TRACE_BLK_OPT_CGROUP
if (css && (blk_tracer_flags.val & TRACE_BLK_OPT_CGROUP))
{ TRACER_OPT(blk_cgroup, TRACE_BLK_OPT_CGROUP) },
if (!bt || !(blk_tracer_flags.val & TRACE_BLK_OPT_CGROUP))