netfilter: nf_conntrack: use this_cpu_inc()

this_cpu_inc() is IRQ safe and faster than
local_bh_disable()/__this_cpu_inc()/local_bh_enable(), at least on x86.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Patrick McHardy <kaber@trash.net>
Cc: Christoph Lameter <cl@linux.com>
Cc: Tejun Heo <tj@kernel.org>
Reviewed-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/net/netfilter/nf_conntrack.h

@@ -321,14 +321,8 @@ extern unsigned int nf_conntrack_max;
 extern unsigned int nf_conntrack_hash_rnd;
 void init_nf_conntrack_hash_rnd(void);
 
-#define NF_CT_STAT_INC(net, count)	\
-	__this_cpu_inc((net)->ct.stat->count)
-#define NF_CT_STAT_INC_ATOMIC(net, count)		\
-do {							\
-	local_bh_disable();				\
-	__this_cpu_inc((net)->ct.stat->count);		\
-	local_bh_enable();				\
-} while (0)
+#define NF_CT_STAT_INC(net, count)	  __this_cpu_inc((net)->ct.stat->count)
+#define NF_CT_STAT_INC_ATOMIC(net, count) this_cpu_inc((net)->ct.stat->count)
 
 #define MODULE_ALIAS_NFCT_HELPER(helper) \
         MODULE_ALIAS("nfct-helper-" helper)