mm/vmscan.c: use add_page_to_lru_list()

Patch series "mm: lru related cleanups", v2.

The cleanups are intended to reduce the verbosity in lru list operations
and make them less error-prone.  A typical example would be how the
patches change __activate_page():

 static void __activate_page(struct page *page, struct lruvec *lruvec)
 {
 	if (!PageActive(page) && !PageUnevictable(page)) {
-		int lru = page_lru_base_type(page);
 		int nr_pages = thp_nr_pages(page);

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

There are a few more places like __activate_page() and they are
unnecessarily repetitive in terms of figuring out which list a page should
be added onto or deleted from.  And with the duplicated code removed, they
are easier to read, IMO.

Patch 1 to 5 basically cover the above.  Patch 6 and 7 make code more
robust by improving bug reporting.  Patch 8, 9 and 10 take care of some
dangling helpers left in header files.

This patch (of 10):

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

Link: https://lkml.kernel.org/r/20210122220600.906146-1-yuzhao@google.com
Link: https://lore.kernel.org/linux-mm/20201207220949.830352-2-yuzhao@google.com/
Link: https://lkml.kernel.org/r/20210122220600.906146-2-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>
Cc: Hugh Dickins <hughd@google.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/vmscan.c

@@ -1823,7 +1823,6 @@ 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);
@@ -1868,11 +1867,8 @@ 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);