netfilter: {ip,ip6,arp}_tables: avoid lockdep false positive

After commit 24b36f01 (netfilter: {ip,ip6,arp}_tables: dont block
bottom half more than necessary), lockdep can raise a warning
because we attempt to lock a spinlock with BH enabled, while
the same lock is usually locked by another cpu in a softirq context.

Disable again BH to avoid these lockdep warnings.
Reported-by: NLinus Torvalds <torvalds@linux-foundation.org>
Diagnosed-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/netfilter/arp_tables.c

@@ -735,6 +735,7 @@ static void get_counters(const struct xt_table_info *t,
 		if (cpu == curcpu)
 			continue;
 		i = 0;
+		local_bh_disable();
 		xt_info_wrlock(cpu);
 		xt_entry_foreach(iter, t->entries[cpu], t->size) {
 			ADD_COUNTER(counters[i], iter->counters.bcnt,
@@ -742,6 +743,7 @@ static void get_counters(const struct xt_table_info *t,
 			++i;
 		}
 		xt_info_wrunlock(cpu);
+		local_bh_enable();
 	}
 	put_cpu();
 }

net/ipv4/netfilter/ip_tables.c

@@ -909,6 +909,7 @@ get_counters(const struct xt_table_info *t,
 		if (cpu == curcpu)
 			continue;
 		i = 0;
+		local_bh_disable();
 		xt_info_wrlock(cpu);
 		xt_entry_foreach(iter, t->entries[cpu], t->size) {
 			ADD_COUNTER(counters[i], iter->counters.bcnt,
@@ -916,6 +917,7 @@ get_counters(const struct xt_table_info *t,
 			++i; /* macro does multi eval of i */
 		}
 		xt_info_wrunlock(cpu);
+		local_bh_enable();
 	}
 	put_cpu();
 }

net/ipv6/netfilter/ip6_tables.c

@@ -922,6 +922,7 @@ get_counters(const struct xt_table_info *t,
 		if (cpu == curcpu)
 			continue;
 		i = 0;
+		local_bh_disable();
 		xt_info_wrlock(cpu);
 		xt_entry_foreach(iter, t->entries[cpu], t->size) {
 			ADD_COUNTER(counters[i], iter->counters.bcnt,
@@ -929,6 +930,7 @@ get_counters(const struct xt_table_info *t,
 			++i;
 		}
 		xt_info_wrunlock(cpu);
+		local_bh_enable();
 	}
 	put_cpu();
 }