netfilter: nf_conntrack: use atomic64 for accounting counters

We can use atomic64_t infrastructure to avoid taking a spinlock in fast
path, and remove inaccuracies while reading values in
ctnetlink_dump_counters() and connbytes_mt() on 32bit arches.

Suggested by Pablo.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
diff --git a/net/netfilter/nf_conntrack_acct.c b/net/netfilter/nf_conntrack_acct.c
index 369df3f..9332906 100644
--- a/net/netfilter/nf_conntrack_acct.c
+++ b/net/netfilter/nf_conntrack_acct.c
@@ -46,8 +46,8 @@
 		return 0;
 
 	return seq_printf(s, "packets=%llu bytes=%llu ",
-			  (unsigned long long)acct[dir].packets,
-			  (unsigned long long)acct[dir].bytes);
+			  (unsigned long long)atomic64_read(&acct[dir].packets),
+			  (unsigned long long)atomic64_read(&acct[dir].bytes));
 };
 EXPORT_SYMBOL_GPL(seq_print_acct);