2 files changed, 9 insertions, 2 deletions

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index dd73d29c15a8..bba82c414ba8 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1149,6 +1149,13 @@ int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page)
 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 5a0b3d4055f3..46936601e37f 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1630,8 +1630,8 @@ shmem_write_end(struct file *file, struct address_space *mapping,
         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 @@ static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *s
                         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)