Commit a716ff52 authored by Eric Dumazet's avatar Eric Dumazet Committed by Jakub Kicinski
Browse files

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: default avatarEric Dumazet <edumazet@google.com>
Reviewed-by: default avatarKuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: default avatarDavid Ahern <dsahern@kernel.org>
Link: https://patch.msgid.link/20241009184405.3752829-2-edumazet@google.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent d677aebd

include/net/fib_rules.h

+1 −1
Original line number Diff line number Diff line
@@ -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);

net/core/fib_rules.c

+8 −6
Original line number Diff line number Diff line
@@ -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;