[PATCH net-next 5/6] inet: prepare inet_base_seq() to run without RTNL

[Eric Dumazet <edumazet@google.com>]

In the following patch, inet_base_seq() will no longer be called
with RTNL held.

Add READ_ONCE()/WRITE_ONCE() annotations in dev_base_seq_inc()
and inet_base_seq().

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/core/dev.c     | 5 +++--
 net/ipv4/devinet.c | 2 +-
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 053fac78305c7322b894ceb07a925f7e64ed70aa..873e095e141db3e631e51763435ddafbf0d280af 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -180,8 +180,9 @@ static DECLARE_RWSEM(devnet_rename_sem);
 
 static inline void dev_base_seq_inc(struct net *net)
 {
-	while (++net->dev_base_seq == 0)
-		;
+	unsigned int val = net->dev_base_seq + 1;
+
+	WRITE_ONCE(net->dev_base_seq, val ?: 1);
 }
 
 static inline struct hlist_head *dev_name_hash(struct net *net, const char *name)
diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index 550b775cbbf3c140c66e224c69996df7051b3d36..2afe78dfc3c2f6c0394925f1c35532a2dfd26d71 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -1837,7 +1837,7 @@ static int in_dev_dump_addr(struct in_device *in_dev, struct sk_buff *skb,
 static u32 inet_base_seq(const struct net *net)
 {
 	u32 res = atomic_read(&net->ipv4.dev_addr_genid) +
-		  net->dev_base_seq;
+		  READ_ONCE(net->dev_base_seq);
 
 	/* Must not return 0 (see nl_dump_check_consistent()).
 	 * Chose a value far away from 0.
-- 
2.44.0.278.ge034bb2e1d-goog