6.6-stable review patch. If anyone has any objections, please let me know.
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From: Toke Høiland-Jørgensen toke@redhat.com
[ Upstream commit 5498227676303e3ffa9a3a46214af96bc3e81314 ]
The openvswitch teardown code will immediately call ovs_netdev_detach_dev() in response to a NETDEV_UNREGISTER notification. It will then start the dp_notify_work workqueue, which will later end up calling the vport destroy() callback. This callback takes the RTNL to do another ovs_netdev_detach_port(), which in this case is unnecessary. This causes extra pressure on the RTNL, in some cases leading to "unregister_netdevice: waiting for XX to become free" warnings on teardown.
We can straight-forwardly avoid the extra RTNL lock acquisition by checking the device flags before taking the lock, and skip the locking altogether if the IFF_OVS_DATAPATH flag has already been unset.
Fixes: b07c26511e94 ("openvswitch: fix vport-netdev unregister") Tested-by: Adrian Moreno amorenoz@redhat.com Signed-off-by: Toke Høiland-Jørgensen toke@redhat.com Acked-by: Eelco Chaudron echaudro@redhat.com Acked-by: Aaron Conole aconole@redhat.com Link: https://patch.msgid.link/20251211115006.228876-1-toke@redhat.com Signed-off-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- net/openvswitch/vport-netdev.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-)
diff --git a/net/openvswitch/vport-netdev.c b/net/openvswitch/vport-netdev.c index 903537a5da22..3c41d53bb9e9 100644 --- a/net/openvswitch/vport-netdev.c +++ b/net/openvswitch/vport-netdev.c @@ -153,10 +153,19 @@ void ovs_netdev_detach_dev(struct vport *vport)
static void netdev_destroy(struct vport *vport) { - rtnl_lock(); - if (netif_is_ovs_port(vport->dev)) - ovs_netdev_detach_dev(vport); - rtnl_unlock(); + /* When called from ovs_db_notify_wq() after a dp_device_event(), the + * port has already been detached, so we can avoid taking the RTNL by + * checking this first. + */ + if (netif_is_ovs_port(vport->dev)) { + rtnl_lock(); + /* Check again while holding the lock to ensure we don't race + * with the netdev notifier and detach twice. + */ + if (netif_is_ovs_port(vport->dev)) + ovs_netdev_detach_dev(vport); + rtnl_unlock(); + }
call_rcu(&vport->rcu, vport_netdev_free); }