linux-kernel - Re: [PATCH v2 25/28] gup: Convert compound_next() to gup_folio

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Date:   Mon, 10 Jan 2022 23:41:31 -0800
From:   John Hubbard <jhubbard@...dia.com>
To:     "Matthew Wilcox (Oracle)" <willy@...radead.org>, linux-mm@...ck.org
Cc:     Christoph Hellwig <hch@...radead.org>,
        William Kucharski <william.kucharski@...cle.com>,
        linux-kernel@...r.kernel.org, Jason Gunthorpe <jgg@...pe.ca>
Subject: Re: [PATCH v2 25/28] gup: Convert compound_next() to gup_folio_next()

On 1/9/22 20:24, Matthew Wilcox (Oracle) wrote:
> Convert both callers to work on folios instead of pages.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
> ---
>   mm/gup.c | 41 ++++++++++++++++++++++-------------------
>   1 file changed, 22 insertions(+), 19 deletions(-)

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


thanks,
-- 
John Hubbard
NVIDIA

> 
> diff --git a/mm/gup.c b/mm/gup.c
> index b5786e83c418..0cf2d5fd8d2d 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -220,20 +220,20 @@ static inline struct page *compound_range_next(unsigned long i,
>   	return page;
>   }
>   
> -static inline struct page *compound_next(unsigned long i,
> +static inline struct folio *gup_folio_next(unsigned long i,
>   		unsigned long npages, struct page **list, unsigned int *ntails)
>   {
> -	struct page *page;
> +	struct folio *folio;
>   	unsigned int nr;
>   
> -	page = compound_head(list[i]);
> +	folio = page_folio(list[i]);
>   	for (nr = i + 1; nr < npages; nr++) {
> -		if (compound_head(list[nr]) != page)
> +		if (page_folio(list[nr]) != folio)
>   			break;
>   	}
>   
>   	*ntails = nr - i;
> -	return page;
> +	return folio;
>   }
>   
>   /**
> @@ -261,17 +261,17 @@ static inline struct page *compound_next(unsigned long i,
>   void unpin_user_pages_dirty_lock(struct page **pages, unsigned long npages,
>   				 bool make_dirty)
>   {
> -	unsigned long index;
> -	struct page *head;
> -	unsigned int ntails;
> +	unsigned long i;
> +	struct folio *folio;
> +	unsigned int nr;
>   
>   	if (!make_dirty) {
>   		unpin_user_pages(pages, npages);
>   		return;
>   	}
>   
> -	for (index = 0; index < npages; index += ntails) {
> -		head = compound_next(index, npages, pages, &ntails);
> +	for (i = 0; i < npages; i += nr) {
> +		folio = gup_folio_next(i, npages, pages, &nr);
>   		/*
>   		 * Checking PageDirty at this point may race with
>   		 * clear_page_dirty_for_io(), but that's OK. Two key
> @@ -292,9 +292,12 @@ void unpin_user_pages_dirty_lock(struct page **pages, unsigned long npages,
>   		 * written back, so it gets written back again in the
>   		 * next writeback cycle. This is harmless.
>   		 */
> -		if (!PageDirty(head))
> -			set_page_dirty_lock(head);
> -		put_compound_head(head, ntails, FOLL_PIN);
> +		if (!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_pages_dirty_lock);
> @@ -347,9 +350,9 @@ EXPORT_SYMBOL(unpin_user_page_range_dirty_lock);
>    */
>   void unpin_user_pages(struct page **pages, unsigned long npages)
>   {
> -	unsigned long index;
> -	struct page *head;
> -	unsigned int ntails;
> +	unsigned long i;
> +	struct folio *folio;
> +	unsigned int nr;
>   
>   	/*
>   	 * If this WARN_ON() fires, then the system *might* be leaking pages (by
> @@ -359,9 +362,9 @@ void unpin_user_pages(struct page **pages, unsigned long npages)
>   	if (WARN_ON(IS_ERR_VALUE(npages)))
>   		return;
>   
> -	for (index = 0; index < npages; index += ntails) {
> -		head = compound_next(index, npages, pages, &ntails);
> -		put_compound_head(head, ntails, FOLL_PIN);
> +	for (i = 0; i < npages; i += nr) {
> +		folio = gup_folio_next(i, npages, pages, &nr);
> +		gup_put_folio(folio, nr, FOLL_PIN);
>   	}
>   }
>   EXPORT_SYMBOL(unpin_user_pages);