percpu: add __percpu sparse annotations to net

Add __percpu sparse annotations to net.

These annotations are to make sparse consider percpu variables to be
in a different address space and warn if accessed without going
through percpu accessors.  This patch doesn't affect normal builds.

The macro and type tricks around snmp stats make things a bit
interesting.  DEFINE/DECLARE_SNMP_STAT() macros mark the target field
as __percpu and SNMP_UPD_PO_STATS() macro is updated accordingly.  All
snmp_mib_*() users which used to cast the argument to (void **) are
updated to cast it to (void __percpu **).

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: David S. Miller <davem@davemloft.net>
Cc: Patrick McHardy <kaber@trash.net>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Vlad Yasevich <vladislav.yasevich@hp.com>
Cc: netdev@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/proc.c

diff --git a/net/ipv6/proc.c b/net/ipv6/proc.c
index bfe2598..58344c0 100644
--- a/net/ipv6/proc.c
+++ b/net/ipv6/proc.c
@@ -136,7 +136,7 @@
 	SNMP_MIB_SENTINEL
 };
 
-static void snmp6_seq_show_icmpv6msg(struct seq_file *seq, void **mib)
+static void snmp6_seq_show_icmpv6msg(struct seq_file *seq, void __percpu **mib)
 {
 	char name[32];
 	int i;
@@ -170,7 +170,7 @@
 	return;
 }
 
-static void snmp6_seq_show_item(struct seq_file *seq, void **mib,
+static void snmp6_seq_show_item(struct seq_file *seq, void __percpu **mib,
 				const struct snmp_mib *itemlist)
 {
 	int i;
@@ -183,14 +183,15 @@
 {
 	struct net *net = (struct net *)seq->private;
 
-	snmp6_seq_show_item(seq, (void **)net->mib.ipv6_statistics,
+	snmp6_seq_show_item(seq, (void __percpu **)net->mib.ipv6_statistics,
 			    snmp6_ipstats_list);
-	snmp6_seq_show_item(seq, (void **)net->mib.icmpv6_statistics,
+	snmp6_seq_show_item(seq, (void __percpu **)net->mib.icmpv6_statistics,
 			    snmp6_icmp6_list);
-	snmp6_seq_show_icmpv6msg(seq, (void **)net->mib.icmpv6msg_statistics);
-	snmp6_seq_show_item(seq, (void **)net->mib.udp_stats_in6,
+	snmp6_seq_show_icmpv6msg(seq,
+			    (void __percpu **)net->mib.icmpv6msg_statistics);
+	snmp6_seq_show_item(seq, (void __percpu **)net->mib.udp_stats_in6,
 			    snmp6_udp6_list);
-	snmp6_seq_show_item(seq, (void **)net->mib.udplite_stats_in6,
+	snmp6_seq_show_item(seq, (void __percpu **)net->mib.udplite_stats_in6,
 			    snmp6_udplite6_list);
 	return 0;
 }
@@ -213,9 +214,11 @@
 	struct inet6_dev *idev = (struct inet6_dev *)seq->private;
 
 	seq_printf(seq, "%-32s\t%u\n", "ifIndex", idev->dev->ifindex);
-	snmp6_seq_show_item(seq, (void **)idev->stats.ipv6, snmp6_ipstats_list);
-	snmp6_seq_show_item(seq, (void **)idev->stats.icmpv6, snmp6_icmp6_list);
-	snmp6_seq_show_icmpv6msg(seq, (void **)idev->stats.icmpv6msg);
+	snmp6_seq_show_item(seq, (void __percpu **)idev->stats.ipv6,
+			    snmp6_ipstats_list);
+	snmp6_seq_show_item(seq, (void __percpu **)idev->stats.icmpv6,
+			    snmp6_icmp6_list);
+	snmp6_seq_show_icmpv6msg(seq, (void __percpu **)idev->stats.icmpv6msg);
 	return 0;
 }