net: fix 64 bit counters on 32 bit arches

There is a small possibility that a reader gets incorrect values on 32
bit arches. SNMP applications could catch incorrect counters when a
32bit high part is changed by another stats consumer/provider.

One way to solve this is to add a rtnl_link_stats64 param to all
ndo_get_stats64() methods, and also add such a parameter to
dev_get_stats().

Rule is that we are not allowed to use dev->stats64 as a temporary
storage for 64bit stats, but a caller provided area (usually on stack)

Old drivers (only providing get_stats() method) need no changes.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/loopback.c b/drivers/net/loopback.c
index 4dd0510..9a09967 100644
--- a/drivers/net/loopback.c
+++ b/drivers/net/loopback.c
@@ -98,10 +98,10 @@
 	return NETDEV_TX_OK;
 }
 
-static struct rtnl_link_stats64 *loopback_get_stats64(struct net_device *dev)
+static struct rtnl_link_stats64 *loopback_get_stats64(struct net_device *dev,
+						      struct rtnl_link_stats64 *stats)
 {
 	const struct pcpu_lstats __percpu *pcpu_lstats;
-	struct rtnl_link_stats64 *stats = &dev->stats64;
 	u64 bytes = 0;
 	u64 packets = 0;
 	u64 drops = 0;