GD_ZONE_APPEND_USED
clear_bit(GD_ZONE_APPEND_USED, &disk->state);
if (!test_bit(GD_ZONE_APPEND_USED, &disk->state))
set_bit(GD_ZONE_APPEND_USED, &disk->state);
!test_bit(GD_ZONE_APPEND_USED, &bdev->bd_disk->state));