netdev - Re: [PATCH net v2 1/2] macvlan: introduce macvlan_dev_real

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Message-ID: <20131114155756.GA4161@lion.mk-sys.cz>
Date:	Thu, 14 Nov 2013 16:57:57 +0100
From:	Michal Kubecek <mkubecek@...e.cz>
To:	Vlad Yasevich <vyasevich@...il.com>
Cc:	netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
	Patrick McHardy <kaber@...sh.net>,
	John Fastabend <john.r.fastabend@...el.com>
Subject: Re: [PATCH net v2 1/2] macvlan: introduce macvlan_dev_real_dev()
 helper function

On Thu, Nov 14, 2013 at 10:03:19AM -0500, Vlad Yasevich wrote:
> On 11/14/2013 09:00 AM, Michal Kubecek wrote:
> >+#if IS_ENABLED(CONFIG_MACVLAN)
> >+static inline struct net_device *
> >+macvlan_dev_real_dev(const struct net_device *dev)
> >+{
> >+	struct macvlan_dev *macvlan = netdev_priv(dev);
> >+
> >+	return macvlan->lowerdev;
> >+}
> >+#else
> >+static inline struct net_device *
> >+macvlan_dev_real_dev(const struct net_device *dev)
> >+{
> >+	return NULL;
> >+}
> >+#endif
> >+
> 
> You may want to do the same here as was done for
> vlan_dev_real_dev(). This function is not intended to be called
> blindly and should always
> be called after netif_is_macvlan().

I'm not sure. It makes sense from the developer point of view: if we
find an inconsistency which must be caused by a bug in kernel code, do
panic so that the bug is found and fixed as soon as possible. However,
I remember a discussion where the point was that BUG() and BUG_ON()
should only be used if there is no way to recover. From this point of
view, WARN or WARN_ONCE might be better choice - but I'm not strictly
opposed to BUG().

                                                       Michal Kubecek

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