[Patch net-next 1/3] net: introduce helper dev_change_tx_queue_len()

[Cong Wang <xiyou.wangcong@gmail.com>]

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>
---
 include/linux/netdevice.h |  1 +
 net/core/dev.c            | 28 ++++++++++++++++++++++++++++
 net/core/net-sysfs.c      | 25 +------------------------
 net/core/rtnetlink.c      | 18 +++++-------------
 4 files changed, 35 insertions(+), 37 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index ed0799a12bf2..75587a053c33 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -3325,6 +3325,7 @@ int dev_get_alias(const struct net_device *, char *, size_t);
 int dev_change_net_namespace(struct net_device *, struct net *, const char *);
 int __dev_set_mtu(struct net_device *, int);
 int dev_set_mtu(struct net_device *, int);
+int dev_change_tx_queue_len(struct net_device *, unsigned long);
 void dev_set_group(struct net_device *, int);
 int dev_set_mac_address(struct net_device *, struct sockaddr *);
 int dev_change_carrier(struct net_device *, bool new_carrier);
diff --git a/net/core/dev.c b/net/core/dev.c
index 94435cd09072..99d353e4cbb2 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -7036,6 +7036,34 @@ 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
diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index 7bf8b85ade16..584a480c6274 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -325,29 +325,6 @@ static ssize_t flags_store(struct device *dev, struct device_attribute *attr,
 }
 NETDEVICE_SHOW_RW(flags, fmt_hex);
 
-static int 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 -EFAULT;
-		}
-	}
-
-	return 0;
-}
-
 static ssize_t tx_queue_len_store(struct device *dev,
 				  struct device_attribute *attr,
 				  const char *buf, size_t len)
@@ -355,7 +332,7 @@ static ssize_t tx_queue_len_store(struct device *dev,
 	if (!capable(CAP_NET_ADMIN))
 		return -EPERM;
 
-	return netdev_store(dev, attr, buf, len, change_tx_queue_len);
+	return netdev_store(dev, attr, buf, len, dev_change_tx_queue_len);
 }
 NETDEVICE_SHOW_RW(tx_queue_len, fmt_dec);
 
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 16d644a4f974..fb2f38193b86 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -2282,19 +2282,11 @@ static int do_setlink(const struct sk_buff *skb,
 
 	if (tb[IFLA_TXQLEN]) {
 		unsigned int value = nla_get_u32(tb[IFLA_TXQLEN]);
-		unsigned int orig_len = dev->tx_queue_len;
-
-		if (dev->tx_queue_len ^ value) {
-			dev->tx_queue_len = value;
-			err = call_netdevice_notifiers(
-			      NETDEV_CHANGE_TX_QUEUE_LEN, dev);
-			err = notifier_to_errno(err);
-			if (err) {
-				dev->tx_queue_len = orig_len;
-				goto errout;
-			}
-			status |= DO_SETLINK_MODIFIED;
-		}
+
+		err = dev_change_tx_queue_len(dev, value);
+		if (err)
+			goto errout;
+		status |= DO_SETLINK_MODIFIED;
 	}
 
 	if (tb[IFLA_GSO_MAX_SIZE]) {
-- 
2.13.0