Re: [PATCH] mm/khugepaged: continue to collapse on SCAN_PMD_NONE

[Lance Yang <lance.yang@linux.dev>]

On 2025/11/12 10:00, Wei Yang wrote:
> SCAN_PMD_NONE means current pmd is empty, but we can still continue
> collapse next pmd range.

Right, bailing out of the whole MADV_COLLAPSE request just because
we encounter one empty PMD is too strict ...

It makes sense to treat SCAN_PMD_NONE like the other whitelisted cases
(e.g., SCAN_PMD_NULL).
> 
> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
> ---

LGTM.

Reviewed-by: Lance Yang <lance.yang@linux.dev>

>   mm/khugepaged.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 7e8cb181d5bd..4c2217076ad3 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -2835,6 +2835,7 @@ int madvise_collapse(struct vm_area_struct *vma, unsigned long start,
>   			goto handle_result;
>   		/* Whitelisted set of results where continuing OK */
>   		case SCAN_PMD_NULL:
> +		case SCAN_PMD_NONE:
>   		case SCAN_PTE_NON_PRESENT:
>   		case SCAN_PTE_UFFD_WP:
>   		case SCAN_LACK_REFERENCED_PAGE: