lbn_count
nextbn += lbn_count(ump, num1);
nextbn += lbn_count(ump, num);
nextbn += off * lbn_count(ump, num - 1);
nextbn += lbn_count(ump, num1);
nextbn += lbn_count(ump, num);
nextbn += off * lbn_count(ump, num - 1);
static ufs_lbn_t lbn_count(struct ufsmount *, int);