Re: net: bridge: propagate error code and extack from br_mc_disabled_update

[Christian Borntraeger <borntraeger@de.ibm.com>]

On 21.04.21 20:18, Christian Borntraeger wrote:
> Whatever version landed in next, according to bisect this broke libvirt/kvms use of bridges:
> 
> 
> # virsh start s31128001
> error: Failed to start domain 's31128001'
> error: Unable to add bridge virbr1 port vnet0: Operation not supported
> 
> # grep vnet0 /var/log/libvirt/libvirtd.log
> 
> 2021-04-21 07:43:09.453+0000: 2460: info : virNetDevTapCreate:240 : created device: 'vnet0'
> 2021-04-21 07:43:09.453+0000: 2460: debug : virNetDevSetMACInternal:287 : SIOCSIFHWADDR vnet0 MAC=fe:bb:83:28:01:02 - Success
> 2021-04-21 07:43:09.453+0000: 2460: error : virNetDevBridgeAddPort:633 : Unable to add bridge virbr1 port vnet0: Operation not supported
> 2021-04-21 07:43:09.466+0000: 2543: debug : udevHandleOneDevice:1695 : udev action: 'add': /sys/devices/virtual/net/vnet0
> 
> Christian
> 

For reference:

ae1ea84b33dab45c7b6c1754231ebda5959b504c is the first bad commit
commit ae1ea84b33dab45c7b6c1754231ebda5959b504c
Author: Florian Fainelli <f.fainelli@gmail.com>
Date:   Wed Apr 14 22:22:57 2021 +0300

     net: bridge: propagate error code and extack from br_mc_disabled_update
     
     Some Ethernet switches might only be able to support disabling multicast
     snooping globally, which is an issue for example when several bridges
     span the same physical device and request contradictory settings.
     
     Propagate the return value of br_mc_disabled_update() such that this
     limitation is transmitted correctly to user-space.
     
     Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
     Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
     Signed-off-by: David S. Miller <davem@davemloft.net>

  net/bridge/br_multicast.c | 28 +++++++++++++++++++++-------
  net/bridge/br_netlink.c   |  4 +++-
  net/bridge/br_private.h   |  3 ++-
  net/bridge/br_sysfs_br.c  |  8 +-------
  4 files changed, 27 insertions(+), 16 deletions(-)

not sure if it matters this is on s390.
A simple reproducer is virt-install, e.g.
virt-install --name test --disk size=12 --memory=2048 --vcpus=2 --location http://ports.ubuntu.com/ubuntu-ports/dists/bionic/main/installer-s390x/