Re: [RFC 06/11] khugepaged: generalize alloc_charge_folio for mTHP support

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

On 09/01/25 5:01 am, Nico Pache wrote:
> alloc_charge_folio allocates the new folio for the khugepaged collapse.
> Generalize the order of the folio allocations to support future mTHP
> collapsing.
> 
> No functional changes in this patch.
> 
> Signed-off-by: Nico Pache <npache@redhat.com>
> ---
>   mm/khugepaged.c | 8 ++++----
>   1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index e2e6ca9265ab..6daf3a943a1a 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -1070,14 +1070,14 @@ static int __collapse_huge_page_swapin(struct mm_struct *mm,
>   }
>   
>   static int alloc_charge_folio(struct folio **foliop, struct mm_struct *mm,
> -			      struct collapse_control *cc)
> +			      struct collapse_control *cc, int order)
>   {
>   	gfp_t gfp = (cc->is_khugepaged ? alloc_hugepage_khugepaged_gfpmask() :
>   		     GFP_TRANSHUGE);
>   	int node = khugepaged_find_target_node(cc);
>   	struct folio *folio;
>   
> -	folio = __folio_alloc(gfp, HPAGE_PMD_ORDER, node, &cc->alloc_nmask);
> +	folio = __folio_alloc(gfp, order, node, &cc->alloc_nmask);
>   	if (!folio) {
>   		*foliop = NULL;
>   		count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
> @@ -1121,7 +1121,7 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
>   	 */
>   	mmap_read_unlock(mm);
>   
> -	result = alloc_charge_folio(&folio, mm, cc);
> +	result = alloc_charge_folio(&folio, mm, cc, HPAGE_PMD_ORDER);
>   	if (result != SCAN_SUCCEED)
>   		goto out_nolock;
>   
> @@ -1834,7 +1834,7 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
>   	VM_BUG_ON(!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !is_shmem);
>   	VM_BUG_ON(start & (HPAGE_PMD_NR - 1));
>   
> -	result = alloc_charge_folio(&new_folio, mm, cc);
> +	result = alloc_charge_folio(&new_folio, mm, cc, HPAGE_PMD_ORDER);
>   	if (result != SCAN_SUCCEED)
>   		goto out;
>   

I guess we will need stat updation like I did in my patch.