#173314 by drewish: mark previously uploaded files as permanent, so they will not be deleted after an upgrade

modules/system/system.install

@@ -3561,6 +3561,9 @@ function system_update_6022() {
       break;
   }
 
+  // Mark all existing files as FILE_STATUS_PERMANENT.
+  $ret[] = update_sql('UPDATE {files} SET status = 1');
+
   return $ret;
 }