Re: [PATCH RFC net-next] net: Allow name change of IFF_UP interfaces

What happens is: __netvsc_vf_setup() does dev_open() for the VF device and
the consecutive dev_change_name() fails with -EBUSY because of the
(dev->flags & IFF_UP) check. The history of this code predates git so I
wasn't able to figure out when and why the check was added, everything
seems to work fine without it. dev_change_name() has only two call sites,
both hold rtnl_lock.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 RFC: I'm probably miossing something obvious and the check can't be just
 dropped. Stephen suggested a different solution to the isuue:
 https://www.spinics.net/lists/netdev/msg448243.html but it has its own
 drawbacks.
---
 net/core/dev.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 1d75499add72..c608e233a78a 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c

@@ -1186,8 +1186,6 @@ int dev_change_name(struct net_device *dev, const char *newname)
        BUG_ON(!dev_net(dev));

        net = dev_net(dev);
-       if (dev->flags & IFF_UP)
-               return -EBUSY;

        write_seqcount_begin(&devnet_rename_seq);