net,rcu: convert call_rcu(free_dm_hw_stat) to kfree_rcu()

The rcu callback free_dm_hw_stat() just calls a kfree(),
so we use kfree_rcu() instead of the call_rcu(free_dm_hw_stat).
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

net/core/drop_monitor.c

@@ -207,14 +207,6 @@ static void trace_napi_poll_hit(void *ignore, struct napi_struct *napi)
 	rcu_read_unlock();
 }
 
-
-static void free_dm_hw_stat(struct rcu_head *head)
-{
-	struct dm_hw_stat_delta *n;
-	n = container_of(head, struct dm_hw_stat_delta, rcu);
-	kfree(n);
-}
-
 static int set_all_monitor_traces(int state)
 {
 	int rc = 0;
@@ -245,7 +237,7 @@ static int set_all_monitor_traces(int state)
 		list_for_each_entry_safe(new_stat, temp, &hw_stats_list, list) {
 			if (new_stat->dev == NULL) {
 				list_del_rcu(&new_stat->list);
-				call_rcu(&new_stat->rcu, free_dm_hw_stat);
+				kfree_rcu(new_stat, rcu);
 			}
 		}
 		break;
@@ -314,7 +306,7 @@ static int dropmon_net_event(struct notifier_block *ev_block,
 				new_stat->dev = NULL;
 				if (trace_state == TRACE_OFF) {
 					list_del_rcu(&new_stat->list);
-					call_rcu(&new_stat->rcu, free_dm_hw_stat);
+					kfree_rcu(new_stat, rcu);
 					break;
 				}
 			}