Merge tag 'locking-urgent-2020-11-29' of git://git.kernel.org/pub/scm/linux/kernel...

[mirror_ubuntu-hirsute-kernel.git] / mm / filemap.c

diff --git a/mm/filemap.c b/mm/filemap.c
index 3ebbe64a0106d61797eaab41837e8be2bb6ba1c8..0b2067b3c32831aa1617123b3dc964d479cbd9d1 100644 (file)
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1484,11 +1484,19 @@ void end_page_writeback(struct page *page)
                rotate_reclaimable_page(page);
        }
 
+       /*
+        * Writeback does not hold a page 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().
+        */
+       get_page(page);
        if (!test_clear_page_writeback(page))
                BUG();
 
        smp_mb__after_atomic();
        wake_up_page(page, PG_writeback);
+       put_page(page);
 }
 EXPORT_SYMBOL(end_page_writeback);