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

On 2016年06月30日 13:59, Jason Wang wrote:

On 2016年06月30日 13:12, Jason Wang wrote:

quoted

On 2016年06月30日 12:56, John Fastabend wrote:

quoted

On 16-06-29 08:52 PM, Jason Wang wrote:

quoted

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 <redacted>
---
  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 <redacted>

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 

Since kbuild test robot has found a minor issue on this series, I will 
post v4 with this fixed.

Thanks
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