mm/vmscan: convert move_pages_to_lru() to use a folio

Remove a few hidden calls to compound_head, saving 387 bytes of text on
my test configuration.

Link: https://lkml.kernel.org/r/20220617154248.700416-4-willy@infradead.orgSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/vmscan.c

@@ -2308,8 +2308,8 @@ static int too_many_isolated(struct pglist_data *pgdat, int file,
 }
 
 /*
- * move_pages_to_lru() moves pages from private @list to appropriate LRU list.
- * On return, @list is reused as a list of pages to be freed by the caller.
+ * move_pages_to_lru() moves folios from private @list to appropriate LRU list.
+ * On return, @list is reused as a list of folios to be freed by the caller.
  *
  * Returns the number of pages moved to the given lruvec.
  */
@@ -2317,42 +2317,42 @@ static unsigned int move_pages_to_lru(struct lruvec *lruvec,
 				      struct list_head *list)
 {
 	int nr_pages, nr_moved = 0;
-	LIST_HEAD(pages_to_free);
-	struct page *page;
+	LIST_HEAD(folios_to_free);
 
 	while (!list_empty(list)) {
-		page = lru_to_page(list);
-		VM_BUG_ON_PAGE(PageLRU(page), page);
-		list_del(&page->lru);
-		if (unlikely(!page_evictable(page))) {
+		struct folio *folio = lru_to_folio(list);
+
+		VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
+		list_del(&folio->lru);
+		if (unlikely(!folio_evictable(folio))) {
 			spin_unlock_irq(&lruvec->lru_lock);
-			putback_lru_page(page);
+			folio_putback_lru(folio);
 			spin_lock_irq(&lruvec->lru_lock);
 			continue;
 		}
 
 		/*
-		 * The SetPageLRU needs to be kept here for list integrity.
+		 * The folio_set_lru needs to be kept here for list integrity.
 		 * Otherwise:
 		 *   #0 move_pages_to_lru             #1 release_pages
-		 *   if !put_page_testzero
-		 *				      if (put_page_testzero())
-		 *				        !PageLRU //skip lru_lock
-		 *     SetPageLRU()
-		 *     list_add(&page->lru,)
-		 *                                        list_add(&page->lru,)
+		 *   if (!folio_put_testzero())
+		 *				      if (folio_put_testzero())
+		 *				        !lru //skip lru_lock
+		 *     folio_set_lru()
+		 *     list_add(&folio->lru,)
+		 *                                        list_add(&folio->lru,)
 		 */
-		SetPageLRU(page);
+		folio_set_lru(folio);
 
-		if (unlikely(put_page_testzero(page))) {
-			__clear_page_lru_flags(page);
+		if (unlikely(folio_put_testzero(folio))) {
+			__folio_clear_lru_flags(folio);
 
-			if (unlikely(PageCompound(page))) {
+			if (unlikely(folio_test_large(folio))) {
 				spin_unlock_irq(&lruvec->lru_lock);
-				destroy_compound_page(page);
+				destroy_compound_page(&folio->page);
 				spin_lock_irq(&lruvec->lru_lock);
 			} else
-				list_add(&page->lru, &pages_to_free);
+				list_add(&folio->lru, &folios_to_free);
 
 			continue;
 		}
@@ -2361,18 +2361,18 @@ static unsigned int move_pages_to_lru(struct lruvec *lruvec,
 		 * All pages were isolated from the same lruvec (and isolation
 		 * inhibits memcg migration).
 		 */
-		VM_BUG_ON_PAGE(!folio_matches_lruvec(page_folio(page), lruvec), page);
-		add_page_to_lru_list(page, lruvec);
-		nr_pages = thp_nr_pages(page);
+		VM_BUG_ON_FOLIO(!folio_matches_lruvec(folio, lruvec), folio);
+		lruvec_add_folio(lruvec, folio);
+		nr_pages = folio_nr_pages(folio);
 		nr_moved += nr_pages;
-		if (PageActive(page))
+		if (folio_test_active(folio))
 			workingset_age_nonresident(lruvec, nr_pages);
 	}
 
 	/*
 	 * To save our caller's stack, now use input list for pages to free.
 	 */
-	list_splice(&pages_to_free, list);
+	list_splice(&folios_to_free, list);
 
 	return nr_moved;
 }