void do_free_page (struct page *page)
{
	page->vme->is_loaded = false;
	del_page_from_lru_list(page);
	pagedir_clear_page(page->thread->pagedir, page->vme->vaddr);
	palloc_free_page(page->kaddr);
	free(page);
}

static void pagevec_move_tail_fn(struct page *page, struct lruvec *lruvec,
				 void *arg)
{
	int *pgmoved = arg;

	if (PageLRU(page) && !PageUnevictable(page)) {
		del_page_from_lru_list(page, lruvec, page_lru(page));
		ClearPageActive(page);
		add_page_to_lru_list_tail(page, lruvec, page_lru(page));
		(*pgmoved)++;
	}
}

/*
 * This path almost never happens for VM activity - pages are normally
 * freed via pagevecs.  But it gets used by networking.
 */
static void __page_cache_release(struct page *page)
{
	if (PageLRU(page)) {
		unsigned long flags;
		struct zone *zone = page_zone(page);

		spin_lock_irqsave(&zone->lru_lock, flags);
		VM_BUG_ON(!PageLRU(page));
		__ClearPageLRU(page);
		del_page_from_lru_list(zone, page, page_off_lru(page));
		spin_unlock_irqrestore(&zone->lru_lock, flags);
	}
}

/*
 * This path almost never happens for VM activity - pages are normally
 * freed via pagevecs.  But it gets used by networking.
 */
static void __page_cache_release(struct page *page)
{
	if (PageLRU(page)) {
		struct zone *zone = page_zone(page);
		struct lruvec *lruvec;
		unsigned long flags;

		spin_lock_irqsave(&zone->lru_lock, flags);
		lruvec = mem_cgroup_page_lruvec(page, zone);
		VM_BUG_ON_PAGE(!PageLRU(page), page);
		__ClearPageLRU(page);
		del_page_from_lru_list(page, lruvec, page_off_lru(page));
		spin_unlock_irqrestore(&zone->lru_lock, flags);
	}
}

static void __activate_page(struct page *page, struct lruvec *lruvec,
			    void *arg)
{
	if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
		int file = page_is_file_cache(page);
		int lru = page_lru_base_type(page);

		del_page_from_lru_list(page, lruvec, lru);
		SetPageActive(page);
		lru += LRU_ACTIVE;
		add_page_to_lru_list(page, lruvec, lru);

		__count_vm_event(PGACTIVATE);
		update_page_reclaim_stat(lruvec, file, 1);
	}
}

static void lru_deactivate_fn(struct page *page, struct lruvec *lruvec,
			    void *arg)
{
	if (PageLRU(page) && PageActive(page) && !PageUnevictable(page)) {
		int file = page_is_file_cache(page);
		int lru = page_lru_base_type(page);

		del_page_from_lru_list(page, lruvec, lru + LRU_ACTIVE);
		ClearPageActive(page);
		ClearPageReferenced(page);
		add_page_to_lru_list(page, lruvec, lru);

		__count_vm_event(PGDEACTIVATE);
		update_page_reclaim_stat(lruvec, file, 0);
	}
}

/*
 * If the page can not be invalidated, it is moved to the
 * inactive list to speed up its reclaim.  It is moved to the
 * head of the list, rather than the tail, to give the flusher
 * threads some time to write it out, as this is much more
 * effective than the single-page writeout from reclaim.
 *
 * If the page isn't page_mapped and dirty/writeback, the page
 * could reclaim asap using PG_reclaim.
 *
 * 1. active, mapped page -> none
 * 2. active, dirty/writeback page -> inactive, head, PG_reclaim
 * 3. inactive, mapped page -> none
 * 4. inactive, dirty/writeback page -> inactive, head, PG_reclaim
 * 5. inactive, clean -> inactive, tail
 * 6. Others -> none
 *
 * In 4, why it moves inactive's head, the VM expects the page would
 * be write it out by flusher threads as this is much more effective
 * than the single-page writeout from reclaim.
 */
static void lru_deactivate_fn(struct page *page, void *arg)
{
	int lru, file;
	bool active;
	struct zone *zone = page_zone(page);

	if (!PageLRU(page))
		return;

	if (PageUnevictable(page))
		return;

	/* Some processes are using the page */
	if (page_mapped(page))
		return;

	active = PageActive(page);

	file = page_is_file_cache(page);
	lru = page_lru_base_type(page);
	del_page_from_lru_list(zone, page, lru + active);
	ClearPageActive(page);
	ClearPageReferenced(page);
	add_page_to_lru_list(zone, page, lru);

	if (PageWriteback(page) || PageDirty(page)) {
		/*
		 * PG_reclaim could be raced with end_page_writeback
		 * It can make readahead confusing.  But race window
		 * is _really_ small and  it's non-critical problem.
		 */
		SetPageReclaim(page);
	} else {
		struct lruvec *lruvec;
		/*
		 * The page's writeback ends up during pagevec
		 * We moves tha page into tail of inactive.
		 */
		lruvec = mem_cgroup_lru_move_lists(zone, page, lru, lru);
		list_move_tail(&page->lru, &lruvec->lists[lru]);
		__count_vm_event(PGROTATED);
	}

	if (active)
		__count_vm_event(PGDEACTIVATE);
	update_page_reclaim_stat(zone, page, file, 0);
}

/*
 * Batched page_cache_release().  Decrement the reference count on all the
 * passed pages.  If it fell to zero then remove the page from the LRU and
 * free it.
 *
 * Avoid taking zone->lru_lock if possible, but if it is taken, retain it
 * for the remainder of the operation.
 *
 * The locking in this function is against shrink_inactive_list(): we recheck
 * the page count inside the lock to see whether shrink_inactive_list()
 * grabbed the page via the LRU.  If it did, give up: shrink_inactive_list()
 * will free it.
 */
void release_pages(struct page **pages, int nr, int cold)
{
	int i;
	LIST_HEAD(pages_to_free);
	struct zone *zone = NULL;
	unsigned long uninitialized_var(flags);

	for (i = 0; i < nr; i++) {
		struct page *page = pages[i];

		if (unlikely(PageCompound(page))) {
			if (zone) {
				spin_unlock_irqrestore(&zone->lru_lock, flags);
				zone = NULL;
			}
			put_compound_page(page);
			continue;
		}

		if (!put_page_testzero(page))
			continue;

		if (PageLRU(page)) {
			struct zone *pagezone = page_zone(page);

			if (pagezone != zone) {
				if (zone)
					spin_unlock_irqrestore(&zone->lru_lock,
									flags);
				zone = pagezone;
				spin_lock_irqsave(&zone->lru_lock, flags);
			}
			VM_BUG_ON(!PageLRU(page));
			__ClearPageLRU(page);
			del_page_from_lru_list(zone, page, page_off_lru(page));
		}

		list_add(&page->lru, &pages_to_free);
	}
	if (zone)
		spin_unlock_irqrestore(&zone->lru_lock, flags);

	free_hot_cold_page_list(&pages_to_free, cold);
}

/*
 * FIXME: speed this up?
 */
void activate_page(struct page *page)
{
	struct zone *zone = page_zone(page);

	spin_lock_irq(&zone->lru_lock);
	if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
		int file = page_is_file_cache(page);
		int lru = LRU_BASE + file;
		del_page_from_lru_list(zone, page, lru);

		SetPageActive(page);
		lru += LRU_ACTIVE;
		add_page_to_lru_list(zone, page, lru);
		__count_vm_event(PGACTIVATE);
		mem_cgroup_move_lists(page, lru);

		zone->recent_rotated[!!file]++;
		zone->recent_scanned[!!file]++;
	}
	spin_unlock_irq(&zone->lru_lock);
}

static void lru_lazyfree_fn(struct page *page, struct lruvec *lruvec,
			    void *arg)
{
	if (PageLRU(page) && PageAnon(page) && PageSwapBacked(page) &&
	    !PageSwapCache(page) && !PageUnevictable(page)) {
		bool active = PageActive(page);

		del_page_from_lru_list(page, lruvec,
				       LRU_INACTIVE_ANON + active);
		ClearPageActive(page);
		ClearPageReferenced(page);
		/*
		 * lazyfree pages are clean anonymous pages. They have
		 * SwapBacked flag cleared to distinguish normal anonymous
		 * pages
		 */
		ClearPageSwapBacked(page);
		add_page_to_lru_list(page, lruvec, LRU_INACTIVE_FILE);

		__count_vm_events(PGLAZYFREE, hpage_nr_pages(page));
		count_memcg_page_event(page, PGLAZYFREE);
		update_page_reclaim_stat(lruvec, 1, 0);
	}
}

/**
 * release_pages - batched put_page()
 * @pages: array of pages to release
 * @nr: number of pages
 *
 * Decrement the reference count on all the pages in @pages.  If it
 * fell to zero, remove the page from the LRU and free it.
 */
void release_pages(struct page **pages, int nr)
{
	int i;
	LIST_HEAD(pages_to_free);
	struct pglist_data *locked_pgdat = NULL;
	struct lruvec *lruvec;
	unsigned long uninitialized_var(flags);
	unsigned int uninitialized_var(lock_batch);

	for (i = 0; i < nr; i++) {
		struct page *page = pages[i];

		/*
		 * Make sure the IRQ-safe lock-holding time does not get
		 * excessive with a continuous string of pages from the
		 * same pgdat. The lock is held only if pgdat != NULL.
		 */
		if (locked_pgdat && ++lock_batch == SWAP_CLUSTER_MAX) {
			spin_unlock_irqrestore(&locked_pgdat->lru_lock, flags);
			locked_pgdat = NULL;
		}

		if (is_huge_zero_page(page))
			continue;

		/* Device public page can not be huge page */
		if (is_device_public_page(page)) {
			if (locked_pgdat) {
				spin_unlock_irqrestore(&locked_pgdat->lru_lock,
						       flags);
				locked_pgdat = NULL;
			}
			put_devmap_managed_page(page);
			continue;
		}

		page = compound_head(page);
		if (!put_page_testzero(page))
			continue;

		if (PageCompound(page)) {
			if (locked_pgdat) {
				spin_unlock_irqrestore(&locked_pgdat->lru_lock, flags);
				locked_pgdat = NULL;
			}
			__put_compound_page(page);
			continue;
		}

		if (PageLRU(page)) {
			struct pglist_data *pgdat = page_pgdat(page);

			if (pgdat != locked_pgdat) {
				if (locked_pgdat)
					spin_unlock_irqrestore(&locked_pgdat->lru_lock,
									flags);
				lock_batch = 0;
				locked_pgdat = pgdat;
				spin_lock_irqsave(&locked_pgdat->lru_lock, flags);
			}

			lruvec = mem_cgroup_page_lruvec(page, locked_pgdat);
			VM_BUG_ON_PAGE(!PageLRU(page), page);
			__ClearPageLRU(page);
			del_page_from_lru_list(page, lruvec, page_off_lru(page));
		}

		/* Clear Active bit in case of parallel mark_page_accessed */
		__ClearPageActive(page);
		__ClearPageWaiters(page);

		list_add(&page->lru, &pages_to_free);
	}
	if (locked_pgdat)
		spin_unlock_irqrestore(&locked_pgdat->lru_lock, flags);

	mem_cgroup_uncharge_list(&pages_to_free);
	free_unref_page_list(&pages_to_free);
}

/**
 * release_pages - batched page_cache_release()
 * @pages: array of pages to release
 * @nr: number of pages
 * @cold: whether the pages are cache cold
 *
 * Decrement the reference count on all the pages in @pages.  If it
 * fell to zero, remove the page from the LRU and free it.
 */
void release_pages(struct page **pages, int nr, bool cold)
{
	int i;
	LIST_HEAD(pages_to_free);
	struct zone *zone = NULL;
	struct lruvec *lruvec;
	unsigned long uninitialized_var(flags);
	unsigned int uninitialized_var(lock_batch);

	for (i = 0; i < nr; i++) {
		struct page *page = pages[i];

		if (unlikely(PageCompound(page))) {
			if (zone) {
				spin_unlock_irqrestore(&zone->lru_lock, flags);
				zone = NULL;
			}
			put_compound_page(page);
			continue;
		}

		/*
		 * Make sure the IRQ-safe lock-holding time does not get
		 * excessive with a continuous string of pages from the
		 * same zone. The lock is held only if zone != NULL.
		 */
		if (zone && ++lock_batch == SWAP_CLUSTER_MAX) {
			spin_unlock_irqrestore(&zone->lru_lock, flags);
			zone = NULL;
		}

		if (!put_page_testzero(page))
			continue;

		if (PageLRU(page)) {
			struct zone *pagezone = page_zone(page);

			if (pagezone != zone) {
				if (zone)
					spin_unlock_irqrestore(&zone->lru_lock,
									flags);
				lock_batch = 0;
				zone = pagezone;
				spin_lock_irqsave(&zone->lru_lock, flags);
			}

			lruvec = mem_cgroup_page_lruvec(page, zone);
			VM_BUG_ON_PAGE(!PageLRU(page), page);
			__ClearPageLRU(page);
			del_page_from_lru_list(page, lruvec, page_off_lru(page));
		}

		/* Clear Active bit in case of parallel mark_page_accessed */
		__ClearPageActive(page);

		list_add(&page->lru, &pages_to_free);
	}
	if (zone)
		spin_unlock_irqrestore(&zone->lru_lock, flags);

	mem_cgroup_uncharge_list(&pages_to_free);
	free_hot_cold_page_list(&pages_to_free, cold);
}