Re: [PATCH 03/12] mm/khugepaged: rename mthp_present_ptes bitmap to eligible_ptes

[Baolin Wang]

On 9/4/26 11:10 PM, Kiryl Shutsemau wrote:
> From: "Kiryl Shutsemau (Meta)" <kas@xxxxxxxxxx>
>
> The name says less than the bit means.  A set bit means not only that the
> PTE is present, but also that it passed the other checks: uffd,
> lazyfree, anonymity, sharing.  The PTE can be considered a collapse
> source.
>
> mthp_collapse() then reads the bitmap starting at the PMD order, so the
> bitmap is not specific to mTHP either.
>
> Name it for what a set bit means, and update the comments that named it.
>
> No functional change.
>
> Assisted-by: Claude-Code:claude-opus-5
> Signed-off-by: Kiryl Shutsemau (Meta) <kas@xxxxxxxxxx>
> ---
>   mm/khugepaged.c | 18 +++++++++---------
>   1 file changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index a6dfd8cddc50..6a437d6fe016 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -115,8 +115,8 @@ struct collapse_control {
>   	/* nodemask for allocation fallback */
>   	nodemask_t alloc_nmask;
>   
> -	/* Each bit represents a single occupied (!none/zero) page. */
> -	DECLARE_BITMAP(mthp_present_ptes, MAX_PTRS_PER_PTE);
> +	/* Each bit marks a PTE the scan accepted as a collapse source */
> +	DECLARE_BITMAP(eligible_ptes, MAX_PTRS_PER_PTE);
>   };
>   
>   /**
> @@ -627,7 +627,7 @@ static void collapse_control_init_scan(struct collapse_control *cc)
>   {
>   	memset(cc->node_load, 0, sizeof(cc->node_load));
>   	nodes_clear(cc->alloc_nmask);
> -	bitmap_zero(cc->mthp_present_ptes, MAX_PTRS_PER_PTE);
> +	bitmap_zero(cc->eligible_ptes, MAX_PTRS_PER_PTE);
>   }
>   
>   static void release_pte_folio(struct folio *folio)
> @@ -1482,8 +1482,8 @@ static unsigned int max_order_from_offset(unsigned int offset)
>    * mthp_collapse() consumes the bitmap that is generated during
>    * collapse_scan_pmd() to determine what regions and mTHP orders fit best.
>    *
> - * Each bit in cc->mthp_present_ptes represents a single occupied (!none/zero)
> - * page. We start at the PMD order and check if it is eligible for collapse;
> + * Each bit in cc->eligible_ptes marks a PTE the scan accepted as a collapse
> + * source. We start at the PMD order and check if it is eligible for collapse;
>    * if not, we check the left and right halves of the PTE page table we are
>    * examining at a lower order.
>    *

Should also update the following comments: s/occupied/accepted as a 
collapse source ?

"
 * For each of these, we determine how many PTE entries are occupied in the
 * range of PTE entries we propose to collapse, then we compare this to a
 * threshold number of PTE entries which would need to be occupied for a
 * collapse to be permitted at that order (accounting for max_ptes_none).
"

With that and Zi's comments addressed,
Reviewed-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>