VV_CROSSLOCK
lowerrootvp->v_vflag |= VV_CROSSLOCK;
mp->mnt_vnodecovered->v_vflag &= ~VV_CROSSLOCK;
mp->mnt_vnodecovered->v_vflag |= VV_CROSSLOCK;
mp->mnt_vnodecovered->v_vflag &= ~VV_CROSSLOCK;
crosslock = (dp->v_vflag & VV_CROSSLOCK) != 0;