NULLB_DEV_FL_UP
if (test_and_set_bit(NULLB_DEV_FL_UP, &dev->flags))
clear_bit(NULLB_DEV_FL_UP, &dev->flags);
if (test_and_clear_bit(NULLB_DEV_FL_UP, &dev->flags)) {
if (test_and_clear_bit(NULLB_DEV_FL_UP, &dev->flags)) {