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

John Fastabend
2016-06-30T04:56:45Z

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@redhat.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@intel.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