Re: [PATCH] mm/huge_memory: update file PUD counter before folio_put()

[Lorenzo Stoakes]

You sent this twice :)

On Tue, May 26, 2026 at 06:13:55PM +0800, Yin Tirui wrote:
> __split_huge_pud_locked() updates the file/shmem RSS counter after
> dropping the PUD mapping's folio reference. If folio_put() drops the
> last reference, mm_counter_file() can later read freed folio state via
> folio_test_swapbacked().
>
> Move the counter update before folio_put().
>
> Fixes: dbe54153296d ("mm/huge_memory: add vmf_insert_folio_pud()")
> Cc: <stable@xxxxxxxxxxxxxxx>
> Signed-off-by: Yin Tirui <yintirui@xxxxxxxxxx>

Patch looks sane to me, so:

Reviewed-by: Lorenzo Stoakes <ljs@xxxxxxxxxx>

There seems to be an identical problem in __split_huge_pmd_locked() - could you
do the same fix there?

Thanks, Lorenzo

> ---
>  mm/huge_memory.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index a5f4a48b7b77..9832ee910d5e 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -3027,9 +3027,9 @@ static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
>  	if (!folio_test_referenced(folio) && pud_young(old_pud))
>  		folio_set_referenced(folio);
>  	folio_remove_rmap_pud(folio, page, vma);
> -	folio_put(folio);
>  	add_mm_counter(vma->vm_mm, mm_counter_file(folio),
>  		-HPAGE_PUD_NR);
> +	folio_put(folio);
>  }
>
>  void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
> --
> 2.43.0
>