diff mbox series

[net-next,1/5] fib: rules: use READ_ONCE()/WRITE_ONCE() on ops->fib_rules_seq

Message ID 20241009184405.3752829-2-edumazet@google.com (mailing list archive)
State Accepted
Commit a716ff52bebfe806fbcf5227cee4c7bda4e6724b
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: 19 this patch: 19
netdev/build_tools success Errors and warnings before: 0 (+1) this patch: 0 (+1)
netdev/cc_maintainers success CCed 5 of 5 maintainers
netdev/build_clang success Errors and warnings before: 39 this patch: 39
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: 2620 this patch: 2620
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 47 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() on readers.

Constify 'struct net' argument of fib_rules_seq_read()
and lookup_rules_ops().

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/net/fib_rules.h |  2 +-
 net/core/fib_rules.c    | 14 ++++++++------
 2 files changed, 9 insertions(+), 7 deletions(-)

Comments

Kuniyuki Iwashima Oct. 9, 2024, 11:47 p.m. UTC | #1 
From: Eric Dumazet <edumazet@google.com>
Date: Wed,  9 Oct 2024 18:44:01 +0000
> Using RTNL to protect ops->fib_rules_seq reads seems a big hammer.
> 
> Writes are protected by RTNL.
> We can use READ_ONCE() on readers.
> 
> Constify 'struct net' argument of fib_rules_seq_read()
> and lookup_rules_ops().
> 
> Signed-off-by: Eric Dumazet <edumazet@google.com>

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

Patch

diff --git a/include/net/fib_rules.h b/include/net/fib_rules.h
index d17855c52ef926383f2585a6f31094899f1e7908..04383d90a1e38847d9d10f8fd0c4bf2ef67af713 100644
--- a/include/net/fib_rules.h
+++ b/include/net/fib_rules.h
@@ -176,7 +176,7 @@  int fib_default_rule_add(struct fib_rules_ops *, u32 pref, u32 table);
 bool fib_rule_matchall(const struct fib_rule *rule);
 int fib_rules_dump(struct net *net, struct notifier_block *nb, int family,
 		   struct netlink_ext_ack *extack);
-unsigned int fib_rules_seq_read(struct net *net, int family);
+unsigned int fib_rules_seq_read(const struct net *net, int family);
 
 int fib_nl_newrule(struct sk_buff *skb, struct nlmsghdr *nlh,
 		   struct netlink_ext_ack *extack);
diff --git a/net/core/fib_rules.c b/net/core/fib_rules.c
index 154a2681f55cc6861d418927c396bec5d840578c..82ef090c0037817f15902d8784467f21419b5af7 100644
--- a/net/core/fib_rules.c
+++ b/net/core/fib_rules.c
@@ -101,7 +101,8 @@  static void notify_rule_change(int event, struct fib_rule *rule,
 			       struct fib_rules_ops *ops, struct nlmsghdr *nlh,
 			       u32 pid);
 
-static struct fib_rules_ops *lookup_rules_ops(struct net *net, int family)
+static struct fib_rules_ops *lookup_rules_ops(const struct net *net,
+					      int family)
 {
 	struct fib_rules_ops *ops;
 
@@ -370,7 +371,9 @@  static int call_fib_rule_notifiers(struct net *net,
 		.rule = rule,
 	};
 
-	ops->fib_rules_seq++;
+	ASSERT_RTNL();
+	/* Paired with READ_ONCE() in fib_rules_seq() */
+	WRITE_ONCE(ops->fib_rules_seq, ops->fib_rules_seq + 1);
 	return call_fib_notifiers(net, event_type, &info.info);
 }
 
@@ -397,17 +400,16 @@  int fib_rules_dump(struct net *net, struct notifier_block *nb, int family,
 }
 EXPORT_SYMBOL_GPL(fib_rules_dump);
 
-unsigned int fib_rules_seq_read(struct net *net, int family)
+unsigned int fib_rules_seq_read(const struct net *net, int family)
 {
 	unsigned int fib_rules_seq;
 	struct fib_rules_ops *ops;
 
-	ASSERT_RTNL();
-
 	ops = lookup_rules_ops(net, family);
 	if (!ops)
 		return 0;
-	fib_rules_seq = ops->fib_rules_seq;
+	/* Paired with WRITE_ONCE() in call_fib_rule_notifiers() */
+	fib_rules_seq = READ_ONCE(ops->fib_rules_seq);
 	rules_ops_put(ops);
 
 	return fib_rules_seq;