kasan/common.c | 12 ++++--------
> 1 file changed, 4 insertions(+), 8 deletions(-)
>
> diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> index 22e5d67ff064..1d27f1bd260b 100644
> --- a/mm/kasan/common.c
> +++ b/mm/kasan/common.c
> @@ -517,24 +517,20 @@ void __kasan_mempool_unpoison_pages(struct page *page, unsigned int order,
>
> bool __kasan_mempool_poison_object(void *ptr, unsigned long ip)
> {
> - struct folio *folio = virt_to_folio(ptr);
> + struct page *page = virt_to_page(ptr);
> struct slab *slab;
>
> - /*
> - * This function can be called for large kmalloc allocation that get
> - * their memory from page_alloc. Thus, the folio might not be a slab.
> - */
> - if (unlikely(!folio_test_slab(folio))) {
> + if (unlikely(PageLargeKmalloc(page))) {
> if (check_page_allocation(ptr, ip))
> return false;
> - kasan_poison(ptr, folio_size(folio), KASAN_PAGE_FREE, false);
> + kasan_poison(ptr, page_size(page), KASAN_PAGE_FREE, false);
> return true;
> }
>
> if (is_kfence_address(ptr))
> return true;
>
> - slab = folio_slab(folio);
> + slab = page_slab(page);
>
> if (check_slab_allocation(slab->slab_cache, ptr, ip))
> return false;