diff mbox series

[net-next,2/5] ipv4: use READ_ONCE()/WRITE_ONCE() on net->ipv4.fib_seq

Message ID 20241009184405.3752829-3-edumazet@google.com (mailing list archive)
State Accepted
Commit 16207384d29287a19f81436e1953b41946aa8258
Delegated to: Netdev Maintainers
Headers show
Series net: remove RTNL from fib_seq_sum() | expand

Checks

Context Check Description
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for net-next
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 43 this patch: 43
netdev/build_tools success Errors and warnings before: 0 (+1) this patch: 0 (+1)
netdev/cc_maintainers warning 1 maintainers not CCed: lixiaoyan@google.com
netdev/build_clang success Errors and warnings before: 92 this patch: 92
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 4295 this patch: 4295
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 51 lines checked
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
netdev/contest success net-next-2024-10-11--15-00 (tests: 776)

Commit Message

Eric Dumazet Oct. 9, 2024, 6:44 p.m. UTC 
Using RTNL to protect ops->fib_rules_seq reads seems a big hammer.

Writes are protected by RTNL.
We can use READ_ONCE() when reading it.

Constify 'struct net' argument of fib4_rules_seq_read()

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/net/ip_fib.h     | 4 ++--
 include/net/netns/ipv4.h | 2 +-
 net/ipv4/fib_notifier.c  | 8 ++++----
 net/ipv4/fib_rules.c     | 2 +-
 4 files changed, 8 insertions(+), 8 deletions(-)

Comments

Kuniyuki Iwashima Oct. 9, 2024, 11:53 p.m. UTC | #1 
From: Eric Dumazet <edumazet@google.com>
Date: Wed,  9 Oct 2024 18:44:02 +0000
> Using RTNL to protect ops->fib_rules_seq reads seems a big hammer.
> 
> Writes are protected by RTNL.
> We can use READ_ONCE() when reading it.
> 
> Constify 'struct net' argument of fib4_rules_seq_read()
> 
> Signed-off-by: Eric Dumazet <edumazet@google.com>

Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
diff mbox series

Patch

diff --git a/include/net/ip_fib.h b/include/net/ip_fib.h
index 967e4dc555face31a736f6108cea6b929478beba..4c2e2d1481ebff5292b9e433f56fa7289ba8e139 100644
--- a/include/net/ip_fib.h
+++ b/include/net/ip_fib.h
@@ -347,7 +347,7 @@  static inline int fib4_rules_dump(struct net *net, struct notifier_block *nb,
 	return 0;
 }
 
-static inline unsigned int fib4_rules_seq_read(struct net *net)
+static inline unsigned int fib4_rules_seq_read(const struct net *net)
 {
 	return 0;
 }
@@ -411,7 +411,7 @@  static inline bool fib4_has_custom_rules(const struct net *net)
 bool fib4_rule_default(const struct fib_rule *rule);
 int fib4_rules_dump(struct net *net, struct notifier_block *nb,
 		    struct netlink_ext_ack *extack);
-unsigned int fib4_rules_seq_read(struct net *net);
+unsigned int fib4_rules_seq_read(const struct net *net);
 
 static inline bool fib4_rules_early_flow_dissect(struct net *net,
 						 struct sk_buff *skb,
diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h
index 276f622f3516871c438be27bafe61c039445b335..10c0a8dc37a23e793007ee47706b402fffbd08da 100644
--- a/include/net/netns/ipv4.h
+++ b/include/net/netns/ipv4.h
@@ -263,7 +263,7 @@  struct netns_ipv4 {
 #endif
 
 	struct fib_notifier_ops	*notifier_ops;
-	unsigned int	fib_seq;	/* protected by rtnl_mutex */
+	unsigned int	fib_seq;	/* writes protected by rtnl_mutex */
 
 	struct fib_notifier_ops	*ipmr_notifier_ops;
 	unsigned int	ipmr_seq;	/* protected by rtnl_mutex */
diff --git a/net/ipv4/fib_notifier.c b/net/ipv4/fib_notifier.c
index 0e23ade74493ce10a3f2572c39e091f132684884..21c85c80de641112d66a28645b1fb17c7071863f 100644
--- a/net/ipv4/fib_notifier.c
+++ b/net/ipv4/fib_notifier.c
@@ -22,15 +22,15 @@  int call_fib4_notifiers(struct net *net, enum fib_event_type event_type,
 	ASSERT_RTNL();
 
 	info->family = AF_INET;
-	net->ipv4.fib_seq++;
+	/* Paired with READ_ONCE() in fib4_seq_read() */
+	WRITE_ONCE(net->ipv4.fib_seq, net->ipv4.fib_seq + 1);
 	return call_fib_notifiers(net, event_type, info);
 }
 
 static unsigned int fib4_seq_read(struct net *net)
 {
-	ASSERT_RTNL();
-
-	return net->ipv4.fib_seq + fib4_rules_seq_read(net);
+	/* Paired with WRITE_ONCE() in call_fib4_notifiers() */
+	return READ_ONCE(net->ipv4.fib_seq) + fib4_rules_seq_read(net);
 }
 
 static int fib4_dump(struct net *net, struct notifier_block *nb,
diff --git a/net/ipv4/fib_rules.c b/net/ipv4/fib_rules.c
index b07292d50ee76603f983c81a55d45abca89266e1..8325224ef07232d05b59c58011625daae847af30 100644
--- a/net/ipv4/fib_rules.c
+++ b/net/ipv4/fib_rules.c
@@ -74,7 +74,7 @@  int fib4_rules_dump(struct net *net, struct notifier_block *nb,
 	return fib_rules_dump(net, nb, AF_INET, extack);
 }
 
-unsigned int fib4_rules_seq_read(struct net *net)
+unsigned int fib4_rules_seq_read(const struct net *net)
 {
 	return fib_rules_seq_read(net, AF_INET);
 }