mm/migrate: convert move_to_new_page() into move_to_new_folio()

Pass in the folios that we already have in each caller.  Saves a
lot of calls to compound_head().

Link: https://lkml.kernel.org/r/20220504182857.4013401-27-willy@infradead.org
Signed-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/migrate.c

@@ -843,21 +843,21 @@ static int fallback_migrate_page(struct address_space *mapping,
  *   < 0 - error code
  *  MIGRATEPAGE_SUCCESS - success
  */
-static int move_to_new_page(struct page *newpage, struct page *page,
+static int move_to_new_folio(struct folio *dst, struct folio *src,
 				enum migrate_mode mode)
 {
 	struct address_space *mapping;
 	int rc = -EAGAIN;
-	bool is_lru = !__PageMovable(page);
+	bool is_lru = !__PageMovable(&src->page);
 
-	VM_BUG_ON_PAGE(!PageLocked(page), page);
-	VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
+	VM_BUG_ON_FOLIO(!folio_test_locked(src), src);
+	VM_BUG_ON_FOLIO(!folio_test_locked(dst), dst);
 
-	mapping = page_mapping(page);
+	mapping = folio_mapping(src);
 
 	if (likely(is_lru)) {
 		if (!mapping)
-			rc = migrate_page(mapping, newpage, page, mode);
+			rc = migrate_page(mapping, &dst->page, &src->page, mode);
 		else if (mapping->a_ops->migratepage)
 			/*
 			 * Most pages have a mapping and most filesystems
@@ -866,54 +866,54 @@ static int move_to_new_page(struct page *newpage, struct page *page,
 			 * migratepage callback. This is the most common path
 			 * for page migration.
 			 */
-			rc = mapping->a_ops->migratepage(mapping, newpage,
-							page, mode);
+			rc = mapping->a_ops->migratepage(mapping, &dst->page,
+							&src->page, mode);
 		else
-			rc = fallback_migrate_page(mapping, newpage,
-							page, mode);
+			rc = fallback_migrate_page(mapping, &dst->page,
+							&src->page, mode);
 	} else {
 		/*
 		 * In case of non-lru page, it could be released after
 		 * isolation step. In that case, we shouldn't try migration.
 		 */
-		VM_BUG_ON_PAGE(!PageIsolated(page), page);
-		if (!PageMovable(page)) {
+		VM_BUG_ON_FOLIO(!folio_test_isolated(src), src);
+		if (!folio_test_movable(src)) {
 			rc = MIGRATEPAGE_SUCCESS;
-			ClearPageIsolated(page);
+			folio_clear_isolated(src);
 			goto out;
 		}
 
-		rc = mapping->a_ops->migratepage(mapping, newpage,
-						page, mode);
+		rc = mapping->a_ops->migratepage(mapping, &dst->page,
+						&src->page, mode);
 		WARN_ON_ONCE(rc == MIGRATEPAGE_SUCCESS &&
-			!PageIsolated(page));
+				!folio_test_isolated(src));
 	}
 
 	/*
-	 * When successful, old pagecache page->mapping must be cleared before
-	 * page is freed; but stats require that PageAnon be left as PageAnon.
+	 * When successful, old pagecache src->mapping must be cleared before
+	 * src is freed; but stats require that PageAnon be left as PageAnon.
 	 */
 	if (rc == MIGRATEPAGE_SUCCESS) {
-		if (__PageMovable(page)) {
-			VM_BUG_ON_PAGE(!PageIsolated(page), page);
+		if (__PageMovable(&src->page)) {
+			VM_BUG_ON_FOLIO(!folio_test_isolated(src), src);
 
 			/*
 			 * We clear PG_movable under page_lock so any compactor
 			 * cannot try to migrate this page.
 			 */
-			ClearPageIsolated(page);
+			folio_clear_isolated(src);
 		}
 
 		/*
-		 * Anonymous and movable page->mapping will be cleared by
+		 * Anonymous and movable src->mapping will be cleared by
 		 * free_pages_prepare so don't reset it here for keeping
 		 * the type to work PageAnon, for example.
 		 */
-		if (!PageMappingFlags(page))
-			page->mapping = NULL;
+		if (!folio_mapping_flags(src))
+			src->mapping = NULL;
 
-		if (likely(!is_zone_device_page(newpage)))
-			flush_dcache_folio(page_folio(newpage));
+		if (likely(!folio_is_zone_device(dst)))
+			flush_dcache_folio(dst);
 	}
 out:
 	return rc;
@@ -1001,7 +1001,7 @@ static int __unmap_and_move(struct page *page, struct page *newpage,
 		goto out_unlock;
 
 	if (unlikely(!is_lru)) {
-		rc = move_to_new_page(newpage, page, mode);
+		rc = move_to_new_folio(dst, folio, mode);
 		goto out_unlock_both;
 	}
 
@@ -1032,7 +1032,7 @@ static int __unmap_and_move(struct page *page, struct page *newpage,
 	}
 
 	if (!page_mapped(page))
-		rc = move_to_new_page(newpage, page, mode);
+		rc = move_to_new_folio(dst, folio, mode);
 
 	/*
 	 * When successful, push newpage to LRU immediately: so that if it
@@ -1261,7 +1261,7 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
 	}
 
 	if (!page_mapped(hpage))
-		rc = move_to_new_page(new_hpage, hpage, mode);
+		rc = move_to_new_folio(dst, src, mode);
 
 	if (page_was_mapped)
 		remove_migration_ptes(src,