linux-kernel - Re: [PATCH net-next V3 5/6] net: introduce NETDEV_CHANGE_TX_QUEUE

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Date:	Thu, 30 Jun 2016 13:12:38 +0800
From:	Jason Wang <jasowang@...hat.com>
To:	John Fastabend <john.fastabend@...il.com>, mst@...hat.com,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	davem@...emloft.net
Cc:	kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
	eric.dumazet@...il.com, brouer@...hat.com
Subject: Re: [PATCH net-next V3 5/6] net: introduce NETDEV_CHANGE_TX_QUEUE_LEN



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 <jasowang@...hat.com>
>> ---
>>   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 <john.r.fastabend@...el.com>
>
> 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