sf_fbytes
sbp->f_bfree = sfp->sf_fbytes / NFS_FABLKSIZE;
sbp->sf_fbytes = fxdr_hyper(tl); tl += 2;
sfp->sf_fbytes != fxdr_hyper(tl))
sfp->sf_fbytes = fxdr_hyper(tl);
txdr_hyper(tval, &sfp->sf_fbytes);
tquad = fxdr_hyper(&sfp->sf_fbytes);