| Message ID | 20160813113559.617b7c55@xeon-e3 |
|---|---|
| State | RFC, archived |
| Delegated to: | David Miller |
| Headers | show |
From: Stephen Hemminger <stephen@networkplumber.org> Date: Sat, 13 Aug 2016 11:35:59 -0700 > This is how I think it should be fixed, but not tested yet. > > Subjec: netvsc: use device not module reference counts > > Fix how the cross-device reference counting is handled. When VF is > associated with the synthetic interface, the VF driver module should > still be able to be unloaded. The module unload code will callback > with NETDEV_UNREGISTER event which breaks the connection safely. > (Fixes 9f4b5ba5db4 hv_netvsc: Implement support for VF drivers on Hyper-V) > > Signed-off-by: Stephen Hemminger <sthemmin@linuxonhyperv.com> This might not work. It is assumed that when a netdev unregister happens, it may be done so at any point in time. Therefore that NETDEV_UNREGISTER event must eliminate any and all references to a given netdev. And that works perfectly fine right now with all existing subsystems that take references to netdevs. You'll have to add something so that a NETDEV_UNREGISTER event tears this VF down and thus releases it's reference to the synthetic device.
--- a/drivers/net/hyperv/netvsc_drv.c 2016-08-13 11:25:40.243995863 -0700 +++ b/drivers/net/hyperv/netvsc_drv.c 2016-08-13 11:25:40.239995844 -0700 @@ -1220,10 +1220,8 @@ static int netvsc_register_vf(struct net return NOTIFY_DONE; netdev_info(ndev, "VF registering: %s\n", vf_netdev->name); - /* - * Take a reference on the module. - */ - try_module_get(THIS_MODULE); + + dev_hold(vf_netdev); netvsc_dev->vf_netdev = vf_netdev; return NOTIFY_OK; } @@ -1345,7 +1343,7 @@ static int netvsc_unregister_vf(struct n netdev_info(ndev, "VF unregistering: %s\n", vf_netdev->name); netvsc_dev->vf_netdev = NULL; - module_put(THIS_MODULE); + dev_put(vf_netdev); return NOTIFY_OK; }
This is how I think it should be fixed, but not tested yet. Subjec: netvsc: use device not module reference counts Fix how the cross-device reference counting is handled. When VF is associated with the synthetic interface, the VF driver module should still be able to be unloaded. The module unload code will callback with NETDEV_UNREGISTER event which breaks the connection safely. (Fixes 9f4b5ba5db4 hv_netvsc: Implement support for VF drivers on Hyper-V) Signed-off-by: Stephen Hemminger <sthemmin@linuxonhyperv.com>