Re: [PATCH] mm/khugepaged: fix the address passed to notifier on testing young

[Dev Jain <dev.jain@arm.com>]

On 22/08/25 12:03 pm, Wei Yang wrote:
> Commit 8ee53820edfd ("thp: mmu_notifier_test_young") introduced
> mmu_notifier_test_young(), but we should pass the address need to test.
> In xxx_scan_pmd(), the actual iteration address is "_address" not
> "address". We seem to misuse the variable on the very beginning.
>
> Change it to the right one.
>
> Fixes: 8ee53820edfd ("thp: mmu_notifier_test_young")
> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
> Cc: David Hildenbrand <david@redhat.com>
> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
> Cc: Zi Yan <ziy@nvidia.com>
> Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
> Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
> Cc: Nico Pache <npache@redhat.com>
> Cc: Ryan Roberts <ryan.roberts@arm.com>
> Cc: Dev Jain <dev.jain@arm.com>
> Cc: Barry Song <baohua@kernel.org>
> CC: <stable@vger.kernel.org>
>
> ---
> The original commit 8ee53820edfd is at 2011.
> Then the code is moved to khugepaged.c in commit b46e756f5e470 ("thp:
> extract khugepaged from mm/huge_memory.c") in 2022.
> ---
>   mm/khugepaged.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 24e18a7f8a93..b000942250d1 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -1418,7 +1418,7 @@ static int hpage_collapse_scan_pmd(struct mm_struct *mm,
>               if (cc->is_khugepaged &&
>                   (pte_young(pteval) || folio_test_young(folio) ||
>                    folio_test_referenced(folio) || mmu_notifier_test_young(vma->vm_mm,
> -                                                                  address)))
> +                                                                  _address)))
>                       referenced++;
>       }
>       if (!writable) {

Wow, I have gone through this code so many times and never noticed this.

Reviewed-by: Dev Jain <dev.jain@arm.com>

IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you.