inet: prepare inet_base_seq() to run without RTNL

edumazet · davem330 · commit 590e92cdc835 · 2024-03-01T11:09:39.000Z
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 &lt;edumazet@google.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
diff --git 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
@@ -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.

Original file line number	Diff line number	Diff line change
`@@ -180,8 +180,9 @@ static DECLARE_RWSEM(devnet_rename_sem);`
`180`	`180`
`181`	`181`	`static inline void dev_base_seq_inc(struct net *net)`
`182`	`182`	`{`
`183`		`- while (++net->dev_base_seq == 0)`
`184`		`- ;`
	`183`	`+ unsigned int val = net->dev_base_seq + 1;`
	`184`	`+`
	`185`	`+ WRITE_ONCE(net->dev_base_seq, val ?: 1);`
`185`	`186`	`}`
`186`	`187`
`187`	`188`	`static inline struct hlist_head dev_name_hash(struct net net, const char *name)`
Original file line number	Diff line number	Diff line change
`@@ -1837,7 +1837,7 @@ static int in_dev_dump_addr(struct in_device in_dev, struct sk_buff skb,`
`1837`	`1837`	`static u32 inet_base_seq(const struct net *net)`
`1838`	`1838`	`{`
`1839`	`1839`	`u32 res = atomic_read(&net->ipv4.dev_addr_genid) +`
`1840`		`- net->dev_base_seq;`
	`1840`	`+ READ_ONCE(net->dev_base_seq);`
`1841`	`1841`
`1842`	`1842`	`/* Must not return 0 (see nl_dump_check_consistent()).`
`1843`	`1843`	`* Chose a value far away from 0.`