Re: [PATCH v2 26/28] gup: Convert compound_range_next() to gup_folio_range_next()

[John Hubbard]

On 1/9/22 20:24, Matthew Wilcox (Oracle) wrote:
> 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>
> ---
>   include/linux/mm.h |  4 ++--
>   mm/gup.c           | 38 ++++++++++++++++++--------------------
>   2 files changed, 20 insertions(+), 22 deletions(-)

Reviewed-by: John Hubbard <jhubbard@xxxxxxxxxx>


thanks,
--
John Hubbard
NVIDIA

> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index c103c6401ecd..1ddb0a55b5ca 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -216,10 +216,10 @@ int overcommit_policy_handler(struct ctl_table *, int, void *, size_t *,
>   
>   #if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP)
>   #define nth_page(page,n) pfn_to_page(page_to_pfn((page)) + (n))
> -#define page_nth(head, tail)	(page_to_pfn(tail) - page_to_pfn(head))
> +#define folio_nth(folio, page)	(page_to_pfn(page) - folio_pfn(folio))
>   #else
>   #define nth_page(page,n) ((page) + (n))
> -#define page_nth(head, tail)	((tail) - (head))
> +#define folio_nth(folio, tail)	((tail) - &(folio)->page)
>   #endif
>   
>   /* to align the pointer to the (next) page boundary */
> diff --git a/mm/gup.c b/mm/gup.c
> index 0cf2d5fd8d2d..1cdd5f2887a8 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -156,12 +156,6 @@ 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
>    *
> @@ -204,20 +198,21 @@ void unpin_user_page(struct page *page)
>   }
>   EXPORT_SYMBOL(unpin_user_page);
>   
> -static inline struct page *compound_range_next(unsigned long i,
> +static inline struct folio *gup_folio_range_next(unsigned long i,
>   		unsigned long npages, struct page *start, unsigned int *ntails)
>   {
> -	struct page *next, *page;
> +	struct page *next;
> +	struct folio *folio;
>   	unsigned int nr = 1;
>   
>   	next = nth_page(start, i);
> -	page = compound_head(next);
> -	if (PageHead(page))
> +	folio = page_folio(next);
> +	if (folio_test_large(folio))
>   		nr = min_t(unsigned int, npages - i,
> -			   compound_nr(page) - page_nth(page, next));
> +			   folio_nr_pages(folio) - folio_nth(folio, next));
>   
>   	*ntails = nr;
> -	return page;
> +	return folio;
>   }
>   
>   static inline struct folio *gup_folio_next(unsigned long i,
> @@ -326,15 +321,18 @@ EXPORT_SYMBOL(unpin_user_pages_dirty_lock);
>   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;
> +	unsigned long i;
> +	struct folio *folio;
> +	unsigned int nr;
>   
> -	for (index = 0; index < npages; index += ntails) {
> -		head = compound_range_next(index, npages, page, &ntails);
> -		if (make_dirty && !PageDirty(head))
> -			set_page_dirty_lock(head);
> -		put_compound_head(head, ntails, FOLL_PIN);
> +	for (i = 0; i < npages; i += nr) {
> +		folio = gup_folio_range_next(i, npages, page, &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);