[PATCH v4 30/36] mm: Support tail pages in wait_for_stable_page

[Matthew Wilcox <willy@xxxxxxxxxxxxx>]

From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>

page->mapping is undefined for tail pages, so operate exclusively on
the head page.

Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
 mm/page-writeback.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 7326b54ab728..e2da7d7e93b8 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2841,6 +2841,7 @@ EXPORT_SYMBOL_GPL(wait_on_page_writeback);
  */
 void wait_for_stable_page(struct page *page)
 {
+	page = compound_head(page);
 	if (bdi_cap_stable_pages_required(inode_to_bdi(page->mapping->host)))
 		wait_on_page_writeback(page);
 }
-- 
2.26.2