getspecialvnode
error = getspecialvnode(VT_NON, NULL, &devfs_vnode_dev_vops_p,
error = getspecialvnode(VT_VFS, mp, &sync_vnode_vops_p, &vp, 0, 0);
int getspecialvnode (enum vtagtype tag, struct mount *mp,
error = getspecialvnode(VT_NON, NULL, &swapdev_vnode_vops_p,