ext4_ext_space_block
neh->eh_max = cpu_to_le16(ext4_ext_space_block(inode, 0));
neh->eh_max = cpu_to_le16(ext4_ext_space_block(inode, 0));
DIV_ROUND_UP(extents, ext4_ext_space_block(inode, 0));
max = ext4_ext_space_block(inode, 1);