cbtocylno
j = cbtocylno(fs, i);
cylno = cbtocylno(&sblock, i);
cg_blktot(&icg)[cbtocylno(&sblock, d)]++;
cg_blks(&sblock, &icg, cbtocylno(&sblock, d))
cg_blks(&sblock, &icg, cbtocylno(&sblock, d))
cg_blktot(&acg)[cbtocylno(&sblock, d)]--;
cg_blks(&sblock, &acg, cbtocylno(&sblock, d))[cbtorpos(&sblock, d)]--;
cno = cbtocylno(&sblock, bit);
cylno = cbtocylno(fs, bpref);
cylno = cbtocylno(fs, bno);
cylno = cbtocylno(fs, bno);
cylno = cbtocylno(fs, bbase);