ntfs_btocn
cpbl = ntfs_btocn(blsize + ntfs_cntob(1) - 1);
ccl -= ntfs_btocn(off);
cn = ccn + ntfs_btocn(off);
ntfs_btocn(off), &vap);
cn = (ntfs_btocn(roff)) & (~(NTFS_COMPUNIT_CL - 1));
vap->va_vcnend = ntfs_btocn(vap->va_allocated);