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)++;
	}
}

void activate_page(struct page *page)
{
	if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
		struct pagevec *pvec = &get_locked_var(swapvec_lock,
						       activate_page_pvecs);

		page_cache_get(page);
		if (!pagevec_add(pvec, page))
			pagevec_lru_move_fn(pvec, __activate_page, NULL);
		put_locked_var(swapvec_lock, activate_page_pvecs);
	}
}

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

	if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
		enum lru_list lru = page_lru_base_type(page);
		list_move_tail(&page->lru, &zone->lru[lru].list);
		mem_cgroup_rotate_reclaimable_page(page);
		(*pgmoved)++;
	}
}

/*
 * Isolate one page from the LRU lists. If successful put it onto
 * the indicated list with elevated page count.
 *
 * Result:
 *  -EBUSY: page not on LRU list
 *  0: page removed from LRU list and added to the specified list.
 */
int isolate_lru_page(struct page *page, struct list_head *pagelist)
{
	int ret = -EBUSY;

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

		spin_lock_irq(&zone->lru_lock);
		if (PageLRU(page) && get_page_unless_zero(page)) {
			ret = 0;
			ClearPageLRU(page);
			if (PageActive(page))
				del_page_from_active_list(zone, page);
			else
				del_page_from_inactive_list(zone, page);
			list_add_tail(&page->lru, pagelist);
		}
		spin_unlock_irq(&zone->lru_lock);
	}
	return ret;
}

void activate_page(struct page *page)
{
	page = compound_head(page);
	if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
		struct pagevec *pvec = &get_cpu_var(activate_page_pvecs);

		get_page(page);
		if (!pagevec_add(pvec, page) || PageCompound(page))
			pagevec_lru_move_fn(pvec, __activate_page, NULL);
		put_cpu_var(activate_page_pvecs);
	}
}

static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec,
				 void *arg)
{
	int file = page_is_file_cache(page);
	int active = PageActive(page);
	enum lru_list lru = page_lru(page);

	VM_BUG_ON(PageLRU(page));

	SetPageLRU(page);
	add_page_to_lru_list(page, lruvec, lru);
	update_page_reclaim_stat(lruvec, file, active);
}

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

	spin_lock_irq(&zone->lru_lock);
	if (PageLRU(page) && !PageActive(page)) {
		del_page_from_inactive_list(zone, page);
		SetPageActive(page);
		add_page_to_active_list(zone, page);
		inc_page_state(pgactivate);
	}
	spin_unlock_irq(&zone->lru_lock);
}

/*
 * Scanning pfn is much easier than scanning lru list.
 * Scan pfn from start to end and Find LRU page.
 */
int scan_lru_pages(unsigned long start, unsigned long end)
{
	unsigned long pfn;
	struct page *page;
	for (pfn = start; pfn < end; pfn++) {
		if (pfn_valid(pfn)) {
			page = pfn_to_page(pfn);
			if (PageLRU(page))
				return pfn;
		}
	}
	return 0;
}

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

	spin_lock_irq(&zone->lru_lock);
	if (PageLRU(page) && !PageActive(page)) {
		del_page_from_inactive_list(zone, page);
		SetPageActive(page);
		add_page_to_active_list(zone, page);
		__count_vm_event(PGACTIVATE);
	}
	spin_unlock_irq(&zone->lru_lock);
}

static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec,
				 void *arg)
{
	int file = page_is_file_cache(page);
	int active = PageActive(page);
	enum lru_list lru = page_lru(page);

	VM_BUG_ON_PAGE(PageLRU(page), page);

	SetPageLRU(page);
	add_page_to_lru_list(page, lruvec, lru);
	update_page_reclaim_stat(lruvec, file, active);
	trace_mm_lru_insertion(page, page_to_pfn(page), lru, trace_pagemap_flags(page));
}

/*
 * mark_page_accessed：页访问的状态变化
 * 非活动页的第一次访问状态变化: inactive,unreferenced	->	inactive,referenced
 * 非活动页的第二次访问状态变化: inactive,referenced	->	active,unreferenced
 * 活动页的第一次访问状态变化:   active,unreferenced	->	active,referenced
 */
void mark_page_accessed(struct page *page)
{
	if (!PageActive(page) && !PageUnevictable(page) &&
			PageReferenced(page) && PageLRU(page)) {
		/* 非活动页的第二次访问:
		 * 将会使页从非活动链表移动到
		 * 活动链表,并且设置unreference*/
		activate_page(page);
		ClearPageReferenced(page);
	} else if (!PageReferenced(page)) { 
		/*第一次访问非活动page或者访问活动页时只设置PG_reference*/
		SetPageReferenced(page);
	}
}

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

	if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
		enum lru_list lru = page_lru_base_type(page);
		struct lruvec *lruvec;

		lruvec = mem_cgroup_lru_move_lists(page_zone(page),
						   page, lru, lru);
		list_move_tail(&page->lru, &lruvec->lists[lru]);
		(*pgmoved)++;
	}
}

/*
 * Writeback is about to end against a page which has been marked for immediate
 * reclaim.  If it still appears to be reclaimable, move it to the tail of the
 * inactive list.
 */
void rotate_reclaimable_page(struct page *page)
{
	if (!PageLocked(page) && !PageDirty(page) &&
	    !PageUnevictable(page) && PageLRU(page)) {
		struct pagevec *pvec;
		unsigned long flags;

		get_page(page);
		local_irq_save(flags);
		pvec = this_cpu_ptr(&lru_rotate_pvecs);
		if (!pagevec_add(pvec, page) || PageCompound(page))
			pagevec_move_tail(pvec);
		local_irq_restore(flags);
	}
}

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);
	}
}

/*
 * pagevec_release() for pages which are known to not be on the LRU
 *
 * This function reinitialises the caller's pagevec.
 */
void __pagevec_release_nonlru(struct pagevec *pvec)
{
	int i;
	struct pagevec pages_to_free;

	pagevec_init(&pages_to_free, pvec->cold);
	for (i = 0; i < pagevec_count(pvec); i++) {
		struct page *page = pvec->pages[i];

		VM_BUG_ON(PageLRU(page));
		if (put_page_testzero(page))
			pagevec_add(&pages_to_free, page);
	}
	pagevec_free(&pages_to_free);
	pagevec_reinit(pvec);
}

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);
	}
}

/*
 * 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);
}

static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec,
				 void *arg)
{
	enum lru_list lru = (enum lru_list)arg;
	int file = is_file_lru(lru);
	int active = is_active_lru(lru);

	VM_BUG_ON(PageActive(page));
	VM_BUG_ON(PageUnevictable(page));
	VM_BUG_ON(PageLRU(page));

	SetPageLRU(page);
	if (active)
		SetPageActive(page);
	add_page_to_lru_list(page, lruvec, lru);
	update_page_reclaim_stat(lruvec, file, active);
}

/*
 * Mark a page as having seen activity.
 *
 * inactive,unreferenced	->	inactive,referenced
 * inactive,referenced		->	active,unreferenced
 * active,unreferenced		->	active,referenced
 */
void mark_page_accessed(struct page *page)
{
	if (!PageActive(page) && !PageUnevictable(page) &&
			PageReferenced(page)) {
		if (PageLRU(page))
			activate_page(page);
		else if (PageIONBacked(page))
			SetPageActive(page);
		else
			return;
		ClearPageReferenced(page);
	} else if (!PageReferenced(page)) {
		SetPageReferenced(page);
		if (PageIONBacked(page) && PageActive(page))
			ion_activate_page(page);
	}
}

/* shrink the LRU cache list by discarding some extents from the list.
 * The expected number of extents discarded is "expected", while the
 * real number of discarded extents is "shrinked".
 */
int LRU_shrink_cache(struct cache_stack *cache, unsigned int expected,
                unsigned int *shrinked)
{
    struct list_head *lru_head, *lru_tail;
    struct extent *victim;
    int ret = 0;

    fprintf(stderr, "%s: expected:%d\n", __FUNCTION__, expected);

    *shrinked = 0;
    lru_head = &cache->active_list;
    lru_tail = lru_head->prev;

    while (*shrinked < expected && lru_tail != (& cache->active_list) ){
        victim = list_entry(lru_tail, struct extent, lru);

        if ( !PageLRU(victim) ){
            NCAC_error("extent flag is wrong. LRU flag is expected\n");
            ret = NCAC_INVAL_FLAGS;
            break;
        }

        lru_tail = lru_tail->prev;

        if (PageReadPending(victim) || PageWritePending(victim)){
            ret = NCAC_check_ioreq(victim);
            if (ret < 0){
                NCAC_error("NCAC_check_ioreq error: index=%ld, ioreq=%lld\n",
                        victim->index, lld(victim->ioreq));
                break;
            }

            if (ret) { /* completion */
                list_set_clean_page(victim);
            }
        }

        if ( is_extent_discardable(victim) ){
            LRU_remove_cache_item(cache, victim);
            list_add_tail(&victim->list, &cache->free_extent_list);
            (*shrinked)++;
        }
    }
    return ret;
}