Btrfs: handle running extent ops with skinny metadata

Chris hit a bug where we weren't finding extent records when running extent ops.
This is because we use the delayed_ref_head when running the extent op, which
means we can't use the ->type checks to see if we are metadata.  We also lose
the level of the metadata we are working on.  So to fix this we can just check
the ->is_data section of the extent_op, and we can store the level of the buffer
we were modifying in the extent_op.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fusionio.com>

fs/btrfs/ctree.c

@@ -951,10 +951,12 @@ static noinline int update_ref_for_cow(struct btrfs_trans_handle *trans,
 			BUG_ON(ret); /* -ENOMEM */
 		}
 		if (new_flags != 0) {
+			int level = btrfs_header_level(buf);
+
 			ret = btrfs_set_disk_extent_flags(trans, root,
 							  buf->start,
 							  buf->len,
-							  new_flags, 0);
+							  new_flags, level, 0);
 			if (ret)
 				return ret;
 		}