From mboxrd@z Thu Jan  1 00:00:00 1970
From: Cong Wang <xiyou.wangcong@gmail.com>
Subject: Re: [PATCH net] ipvlan: call dev_change_flags when reset ipvlan mode
Date: Tue, 19 Jun 2018 14:10:18 -0700
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References: <1529330677-15328-1-git-send-email-liuhangbin@gmail.com>
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Cc: Linux Kernel Network Developers <netdev@vger.kernel.org>,
        Stefano Brivio <sbrivio@redhat.com>,
        Paolo Abeni <pabeni@redhat.com>,
        David Miller <davem@davemloft.net>,
        Mahesh Bandewar <maheshb@google.com>
To: Hangbin Liu <liuhangbin@gmail.com>
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On Mon, Jun 18, 2018 at 7:04 AM, Hangbin Liu <liuhangbin@gmail.com> wrote:
> @@ -94,10 +95,13 @@ static int ipvlan_set_port_mode(struct ipvl_port *port, u16 nval)
>                         mdev->l3mdev_ops = NULL;
>                 }
>                 list_for_each_entry(ipvlan, &port->ipvlans, pnode) {
> +                       flags = ipvlan->dev->flags;
>                         if (nval == IPVLAN_MODE_L3 || nval == IPVLAN_MODE_L3S)
> -                               ipvlan->dev->flags |= IFF_NOARP;
> +                               dev_change_flags(ipvlan->dev,
> +                                                flags | IFF_NOARP);
>                         else
> -                               ipvlan->dev->flags &= ~IFF_NOARP;
> +                               dev_change_flags(ipvlan->dev,
> +                                                flags & ~IFF_NOARP);

You need to check the return value of dev_change_flags().