diff mbox series

[v4,01/16] mm: Make pagecache tagged lookups return only head pages

Message ID 20201112212641.27837-2-willy@infradead.org (mailing list archive)
State New, archived
Headers show
Series Overhaul multi-page lookups for THP | expand

Commit Message

Matthew Wilcox Nov. 12, 2020, 9:26 p.m. UTC 
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@infradead.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
---
 mm/filemap.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

Comments

Christoph Hellwig Nov. 14, 2020, 9:53 a.m. UTC | #1 
On Thu, Nov 12, 2020 at 09:26:26PM +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@infradead.org>
> Reviewed-by: Jan Kara <jack@suse.cz>
> Reviewed-by: William Kucharski <william.kucharski@oracle.com>

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>
diff mbox series

Patch

diff --git a/mm/filemap.c b/mm/filemap.c
index 249cf489f5df..bb6f2ae5a68c 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 +2074,9 @@  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.  @index is updated to the index immediately after the last
+ * page we return, ready for the next iteration.
  *
  * Return: the number of pages which were found.
  */
@@ -2109,9 +2110,9 @@  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;