ipv6: convert fib6_ref to refcount_t

We suspect some issues involving fib6_ref 0 -> 1 transitions might
cause strange syzbot reports.

Lets convert fib6_ref to refcount_t to catch them earlier.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Wei Wang <weiwan@google.com>
Acked-by: Wei Wang <weiwan@google.com>
Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 844b16d..923af51 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -296,7 +296,7 @@ static const struct fib6_info fib6_null_entry_template = {
 	.fib6_flags	= (RTF_REJECT | RTF_NONEXTHOP),
 	.fib6_protocol  = RTPROT_KERNEL,
 	.fib6_metric	= ~(u32)0,
-	.fib6_ref	= ATOMIC_INIT(1),
+	.fib6_ref	= REFCOUNT_INIT(1),
 	.fib6_type	= RTN_UNREACHABLE,
 	.fib6_metrics	= (struct dst_metrics *)&dst_default_metrics,
 };