[PATCH v6 22/27] mm/filemap: Add end_folio_writeback

["Matthew Wilcox (Oracle)" <willy@infradead.org>]

Add an end_page_writeback() wrapper function for users that are not yet
converted to folios.

end_folio_writeback() is less than half the size of end_page_writeback()
at just 105 bytes compared to 213 bytes, due to removing all the
compound_head() calls.  The 30 byte wrapper function makes this a net
saving of 70 bytes.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 include/linux/pagemap.h |  3 ++-
 mm/filemap.c            | 38 +++++++++++++++++++-------------------
 mm/folio-compat.c       |  6 ++++++
 3 files changed, 27 insertions(+), 20 deletions(-)

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index a7bbc34d92cb..36c31cfa3e64 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -830,7 +830,8 @@ static inline int wait_on_page_locked_killable(struct page *page)
 int put_and_wait_on_page_locked(struct page *page, int state);
 void wait_on_page_writeback(struct page *page);
 int wait_on_page_writeback_killable(struct page *page);
-extern void end_page_writeback(struct page *page);
+void end_page_writeback(struct page *page);
+void end_folio_writeback(struct folio *folio);
 void wait_for_stable_page(struct page *page);
 
 void page_endio(struct page *page, bool is_write, int err);
diff --git a/mm/filemap.c b/mm/filemap.c
index 21607db04835..4591974f2c28 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1175,11 +1175,11 @@ 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);
 }
 
 /*
@@ -1473,38 +1473,38 @@ void unlock_page_private_2(struct page *page)
 EXPORT_SYMBOL(unlock_page_private_2);
 
 /**
- * end_page_writeback - end writeback against a page
- * @page: the page
+ * end_folio_writeback - End writeback against a folio.
+ * @folio: The folio.
  */
-void end_page_writeback(struct page *page)
+void end_folio_writeback(struct folio *folio)
 {
 	/*
 	 * TestClearPageReclaim could be used here but it is an atomic
 	 * operation and overkill in this particular case. Failing to
-	 * shuffle a page marked for immediate reclaim is too mild to
+	 * shuffle a folio marked for immediate reclaim is too mild to
 	 * justify taking an atomic operation penalty at the end of
-	 * ever page writeback.
+	 * every folio writeback.
 	 */
-	if (PageReclaim(page)) {
-		ClearPageReclaim(page);
-		rotate_reclaimable_page(page);
+	if (FolioReclaim(folio)) {
+		ClearFolioReclaim(folio);
+		rotate_reclaimable_page(&folio->page);
 	}
 
 	/*
-	 * Writeback does not hold a page reference of its own, relying
+	 * Writeback does not hold a folio reference of its own, relying
 	 * on truncation to wait for the clearing of PG_writeback.
-	 * But here we must make sure that the page is not freed and
-	 * reused before the wake_up_page().
+	 * But here we must make sure that the folio is not freed and
+	 * reused before the wake_up_folio().
 	 */
-	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);
+EXPORT_SYMBOL(end_folio_writeback);
 
 /*
  * After completing I/O on a page, call this routine to update the page
diff --git a/mm/folio-compat.c b/mm/folio-compat.c
index 02798abf19a1..d1a1dfe52589 100644
--- a/mm/folio-compat.c
+++ b/mm/folio-compat.c
@@ -17,3 +17,9 @@ void unlock_page(struct page *page)
 	return unlock_folio(page_folio(page));
 }
 EXPORT_SYMBOL(unlock_page);
+
+void end_page_writeback(struct page *page)
+{
+	return end_folio_writeback(page_folio(page));
+}
+EXPORT_SYMBOL(end_page_writeback);
-- 
2.30.2