Re: [PATCH 13/17] gup: Convert gup_huge_pgd() to use a folio

[John Hubbard <jhubbard@nvidia.com>]

On 1/2/22 13:57, Matthew Wilcox (Oracle) wrote:
> Use the new folio-based APIs.  Also fix an assumption that memmap is
> contiguous.  This was the last user of try_grab_compound_head(),
> so remove it.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> ---
>   mm/gup.c | 19 +++++++------------
>   1 file changed, 7 insertions(+), 12 deletions(-)

Reviewed-by: John Hubbard <jhubbard@nvidia.com>


thanks,
-- 
John Hubbard
NVIDIA

> 
> diff --git a/mm/gup.c b/mm/gup.c
> index e7bcee8776e1..7bd1e4a2648a 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -152,12 +152,6 @@ struct folio *try_grab_folio(struct page *page, int refs, unsigned int flags)
>   	return NULL;
>   }
>   
> -static inline struct page *try_grab_compound_head(struct page *page,
> -		int refs, unsigned int flags)
> -{
> -	return &try_grab_folio(page, refs, flags)->page;
> -}
> -
>   static void gup_put_folio(struct folio *folio, int refs, unsigned int flags)
>   {
>   	if (flags & FOLL_PIN) {
> @@ -2588,27 +2582,28 @@ static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr,
>   			struct page **pages, int *nr)
>   {
>   	int refs;
> -	struct page *head, *page;
> +	struct page *page;
> +	struct folio *folio;
>   
>   	if (!pgd_access_permitted(orig, flags & FOLL_WRITE))
>   		return 0;
>   
>   	BUILD_BUG_ON(pgd_devmap(orig));
>   
> -	page = pgd_page(orig) + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT);
> +	page = nth_page(pgd_page(orig), (addr & ~PGDIR_MASK) >> PAGE_SHIFT);
>   	refs = record_subpages(page, addr, end, pages + *nr);
>   
> -	head = try_grab_compound_head(pgd_page(orig), refs, flags);
> -	if (!head)
> +	folio = try_grab_folio(page, refs, flags);
> +	if (!folio)
>   		return 0;
>   
>   	if (unlikely(pgd_val(orig) != pgd_val(*pgdp))) {
> -		put_compound_head(head, refs, flags);
> +		gup_put_folio(folio, refs, flags);
>   		return 0;
>   	}
>   
>   	*nr += refs;
> -	SetPageReferenced(head);
> +	folio_set_referenced(folio);
>   	return 1;
>   }
>