diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index dd73d29..bba82c4 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1149,6 +1149,13 @@
 EXPORT_SYMBOL(redirty_page_for_writepage);
 
 /*
+ * Dirty a page.
+ *
+ * For pages with a mapping this should be done under the page lock
+ * for the benefit of asynchronous memory errors who prefer a consistent
+ * dirty state. This rule can be broken in some special cases,
+ * but should be better not to.
+ *
  * If the mapping doesn't provide a set_page_dirty a_op, then
  * just fall through and assume that it wants buffer_heads.
  */
diff --git a/mm/shmem.c b/mm/shmem.c
index 5a0b3d4..4693660 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1630,8 +1630,8 @@
 	if (pos + copied > inode->i_size)
 		i_size_write(inode, pos + copied);
 
-	unlock_page(page);
 	set_page_dirty(page);
+	unlock_page(page);
 	page_cache_release(page);
 
 	return copied;
@@ -1968,13 +1968,13 @@
 			iput(inode);
 			return error;
 		}
-		unlock_page(page);
 		inode->i_mapping->a_ops = &shmem_aops;
 		inode->i_op = &shmem_symlink_inode_operations;
 		kaddr = kmap_atomic(page, KM_USER0);
 		memcpy(kaddr, symname, len);
 		kunmap_atomic(kaddr, KM_USER0);
 		set_page_dirty(page);
+		unlock_page(page);
 		page_cache_release(page);
 	}
 	if (dir->i_mode & S_ISGID)