xen-netfront: Improve error handling during initialization

This fixes a crash when running out of grant refs when creating many
queues across many netdevs.

* 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 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>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit e2e004acc7cbe3c531e752a270a74e95cde3ea48)

Conflicts:
	drivers/net/xen-netfront.c

We have a additional feature that is probed (feature_staging_gnts), hence
it couldn't directly apply the chunk. But the chunks added/modified are
still the same as the backport.

Orabug: 22817043
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index ca06a0b7b3142c251efd50d84a406fb2dd301ea9..704e9b013ef89eff52871f6f89d7a6265c1ba985 100644 (file)
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -2385,28 +2385,20 @@ 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");
+               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,
                                     feature_staging_gnts);
-               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:
@@ -2496,9 +2488,10 @@ abort_transaction_no_dev_fatal:
        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;
 }