[PATCH v2 21/27] mm: Add wait_for_stable_folio and wait_on_folio_writeback

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

Add compatibility wrappers for code which has not yet been converted
to use folios.

Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
 include/linux/pagemap.h | 12 ++++++++++--
 mm/page-writeback.c     | 27 +++++++++++++--------------
 2 files changed, 23 insertions(+), 16 deletions(-)

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 685f1b394629..619bfc6ea1ff 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -746,13 +746,21 @@ static inline int wait_on_page_locked_killable(struct page *page)
 
 extern void put_and_wait_on_page_locked(struct page *page);
 
-void wait_on_page_writeback(struct page *page);
+void wait_on_folio_writeback(struct folio *folio);
+static inline void wait_on_page_writeback(struct page *page)
+{
+	return wait_on_folio_writeback(page_folio(page));
+}
 void end_folio_writeback(struct folio *folio);
 static inline void end_page_writeback(struct page *page)
 {
 	return end_folio_writeback(page_folio(page));
 }
-void wait_for_stable_page(struct page *page);
+void wait_for_stable_folio(struct folio *folio);
+static inline void wait_for_stable_page(struct page *page)
+{
+	return wait_for_stable_folio(page_folio(page));
+}
 
 void page_endio(struct page *page, bool is_write, int err);
 
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 51b4326f0aaa..908fc7f60ae7 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2822,30 +2822,29 @@ int __test_set_page_writeback(struct page *page, bool keep_write)
 EXPORT_SYMBOL(__test_set_page_writeback);
 
 /*
- * Wait for a page to complete writeback
+ * Wait for a folio to complete writeback
  */
-void wait_on_page_writeback(struct page *page)
+void wait_on_folio_writeback(struct folio *folio)
 {
-	struct folio *folio = page_folio(page);
 	while (FolioWriteback(folio)) {
-		trace_wait_on_page_writeback(page, folio_mapping(folio));
+		trace_wait_on_page_writeback(&folio->page,
+						folio_mapping(folio));
 		wait_on_folio_bit(folio, PG_writeback);
 	}
 }
-EXPORT_SYMBOL_GPL(wait_on_page_writeback);
+EXPORT_SYMBOL_GPL(wait_on_folio_writeback);
 
 /**
- * wait_for_stable_page() - wait for writeback to finish, if necessary.
- * @page:	The page to wait on.
+ * wait_for_stable_folio() - wait for writeback to finish, if necessary.
+ * @folio: The folio to wait on.
  *
- * This function determines if the given page is related to a backing device
- * that requires page contents to be held stable during writeback.  If so, then
+ * This function determines if the given folio is related to a backing device
+ * that requires folio contents to be held stable during writeback.  If so, then
  * it will wait for any pending writeback to complete.
  */
-void wait_for_stable_page(struct page *page)
+void wait_for_stable_folio(struct folio *folio)
 {
-	page = thp_head(page);
-	if (page->mapping->host->i_sb->s_iflags & SB_I_STABLE_WRITES)
-		wait_on_page_writeback(page);
+	if (folio->page.mapping->host->i_sb->s_iflags & SB_I_STABLE_WRITES)
+		wait_on_folio_writeback(folio);
 }
-EXPORT_SYMBOL_GPL(wait_for_stable_page);
+EXPORT_SYMBOL_GPL(wait_for_stable_folio);
-- 
2.29.2