linux-kernel - Re: [PATCH net-next 00/15] ethernet: use core min/max MTU checking

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Date:   Tue, 18 Oct 2016 18:28:20 -0400
From:   Jarod Wilson <jarod@...hat.com>
To:     David Miller <davem@...emloft.net>
Cc:     linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH net-next 00/15] ethernet: use core min/max MTU checking

On Tue, Oct 18, 2016 at 11:33:27AM -0400, David Miller wrote:
> From: Jarod Wilson <jarod@...hat.com>
> Date: Mon, 17 Oct 2016 16:29:43 -0400
> 
> > On Mon, Oct 17, 2016 at 04:03:41PM -0400, David Miller wrote:
> >> From: Jarod Wilson <jarod@...hat.com>
> >> Date: Mon, 17 Oct 2016 15:54:02 -0400
> >> 
> >> > For the most part, every patch does the same essential thing: removes the
> >> > MTU range checking from the drivers' ndo_change_mtu function, puts those
> >> > ranges into the core net_device min_mtu and max_mtu fields, and where
> >> > possible, removes ndo_change_mtu functions entirely.
> >> 
> >> Jarod, please read my other posting.
> > 
> > Done, didn't see it until just after I'd hit send, have replied there as
> > well.
> > 
> >> You've positively broken the maximum MTU for all of these drivers.
> >> 
> >> That's not cool.
> >>
> >> And this series fixing things doesn't make things better, because now
> >> we've significanyly broken bisection for anyone running into this
> >> regression.
> > 
> > Agreed, and my suggestion right now is to revert the 2nd patch from the
> > prior series. I believe it can be resubmitted after all other callers of
> > ether_setup() have been converted to have their own min/max_mtu.
> > 
> >> You should have arranged this in such a way that the drivers needing
> >> > 1500 byte MTU were not impacted at all by your changes, but that
> >> isn't what happened.
> > 
> > Yeah, I must admit to not looking closely enough at the state the first
> > two patches left things in. It was absolutely my intention to not alter
> > behaviour in any way, but I neglected to test sufficiently without this
> > additional set applied.
> 
> So what I'm going to do now it simply just apply your current patch series
> to net-next and hope this gets everything working again.

Unfortunately, no, it doesn't get *everything* working again, because...

direct ether_setup() callers:

drivers/misc/sgi-xp/xpnet.c
drivers/net/geneve.c
drivers/net/macvlan.c
drivers/net/tun.c
drivers/net/vxlan.c
drivers/net/wan/hdlc.c
drivers/net/wan/hdlc_fr.c
drivers/net/wireless/ath/wil6210/netdev.c
drivers/net/wireless/cisco/airo.c
drivers/staging/wlan-ng/p80211netdev.c
net/batman-adv/soft-interface.c
net/bridge/br_device.c
net/openvswitch/vport-internal_dev.c

alloc_etherdev*() callers:
drivers/infiniband/hw/nes/nes_nic.c
drivers/net/hyperv/netvsc_drv.c
drivers/net/rionet.c
drivers/net/usb/lan78xx.c
drivers/net/usb/r8152.c
drivers/net/usb/usbnet.c
drivers/net/virtio_net.c
drivers/net/vmxnet3/vmxnet3_drv.c
drivers/net/wireless/atmel/atmel.c
drivers/net/wireless/cisco/airo.c
drivers/net/wireless/intel/ipw2x00/libipw_module.c
net/atm/lec.c

I have additional patches for all of these that I haven't yet posted, so
I'd still suggest backing out the one patch to keep the above working too
until the subsequent patches are posted.

> I'm just happy that you acknowledged how badly things got broken, so let's
> move on and try to avoid this happening again in the future.
> 
> Thanks.

I profusely apologize again for the mess. Was trying to clean up a mess,
made another one. Story of my life right now, it seems... :\

-- 
Jarod Wilson
jarod@...hat.com