Re: [RFC PATCH 2/5] mm: page_owner: add support for splitting to any order in split page_owner.

[Roman Gushchin <roman.gushchin@linux.dev>]

On Mon, Mar 21, 2022 at 10:21:25AM -0400, Zi Yan wrote:
> From: Zi Yan <ziy@nvidia.com>
> 
> It adds a new_order parameter to set new page order in page owner and
> uses old_order instead of nr to make the parameters look consistent.
> It prepares for upcoming changes to support split huge page to any
> lower order.
> 
> Signed-off-by: Zi Yan <ziy@nvidia.com>
> ---
>  include/linux/page_owner.h | 12 +++++++-----
>  mm/huge_memory.c           |  3 ++-
>  mm/page_alloc.c            |  2 +-
>  mm/page_owner.c            | 13 +++++++------
>  4 files changed, 17 insertions(+), 13 deletions(-)
> 
> diff --git a/include/linux/page_owner.h b/include/linux/page_owner.h
> index 119a0c9d2a8b..16050cc89274 100644
> --- a/include/linux/page_owner.h
> +++ b/include/linux/page_owner.h
> @@ -11,7 +11,8 @@ extern struct page_ext_operations page_owner_ops;
>  extern void __reset_page_owner(struct page *page, unsigned short order);
>  extern void __set_page_owner(struct page *page,
>  			unsigned short order, gfp_t gfp_mask);
> -extern void __split_page_owner(struct page *page, unsigned int nr);
> +extern void __split_page_owner(struct page *page, unsigned short old_order,
> +			unsigned short new_order);

Unsigned short here,

>  extern void __folio_copy_owner(struct folio *newfolio, struct folio *old);
>  extern void __set_page_owner_migrate_reason(struct page *page, int reason);
>  extern void __dump_page_owner(const struct page *page);
> @@ -31,10 +32,11 @@ static inline void set_page_owner(struct page *page,
>  		__set_page_owner(page, order, gfp_mask);
>  }
>  
> -static inline void split_page_owner(struct page *page, unsigned int nr)
> +static inline void split_page_owner(struct page *page, unsigned int old_order,
> +			unsigned int new_order)

but unsigned int here.

>  {
>  	if (static_branch_unlikely(&page_owner_inited))
> -		__split_page_owner(page, nr);
> +		__split_page_owner(page, old_order, new_order);
>  }
>  static inline void folio_copy_owner(struct folio *newfolio, struct folio *old)
>  {
> @@ -56,11 +58,11 @@ static inline void reset_page_owner(struct page *page, unsigned short order)
>  {
>  }
>  static inline void set_page_owner(struct page *page,
> -			unsigned int order, gfp_t gfp_mask)
> +			unsigned short order, gfp_t gfp_mask)
>  {
>  }
>  static inline void split_page_owner(struct page *page,
> -			unsigned short order)
> +			unsigned short old_order, unsigned short new_order)
>  {
>  }
>  static inline void folio_copy_owner(struct folio *newfolio, struct folio *folio)
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 640040c386f0..fcfa46af6c4c 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -2367,6 +2367,7 @@ static void __split_huge_page(struct page *page, struct list_head *list,
>  	struct lruvec *lruvec;
>  	struct address_space *swap_cache = NULL;
>  	unsigned long offset = 0;
> +	unsigned int order = thp_order(head);
>  	unsigned int nr = thp_nr_pages(head);
>  	int i;
>  
> @@ -2408,7 +2409,7 @@ static void __split_huge_page(struct page *page, struct list_head *list,
>  	unlock_page_lruvec(lruvec);
>  	/* Caller disabled irqs, so they are still disabled here */
>  
> -	split_page_owner(head, nr);
> +	split_page_owner(head, order, 0);
>  
>  	/* See comment in __split_huge_page_tail() */
>  	if (PageAnon(head)) {
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index d982919b9e51..9cac40c26c58 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -3514,7 +3514,7 @@ void split_page(struct page *page, unsigned int order)
>  
>  	for (i = 1; i < (1 << order); i++)
>  		set_page_refcounted(page + i);
> -	split_page_owner(page, 1 << order);
> +	split_page_owner(page, order, 0);
>  	split_page_memcg(page, 1 << order, 0);
>  }
>  EXPORT_SYMBOL_GPL(split_page);
> diff --git a/mm/page_owner.c b/mm/page_owner.c
> index 0a9588506571..52013c846d19 100644
> --- a/mm/page_owner.c
> +++ b/mm/page_owner.c
> @@ -202,19 +202,20 @@ void __set_page_owner_migrate_reason(struct page *page, int reason)
>  	page_owner->last_migrate_reason = reason;
>  }
>  
> -void __split_page_owner(struct page *page, unsigned int nr)
> +void __split_page_owner(struct page *page, unsigned short old_order,
> +			unsigned short new_order)

And short again here. Please, make it consistent.

Other than that, looks good to me. Please, feel free to add
Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>
after fixing the type inconsistency.

Thank you!