linux-kernel - Re: [PATCH v4 09/25] mm: Add folio_index, folio_page and folio

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Sat, 13 Mar 2021 12:37:16 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     "Matthew Wilcox (Oracle)" <willy@...radead.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v4 09/25] mm: Add folio_index, folio_page and
 folio_contains

On Fri,  5 Mar 2021 04:18:45 +0000 "Matthew Wilcox (Oracle)" <willy@...radead.org> wrote:

> folio_index() is the equivalent of page_index() for folios.  folio_page()
> finds the page in a folio for a page cache index.  folio_contains()
> tells you whether a folio contains a particular page cache index.
> 

copy-paste changelog into each function's covering comment?

> ---
>  include/linux/pagemap.h | 23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
> 
> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> index f07c03da83f6..5094b50f7680 100644
> --- a/include/linux/pagemap.h
> +++ b/include/linux/pagemap.h
> @@ -447,6 +447,29 @@ static inline bool thp_contains(struct page *head, pgoff_t index)
>  	return page_index(head) == (index & ~(thp_nr_pages(head) - 1UL));
>  }
>  
> +static inline pgoff_t folio_index(struct folio *folio)
> +{
> +        if (unlikely(FolioSwapCache(folio)))
> +                return __page_file_index(&folio->page);
> +        return folio->page.index;
> +}
> +
> +static inline struct page *folio_page(struct folio *folio, pgoff_t index)
> +{
> +	index -= folio_index(folio);
> +	VM_BUG_ON_FOLIO(index >= folio_nr_pages(folio), folio);
> +	return &folio->page + index;
> +}

One would expect folio_page() to be the reverse of page_folio(), only
it isn't anything like that.

> +/* Does this folio contain this index? */
> +static inline bool folio_contains(struct folio *folio, pgoff_t index)
> +{
> +	/* HugeTLBfs indexes the page cache in units of hpage_size */
> +	if (PageHuge(&folio->page))
> +		return folio->page.index == index;
> +	return index - folio_index(folio) < folio_nr_pages(folio);
> +}
> +
>  /*
>   * Given the page we found in the page cache, return the page corresponding
>   * to this index in the file