net: add netdev_set_operstate() helper

dev_base_lock is going away, add netdev_set_operstate() helper
so that hsr does not have to know core internals.

Remove dev_base_lock acquisition from rfc2863_policy()

v3: use an "unsigned int" for dev->operstate,
    so that try_cmpxchg() can work on all arches.
        ( https://lore.kernel.org/oe-kbuild-all/202402081918.OLyGaea3-lkp@intel.com/ )
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netdevice.h

@@ -2258,7 +2258,7 @@ struct net_device {
 	const struct tlsdev_ops *tlsdev_ops;
 #endif
 
-	unsigned char		operstate;
+	unsigned int		operstate;
 	unsigned char		link_mode;
 
 	unsigned char		if_port;

include/linux/rtnetlink.h

@@ -172,4 +172,6 @@ rtnl_notify_needed(const struct net *net, u16 nlflags, u32 group)
 	return (nlflags & NLM_F_ECHO) || rtnl_has_listeners(net, group);
 }
 
+void netdev_set_operstate(struct net_device *dev, int newstate);
+
 #endif	/* __LINUX_RTNETLINK_H */

net/core/link_watch.c

@@ -33,7 +33,7 @@ static DECLARE_DELAYED_WORK(linkwatch_work, linkwatch_event);
 static LIST_HEAD(lweventlist);
 static DEFINE_SPINLOCK(lweventlist_lock);
 
-static unsigned char default_operstate(const struct net_device *dev)
+static unsigned int default_operstate(const struct net_device *dev)
 {
 	if (netif_testing(dev))
 		return IF_OPER_TESTING;
@@ -62,16 +62,13 @@ static unsigned char default_operstate(const struct net_device *dev)
 	return IF_OPER_UP;
 }
 
-
 static void rfc2863_policy(struct net_device *dev)
 {
-	unsigned char operstate = default_operstate(dev);
+	unsigned int operstate = default_operstate(dev);
 
 	if (operstate == READ_ONCE(dev->operstate))
 		return;
 
-	write_lock(&dev_base_lock);
-
 	switch(dev->link_mode) {
 	case IF_LINK_MODE_TESTING:
 		if (operstate == IF_OPER_UP)
@@ -88,8 +85,6 @@ static void rfc2863_policy(struct net_device *dev)
 	}
 
 	WRITE_ONCE(dev->operstate, operstate);
-
-	write_unlock(&dev_base_lock);
 }
 
 

net/core/rtnetlink.c

@@ -842,9 +842,22 @@ int rtnl_put_cacheinfo(struct sk_buff *skb, struct dst_entry *dst, u32 id,
 }
 EXPORT_SYMBOL_GPL(rtnl_put_cacheinfo);
 
+void netdev_set_operstate(struct net_device *dev, int newstate)
+{
+	unsigned int old = READ_ONCE(dev->operstate);
+
+	do {
+		if (old == newstate)
+			return;
+	} while (!try_cmpxchg(&dev->operstate, &old, newstate));
+
+	netdev_state_change(dev);
+}
+EXPORT_SYMBOL(netdev_set_operstate);
+
 static void set_operstate(struct net_device *dev, unsigned char transition)
 {
-	unsigned char operstate = dev->operstate;
+	unsigned char operstate = READ_ONCE(dev->operstate);
 
 	switch (transition) {
 	case IF_OPER_UP:
@@ -866,12 +879,7 @@ static void set_operstate(struct net_device *dev, unsigned char transition)
 		break;
 	}
 
-	if (READ_ONCE(dev->operstate) != operstate) {
-		write_lock(&dev_base_lock);
-		WRITE_ONCE(dev->operstate, operstate);
-		write_unlock(&dev_base_lock);
-		netdev_state_change(dev);
-	}
+	netdev_set_operstate(dev, operstate);
 }
 
 static unsigned int rtnl_dev_get_flags(const struct net_device *dev)

net/hsr/hsr_device.c

@@ -28,29 +28,19 @@ static bool is_slave_up(struct net_device *dev)
 	return dev && is_admin_up(dev) && netif_oper_up(dev);
 }
 
-static void __hsr_set_operstate(struct net_device *dev, int transition)
-{
-	write_lock(&dev_base_lock);
-	if (READ_ONCE(dev->operstate) != transition) {
-		WRITE_ONCE(dev->operstate, transition);
-		write_unlock(&dev_base_lock);
-		netdev_state_change(dev);
-	} else {
-		write_unlock(&dev_base_lock);
-	}
-}
-
 static void hsr_set_operstate(struct hsr_port *master, bool has_carrier)
 {
-	if (!is_admin_up(master->dev)) {
-		__hsr_set_operstate(master->dev, IF_OPER_DOWN);
+	struct net_device *dev = master->dev;
+
+	if (!is_admin_up(dev)) {
+		netdev_set_operstate(dev, IF_OPER_DOWN);
 		return;
 	}
 
 	if (has_carrier)
-		__hsr_set_operstate(master->dev, IF_OPER_UP);
+		netdev_set_operstate(dev, IF_OPER_UP);
 	else
-		__hsr_set_operstate(master->dev, IF_OPER_LOWERLAYERDOWN);
+		netdev_set_operstate(dev, IF_OPER_LOWERLAYERDOWN);
 }
 
 static bool hsr_check_carrier(struct hsr_port *master)