UBERBLOCK_MAGIC
if (ub->ub_magic == BSWAP_64((uint64_t)UBERBLOCK_MAGIC)) {
if (ub->ub_magic != UBERBLOCK_MAGIC ||
#define MMP_VALID(ubp) (ubp->ub_magic == UBERBLOCK_MAGIC && \
ub->ub_magic = UBERBLOCK_MAGIC;