Subject: Re: [PATCH net-next V3 5/6] net: introduce NETDEV_CHANGE_TX_QUEUE_LEN

From: Jason Wang <[email-masked]>
Date: Thu, 30 Jun 2016 13:59:47 +0800

On 2016年06月30日 13:12, Jason Wang wrote:
>
>
> On 2016年06月30日 12:56, John Fastabend wrote:
>> On 16-06-29 08:52 PM, Jason Wang wrote:
>>> This patch introduces a new event - NETDEV_CHANGE_TX_QUEUE_LEN, this
>>> will be triggered when tx_queue_len. It could be used by net device
>>> who want to do some processing at that time. An example is tun who may
>>> want to resize tx array when tx_queue_len is changed.
>>>
>>> Signed-off-by: Jason Wang <[email-masked]>
>>> ---
>>>   include/linux/netdevice.h |  1 +
>>>   net/core/net-sysfs.c      | 15 ++++++++++++++-
>>>   2 files changed, 15 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
>>> index e84d9d2..7dc2ec7 100644
>>> --- a/include/linux/netdevice.h
>>> +++ b/include/linux/netdevice.h
>>> @@ -2237,6 +2237,7 @@ struct netdev_lag_lower_state_info {
>>>   #define NETDEV_PRECHANGEUPPER    0x001A
>>>   #define NETDEV_CHANGELOWERSTATE    0x001B
>>>   #define NETDEV_UDP_TUNNEL_PUSH_INFO    0x001C
>>> +#define NETDEV_CHANGE_TX_QUEUE_LEN    0x001E
>>>     int register_netdevice_notifier(struct notifier_block *nb);
>>>   int unregister_netdevice_notifier(struct notifier_block *nb);
>>> diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
>>> index 7a0b616..6e4f347 100644
>>> --- a/net/core/net-sysfs.c
>>> +++ b/net/core/net-sysfs.c
>>> @@ -322,7 +322,20 @@ NETDEVICE_SHOW_RW(flags, fmt_hex);
>>>     static int change_tx_queue_len(struct net_device *dev, unsigned 
>>> long new_len)
>>>   {
>>> -    dev->tx_queue_len = new_len;
>>> +    int res, orig_len = dev->tx_queue_len;
>>> +
>>> +    if (new_len != orig_len) {
>>> +        dev->tx_queue_len = new_len;
>>> +        res = call_netdevice_notifiers(NETDEV_CHANGE_TX_QUEUE_LEN, 
>>> dev);
>>> +        res = notifier_to_errno(res);
>>> +        if (res) {
>>> +            netdev_err(dev,
>>> +                   "refused to change device tx_queue_len\n");
>>> +            dev->tx_queue_len = orig_len;
>>> +            return -EFAULT;
>>> +        }
>>> +    }
>>> +
>>>       return 0;
>>>   }
>>>
>> Acked-by: John Fastabend <[email-masked]>
>>
>> Great timing I was just looking into this because I need it for the
>> qdisc side.
>>
>> It looks like this covers the sysfs change but the tx_queue_len can
>> also be changed via rtnetlink as well. So we need another patch for
>> that path right?
>>
>>          if (tb[IFLA_TXQLEN]) {
>>                  unsigned long value = nla_get_u32(tb[IFLA_TXQLEN]);
>>
>>                  if (dev->tx_queue_len ^ value)
>>                          status |= DO_SETLINK_NOTIFY;
>>
>>                  dev->tx_queue_len = value;
>>          }
>>
>> Thanks,
>> John
>>
>
> Right, will do this in next version.
>
> Thanks

Ok, since Michael has acked on the series, will prepare a patch on top.

Thanks
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