SDTX_DEVICE_DIRTY_LATCH_BIT
clear_bit(SDTX_DEVICE_DIRTY_LATCH_BIT, &ddev->flags);
set_bit(SDTX_DEVICE_DIRTY_LATCH_BIT, &ddev->flags);
if (test_and_clear_bit(SDTX_DEVICE_DIRTY_LATCH_BIT, &ddev->flags))