netdev - Re: [PATCH net v2] net: bareudp: add missing error handling for bareudp_link

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Date:   Tue, 5 Jan 2021 12:38:54 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     David Miller <davem@...emloft.net>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        martin.varghese@...ia.com, Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH net v2] net: bareudp: add missing error handling for bareudp_link_config()

On Tue, Jan 5, 2021 at 11:07 AM Jakub Kicinski <kuba@...nel.org> wrote:
>
> .dellink does not get called after .newlink fails,
> bareudp_newlink() must undo what bareudp_configure()
> has done if bareudp_link_config() fails.
>
> v2: call bareudp_dellink(), like bareudp_dev_create() does

Thanks for the update. Just one question below.

>
> Fixes: 571912c69f0e ("net: UDP tunnel encapsulation module for tunnelling different protocols like MPLS, IP, NSH etc.")
> Signed-off-by: Jakub Kicinski <kuba@...nel.org>
> ---
>  drivers/net/bareudp.c | 22 ++++++++++++++--------
>  1 file changed, 14 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/net/bareudp.c b/drivers/net/bareudp.c
> index 708171c0d628..85de5f96c02b 100644
> --- a/drivers/net/bareudp.c
> +++ b/drivers/net/bareudp.c
> @@ -645,11 +645,20 @@ static int bareudp_link_config(struct net_device *dev,
>         return 0;
>  }
>
> +static void bareudp_dellink(struct net_device *dev, struct list_head *head)
> +{
> +       struct bareudp_dev *bareudp = netdev_priv(dev);
> +
> +       list_del(&bareudp->next);
> +       unregister_netdevice_queue(dev, head);
> +}
> +
>  static int bareudp_newlink(struct net *net, struct net_device *dev,
>                            struct nlattr *tb[], struct nlattr *data[],
>                            struct netlink_ext_ack *extack)
>  {
>         struct bareudp_conf conf;
> +       LIST_HEAD(list_kill);
>         int err;
>
>         err = bareudp2info(data, &conf, extack);
> @@ -662,17 +671,14 @@ static int bareudp_newlink(struct net *net, struct net_device *dev,
>
>         err = bareudp_link_config(dev, tb);
>         if (err)
> -               return err;
> +               goto err_unconfig;
>
>         return 0;
> -}
> -
> -static void bareudp_dellink(struct net_device *dev, struct list_head *head)
> -{
> -       struct bareudp_dev *bareudp = netdev_priv(dev);
>
> -       list_del(&bareudp->next);
> -       unregister_netdevice_queue(dev, head);
> +err_unconfig:
> +       bareudp_dellink(dev, &list_kill);
> +       unregister_netdevice_many(&list_kill);

Why do we need unregister_netdevice_many() here? I think
bareudp_dellink(dev, NULL) is sufficient as we always have
one instance to unregister?

(For the same reason, bareudp_dev_create() does not need it
either.)

Thanks.