[PATCH AUTOSEL 5.19 52/73] net/sched: taprio: taprio_dump and taprio_change are protected by rtnl_mutex

[Sasha Levin]

From: Vladimir Oltean <vladimir.oltean@xxxxxxx>

[ Upstream commit 18cdd2f0998a4967b1fff4c43ed9aef049e42c39 ]

Since the writer-side lock is taken here, we do not need to open an RCU
read-side critical section, instead we can use rtnl_dereference() to
tell lockdep we are serialized with concurrent writes.

Signed-off-by: Vladimir Oltean <vladimir.oltean@xxxxxxx>
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 net/sched/sch_taprio.c | 14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
index 86675a79da1e..71408136d4a0 100644
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -1492,10 +1492,8 @@ static int taprio_change(struct Qdisc *sch, struct nlattr *opt,
 	}
 	INIT_LIST_HEAD(&new_admin->entries);
 
-	rcu_read_lock();
-	oper = rcu_dereference(q->oper_sched);
-	admin = rcu_dereference(q->admin_sched);
-	rcu_read_unlock();
+	oper = rtnl_dereference(q->oper_sched);
+	admin = rtnl_dereference(q->admin_sched);
 
 	/* no changes - no new mqprio settings */
 	if (!taprio_mqprio_cmp(dev, mqprio))
@@ -1888,9 +1886,8 @@ static int taprio_dump(struct Qdisc *sch, struct sk_buff *skb)
 	struct nlattr *nest, *sched_nest;
 	unsigned int i;
 
-	rcu_read_lock();
-	oper = rcu_dereference(q->oper_sched);
-	admin = rcu_dereference(q->admin_sched);
+	oper = rtnl_dereference(q->oper_sched);
+	admin = rtnl_dereference(q->admin_sched);
 
 	opt.num_tc = netdev_get_num_tc(dev);
 	memcpy(opt.prio_tc_map, dev->prio_tc_map, sizeof(opt.prio_tc_map));
@@ -1934,8 +1931,6 @@ static int taprio_dump(struct Qdisc *sch, struct sk_buff *skb)
 	nla_nest_end(skb, sched_nest);
 
 done:
-	rcu_read_unlock();
-
 	return nla_nest_end(skb, nest);
 
 admin_error:
@@ -1945,7 +1940,6 @@ static int taprio_dump(struct Qdisc *sch, struct sk_buff *skb)
 	nla_nest_cancel(skb, nest);
 
 start_error:
-	rcu_read_unlock();
 	return -ENOSPC;
 }
 
-- 
2.35.1