ext4_ext_space_root
unsigned max_root = ext4_ext_space_root(inode, 0);
cpu_to_le16(ext4_ext_space_root(inode, 0));
max = ext4_ext_space_root(inode, 1);
eh->eh_max = cpu_to_le16(ext4_ext_space_root(inode, 0));