UMEM_HASH
uintptr_t bucket = (uintptr_t)UMEM_HASH(cp, buf);
for (bcp = *UMEM_HASH(cp, buf); bcp; bcp = bcp->bc_next)
hash_bucket = UMEM_HASH(cp, buf);
prev_bcpp = UMEM_HASH(cp, buf);
umem_bufctl_t **hash_bucket = UMEM_HASH(cp, addr);