SDF_NOBARRIERS
if (test_bit(SDF_NOBARRIERS, &sdp->sd_flags)) {
set_bit(SDF_NOBARRIERS, &sdp->sd_flags);
set_bit(SDF_NOBARRIERS, &sdp->sd_flags);
clear_bit(SDF_NOBARRIERS, &sdp->sd_flags);
if (test_bit(SDF_NOBARRIERS, &sdp->sd_flags))
test_bit(SDF_NOBARRIERS, &f),