2.6.26-rc1

 mm

diff --git a/mm/migrate.c b/mm/migrate.c
index 4e0eccc..449d77d 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -383,7 +383,14 @@ static void migrate_page_copy(struct page *newpage, struct page *page)
 
    if (PageDirty(page)) {
       clear_page_dirty_for_io(page);
-      set_page_dirty(newpage);
+      /*
+       * Want to mark the page and the radix tree as dirty, and
+       * redo the accounting that clear_page_dirty_for_io undid,
+       * but we can't use set_page_dirty because that function
+       * is actually a signal that all of the page has become dirty.
+       * Wheras only part of our page may be dirty.
+       */
+      __set_page_dirty_nobuffers(newpage);
     }
 
 #ifdef CONFIG_SWAP