Re: [PATCH v1 1/2] mm/huge_memory: introduce uniform_split_unmapped_folio_to_zero_order

[David Hildenbrand (Red Hat)]

On 16.11.25 02:47, Jiaqi Yan wrote:
> When freeing a high-order folio that contains HWPoison pages,
> to ensure these HWPoison pages are not added to buddy allocator,
> we can first uniformly split a free and unmapped high-order folio
> to 0-order folios first, then only add non-HWPoison folios to
> buddy allocator and exclude HWPoison ones.
>
> Introduce uniform_split_unmapped_folio_to_zero_order, a wrapper
> to the existing __split_unmapped_folio. Caller can use it to
> uniformly split an unmapped high-order folio into 0-order folios.
>
> No functional change. It will be used in a subsequent commit.
>
> Signed-off-by: Jiaqi Yan <jiaqiyan@xxxxxxxxxx>
> ---
>   include/linux/huge_mm.h | 6 ++++++
>   mm/huge_memory.c        | 8 ++++++++
>   2 files changed, 14 insertions(+)
>
> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> index 71ac78b9f834f..ef6a84973e157 100644
> --- a/include/linux/huge_mm.h
> +++ b/include/linux/huge_mm.h
> @@ -365,6 +365,7 @@ unsigned long thp_get_unmapped_area_vmflags(struct file *filp, unsigned long add
>   		vm_flags_t vm_flags);
>   
>   bool can_split_folio(struct folio *folio, int caller_pins, int *pextra_pins);
> +int uniform_split_unmapped_folio_to_zero_order(struct folio *folio);
>   int split_huge_page_to_list_to_order(struct page *page, struct list_head *list,
>   		unsigned int new_order);
>   int min_order_for_split(struct folio *folio);
> @@ -569,6 +570,11 @@ can_split_folio(struct folio *folio, int caller_pins, int *pextra_pins)
>   {
>   	return false;
>   }
> +static inline int uniform_split_unmapped_folio_to_zero_order(struct folio *folio)
> +{
> +	VM_WARN_ON_ONCE_PAGE(1, page);
> +	return -EINVAL;
> +}

IIUC this patch won't be required (I agree that ideally the page 
allocator takes care of this), but for the future, let's consistently 
name these things "folio_split_XXX".

--
Cheers

David