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Subject[PATCH] xen-netfront: Improve error handling during initialization
Date
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@citrix.com>
---
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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