netdev - [PATCH net-next 2/4] net: sched: refactor police action helpers to require tcf

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Message-Id: <20200211091918.20974-3-vladbu@mellanox.com>
Date:   Tue, 11 Feb 2020 11:19:16 +0200
From:   Vlad Buslov <vladbu@...lanox.com>
To:     netdev@...r.kernel.org, davem@...emloft.net
Cc:     jhs@...atatu.com, xiyou.wangcong@...il.com, jiri@...nulli.us,
        pablo@...filter.org, marcelo.leitner@...il.com,
        Vlad Buslov <vladbu@...lanox.com>,
        Jiri Pirko <jiri@...lanox.com>
Subject: [PATCH net-next 2/4] net: sched: refactor police action helpers to require tcf_lock

In order to remove rtnl lock dependency from flow_action representation
translator, change rcu_dereference_bh_rtnl() to rcu_dereference_protected()
in police action helpers that provide external access to rate and burst
values. This is safe to do because the functions are not called from
anywhere else outside flow_action infrastructure which was modified to
obtain tcf_lock when accessing action data in one of previous patches in
the series.

Signed-off-by: Vlad Buslov <vladbu@...lanox.com>
Acked-by: Jiri Pirko <jiri@...lanox.com>
---
 include/net/tc_act/tc_police.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/include/net/tc_act/tc_police.h b/include/net/tc_act/tc_police.h
index cfdc7cb82cad..f098ad4424be 100644
--- a/include/net/tc_act/tc_police.h
+++ b/include/net/tc_act/tc_police.h
@@ -54,7 +54,8 @@ static inline u64 tcf_police_rate_bytes_ps(const struct tc_action *act)
 	struct tcf_police *police = to_police(act);
 	struct tcf_police_params *params;
 
-	params = rcu_dereference_bh_rtnl(police->params);
+	params = rcu_dereference_protected(police->params,
+					   lockdep_is_held(&police->tcf_lock));
 	return params->rate.rate_bytes_ps;
 }
 
@@ -63,7 +64,8 @@ static inline s64 tcf_police_tcfp_burst(const struct tc_action *act)
 	struct tcf_police *police = to_police(act);
 	struct tcf_police_params *params;
 
-	params = rcu_dereference_bh_rtnl(police->params);
+	params = rcu_dereference_protected(police->params,
+					   lockdep_is_held(&police->tcf_lock));
 	return params->tcfp_burst;
 }
 
-- 
2.21.0