blk_trace_startstop
return blk_trace_startstop(sdp->device->request_queue, 1);
return blk_trace_startstop(sdp->device->request_queue, 0);
extern int blk_trace_startstop(struct request_queue *q, int start);
EXPORT_SYMBOL_GPL(blk_trace_startstop);
ret = blk_trace_startstop(q, start);