BDEV_STATE_DIRTY
if (BDEV_STATE(&dc->sb) == BDEV_STATE_DIRTY) {
if (BDEV_STATE(&dc->sb) == BDEV_STATE_DIRTY) {
if (BDEV_STATE(&dc->sb) != BDEV_STATE_DIRTY) {
SET_BDEV_STATE(&dc->sb, BDEV_STATE_DIRTY);