use list_add_tail in buffer_insert_list

This is a really old patch from the XFS tree.

We need to call list_add_tail in buffer_insert_list to preserve buffer ordering. This essential for a good extent layout with XFS's delayed allocation and a while ago the reiserfs group requested the same change.

ACKed by sct.

@@ -619,7 +655,7 @@
 	if (buffer_attached(bh))
 		list_del(&bh->b_inode_buffers);
 	set_buffer_attached(bh);
-	list_add(&bh->b_inode_buffers, list);
+	list_add_tail(&bh->b_inode_buffers, list);
 	spin_unlock(&lru_list_lock);
 }