UNIONFSTOV
KASSERT(VOP_ISLOCKED(UNIONFSTOV(unp)) == LK_EXCLUSIVE);
KASSERT(VOP_ISLOCKED(UNIONFSTOV(unp)) == LK_EXCLUSIVE);
vp = UNIONFSTOV(unp);
ump = MOUNTTOUNIONFSMOUNT(UNIONFSTOV(unp)->v_mount);
if ((UNIONFSTOV(unp)->v_mount->mnt_flag & MNT_RDONLY))