Re: [PATCH 15/17] gup: Convert for_each_compound_range() to gup_for_each_folio_range()

[John Hubbard <jhubbard@xxxxxxxxxx>]

On 1/2/22 13:57, Matthew Wilcox (Oracle) wrote:
> This macro can be considerably simplified by returning the folio from
> gup_folio_range_next() instead of void from compound_next().  Convert the
> only caller to work on folios instead of pages.
>
> This removes the last caller of put_compound_head(), so delete it.
>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
> ---
>   mm/gup.c | 50 +++++++++++++++++++++++---------------------------
>   1 file changed, 23 insertions(+), 27 deletions(-)

Reviewed-by: John Hubbard <jhubbard@xxxxxxxxxx>


thanks,
--
John Hubbard
NVIDIA

> diff --git a/mm/gup.c b/mm/gup.c
> index eaffa6807609..76717e05413d 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -165,12 +165,6 @@ static void gup_put_folio(struct folio *folio, int refs, unsigned int flags)
>   	folio_put_refs(folio, refs);
>   }
>   
> -static void put_compound_head(struct page *page, int refs, unsigned int flags)
> -{
> -	VM_BUG_ON_PAGE(PageTail(page), page);
> -	gup_put_folio((struct folio *)page, refs, flags);
> -}
> -
>   /**
>    * try_grab_page() - elevate a page's refcount by a flag-dependent amount
>    *
> @@ -213,31 +207,30 @@ void unpin_user_page(struct page *page)
>   }
>   EXPORT_SYMBOL(unpin_user_page);
>   
> -static inline void compound_range_next(unsigned long i, unsigned long npages,
> -				       struct page **list, struct page **head,
> -				       unsigned int *ntails)
> +static inline struct folio *gup_folio_range_next(unsigned long i,
> +		unsigned long npages, struct page **list, unsigned int *ntails)
>   {
> -	struct page *next, *page;
> +	struct page *next;
> +	struct folio *folio;
>   	unsigned int nr = 1;
>   
>   	if (i >= npages)
> -		return;
> +		return NULL;
>   
>   	next = *list + i;
> -	page = compound_head(next);
> -	if (PageCompound(page) && compound_order(page) >= 1)
> -		nr = min_t(unsigned int,
> -			   page + compound_nr(page) - next, npages - i);
> +	folio = page_folio(next);
> +	if (folio_test_large(folio))
> +		nr = min_t(unsigned int, npages - i,
> +			   &folio->page + folio_nr_pages(folio) - next);
>   
> -	*head = page;
>   	*ntails = nr;
> +	return folio;
>   }
>   
> -#define for_each_compound_range(__i, __list, __npages, __head, __ntails) \
> -	for (__i = 0, \
> -	     compound_range_next(__i, __npages, __list, &(__head), &(__ntails)); \
> -	     __i < __npages; __i += __ntails, \
> -	     compound_range_next(__i, __npages, __list, &(__head), &(__ntails)))
> +#define gup_for_each_folio_range(__i, __list, __npages, __folio, __ntails) \
> +	for (__i = 0; \
> +	     (__folio = gup_folio_range_next(__i, __npages, __list, &(__ntails))) != NULL; \
> +	     __i += __ntails)
>   
>   static inline struct folio *gup_folio_next(unsigned long i,
>   		unsigned long npages, struct page **list, unsigned int *ntails)
> @@ -353,13 +346,16 @@ void unpin_user_page_range_dirty_lock(struct page *page, unsigned long npages,
>   				      bool make_dirty)
>   {
>   	unsigned long index;
> -	struct page *head;
> -	unsigned int ntails;
> +	struct folio *folio;
> +	unsigned int nr;
>   
> -	for_each_compound_range(index, &page, npages, head, ntails) {
> -		if (make_dirty && !PageDirty(head))
> -			set_page_dirty_lock(head);
> -		put_compound_head(head, ntails, FOLL_PIN);
> +	gup_for_each_folio_range(index, &page, npages, folio, nr) {
> +		if (make_dirty && !folio_test_dirty(folio)) {
> +			folio_lock(folio);
> +			folio_mark_dirty(folio);
> +			folio_unlock(folio);
> +		}
> +		gup_put_folio(folio, nr, FOLL_PIN);
>   	}
>   }
>   EXPORT_SYMBOL(unpin_user_page_range_dirty_lock);