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

[Jason Wang]

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;
 }
 
-- 
2.7.4