ZBT_HEADER
case ZBT_HEADER:
} else if (block_type == ZBT_HEADER) {
zp->zap_block_type = ZBT_HEADER;
zap_f_phys(zap)->zap_block_type != ZBT_HEADER) ||
if (zap_block_type != ZBT_HEADER || zap_magic != ZAP_MAGIC) {