nfs_getrootfh
if (nfs_getrootfh(&d, spec, mntvers, &nfhret) == 0)
int nfs_getrootfh(struct iodesc *, char *, u_char *, int *);
if (nfs_getrootfh(desc, path, nfs_root_node.fh, &nfs_root_node.version))