On Mon, Oct 26, 2020 at 04:13:57AM +0000, Matthew Wilcox (Oracle) wrote:
> Pagecache tags are used for dirty page writeback. Since dirtiness is
> tracked on a per-THP basis, we only want to return the head page rather
> than each subpage of a tagged page. All the filesystems which use huge
> pages today are in-memory, so there are no tagged huge pages today.
>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
> Reviewed-by: Jan Kara <jack@xxxxxxx>
> Reviewed-by: William Kucharski <william.kucharski@xxxxxxxxxx>
> ---
> mm/filemap.c | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/mm/filemap.c b/mm/filemap.c
> index d5e7c2029d16..edde5dc0d28f 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -2066,7 +2066,7 @@ unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
> EXPORT_SYMBOL(find_get_pages_contig);
>
> /**
> - * find_get_pages_range_tag - find and return pages in given range matching @tag
> + * find_get_pages_range_tag - Find and return head pages matching @tag.
> * @mapping: the address_space to search
> * @index: the starting page index
> * @end: The final page index (inclusive)
> @@ -2074,8 +2074,8 @@ EXPORT_SYMBOL(find_get_pages_contig);
> * @nr_pages: the maximum number of pages
> * @pages: where the resulting pages are placed
> *
> - * Like find_get_pages, except we only return pages which are tagged with
> - * @tag. We update @index to index the next page for the traversal.
> + * Like find_get_pages(), except we only return head pages which are tagged
> + * with @tag. We update @index to index the next page for the traversal.
Nit: ^ next head page
> *
> * Return: the number of pages which were found.
> */
> @@ -2109,9 +2109,9 @@ unsigned find_get_pages_range_tag(struct address_space *mapping, pgoff_t *index,
> if (unlikely(page != xas_reload(&xas)))
> goto put_page;
>
> - pages[ret] = find_subpage(page, xas.xa_index);
> + pages[ret] = page;
> if (++ret == nr_pages) {
> - *index = xas.xa_index + 1;
> + *index = page->index + thp_nr_pages(page);
> goto out;
> }
> continue;
> --
> 2.28.0
>
>
--
Sincerely yours,
Mike.
