net/sched: taprio: taprio_dump and taprio_change are protected by rtnl_mutex

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@nxp.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
index e9f57ef..017ccf5 100644 (file)
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -1484,10 +1484,8 @@ 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))
@@ -1878,9 +1876,8 @@ 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));
@@ -1924,8 +1921,6 @@ 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:
@@ -1935,7 +1930,6 @@ options_error:
        nla_nest_cancel(skb, nest);
 
 start_error:
-       rcu_read_unlock();
        return -ENOSPC;
 }