linux-kernel - Re: [RFC PATCH 10/11] mm/filemap: Add folio_add_to_page

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Date:   Fri, 11 Dec 2020 10:32:57 +0200
From:   Nikolay Borisov <nborisov@...e.com>
To:     "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 10/11] mm/filemap: Add folio_add_to_page_cache



On 8.12.20 г. 21:46 ч., Matthew Wilcox (Oracle) wrote:
> Pages being added to the page cache should already be folios, so
> turn add_to_page_cache_lru() into a wrapper.  Saves hundreds of
> bytes of text.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
> ---
>  include/linux/pagemap.h | 13 +++++++--
>  mm/filemap.c            | 62 ++++++++++++++++++++---------------------
>  2 files changed, 41 insertions(+), 34 deletions(-)
> 
> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> index 060faeb8d701..3bc56b3aa384 100644
> --- a/include/linux/pagemap.h
> +++ b/include/linux/pagemap.h
> @@ -778,9 +778,9 @@ static inline int fault_in_pages_readable(const char __user *uaddr, int size)
>  }
>  
>  int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
> -				pgoff_t index, gfp_t gfp_mask);
> -int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
> -				pgoff_t index, gfp_t gfp_mask);
> +				pgoff_t index, gfp_t gfp);
> +int folio_add_to_page_cache(struct folio *folio, struct address_space *mapping,
> +				pgoff_t index, gfp_t gfp);
>  extern void delete_from_page_cache(struct page *page);
>  extern void __delete_from_page_cache(struct page *page, void *shadow);
>  int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask);
> @@ -805,6 +805,13 @@ static inline int add_to_page_cache(struct page *page,
>  	return error;
>  }
>  
> +static inline int add_to_page_cache_lru(struct page *page,
> +		struct address_space *mapping, pgoff_t index, gfp_t gfp)
> +{
> +	return folio_add_to_page_cache((struct folio *)page, mapping,
> +			index, gfp);
> +}
> +
>  /**
>   * struct readahead_control - Describes a readahead request.
>   *
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 56ff6aa24265..297144524f58 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -828,25 +828,25 @@ int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
>  }
>  EXPORT_SYMBOL_GPL(replace_page_cache_page);
>  
> -static noinline int __add_to_page_cache_locked(struct page *page,
> +static noinline int __add_to_page_cache_locked(struct folio *folio,
>  					struct address_space *mapping,
> -					pgoff_t offset, gfp_t gfp,
> +					pgoff_t index, gfp_t gfp,
>  					void **shadowp)
>  {
> -	XA_STATE(xas, &mapping->i_pages, offset);
> -	int huge = PageHuge(page);
> +	XA_STATE(xas, &mapping->i_pages, index);
> +	int huge = PageHuge(&folio->page);

PageHuge also does page_compound, since you know this is either the head
page or not you could use PageHeadHuge which simply checks if it's a
head page and then goes directly to perform the hugepage check via the
dtor.

<snip>