bool vhost_enable_notify()

in vhost.c [2514:2548]

• 31 lines of code
• 6 McCabe index (conditional complexity)

bool vhost_enable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
{
	__virtio16 avail_idx;
	int r;

	if (!(vq->used_flags & VRING_USED_F_NO_NOTIFY))
		return false;
	vq->used_flags &= ~VRING_USED_F_NO_NOTIFY;
	if (!vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX)) {
		r = vhost_update_used_flags(vq);
		if (r) {
			vq_err(vq, "Failed to enable notification at %p: %d\n",
			       &vq->used->flags, r);
			return false;
		}
	} else {
		r = vhost_update_avail_event(vq, vq->avail_idx);
		if (r) {
			vq_err(vq, "Failed to update avail event index at %p: %d\n",
			       vhost_avail_event(vq), r);
			return false;
		}
	}
	/* They could have slipped one in as we were doing that: make
	 * sure it's written, then check again. */
	smp_mb();
	r = vhost_get_avail_idx(vq, &avail_idx);
	if (r) {
		vq_err(vq, "Failed to check avail idx at %p: %d\n",
		       &vq->avail->idx, r);
		return false;
	}

	return vhost16_to_cpu(vq, avail_idx) != vq->avail_idx;
}