From a716ff52bebfe806fbcf5227cee4c7bda4e6724b Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 9 Oct 2024 18:44:01 +0000 Subject: [PATCH] fib: rules: use READ_ONCE()/WRITE_ONCE() on ops->fib_rules_seq 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 Reviewed-by: Kuniyuki Iwashima Reviewed-by: David Ahern Link: https://patch.msgid.link/20241009184405.3752829-2-edumazet@google.com Signed-off-by: Jakub Kicinski --- include/net/fib_rules.h | 2 +- net/core/fib_rules.c | 14 ++++++++------ 2 files changed, 9 insertions(+), 7 deletions(-) diff --git a/include/net/fib_rules.h b/include/net/fib_rules.h index d17855c52ef9..04383d90a1e3 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 154a2681f55c..82ef090c0037 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; -- 2.25.1