netdev - Re: [patch net-next] net: call notifiers for mtu change even if iface is not up

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Message-ID: <20121207150708.GA29819@shamino.rdu.redhat.com>
Date:	Fri, 7 Dec 2012 10:07:08 -0500
From:	Neil Horman <nhorman@...driver.com>
To:	Jiri Pirko <jiri@...nulli.us>
Cc:	netdev@...r.kernel.org, davem@...emloft.net, edumazet@...gle.com,
	bhutchings@...arflare.com, psimerda@...hat.com
Subject: Re: [patch net-next] net: call notifiers for mtu change even if
 iface is not up

On Fri, Dec 07, 2012 at 01:29:20PM +0100, Jiri Pirko wrote:
> Mon, Dec 03, 2012 at 04:22:50PM CET, nhorman@...driver.com wrote:
> >On Mon, Dec 03, 2012 at 03:22:29PM +0100, Jiri Pirko wrote:
> >> Mon, Dec 03, 2012 at 03:18:23PM CET, nhorman@...driver.com wrote:
> >> >On Mon, Dec 03, 2012 at 12:16:32PM +0100, Jiri Pirko wrote:
> >> >> Do the same thing as in set mac. Call notifiers every time.
> >> >> 
> >> >> Signed-off-by: Jiri Pirko <jiri@...nulli.us>
> >> >> ---
> >> >>  net/core/dev.c | 2 +-
> >> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >> >> 
> >> >> diff --git a/net/core/dev.c b/net/core/dev.c
> >> >> index 2f94df2..0685a72 100644
> >> >> --- a/net/core/dev.c
> >> >> +++ b/net/core/dev.c
> >> >> @@ -4971,7 +4971,7 @@ int dev_set_mtu(struct net_device *dev, int new_mtu)
> >> >>  	else
> >> >>  		dev->mtu = new_mtu;
> >> >>  
> >> >> -	if (!err && dev->flags & IFF_UP)
> >> >> +	if (!err)
> >> >>  		call_netdevice_notifiers(NETDEV_CHANGEMTU, dev);
> >> >>  	return err;
> >> >>  }
> >> >
> >> >I'm not opposed to this change, but is there something that it expressly fixes?
> >> 
> >> This is about a consistency. To have the same behaviour as set_mac
> >> for example.
> >> 
> >> >While it doesn't hurt to send around mtu change events, one would presume that
> >> >listeners would pick up mtu changes when the NETDEV_UP event went' around.
> >> >
> >> >Neil
> >> >
> >I figured, I just wanted to be sure that there wasn't a bug fix that needed
> >documenting in the changelog, or that listeners for this event didn't expect the
> >interface to already be up.  It looks pretty clean, with the exception of the
> >TIPC protocol.  It appears that it might require enable_bearer to be called
> >prior to any netdevice CHANGEMTU events, so that the eth_bearers array gets
> >filled out, and it looks like that has to get triggered either by user space, or
> >the receipt of a message over the network.  Let me know what you think
> 
> I'm looking at the code. What is the difference between CHANGEMTU and
> CHANGEADDR here? It looks to me that it should work for both in the same
> way.
> 
Hmm, they do work in the same way, which likely means that tipc is probably
begging to oops there regardless of having your patch or not :)

I'll get around to fixing that shortly.  Since your patch then isn't going to
break anything that isn't already broken
Acked-by: Neil Horman <nhorman@...driver.com>

> 
> >
> >Neil
> >
> >> >--
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> 
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