ext2_crc16
crc = ext2_crc16(~0, fs->e2fs->e2fs_uuid,
crc = ext2_crc16(crc, (uint8_t *)&block_group,
crc = ext2_crc16(crc, (uint8_t *)gd, offset);
crc = ext2_crc16(crc, (uint8_t *)gd + offset,