1 files changed, 13 insertions, 4 deletions

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index c3fb38b1ea43..2e8c2b01d5d5 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -945,11 +945,20 @@ continue_unlock:
                                 goto continue_unlock;
                         }
 
-                        if (wbc->sync_mode != WB_SYNC_NONE)
-                                wait_on_page_writeback(page);
+                        if (!PageDirty(page)) {
+                                /* someone wrote it for us */
+                                goto continue_unlock;
+                        }
+
+                        if (PageWriteback(page)) {
+                                if (wbc->sync_mode != WB_SYNC_NONE)
+                                        wait_on_page_writeback(page);
+                                else
+                                        goto continue_unlock;
+                        }
 
-                        if (PageWriteback(page) ||
-                            !clear_page_dirty_for_io(page))
+                        BUG_ON(PageWriteback(page));
+                        if (!clear_page_dirty_for_io(page))
                                 goto continue_unlock;
 
                         ret = (*writepage)(page, wbc, data);