Function vm_page_wire

freebsd/vm/vm_page.c:3900–3922

* Mark this page as wired down. For managed pages, this prevents reclamation * by the page daemon, or when the containing object, if any, is destroyed. */

 * by the page daemon, or when the containing object, if any, is destroyed.
 */
void
vm_page_wire(vm_page_t m)
{
	u_int old;

#ifdef INVARIANTS
	if (m->object != NULL && !vm_page_busied(m) &&
	    !vm_object_busied(m->object))
		VM_OBJECT_ASSERT_LOCKED(m->object);
#endif
	KASSERT((m->flags & PG_FICTITIOUS) == 0 ||
	    VPRC_WIRE_COUNT(m->ref_count) >= 1,
	    ("vm_page_wire: fictitious page %p has zero wirings", m));

	old = atomic_fetchadd_int(&m->ref_count, 1);
	KASSERT(VPRC_WIRE_COUNT(old) != VPRC_WIRE_COUNT_MAX,
	    ("vm_page_wire: counter overflow for page %p", m));
	if (VPRC_WIRE_COUNT(old) == 0) {
		if ((m->oflags & VPO_UNMANAGED) == 0)
			vm_page_aflag_set(m, PGA_DEQUEUE);
		vm_wire_add(1);
	}
}

/*
 * Attempt to wire a mapped page following a pmap lookup of that page.