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

[David Hildenbrand <david@redhat.com>]

On 22.08.25 08:33, Wei Yang wrote:
> Commit 8ee53820edfd ("thp: mmu_notifier_test_young") introduced
> mmu_notifier_test_young(), but we should pass the address need to test.

... "but we are passing the wrong address".

> 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)))

Please just put that into a single line, that's a perfectly reasonable 
case to exceed 80 chars.


Acked-by: David Hildenbrand <david@redhat.com>

>   			referenced++;
>   	}
>   	if (!writable) {

Maybe, just maybe, it's because of *horrible* variable naming.

Can someone please send a cleanup to rename address -> pmd_addr and
_address -> pte_addr or sth like that?

pretty much any naming is better than this.

-- 
Cheers

David / dhildenb