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SubjectRe: [PATCH net-next] net/core: ensure features get disabled on new lower devs
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On 11/03/2015 12:36 PM, Jarod Wilson wrote:
> With moving netdev_sync_lower_features() after the .ndo_set_features
> calls, I neglected to verify that devices added *after* a flag had been
> disabled on an upper device were properly added with that flag disabled as
> well. This currently happens, because we exit __netdev_update_features()
> when we see dev->features == features for the upper dev. We can retain the
> optimization of leaving without calling .ndo_set_features with a bit of
> tweaking and a goto here.
>
> Changing err to ret was somewhat arbitrary and makes the patch look more
> involved, but seems to better fit the altered use.
>
> Fixes: fd867d51f ("net/core: generic support for disabling netdev features down stack")
> CC: "David S. Miller" <davem@davemloft.net>
> CC: Eric Dumazet <edumazet@google.com>
> CC: Jay Vosburgh <j.vosburgh@gmail.com>
> CC: Veaceslav Falico <vfalico@gmail.com>
> CC: Andy Gospodarek <gospo@cumulusnetworks.com>
> CC: Jiri Pirko <jiri@resnulli.us>
> CC: Nikolay Aleksandrov <razor@blackwall.org>
> CC: Michal Kubecek <mkubecek@suse.cz>
> CC: Alexander Duyck <alexander.duyck@gmail.com>
> CC: netdev@vger.kernel.org
> Signed-off-by: Jarod Wilson <jarod@redhat.com>
> ---
> net/core/dev.c | 21 ++++++++++++---------
> 1 file changed, 12 insertions(+), 9 deletions(-)
>
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 8ce3f74..90e0a62 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -6402,7 +6402,7 @@ int __netdev_update_features(struct net_device *dev)
> struct net_device *upper, *lower;
> netdev_features_t features;
> struct list_head *iter;
> - int err = 0;
> + int ret = 0;
>
> ASSERT_RTNL();
>
> @@ -6419,31 +6419,34 @@ int __netdev_update_features(struct net_device *dev)
> features = netdev_sync_upper_features(dev, upper, features);
>
> if (dev->features == features)
> - return 0;
> + goto sync_lower;
>
> netdev_dbg(dev, "Features changed: %pNF -> %pNF\n",
> &dev->features, &features);
>
> if (dev->netdev_ops->ndo_set_features)
> - err = dev->netdev_ops->ndo_set_features(dev, features);
> + ret = dev->netdev_ops->ndo_set_features(dev, features);
>
> - if (unlikely(err < 0)) {
> + if (unlikely(ret < 0)) {
> netdev_err(dev,
> "set_features() failed (%d); wanted %pNF, left %pNF\n",
> - err, &features, &dev->features);
> + ret, &features, &dev->features);
> return -1;
> }
>
> + if (!ret) {
> + dev->features = features;
> + ret = 1;
> + }
> +

I would take the "ret = 1;" out of the if statement and let it stay here
by itself. Technically anything that traversed this path was returning
1 previously so we probably want to retain that behavior.

> +sync_lower:
> /* some features must be disabled on lower devices when disabled
> * on an upper device (think: bonding master or bridge)
> */
> netdev_for_each_lower_dev(dev, lower, iter)
> netdev_sync_lower_features(dev, lower, features);
>
> - if (!err)
> - dev->features = features;

You could just alter the if statement here to check for a non-zero ret
value since you should have it as either 0 or 1. It shouldn't have any
other values.

That way you will have disabled the feature on the lower devices before
advertising that it has been disabled on the upper device.

> - return 1;
> + return ret;
> }
>
> /**
>



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