static long vhost_net_set_backend()

in net.c [1503:1595]

• 79 lines of code
• 15 McCabe index (conditional complexity)

static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
{
	struct socket *sock, *oldsock;
	struct vhost_virtqueue *vq;
	struct vhost_net_virtqueue *nvq;
	struct vhost_net_ubuf_ref *ubufs, *oldubufs = NULL;
	int r;

	mutex_lock(&n->dev.mutex);
	r = vhost_dev_check_owner(&n->dev);
	if (r)
		goto err;

	if (index >= VHOST_NET_VQ_MAX) {
		r = -ENOBUFS;
		goto err;
	}
	vq = &n->vqs[index].vq;
	nvq = &n->vqs[index];
	mutex_lock(&vq->mutex);

	/* Verify that ring has been setup correctly. */
	if (!vhost_vq_access_ok(vq)) {
		r = -EFAULT;
		goto err_vq;
	}
	sock = get_socket(fd);
	if (IS_ERR(sock)) {
		r = PTR_ERR(sock);
		goto err_vq;
	}

	/* start polling new socket */
	oldsock = vhost_vq_get_backend(vq);
	if (sock != oldsock) {
		ubufs = vhost_net_ubuf_alloc(vq,
					     sock && vhost_sock_zcopy(sock));
		if (IS_ERR(ubufs)) {
			r = PTR_ERR(ubufs);
			goto err_ubufs;
		}

		vhost_net_disable_vq(n, vq);
		vhost_vq_set_backend(vq, sock);
		vhost_net_buf_unproduce(nvq);
		r = vhost_vq_init_access(vq);
		if (r)
			goto err_used;
		r = vhost_net_enable_vq(n, vq);
		if (r)
			goto err_used;
		if (index == VHOST_NET_VQ_RX)
			nvq->rx_ring = get_tap_ptr_ring(fd);

		oldubufs = nvq->ubufs;
		nvq->ubufs = ubufs;

		n->tx_packets = 0;
		n->tx_zcopy_err = 0;
		n->tx_flush = false;
	}

	mutex_unlock(&vq->mutex);

	if (oldubufs) {
		vhost_net_ubuf_put_wait_and_free(oldubufs);
		mutex_lock(&vq->mutex);
		vhost_zerocopy_signal_used(n, vq);
		mutex_unlock(&vq->mutex);
	}

	if (oldsock) {
		vhost_net_flush_vq(n, index);
		sockfd_put(oldsock);
	}

	mutex_unlock(&n->dev.mutex);
	return 0;

err_used:
	vhost_vq_set_backend(vq, oldsock);
	vhost_net_enable_vq(n, vq);
	if (ubufs)
		vhost_net_ubuf_put_wait_and_free(ubufs);
err_ubufs:
	if (sock)
		sockfd_put(sock);
err_vq:
	mutex_unlock(&vq->mutex);
err:
	mutex_unlock(&n->dev.mutex);
	return r;
}