dtog
c = dtog(&sblock, blk);
cylno = dtog(&sblock, cg_frag);
cg = dtog(fs, bpref);
cg = dtog(fs, bprev);
startcg = dtog(fs, bap[indx - 1]) + 1;
cg = dtog(fs, bno);
c = dtog(ip->i_fs, bn);