[Patch net-next v2] act_mirred: get rid of mirred_list_lock spinlock

[Cong Wang]

TC actions are no longer freed in RCU callbacks and we should
always have RTNL lock, so this spinlock is no longer needed.

Cc: Eric Dumazet <eric.duma...@gmail.com>
Cc: Jiri Pirko <j...@mellanox.com>
Cc: Jamal Hadi Salim <j...@mojatatu.com>
Signed-off-by: Cong Wang <xiyou.wangc...@gmail.com>
---
 net/sched/act_mirred.c | 10 +---------
 1 file changed, 1 insertion(+), 9 deletions(-)

diff --git a/net/sched/act_mirred.c b/net/sched/act_mirred.c
index ff497909c0ad..cee2d413bf57 100644
--- a/net/sched/act_mirred.c
+++ b/net/sched/act_mirred.c
@@ -29,7 +29,6 @@
 #include <net/tc_act/tc_mirred.h>
 
 static LIST_HEAD(mirred_list);
-static DEFINE_SPINLOCK(mirred_list_lock);
 
 static bool tcf_mirred_is_act_redirect(int action)
 {
@@ -55,13 +54,10 @@ static void tcf_mirred_release(struct tc_action *a)
        struct tcf_mirred *m = to_mirred(a);
        struct net_device *dev;
 
-       /* We could be called either in a RCU callback or with RTNL lock held. 
*/
-       spin_lock_bh(&mirred_list_lock);
        list_del(&m->tcfm_list);
-       dev = rcu_dereference_protected(m->tcfm_dev, 1);
+       dev = rtnl_dereference(m->tcfm_dev);
        if (dev)
                dev_put(dev);
-       spin_unlock_bh(&mirred_list_lock);
 }
 
 static const struct nla_policy mirred_policy[TCA_MIRRED_MAX + 1] = {
@@ -147,9 +143,7 @@ static int tcf_mirred_init(struct net *net, struct nlattr 
*nla,
        }
 
        if (ret == ACT_P_CREATED) {
-               spin_lock_bh(&mirred_list_lock);
                list_add(&m->tcfm_list, &mirred_list);
-               spin_unlock_bh(&mirred_list_lock);
                tcf_idr_insert(tn, *a);
        }
 
@@ -293,7 +287,6 @@ static int mirred_device_event(struct notifier_block 
*unused,
 
        ASSERT_RTNL();
        if (event == NETDEV_UNREGISTER) {
-               spin_lock_bh(&mirred_list_lock);
                list_for_each_entry(m, &mirred_list, tcfm_list) {
                        if (rcu_access_pointer(m->tcfm_dev) == dev) {
                                dev_put(dev);
@@ -303,7 +296,6 @@ static int mirred_device_event(struct notifier_block 
*unused,
                                RCU_INIT_POINTER(m->tcfm_dev, NULL);
                        }
                }
-               spin_unlock_bh(&mirred_list_lock);
        }
 
        return NOTIFY_DONE;
-- 
2.13.0