ipmr: adopt rcu_read_lock() in mr_dump()

We no longer need to acquire mrt_lock() in mr_dump,
using rcu_read_lock() is enough.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/mroute_base.h

@@ -308,7 +308,7 @@ int mr_dump(struct net *net, struct notifier_block *nb, unsigned short family,
 			      struct netlink_ext_ack *extack),
 	    struct mr_table *(*mr_iter)(struct net *net,
 					struct mr_table *mrt),
-	    rwlock_t *mrt_lock, struct netlink_ext_ack *extack);
+	    struct netlink_ext_ack *extack);
 #else
 static inline void vif_device_init(struct vif_device *v,
 				   struct net_device *dev,
@@ -363,7 +363,7 @@ static inline int mr_dump(struct net *net, struct notifier_block *nb,
 					    struct netlink_ext_ack *extack),
 			  struct mr_table *(*mr_iter)(struct net *net,
 						      struct mr_table *mrt),
-			  rwlock_t *mrt_lock, struct netlink_ext_ack *extack)
+			  struct netlink_ext_ack *extack)
 {
 	return -EINVAL;
 }

net/ipv4/ipmr.c

@@ -3027,7 +3027,7 @@ static int ipmr_dump(struct net *net, struct notifier_block *nb,
 		     struct netlink_ext_ack *extack)
 {
 	return mr_dump(net, nb, RTNL_FAMILY_IPMR, ipmr_rules_dump,
-		       ipmr_mr_table_iter, &mrt_lock, extack);
+		       ipmr_mr_table_iter, extack);
 }
 
 static const struct fib_notifier_ops ipmr_notifier_ops_template = {

net/ipv4/ipmr_base.c

@@ -399,7 +399,6 @@ int mr_dump(struct net *net, struct notifier_block *nb, unsigned short family,
 			      struct netlink_ext_ack *extack),
 	    struct mr_table *(*mr_iter)(struct net *net,
 					struct mr_table *mrt),
-	    rwlock_t *mrt_lock,
 	    struct netlink_ext_ack *extack)
 {
 	struct mr_table *mrt;
@@ -416,10 +415,9 @@ int mr_dump(struct net *net, struct notifier_block *nb, unsigned short family,
 		int vifi;
 
 		/* Notifiy on table VIF entries */
-		read_lock(mrt_lock);
+		rcu_read_lock();
 		for (vifi = 0; vifi < mrt->maxvif; vifi++, v++) {
-			vif_dev = rcu_dereference_check(v->dev,
-							lockdep_is_held(mrt_lock));
+			vif_dev = rcu_dereference(v->dev);
 			if (!vif_dev)
 				continue;
 
@@ -430,7 +428,7 @@ int mr_dump(struct net *net, struct notifier_block *nb, unsigned short family,
 			if (err)
 				break;
 		}
-		read_unlock(mrt_lock);
+		rcu_read_unlock();
 
 		if (err)
 			return err;

net/ipv6/ip6mr.c

@@ -1267,7 +1267,7 @@ static int ip6mr_dump(struct net *net, struct notifier_block *nb,
 		      struct netlink_ext_ack *extack)
 {
 	return mr_dump(net, nb, RTNL_FAMILY_IP6MR, ip6mr_rules_dump,
-		       ip6mr_mr_table_iter, &mrt_lock, extack);
+		       ip6mr_mr_table_iter, extack);
 }
 
 static struct notifier_block ip6_mr_notifier = {