[RFC PATCH 08/11] mm/filemap: Convert end_page_writeback to use a folio

["Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>]

With my config, this function shrinks from 480 bytes to 240 bytes
due to elimination of repeated calls to compound_head().

Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
 mm/filemap.c | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 50535b21b452..f1b65f777539 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1148,11 +1148,11 @@ static void wake_up_page_bit(struct page *page, int bit_nr)
 	spin_unlock_irqrestore(&q->lock, flags);
 }
 
-static void wake_up_page(struct page *page, int bit)
+static void wake_up_folio(struct folio *folio, int bit)
 {
-	if (!PageWaiters(page))
+	if (!FolioWaiters(folio))
 		return;
-	wake_up_page_bit(page, bit);
+	wake_up_page_bit(&folio->page, bit);
 }
 
 /*
@@ -1466,6 +1466,8 @@ EXPORT_SYMBOL(unlock_folio);
  */
 void end_page_writeback(struct page *page)
 {
+	struct folio *folio = page_folio(page);
+
 	/*
 	 * TestClearPageReclaim could be used here but it is an atomic
 	 * operation and overkill in this particular case. Failing to
@@ -1473,9 +1475,9 @@ void end_page_writeback(struct page *page)
 	 * justify taking an atomic operation penalty at the end of
 	 * ever page writeback.
 	 */
-	if (PageReclaim(page)) {
-		ClearPageReclaim(page);
-		rotate_reclaimable_page(page);
+	if (FolioReclaim(folio)) {
+		ClearFolioReclaim(folio);
+		rotate_reclaimable_page(&folio->page);
 	}
 
 	/*
@@ -1484,13 +1486,13 @@ void end_page_writeback(struct page *page)
 	 * But here we must make sure that the page is not freed and
 	 * reused before the wake_up_page().
 	 */
-	get_page(page);
-	if (!test_clear_page_writeback(page))
+	get_folio(folio);
+	if (!test_clear_page_writeback(&folio->page))
 		BUG();
 
 	smp_mb__after_atomic();
-	wake_up_page(page, PG_writeback);
-	put_page(page);
+	wake_up_folio(folio, PG_writeback);
+	put_folio(folio);
 }
 EXPORT_SYMBOL(end_page_writeback);
 
-- 
2.29.2