Function pmap_ts_referenced

freebsd/arm64/arm64/pmap.c:5500–5649

* pmap_ts_referenced: * * Return a count of reference bits for a page, clearing those bits. * It is not necessary for every reference bit to be cleared, but it * is necessary that 0 only be returned when there are truly no * reference bits set. * * As an optimization, update the page's dirty field if a modified bit is * found while counting reference bits. This opportunistic update can be

 *	to pmap_is_modified().
 */
int
pmap_ts_referenced(vm_page_t m)
{
	struct md_page *pvh;
	pv_entry_t pv, pvf;
	pmap_t pmap;
	struct rwlock *lock;
	pd_entry_t *pde, tpde;
	pt_entry_t *pte, tpte;
	vm_offset_t va;
	vm_paddr_t pa;
	int cleared, lvl, md_gen, not_cleared, pvh_gen;
	struct spglist free;

	KASSERT((m->oflags & VPO_UNMANAGED) == 0,
	    ("pmap_ts_referenced: page %p is not managed", m));
	SLIST_INIT(&free);
	cleared = 0;
	pa = VM_PAGE_TO_PHYS(m);
	lock = PHYS_TO_PV_LIST_LOCK(pa);
	pvh = (m->flags & PG_FICTITIOUS) != 0 ? &pv_dummy : page_to_pvh(m);
	rw_wlock(lock);
retry:
	not_cleared = 0;
	if ((pvf = TAILQ_FIRST(&pvh->pv_list)) == NULL)
		goto small_mappings;
	pv = pvf;
	do {
		if (pvf == NULL)
			pvf = pv;
		pmap = PV_PMAP(pv);
		if (!PMAP_TRYLOCK(pmap)) {
			pvh_gen = pvh->pv_gen;
			rw_wunlock(lock);
			PMAP_LOCK(pmap);
			rw_wlock(lock);
			if (pvh_gen != pvh->pv_gen) {
				PMAP_UNLOCK(pmap);
				goto retry;
			}
		}
		va = pv->pv_va;
		pde = pmap_pde(pmap, pv->pv_va, &lvl);
		KASSERT(pde != NULL, ("pmap_ts_referenced: no l1 table found"));
		KASSERT(lvl == 1,
		    ("pmap_ts_referenced: invalid pde level %d", lvl));
		tpde = pmap_load(pde);
		KASSERT((tpde & ATTR_DESCR_MASK) == L1_TABLE,
		    ("pmap_ts_referenced: found an invalid l1 table"));
		pte = pmap_l1_to_l2(pde, pv->pv_va);
		tpte = pmap_load(pte);
		if (pmap_pte_dirty(pmap, tpte)) {
			/*
			 * Although "tpte" is mapping a 2MB page, because
			 * this function is called at a 4KB page granularity,
			 * we only update the 4KB page under test.
			 */
			vm_page_dirty(m);