diff --git a/fs/btrfs/disk-io.h b/fs/btrfs/disk-io.h
index ee95fa0..41acb65 100644
--- a/fs/btrfs/disk-io.h
+++ b/fs/btrfs/disk-io.h
@@ -17,5 +17,8 @@
 void tree_block_release(struct ctree_root *root, struct tree_buffer *buf);
 struct tree_buffer *alloc_free_block(struct ctree_root *root);
 int update_root_block(struct ctree_root *root);
+int mkfs(int fd);
+
+#define CTREE_SUPER_INFO_OFFSET(bs) (16 * (bs))
 
 #endif