[PATCH net-next 10/13] net: add netdev_set_operstate() helper

[Eric Dumazet <edumazet@google.com>]

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()

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/linux/rtnetlink.h |  2 ++
 net/core/link_watch.c     |  4 ----
 net/core/rtnetlink.c      | 22 +++++++++++++++-------
 net/hsr/hsr_device.c      | 22 ++++++----------------
 4 files changed, 23 insertions(+), 27 deletions(-)

diff --git a/include/linux/rtnetlink.h b/include/linux/rtnetlink.h
index 21780608cf47ca0687dbaaf0d07b561e8631412c..cdfc897f1e3c683940a0958bc8a790c07ae819b0 100644
--- a/include/linux/rtnetlink.h
+++ b/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 */
diff --git a/net/core/link_watch.c b/net/core/link_watch.c
index 1b93e054c9a3cfcdd5d1251a9982d88a071abbaa..83fdeb60dbd21169ab7a52def3674615b2ddedbd 100644
--- a/net/core/link_watch.c
+++ b/net/core/link_watch.c
@@ -70,8 +70,6 @@ static void rfc2863_policy(struct net_device *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 +86,6 @@ static void rfc2863_policy(struct net_device *dev)
 	}
 
 	WRITE_ONCE(dev->operstate, operstate);
-
-	write_unlock(&dev_base_lock);
 }
 
 
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 4e797326c88fe1e23ca66e82103176767fe5c32e..46710e5f9bd19298403cdb8c179f33f155a4c9ad 100644
--- a/net/core/rtnetlink.c
+++ b/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 char 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)
diff --git a/net/hsr/hsr_device.c b/net/hsr/hsr_device.c
index be0e43f46556e028e675147e63c6b787aa72e894..5ef6d437db727e60bfd8cf68f010f0151d0db98b 100644
--- a/net/hsr/hsr_device.c
+++ b/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)
-- 
2.43.0.594.gd9cf4e227d-goog