[Xen-devel] [PATCH] xen-netfront: Improve error handling during initialization

[Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>]

Improve error handling during initialization. This fixes a crash when
running out of grant refs when creating many queues across many netdevs.

* Delay timer creation so that if initializing a queue fails, the timer
has not been setup yet.
* If creating queues fails (i.e. there are no grant refs available),
call xenbus_dev_fatal() to ensure that the xenbus device is set to the
closed state.
* If no queues are created, don't call xennet_disconnect_backend as
netdev->real_num_tx_queues will not have been set correctly.
* If setup_netfront() fails, ensure that all the queues created are
cleaned up, not just those that have been set up.
* If any queues were set up and an error occurs, call
xennet_destroy_queues() to stop the timer and clean up the napi context.
* If any fatal error occurs, unregister and destroy the netdev to avoid
leaving around a half setup network device.

Signed-off-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
---
 drivers/net/xen-netfront.c | 39 ++++++++++++++++++---------------------
 1 file changed, 18 insertions(+), 21 deletions(-)

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index 8315fe7..8ca85af 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -1596,9 +1596,6 @@ static int xennet_init_queue(struct netfront_queue *queue)
        spin_lock_init(&queue->tx_lock);
        spin_lock_init(&queue->rx_lock);
 
-       setup_timer(&queue->rx_refill_timer, rx_refill_timeout,
-                   (unsigned long)queue);
-
        snprintf(queue->name, sizeof(queue->name), "%s-q%u",
                 queue->info->netdev->name, queue->id);
 
@@ -1632,6 +1629,9 @@ static int xennet_init_queue(struct netfront_queue *queue)
                goto exit_free_tx;
        }
 
+       setup_timer(&queue->rx_refill_timer, rx_refill_timeout,
+                   (unsigned long)queue);
+
        return 0;
 
  exit_free_tx:
@@ -1822,27 +1822,23 @@ static int talk_to_netback(struct xenbus_device *dev,
                xennet_destroy_queues(info);
 
        err = xennet_create_queues(info, &num_queues);
-       if (err < 0)
-               goto destroy_ring;
+       if (err < 0) {
+               xenbus_dev_fatal(dev, err, "creating queues");
+               if (num_queues > 0) {
+                       goto destroy_ring;
+               } else {
+                       kfree(info->queues);
+                       info->queues = NULL;
+                       goto out;
+               }
+       }
 
        /* Create shared ring, alloc event channel -- for each queue */
        for (i = 0; i < num_queues; ++i) {
                queue = &info->queues[i];
                err = setup_netfront(dev, queue, feature_split_evtchn);
-               if (err) {
-                       /* setup_netfront() will tidy up the current
-                        * queue on error, but we need to clean up
-                        * those already allocated.
-                        */
-                       if (i > 0) {
-                               rtnl_lock();
-                               netif_set_real_num_tx_queues(info->netdev, i);
-                               rtnl_unlock();
-                               goto destroy_ring;
-                       } else {
-                               goto out;
-                       }
-               }
+               if (err)
+                       goto destroy_ring;
        }
 
 again:
@@ -1932,9 +1928,10 @@ static int talk_to_netback(struct xenbus_device *dev,
        xenbus_transaction_end(xbt, 1);
  destroy_ring:
        xennet_disconnect_backend(info);
-       kfree(info->queues);
-       info->queues = NULL;
+       xennet_destroy_queues(info);
  out:
+       unregister_netdev(info->netdev);
+       xennet_free_netdev(info->netdev);
        return err;
 }
 
-- 
2.7.4


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