[PATCH net v2] hv_netvsc: Fix a warning of suspicious RCU usage

[Dexuan Cui]

This fixes a warning of "suspicious rcu_dereference_check() usage"
when nload runs.

Fixes: 776e726bfb34 ("netvsc: fix RCU warning in get_stats")
Signed-off-by: Dexuan Cui <de...@microsoft.com>
---

Changes in v2:
    Made the minimal required change.
        Added a Fixes tag.
        Removed Stephen H.'s Signed-off-by since this is somewhat different 
from the 
                v1 from him; if there is any bug in v2, it's all my fault. :-)

 drivers/net/hyperv/netvsc_drv.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index f9209594624b..b6357a75712c 100644
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -1240,12 +1240,15 @@ static void netvsc_get_stats64(struct net_device *net,
                               struct rtnl_link_stats64 *t)
 {
        struct net_device_context *ndev_ctx = netdev_priv(net);
-       struct netvsc_device *nvdev = rcu_dereference_rtnl(ndev_ctx->nvdev);
+       struct netvsc_device *nvdev;
        struct netvsc_vf_pcpu_stats vf_tot;
        int i;
 
+       rcu_read_lock();
+
+       nvdev = rcu_dereference(ndev_ctx->nvdev);
        if (!nvdev)
-               return;
+               goto out;
 
        netdev_stats_to_stats64(t, &net->stats);
 
@@ -1284,6 +1287,8 @@ static void netvsc_get_stats64(struct net_device *net,
                t->rx_packets   += packets;
                t->multicast    += multicast;
        }
+out:
+       rcu_read_unlock();
 }
 
 static int netvsc_set_mac_addr(struct net_device *ndev, void *p)
-- 
2.19.1