mm: use add_page_to_lru_list()

There is add_page_to_lru_list(), and move_pages_to_lru() should reuse
it, not duplicate it.

Link: https://lore.kernel.org/linux-mm/20201207220949.830352-2-yuzhao@google.com/
Signed-off-by: Yu Zhao <yuzhao@google.com>
Reviewed-by: Alex Shi <alex.shi@linux.alibaba.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>

mm/vmscan.c

@@ -1829,7 +1829,6 @@ static unsigned noinline_for_stack move_pages_to_lru(struct lruvec *lruvec,
 	int nr_pages, nr_moved = 0;
 	LIST_HEAD(pages_to_free);
 	struct page *page;
-	enum lru_list lru;
 
 	while (!list_empty(list)) {
 		page = lru_to_page(list);
@@ -1874,11 +1873,8 @@ static unsigned noinline_for_stack move_pages_to_lru(struct lruvec *lruvec,
 		 * inhibits memcg migration).
 		 */
 		VM_BUG_ON_PAGE(!lruvec_holds_page_lru_lock(page, lruvec), page);
-		lru = page_lru(page);
+		add_page_to_lru_list(page, lruvec, page_lru(page));
 		nr_pages = thp_nr_pages(page);
-
-		update_lru_size(lruvec, lru, page_zonenum(page), nr_pages);
-		list_add(&page->lru, &lruvec->lists[lru]);
 		nr_moved += nr_pages;
 		if (PageActive(page))
 			workingset_age_nonresident(lruvec, nr_pages);