VPF_DEFER_DIRTY
CTASSERT(VMPF_DEFER_DIRTY == VPF_DEFER_DIRTY);
atomic_and_8(&vmp->vmp_flags, ~VPF_DEFER_DIRTY);
(vmp->vmp_flags & VPF_DEFER_DIRTY) == 0 &&
#define VPF_ALL (VPF_DEFER_DIRTY)