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

[Jason Wang]

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 <jasow...@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.fastab...@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

Right, will do this in next version.

Thanks