Merge branch 'akpm' (patches from Andrew)

Merge two fixes from Andrew Morton.

* emailed patches from Andrew Morton <akpm@linux-foundation.org>:
  mm: fix the NULL mapping case in __isolate_lru_page()
  mm/huge_memory.c: __split_huge_page() use atomic ClearPageDirty()

mm/huge_memory.c

@@ -2431,7 +2431,7 @@ static void __split_huge_page(struct page *page, struct list_head *list,
 		__split_huge_page_tail(head, i, lruvec, list);
 		/* Some pages can be beyond i_size: drop them from page cache */
 		if (head[i].index >= end) {
-			__ClearPageDirty(head + i);
+			ClearPageDirty(head + i);
 			__delete_from_page_cache(head + i, NULL);
 			if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head))
 				shmem_uncharge(head->mapping->host, 1);

mm/vmscan.c

@@ -1418,7 +1418,7 @@ int __isolate_lru_page(struct page *page, isolate_mode_t mode)
 				return ret;
 
 			mapping = page_mapping(page);
-			migrate_dirty = mapping && mapping->a_ops->migratepage;
+			migrate_dirty = !mapping || mapping->a_ops->migratepage;
 			unlock_page(page);
 			if (!migrate_dirty)
 				return ret;