ipv6: take care of rt6_stats

Currently, most of the rt6_stats are not hooked up correctly. As the
last part of this patch series, hook up all existing rt6_stats and add
one new stat fib_rt_uncache to indicate the number of routes in the
uncached list.
For details of the stats, please refer to the comments added in
include/net/ip6_fib.h.

Note: fib_rt_alloc and fib_rt_uncache are not guaranteed to be modified
under a lock. So atomic_t is used for them.

Signed-off-by: Wei Wang <weiwan@google.com>
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/ip6_fib.h

@@ -297,12 +297,15 @@ struct fib6_walker {
 };
 
 struct rt6_statistics {
-	__u32		fib_nodes;
-	__u32		fib_route_nodes;
-	__u32		fib_rt_alloc;		/* permanent routes	*/
-	__u32		fib_rt_entries;		/* rt entries in table	*/
-	__u32		fib_rt_cache;		/* cache routes		*/
-	__u32		fib_discarded_routes;
+	__u32		fib_nodes;		/* all fib6 nodes */
+	__u32		fib_route_nodes;	/* intermediate nodes */
+	__u32		fib_rt_entries;		/* rt entries in fib table */
+	__u32		fib_rt_cache;		/* cached rt entries in exception table */
+	__u32		fib_discarded_routes;	/* total number of routes delete */
+
+	/* The following stats are not protected by any lock */
+	atomic_t	fib_rt_alloc;		/* total number of routes alloced */
+	atomic_t	fib_rt_uncache;		/* rt entries in uncached list */
 };
 
 #define RTN_TL_ROOT	0x0001