VOP_MKDIR
error = VOP_MKDIR(nd.ni_dvp, &nd.ni_vp, &nd.ni_cnd, &vattr);
error = VOP_MKDIR(nd.ni_dvp, &nd.ni_vp, &nd.ni_cnd, &va);
int VOP_MKDIR(struct vnode *, struct vnode **, struct componentname *,