netdev - Re: [PATCH net,v2] hv_netvsc: Fix VF namespace also in synthetic NIC NETDEV

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Message-ID: <20241017154433.GV1697@kernel.org>
Date: Thu, 17 Oct 2024 16:44:33 +0100
From: Simon Horman <horms@...nel.org>
To: Haiyang Zhang <haiyangz@...rosoft.com>
Cc: linux-hyperv@...r.kernel.org, netdev@...r.kernel.org, kys@...rosoft.com,
	wei.liu@...nel.org, decui@...rosoft.com, edumazet@...gle.com,
	kuba@...nel.org, pabeni@...hat.com, stephen@...workplumber.org,
	davem@...emloft.net, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH net,v2] hv_netvsc: Fix VF namespace also in synthetic NIC
 NETDEV_REGISTER event

On Wed, Oct 16, 2024 at 08:43:57AM -0700, Haiyang Zhang wrote:
> The existing code moves VF to the same namespace as the synthetic NIC
> during netvsc_register_vf(). But, if the synthetic device is moved to a
> new namespace after the VF registration, the VF won't be moved together.
> 
> To make the behavior more consistent, add a namespace check for synthetic
> NIC's NETDEV_REGISTER event (generated during its move), and move the VF
> if it is not in the same namespace.
> 
> Cc: stable@...r.kernel.org
> Fixes: c0a41b887ce6 ("hv_netvsc: move VF to same namespace as netvsc device")
> Suggested-by: Stephen Hemminger <stephen@...workplumber.org>
> Signed-off-by: Haiyang Zhang <haiyangz@...rosoft.com>
> ---
> v2: Move my fix to synthetic NIC's NETDEV_REGISTER event as suggested by Stephen.
> 
> ---
>  drivers/net/hyperv/netvsc_drv.c | 29 +++++++++++++++++++++++++++++
>  1 file changed, 29 insertions(+)
> 
> diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
> index 153b97f8ec0d..54e98356ee93 100644
> --- a/drivers/net/hyperv/netvsc_drv.c
> +++ b/drivers/net/hyperv/netvsc_drv.c
> @@ -2798,6 +2798,30 @@ static struct  hv_driver netvsc_drv = {
>  	},
>  };
>  
> +/* Set VF's namespace same as the synthetic NIC */
> +static void netvsc_event_set_vf_ns(struct net_device *ndev)
> +{
> +	struct net_device_context *ndev_ctx = netdev_priv(ndev);
> +	struct net_device *vf_netdev = rtnl_dereference(ndev_ctx->vf_netdev);
> +	int ret;

In Networking code it is preferred to arrange local variables in reverse
xmas tree order - longest line to shortest.

I believe that could be achieved as follows (completely untested!):

	struct net_device_context *ndev_ctx = netdev_priv(ndev);
	struct net_device *vf_netdev;
	int ret;

	vf_netdev = rtnl_dereference(ndev_ctx->vf_netdev);
	if (!vf_netdev)
		return;

With that addressed please feel free to add:

Reviewed-by: Simon Horman <horms@...nel.org>

> +
> +	if (!vf_netdev)
> +		return;
> +
> +	if (!net_eq(dev_net(ndev), dev_net(vf_netdev))) {
> +		ret = dev_change_net_namespace(vf_netdev, dev_net(ndev),
> +					       "eth%d");
> +		if (ret)
> +			netdev_err(vf_netdev,
> +				   "Cannot move to same namespace as %s: %d\n",
> +				   ndev->name, ret);
> +		else
> +			netdev_info(vf_netdev,
> +				    "Moved VF to namespace with: %s\n",
> +				    ndev->name);
> +	}
> +}
> +
>  /*
>   * On Hyper-V, every VF interface is matched with a corresponding
>   * synthetic interface. The synthetic interface is presented first
> @@ -2810,6 +2834,11 @@ static int netvsc_netdev_event(struct notifier_block *this,
>  	struct net_device *event_dev = netdev_notifier_info_to_dev(ptr);
>  	int ret = 0;
>  
> +	if (event_dev->netdev_ops == &device_ops && event == NETDEV_REGISTER) {
> +		netvsc_event_set_vf_ns(event_dev);
> +		return NOTIFY_DONE;
> +	}
> +
>  	ret = check_dev_is_matching_vf(event_dev);
>  	if (ret != 0)
>  		return NOTIFY_DONE;

-- 
pw-bot: changes-requested