net: introduce netdev_alloc_pcpu_stats() for drivers

There are many drivers calling alloc_percpu() to allocate pcpu stats
and then initializing ->syncp. So just introduce a helper function for them.

Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netdevice.h

@@ -1726,6 +1726,20 @@ struct pcpu_sw_netstats {
 	struct u64_stats_sync   syncp;
 };
 
+#define netdev_alloc_pcpu_stats(type)				\
+({								\
+	typeof(type) *pcpu_stats = alloc_percpu(type);		\
+	if (pcpu_stats)	{					\
+		int i;						\
+		for_each_possible_cpu(i) {			\
+			typeof(type) *stat;			\
+			stat = per_cpu_ptr(pcpu_stats, i);	\
+			u64_stats_init(&stat->syncp);		\
+		}						\
+	}							\
+	pcpu_stats;						\
+})
+
 #include <linux/notifier.h>
 
 /* netdevice notifier chain. Please remember to update the rtnetlink