Re: [PATCH net] net: fix feature changes on devices without ndo_set_features

[Nikolay Aleksandrov <nikolay@cumulusnetworks.com>]

On 11/18/2015 12:03 AM, Sergei Shtylyov wrote:
> Hello.
> 
> On 11/13/2015 04:54 PM, Nikolay Aleksandrov wrote:
> 
>> From: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
>>
>> When __netdev_update_features() was updated to ensure some features are
>> disabled on new lower devices, an error was introduced for devices which
>> don't have the ndo_set_features() method set. Before we'll just set the
>> new features, but now we return an error and don't set them. Fix this by
>> returning the old behaviour and setting err to 0 when ndo_set_features
>> is not present.
>>
>> Fixes: e7868a85e1b2 ("net/core: ensure features get disabled on new lower devs")
>> CC: Jarod Wilson <jarod@redhat.com>
>> CC: Jiri Pirko <jiri@resnulli.us>
>> CC: Ido Schimmel <idosch@mellanox.com>
>> CC: Sander Eikelenboom <linux@eikelenboom.it>
>> CC: Andy Gospodarek <gospo@cumulusnetworks.com>
>> CC: Florian Fainelli <f.fainelli@gmail.com>
>> Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
>> ---
>> Sander please feel free to give your Tested-by.
>>
>>   net/core/dev.c | 2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/net/core/dev.c b/net/core/dev.c
>> index ab9b8d0d115e..4a1d198dbbff 100644
>> --- a/net/core/dev.c
>> +++ b/net/core/dev.c
>> @@ -6426,6 +6426,8 @@ int __netdev_update_features(struct net_device *dev)
>>
>>       if (dev->netdev_ops->ndo_set_features)
>>           err = dev->netdev_ops->ndo_set_features(dev, features);
>> +    else
>> +        err = 0;
> 
>    This makes the 'err' initializer pointless.
> 
> MBR, Sergei
> 

It doesn't, there's a previous goto statement that might get hit and we
need it to be -1 so we don't signal a feature change.