Commit ce58725f authored by David Vrabel's avatar David Vrabel Committed by David S. Miller
Browse files

xen-netfront: recreate queues correctly when reconnecting 



When reconnecting to the backend (after a resume/migration, for example),
a different number of queues may be required (since the guest may have
moved to a different host with different capabilities).  During the
reconnection the old queues are torn down and new ones created.

Introduce xennet_create_queues() and xennet_destroy_queues() that fixes
three bugs during the reconnection.

- The old info->queues was leaked.
- The old queue's napi instances were not deleted.
- The new queue's napi instances were left disabled (which meant no
  packets could be received).

The xennet_destroy_queues() calls is deferred until the reconnection
instead of the disconnection (in xennet_disconnect_backend()) because
napi_disable() might sleep.

Signed-off-by: default avatarDavid Vrabel <david.vrabel@citrix.com>
Reviewed-by: default avatarWei Liu <wei.liu2@citrix.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 76541869

drivers/net/xen-netfront.c

+72 −32
Original line number Diff line number Diff line
@@ -1699,8 +1699,6 @@ static int xennet_init_queue(struct netfront_queue *queue) 
		goto exit_free_tx;

	}



	netif_napi_add(queue->info->netdev, &queue->napi, xennet_poll, 64);



	return 0;



 exit_free_tx:
@@ -1791,6 +1789,70 @@ error: 
	return err;

}



static void xennet_destroy_queues(struct netfront_info *info)

{

	unsigned int i;



	rtnl_lock();



	for (i = 0; i < info->netdev->real_num_tx_queues; i++) {

		struct netfront_queue *queue = &info->queues[i];



		if (netif_running(info->netdev))

			napi_disable(&queue->napi);

		netif_napi_del(&queue->napi);

	}



	rtnl_unlock();



	kfree(info->queues);

	info->queues = NULL;

}



static int xennet_create_queues(struct netfront_info *info,

				unsigned int num_queues)

{

	unsigned int i;

	int ret;



	info->queues = kcalloc(num_queues, sizeof(struct netfront_queue),

			       GFP_KERNEL);

	if (!info->queues)

		return -ENOMEM;



	rtnl_lock();



	for (i = 0; i < num_queues; i++) {

		struct netfront_queue *queue = &info->queues[i];



		queue->id = i;

		queue->info = info;



		ret = xennet_init_queue(queue);

		if (ret < 0) {

			dev_warn(&info->netdev->dev, "only created %d queues\n",

				 num_queues);

			num_queues = i;

			break;

		}



		netif_napi_add(queue->info->netdev, &queue->napi,

			       xennet_poll, 64);

		if (netif_running(info->netdev))

			napi_enable(&queue->napi);

	}



	netif_set_real_num_tx_queues(info->netdev, num_queues);



	rtnl_unlock();



	if (num_queues == 0) {

		dev_err(&info->netdev->dev, "no queues\n");

		return -EINVAL;

	}

	return 0;

}



/* Common code used when first setting up, and when resuming. */

static int talk_to_netback(struct xenbus_device *dev,

			   struct netfront_info *info)
@@ -1827,42 +1889,20 @@ static int talk_to_netback(struct xenbus_device *dev, 
		goto out;

	}



	/* Allocate array of queues */

	info->queues = kcalloc(num_queues, sizeof(struct netfront_queue), GFP_KERNEL);

	if (!info->queues) {

		err = -ENOMEM;

		goto out;

	}

	rtnl_lock();

	netif_set_real_num_tx_queues(info->netdev, num_queues);

	rtnl_unlock();

	if (info->queues)

		xennet_destroy_queues(info);



	err = xennet_create_queues(info, num_queues);

	if (err < 0)

		goto destroy_ring;



	/* Create shared ring, alloc event channel -- for each queue */

	for (i = 0; i < num_queues; ++i) {

		queue = &info->queues[i];

		queue->id = i;

		queue->info = info;

		err = xennet_init_queue(queue);

		if (err) {

			/* xennet_init_queue() cleans up after itself on failure,

			 * but we still have to clean up any previously initialised

			 * queues. If i > 0, set num_queues to i, then goto

			 * destroy_ring, which calls xennet_disconnect_backend()

			 * to tidy up.

			 */

			if (i > 0) {

				rtnl_lock();

				netif_set_real_num_tx_queues(info->netdev, i);

				rtnl_unlock();

				goto destroy_ring;

			} else {

				goto out;

			}

		}

		err = setup_netfront(dev, queue, feature_split_evtchn);

		if (err) {

			/* As for xennet_init_queue(), setup_netfront() will tidy

			 * up the current queue on error, but we need to clean up

			/* setup_netfront() will tidy up the current

			 * queue on error, but we need to clean up

			 * those already allocated.

			 */

			if (i > 0) {

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