Re: [PATCH v8 02/15] introduce khugepaged_collapse_single_pmd to unify khugepaged and madvise_collapse

[Baolin Wang]

On 2025/7/2 13:57, Nico Pache wrote:
> The khugepaged daemon and madvise_collapse have two different
> implementations that do almost the same thing.
>
> Create khugepaged_collapse_single_pmd to increase code reuse and create an
> entry point these two users.
>
> Refactor madvise_collapse and khugepaged_scan_mm_slot to use the new
> khugepaged_collapse_single_pmd function. This introduces a minor
> behavioral change that is most likely an undiscovered bug. The current
> implementation of khugepaged tests khugepaged_test_exit_or_disable
> before calling khugepaged_pte_mapped_thp, but we weren't doing it in the
> madvise_collapse case. By unifying these two callers madvise_collapse
> now also performs this check.
>
> Reviewed-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
> Signed-off-by: Nico Pache <npache@xxxxxxxxxx>
> ---
>   mm/khugepaged.c | 95 +++++++++++++++++++++++++------------------------
>   1 file changed, 49 insertions(+), 46 deletions(-)
>
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index f27fe7ca9b86..bf69e81a3d82 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -2354,6 +2354,50 @@ static int khugepaged_scan_file(struct mm_struct *mm, unsigned long addr,
>   	return result;
>   }
>   
> +/*
> + * Try to collapse a single PMD starting at a PMD aligned addr, and return
> + * the results.
> + */
> +static int khugepaged_collapse_single_pmd(unsigned long addr,
> +				   struct vm_area_struct *vma, bool *mmap_locked,
> +				   struct collapse_control *cc)
> +{
> +	int result = SCAN_FAIL;
> +	struct mm_struct *mm = vma->vm_mm;
> +
> +	if (IS_ENABLED(CONFIG_SHMEM) && !vma_is_anonymous(vma)) {

Seems you still forgot to drop 'IS_ENABLED(CONFIG_SHMEM)' :)