mm/gup: add folio to list when folio_isolate_lru() succeed

If we call folio_isolate_lru() successfully, we will get return value 0. 
We need to add this folio to the movable_pages_list.

Link: https://lkml.kernel.org/r/[email protected]
Fixes: 67e139b ("mm/gup.c: refactor check_and_migrate_movable_pages()")
Signed-off-by: Kuan-Ying Lee <[email protected]>
Reviewed-by: Alistair Popple <[email protected]>
Acked-by: David Hildenbrand <[email protected]>
Reviewed-by: Baolin Wang <[email protected]>
Cc: Andrew Yang <[email protected]>
Cc: Chinwen Chang <[email protected]>
Cc: John Hubbard <[email protected]>
Cc: Matthias Brugger <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: Kuan-Ying Lee

mm/gup.c

@@ -1914,7 +1914,7 @@ static unsigned long collect_longterm_unpinnable_pages(
 			drain_allow = false;
 		}
 
-		if (!folio_isolate_lru(folio))
+		if (folio_isolate_lru(folio))
 			continue;
 
 		list_add_tail(&folio->lru, movable_page_list);