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