completion_work
struct completion_work *completion_work =
container_of(w, struct completion_work, w);
complete(&completion_work->done);
struct completion_work completion_work;
completion_work.w.cb = w_complete;
init_completion(&completion_work.done);
drbd_queue_work(work_queue, &completion_work.w);
wait_for_completion(&completion_work.done);
vhost_work_init(&svq->completion_work,
struct vhost_work completion_work;
if (!vhost_vq_work_queue(&svq->vq, &svq->completion_work))
struct vhost_scsi_virtqueue, completion_work);