int pvcalls_front_accept()

in pvcalls-front.c [763:898]

• 118 lines of code
• 16 McCabe index (conditional complexity)

int pvcalls_front_accept(struct socket *sock, struct socket *newsock, int flags)
{
	struct pvcalls_bedata *bedata;
	struct sock_mapping *map;
	struct sock_mapping *map2 = NULL;
	struct xen_pvcalls_request *req;
	int notify, req_id, ret, nonblock;
	evtchn_port_t evtchn;

	map = pvcalls_enter_sock(sock);
	if (IS_ERR(map))
		return PTR_ERR(map);
	bedata = dev_get_drvdata(&pvcalls_front_dev->dev);

	if (map->passive.status != PVCALLS_STATUS_LISTEN) {
		pvcalls_exit_sock(sock);
		return -EINVAL;
	}

	nonblock = flags & SOCK_NONBLOCK;
	/*
	 * Backend only supports 1 inflight accept request, will return
	 * errors for the others
	 */
	if (test_and_set_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
			     (void *)&map->passive.flags)) {
		req_id = READ_ONCE(map->passive.inflight_req_id);
		if (req_id != PVCALLS_INVALID_ID &&
		    READ_ONCE(bedata->rsp[req_id].req_id) == req_id) {
			map2 = map->passive.accept_map;
			goto received;
		}
		if (nonblock) {
			pvcalls_exit_sock(sock);
			return -EAGAIN;
		}
		if (wait_event_interruptible(map->passive.inflight_accept_req,
			!test_and_set_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
					  (void *)&map->passive.flags))) {
			pvcalls_exit_sock(sock);
			return -EINTR;
		}
	}

	map2 = kzalloc(sizeof(*map2), GFP_KERNEL);
	if (map2 == NULL) {
		clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
			  (void *)&map->passive.flags);
		pvcalls_exit_sock(sock);
		return -ENOMEM;
	}
	ret = alloc_active_ring(map2);
	if (ret < 0) {
		clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
				(void *)&map->passive.flags);
		kfree(map2);
		pvcalls_exit_sock(sock);
		return ret;
	}
	spin_lock(&bedata->socket_lock);
	ret = get_request(bedata, &req_id);
	if (ret < 0) {
		clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
			  (void *)&map->passive.flags);
		spin_unlock(&bedata->socket_lock);
		free_active_ring(map2);
		kfree(map2);
		pvcalls_exit_sock(sock);
		return ret;
	}

	ret = create_active(map2, &evtchn);
	if (ret < 0) {
		free_active_ring(map2);
		kfree(map2);
		clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
			  (void *)&map->passive.flags);
		spin_unlock(&bedata->socket_lock);
		pvcalls_exit_sock(sock);
		return ret;
	}
	list_add_tail(&map2->list, &bedata->socket_mappings);

	req = RING_GET_REQUEST(&bedata->ring, req_id);
	req->req_id = req_id;
	req->cmd = PVCALLS_ACCEPT;
	req->u.accept.id = (uintptr_t) map;
	req->u.accept.ref = map2->active.ref;
	req->u.accept.id_new = (uintptr_t) map2;
	req->u.accept.evtchn = evtchn;
	map->passive.accept_map = map2;

	bedata->ring.req_prod_pvt++;
	RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
	spin_unlock(&bedata->socket_lock);
	if (notify)
		notify_remote_via_irq(bedata->irq);
	/* We could check if we have received a response before returning. */
	if (nonblock) {
		WRITE_ONCE(map->passive.inflight_req_id, req_id);
		pvcalls_exit_sock(sock);
		return -EAGAIN;
	}

	if (wait_event_interruptible(bedata->inflight_req,
		READ_ONCE(bedata->rsp[req_id].req_id) == req_id)) {
		pvcalls_exit_sock(sock);
		return -EINTR;
	}
	/* read req_id, then the content */
	smp_rmb();

received:
	map2->sock = newsock;
	newsock->sk = sk_alloc(sock_net(sock->sk), PF_INET, GFP_KERNEL, &pvcalls_proto, false);
	if (!newsock->sk) {
		bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
		map->passive.inflight_req_id = PVCALLS_INVALID_ID;
		clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
			  (void *)&map->passive.flags);
		pvcalls_front_free_map(bedata, map2);
		pvcalls_exit_sock(sock);
		return -ENOMEM;
	}
	newsock->sk->sk_send_head = (void *)map2;

	ret = bedata->rsp[req_id].ret;
	bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
	map->passive.inflight_req_id = PVCALLS_INVALID_ID;

	clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT, (void *)&map->passive.flags);
	wake_up(&map->passive.inflight_accept_req);

	pvcalls_exit_sock(sock);
	return ret;
}