v_specparent
if (KREAD(kd, (u_long)vp->v_specparent, &parent)) {
vp->v_specparent);
pvp = vp->v_specparent; /* get parent device */
vn_lock(vp->v_specparent, LK_EXCLUSIVE|LK_RETRY);
error = VOP_GETATTR(vp->v_specparent, ap->a_vap, ap->a_cred, ap->a_p);
VOP_UNLOCK(vp->v_specparent);
vn_lock(vp->v_specparent, LK_EXCLUSIVE|LK_RETRY);
error = VOP_SETATTR(vp->v_specparent, ap->a_vap, ap->a_cred, p);
VOP_UNLOCK(vp->v_specparent);
vn_lock(vp->v_specparent, LK_EXCLUSIVE|LK_RETRY);
error = VOP_ACCESS(vp->v_specparent, ap->a_mode, ap->a_cred, ap->a_p);
VOP_UNLOCK(vp->v_specparent);
cvp->v_specparent = vp;