vn_vfsrlock
error = vn_vfsrlock(cvp);
if (vn_vfsrlock(nvp)) {
if (vn_vfsrlock(vp)) {
if (vn_vfsrlock(ITOV(tip))) {
if (vn_vfsrlock(vp)) {
int vn_vfsrlock(struct vnode *vp);