Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1502422

Re: [PATCH v3 net-next 2/2] net: deprecate eth_change_mtu, remove usage

Show all headers | View raw

On Mon, Oct 17, 2016 at 01:25:53PM -0400, David Miller wrote:
> From: Jakub Kicinski <kubakici@wp.pl>
> Date: Mon, 17 Oct 2016 18:20:49 +0100
> 
> > Hm.  I must be missing something really obvious.  I just booted
> > net-next an hour ago and couldn't set MTU to anything larger than 1500
> > on either nfp or igb.  As far as I can read the code it will set the
> > max_mtu to 1500 in setup_ether() but none of the jumbo-capable drivers
> > had been touched by Jarod so far...
> 
> Indeed.
> 
> Jarod, this doesn't work.
> 
> I guess the idea was that if the driver overrides ndo_change_mtu and
> enforeced it's limits there, the driver would still work after your
> changes.
> 
> But that isn't what is happening, look at the IGB example.
> 
> It uses ether_setup(), which sets those new defaults, but now when
> the MTU is changed you enforce those default min/max before the
> driver's ->ndo_change_mtu() has a change to step in front and make
> the decision on it's own.
> 
> This means your changes pretty much did indeed break a lot of
> drivers's ability to set larger than a 1500 byte MTU.

Argh. Yeah, I see it now. I was primarily operating with the follow-on
patches also in play, which do touch all the ethernet drivers and set
max_mtu to match current behavior, didn't consider the max_mtu case where
only the initial patches were applied and the follow-on ones weren't. I've
sent that set, which should theoretically make this problem go away, but I
can also try to rework things if need be to restore intermediate jumbo
frames functionality. (And there are actually non-ethernet devices that
also call ether_setup and may or may not have larger than 1500 mtu that
aren't yet addressed by that follow-on set).

-- 
Jarod Wilson
jarod@redhat.com

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Re: [PATCH v3 net-next 2/2] net: deprecate eth_change_mtu, remove  usage Jakub Kicinski <kubakici@wp.pl> - 2016-10-17 18:30 +0200
  Re: [PATCH v3 net-next 2/2] net: deprecate eth_change_mtu, remove  usage David Miller <davem@davemloft.net> - 2016-10-17 19:00 +0200
    Re: [PATCH v3 net-next 2/2] net: deprecate eth_change_mtu, remove  usage Jakub Kicinski <kubakici@wp.pl> - 2016-10-17 19:10 +0200
      Re: [PATCH v3 net-next 2/2] net: deprecate eth_change_mtu, remove  usage Jakub Kicinski <kubakici@wp.pl> - 2016-10-17 19:10 +0200
      Re: [PATCH v3 net-next 2/2] net: deprecate eth_change_mtu, remove  usage David Miller <davem@davemloft.net> - 2016-10-17 19:20 +0200
        Re: [PATCH v3 net-next 2/2] net: deprecate eth_change_mtu, remove  usage David Miller <davem@davemloft.net> - 2016-10-17 19:30 +0200
          Re: [PATCH v3 net-next 2/2] net: deprecate eth_change_mtu, remove  usage Jarod Wilson <jarod@redhat.com> - 2016-10-17 22:10 +0200
            Re: [PATCH v3 net-next 2/2] net: deprecate eth_change_mtu, remove  usage Jarod Wilson <jarod@redhat.com> - 2016-10-17 22:30 +0200
        Re: [PATCH v3 net-next 2/2] net: deprecate eth_change_mtu, remove  usage Jakub Kicinski <kubakici@wp.pl> - 2016-10-17 19:30 +0200

csiph-web