static void cifs_fscache_inode_now_uncached(void *cookie_netfs_data)
{
	struct cifsInodeInfo *cifsi = cookie_netfs_data;
	struct pagevec pvec;
	pgoff_t first;
	int loop, nr_pages;

	pagevec_init(&pvec, 0);
	first = 0;

	cFYI(1, "%s: cifs inode 0x%p now uncached", __func__, cifsi);

	for (;;) {
		nr_pages = pagevec_lookup(&pvec,
					  cifsi->vfs_inode.i_mapping, first,
					  PAGEVEC_SIZE - pagevec_count(&pvec));
		if (!nr_pages)
			break;

		for (loop = 0; loop < nr_pages; loop++)
			ClearPageFsCache(pvec.pages[loop]);

		first = pvec.pages[nr_pages - 1]->index + 1;

		pvec.nr = nr_pages;
		pagevec_release(&pvec);
		cond_resched();
	}
}

// dyc: add all pages into inactive list
void __pagevec_lru_add(struct pagevec *pvec)
{
	int i;
	struct zone *zone = NULL;
    // dyc: iterate all pages and add them to inactive list
	for (i = 0; i < pagevec_count(pvec); i++) {
		struct page *page = pvec->pages[i];
		struct zone *pagezone = page_zone(page);
        // dyc: lock/unlock until next zone
		if (pagezone != zone) {
			if (zone)
				spin_unlock_irq(&zone->lru_lock);
			zone = pagezone;
			spin_lock_irq(&zone->lru_lock);
		}
		VM_BUG_ON(PageLRU(page));
        // dyc: set pg LRU flag
		SetPageLRU(page);
        // dyc: add to inactive list and increase vm_stat
		add_page_to_inactive_list(zone, page);
	}
	if (zone)
		spin_unlock_irq(&zone->lru_lock);
	release_pages(pvec->pages, pvec->nr, pvec->cold);
	pagevec_reinit(pvec);
}

unsigned pagevec_lookup_tag(struct pagevec *pvec, struct address_space *mapping,
		pgoff_t *index, int tag, unsigned nr_pages)
{
	pvec->nr = find_get_pages_tag(mapping, index, tag,
					nr_pages, pvec->pages);
	return pagevec_count(pvec);
}

/*
 * pagevec_move_tail() must be called with IRQ disabled.
 * Otherwise this may cause nasty races.
 */
static void pagevec_move_tail(struct pagevec *pvec)
{
	int i;
	int pgmoved = 0;
	struct zone *zone = NULL;

	for (i = 0; i < pagevec_count(pvec); i++) {
		struct page *page = pvec->pages[i];
		struct zone *pagezone = page_zone(page);

		if (pagezone != zone) {
			if (zone)
				spin_unlock(&zone->lru_lock);
			zone = pagezone;
			spin_lock(&zone->lru_lock);
		}
		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++;
		}
	}
	if (zone)
		spin_unlock(&zone->lru_lock);
	__count_vm_events(PGROTATED, pgmoved);
	release_pages(pvec->pages, pvec->nr, pvec->cold);
	pagevec_reinit(pvec);
}

/**
 * pagevec_lookup_range - gang pagecache lookup
 * @pvec:	Where the resulting pages are placed
 * @mapping:	The address_space to search
 * @start:	The starting page index
 * @end:	The final page index
 *
 * pagevec_lookup_range() will search for & return a group of up to PAGEVEC_SIZE
 * pages in the mapping starting from index @start and upto index @end
 * (inclusive).  The pages are placed in @pvec.  pagevec_lookup() takes a
 * reference against the pages in @pvec.
 *
 * The search returns a group of mapping-contiguous pages with ascending
 * indexes.  There may be holes in the indices due to not-present pages. We
 * also update @start to index the next page for the traversal.
 *
 * pagevec_lookup_range() returns the number of pages which were found. If this
 * number is smaller than PAGEVEC_SIZE, the end of specified range has been
 * reached.
 */
unsigned pagevec_lookup_range(struct pagevec *pvec,
		struct address_space *mapping, pgoff_t *start, pgoff_t end)
{
	pvec->nr = find_get_pages_range(mapping, start, end, PAGEVEC_SIZE,
					pvec->pages);
	return pagevec_count(pvec);
}

void nilfs_clear_dirty_pages(struct address_space *mapping)
{
	struct pagevec pvec;
	unsigned int i;
	pgoff_t index = 0;

	pagevec_init(&pvec, 0);

	while (pagevec_lookup_tag(&pvec, mapping, &index, PAGECACHE_TAG_DIRTY,
				  PAGEVEC_SIZE)) {
		for (i = 0; i < pagevec_count(&pvec); i++) {
			struct page *page = pvec.pages[i];
			struct buffer_head *bh, *head;

			lock_page(page);
			ClearPageUptodate(page);
			ClearPageMappedToDisk(page);
			bh = head = page_buffers(page);
			do {
				lock_buffer(bh);
				clear_buffer_dirty(bh);
				clear_buffer_nilfs_volatile(bh);
				clear_buffer_uptodate(bh);
				clear_buffer_mapped(bh);
				unlock_buffer(bh);
				bh = bh->b_this_page;
			} while (bh != head);

			__nilfs_clear_page_dirty(page);
			unlock_page(page);
		}
		pagevec_release(&pvec);
		cond_resched();
	}
}

/*
 * The pages which we're about to release may be in the deferred lru-addition
 * queues.  That would prevent them from really being freed right now.  That's
 * OK from a correctness point of view but is inefficient - those pages may be
 * cache-warm and we want to give them back to the page allocator as soon as possible
 *
 * So __pagevec_release() will drain those queues here.  __pagevec_lru_add()
 * and __pagevec_lru_add_active() call release_pages() directly to avoid
 * mutual recursion.
 */
void __pagevec_release(struct pagevec *pvec)
{
	lru_add_drain();
	release_pages(pvec->pages, pagevec_count(pvec), pvec->cold);
    // dyc: set pvec->nr to 0
	pagevec_reinit(pvec);
}

static void activate_page_drain(int cpu)
{
	struct pagevec *pvec = &per_cpu(activate_page_pvecs, cpu);

	if (pagevec_count(pvec))
		pagevec_lru_move_fn(pvec, __activate_page, NULL);
}

static void pagevec_lru_move_fn(struct pagevec *pvec,
				void (*move_fn)(struct page *page, void *arg),
				void *arg)
{
	int i;
	struct zone *zone = NULL;
	unsigned long flags = 0;

	for (i = 0; i < pagevec_count(pvec); i++) {
		struct page *page = pvec->pages[i];
		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);
		}

		(*move_fn)(page, arg);
	}
	if (zone)
		spin_unlock_irqrestore(&zone->lru_lock, flags);
	release_pages(pvec->pages, pvec->nr, pvec->cold);
	pagevec_reinit(pvec);
}

/*
 * indication the cookie is no longer uncached
 * - this function is called when the backing store currently caching a cookie
 *   is removed
 * - the netfs should use this to clean up any markers indicating cached pages
 * - this is mandatory for any object that may have data
 */
static void afs_vnode_cache_now_uncached(void *cookie_netfs_data)
{
	struct afs_vnode *vnode = cookie_netfs_data;
	struct pagevec pvec;
	pgoff_t first;
	int loop, nr_pages;

	_enter("{%x,%x,%Lx}",
	       vnode->fid.vnode, vnode->fid.unique, vnode->status.data_version);

	pagevec_init(&pvec, 0);
	first = 0;

	for (;;) {
		/* grab a bunch of pages to clean */
		nr_pages = pagevec_lookup(&pvec, vnode->vfs_inode.i_mapping,
					  first,
					  PAGEVEC_SIZE - pagevec_count(&pvec));
		if (!nr_pages)
			break;

		for (loop = 0; loop < nr_pages; loop++)
			ClearPageFsCache(pvec.pages[loop]);

		first = pvec.pages[nr_pages - 1]->index + 1;

		pvec.nr = nr_pages;
		pagevec_release(&pvec);
		cond_resched();
	}

	_leave("");
}

void __pagevec_lru_add_active(struct pagevec *pvec)
{
	int i;
	struct zone *zone = NULL;

	for (i = 0; i < pagevec_count(pvec); i++) {
		struct page *page = pvec->pages[i];
		struct zone *pagezone = page_zone(page);

		if (pagezone != zone) {
			if (zone)
				spin_unlock_irq(&zone->lru_lock);
			zone = pagezone;
			spin_lock_irq(&zone->lru_lock);
		}
		VM_BUG_ON(PageLRU(page));
		SetPageLRU(page);
		VM_BUG_ON(PageActive(page));
		SetPageActive(page);
		add_page_to_active_list(zone, page);
	}
	if (zone)
		spin_unlock_irq(&zone->lru_lock);
	release_pages(pvec->pages, pvec->nr, pvec->cold);
	pagevec_reinit(pvec);
}

/**
 * nilfs_copy_back_pages -- copy back pages to original cache from shadow cache
 * @dmap: destination page cache
 * @smap: source page cache
 *
 * No pages must no be added to the cache during this process.
 * This must be ensured by the caller.
 */
void nilfs_copy_back_pages(struct address_space *dmap,
			   struct address_space *smap)
{
	struct pagevec pvec;
	unsigned int i, n;
	pgoff_t index = 0;
	int err;

	pagevec_init(&pvec, 0);
repeat:
	n = pagevec_lookup(&pvec, smap, &index);
	if (!n)
		return;

	for (i = 0; i < pagevec_count(&pvec); i++) {
		struct page *page = pvec.pages[i], *dpage;
		pgoff_t offset = page->index;

		lock_page(page);
		dpage = find_lock_page(dmap, offset);
		if (dpage) {
			/* override existing page on the destination cache */
			WARN_ON(PageDirty(dpage));
			nilfs_copy_page(dpage, page, 0);
			unlock_page(dpage);
			put_page(dpage);
		} else {
			struct page *page2;

			/* move the page to the destination cache */
			spin_lock_irq(&smap->tree_lock);
			page2 = radix_tree_delete(&smap->page_tree, offset);
			WARN_ON(page2 != page);

			smap->nrpages--;
			spin_unlock_irq(&smap->tree_lock);

			spin_lock_irq(&dmap->tree_lock);
			err = radix_tree_insert(&dmap->page_tree, offset, page);
			if (unlikely(err < 0)) {
				WARN_ON(err == -EEXIST);
				page->mapping = NULL;
				put_page(page); /* for cache */
			} else {
				page->mapping = dmap;
				dmap->nrpages++;
				if (PageDirty(page))
					radix_tree_tag_set(&dmap->page_tree,
							   offset,
							   PAGECACHE_TAG_DIRTY);
			}
			spin_unlock_irq(&dmap->tree_lock);
		}
		unlock_page(page);
	}
	pagevec_release(&pvec);
	cond_resched();

	goto repeat;
}

/*
 * Indication from FS-Cache that the cookie is no longer cached
 * - This function is called when the backing store currently caching a cookie
 *   is removed
 * - The netfs should use this to clean up any markers indicating cached pages
 * - This is mandatory for any object that may have data
 */
static void nfs_fscache_inode_now_uncached(void *cookie_netfs_data)
{
	struct nfs_inode *nfsi = cookie_netfs_data;
	struct pagevec pvec;
	pgoff_t first;
	int loop, nr_pages;

	pagevec_init(&pvec, 0);
	first = 0;

	dprintk("NFS: nfs_inode_now_uncached: nfs_inode 0x%p\n", nfsi);

	for (;;) {
		/* grab a bunch of pages to unmark */
		nr_pages = pagevec_lookup(&pvec,
					  nfsi->vfs_inode.i_mapping,
					  first,
					  PAGEVEC_SIZE - pagevec_count(&pvec));
		if (!nr_pages)
			break;

		for (loop = 0; loop < nr_pages; loop++)
			ClearPageFsCache(pvec.pages[loop]);

		first = pvec.pages[nr_pages - 1]->index + 1;

		pvec.nr = nr_pages;
		pagevec_release(&pvec);
		cond_resched();
	}
}

static void v9fs_cache_inode_now_uncached(void *cookie_netfs_data)
{
	struct v9fs_inode *v9inode = cookie_netfs_data;
	struct pagevec pvec;
	pgoff_t first;
	int loop, nr_pages;

	pagevec_init(&pvec, 0);
	first = 0;

	for (;;) {
		nr_pages = pagevec_lookup(&pvec, v9inode->vfs_inode.i_mapping,
					  first,
					  PAGEVEC_SIZE - pagevec_count(&pvec));
		if (!nr_pages)
			break;

		for (loop = 0; loop < nr_pages; loop++)
			ClearPageFsCache(pvec.pages[loop]);

		first = pvec.pages[nr_pages - 1]->index + 1;

		pvec.nr = nr_pages;
		pagevec_release(&pvec);
		cond_resched();
	}
}

static void __lru_cache_activate_page(struct page *page)
{
	struct pagevec *pvec = &get_cpu_var(lru_add_pvec);
	int i;

	/*
	 * Search backwards on the optimistic assumption that the page being
	 * activated has just been added to this pagevec. Note that only
	 * the local pagevec is examined as a !PageLRU page could be in the
	 * process of being released, reclaimed, migrated or on a remote
	 * pagevec that is currently being drained. Furthermore, marking
	 * a remote pagevec's page PageActive potentially hits a race where
	 * a page is marked PageActive just after it is added to the inactive
	 * list causing accounting errors and BUG_ON checks to trigger.
	 */
	for (i = pagevec_count(pvec) - 1; i >= 0; i--) {
		struct page *pagevec_page = pvec->pages[i];

		if (pagevec_page == page) {
			SetPageActive(page);
			break;
		}
	}

	put_cpu_var(lru_add_pvec);
}

unsigned pagevec_lookup_range_tag(struct pagevec *pvec,
		struct address_space *mapping, pgoff_t *index, pgoff_t end,
		int tag)
{
	pvec->nr = find_get_pages_range_tag(mapping, index, end, tag,
					PAGEVEC_SIZE, pvec->pages);
	return pagevec_count(pvec);
}

/*
 * The pages which we're about to release may be in the deferred lru-addition
 * queues.  That would prevent them from really being freed right now.  That's
 * OK from a correctness point of view but is inefficient - those pages may be
 * cache-warm and we want to give them back to the page allocator ASAP.
 *
 * So __pagevec_release() will drain those queues here.  __pagevec_lru_add()
 * and __pagevec_lru_add_active() call release_pages() directly to avoid
 * mutual recursion.
 */
void __pagevec_release(struct pagevec *pvec)
{
	if (!pvec->percpu_pvec_drained) {
		lru_add_drain();
		pvec->percpu_pvec_drained = true;
	}
	release_pages(pvec->pages, pagevec_count(pvec));
	pagevec_reinit(pvec);
}

/**
 * pagevec_lookup_entries - gang pagecache lookup
 * @pvec:	Where the resulting entries are placed
 * @mapping:	The address_space to search
 * @start:	The starting entry index
 * @nr_entries:	The maximum number of pages
 * @indices:	The cache indices corresponding to the entries in @pvec
 *
 * pagevec_lookup_entries() will search for and return a group of up
 * to @nr_pages pages and shadow entries in the mapping.  All
 * entries are placed in @pvec.  pagevec_lookup_entries() takes a
 * reference against actual pages in @pvec.
 *
 * The search returns a group of mapping-contiguous entries with
 * ascending indexes.  There may be holes in the indices due to
 * not-present entries.
 *
 * pagevec_lookup_entries() returns the number of entries which were
 * found.
 */
unsigned pagevec_lookup_entries(struct pagevec *pvec,
				struct address_space *mapping,
				pgoff_t start, unsigned nr_entries,
				pgoff_t *indices)
{
	pvec->nr = find_get_entries(mapping, start, nr_entries,
				    pvec->pages, indices);
	return pagevec_count(pvec);
}

/**
 * pagevec_remove_exceptionals - pagevec exceptionals pruning
 * @pvec:	The pagevec to prune
 *
 * pagevec_lookup_entries() fills both pages and exceptional radix
 * tree entries into the pagevec.  This function prunes all
 * exceptionals from @pvec without leaving holes, so that it can be
 * passed on to page-only pagevec operations.
 */
void pagevec_remove_exceptionals(struct pagevec *pvec)
{
	int i, j;

	for (i = 0, j = 0; i < pagevec_count(pvec); i++) {
		struct page *page = pvec->pages[i];
		if (!xa_is_value(page))
			pvec->pages[j++] = page;
	}
	pvec->nr = j;
}

/**
 * pagevec_remove_exceptionals - pagevec exceptionals pruning
 * @pvec:	The pagevec to prune
 *
 * pagevec_lookup_entries() fills both pages and exceptional radix
 * tree entries into the pagevec.  This function prunes all
 * exceptionals from @pvec without leaving holes, so that it can be
 * passed on to page-only pagevec operations.
 */
void pagevec_remove_exceptionals(struct pagevec *pvec)
{
	int i, j;

	for (i = 0, j = 0; i < pagevec_count(pvec); i++) {
		struct page *page = pvec->pages[i];
		if (!radix_tree_exceptional_entry(page))
			pvec->pages[j++] = page;
	}
	pvec->nr = j;
}