--- x/mm/rmap.c
+++ y/mm/rmap.c
@@ -1279,7 +1279,7 @@ void folio_add_new_anon_rmap(struct foli
 
 	if (likely(!folio_test_pmd_mappable(folio))) {
 		/* increment count (starts at -1) */
-		atomic_set(&folio->_mapcount, 0);
+		atomic_inc(&folio->_mapcount);
 		nr = 1;
 	} else {
 		/* increment count (starts at -1) */