net: introduce helper dev_change_tx_queue_len()

This patch promotes the local change_tx_queue_len() to a core
helper function, dev_change_tx_queue_len(), so that rtnetlink
and net-sysfs could share the code. This also prepares for the
following patch.

Note, the -EFAULT in the original code doesn't make sense,
we should propagate the errno from notifiers.

Cc: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 28 insertions, 0 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index 858501b12869..520c24671bc5 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -7048,6 +7048,34 @@ int dev_set_mtu(struct net_device *dev, int new_mtu)
 EXPORT_SYMBOL(dev_set_mtu);
 
 /**
+ *	dev_change_tx_queue_len - Change TX queue length of a netdevice
+ *	@dev: device
+ *	@new_len: new tx queue length
+ */
+int dev_change_tx_queue_len(struct net_device *dev, unsigned long new_len)
+{
+	unsigned int orig_len = dev->tx_queue_len;
+	int res;
+
+	if (new_len != (unsigned int)new_len)
+		return -ERANGE;
+
+	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 res;
+		}
+	}
+
+	return 0;
+}
+
+/**
  *	dev_set_group - Change group this device belongs to
  *	@dev: device
  *	@new_group: group this device should belong to