ubh_clrbit
ubh_clrbit (UCPI_UBH(ucpi), ucpi->c_freeoff, fragno + i);
ubh_clrbit (UCPI_UBH(ucpi), ucpi->c_freeoff, result + i);
ubh_clrbit(UCPI_UBH(ucpi), ucpi->c_clusteroff, blkno);
ubh_clrbit (UCPI_UBH(ucpi), ucpi->c_iusedoff, bit);