[PATCH 2/3][SRU][Y, Z] netfilter: x_tables: pass xt_counters struct to counter allocator

[Eric Desrochers]

From: Florian Westphal <fw at strlen.de>

BugLink: https://bugs.launchpad.net/bugs/1640786

Keeps some noise away from a followup patch.

Signed-off-by: Florian Westphal <fw at strlen.de>
Acked-by: Eric Dumazet <edumazet at google.com>
Signed-off-by: Pablo Neira Ayuso <pablo at netfilter.org>
(cherry picked from commit f28e15bacedd444608e25421c72eb2cf4527c9ca)
Signed-off-by: Eric Desrochers <eric.desrochers at canonical.com>
---
 include/linux/netfilter/x_tables.h | 27 +--------------------------
 net/ipv4/netfilter/arp_tables.c    |  5 +----
 net/ipv4/netfilter/ip_tables.c     |  5 +----
 net/ipv6/netfilter/ip6_tables.c    |  5 +----
 net/netfilter/x_tables.c           | 30 ++++++++++++++++++++++++++++++
 5 files changed, 34 insertions(+), 38 deletions(-)

diff --git a/include/linux/netfilter/x_tables.h b/include/linux/netfilter/x_tables.h
index dfd56c1..58f37f8 100644
--- a/include/linux/netfilter/x_tables.h
+++ b/include/linux/netfilter/x_tables.h
@@ -376,32 +376,7 @@ static inline unsigned long ifname_compare_aligned(const char *_a,
 }
 
 
-/* On SMP, ip(6)t_entry->counters.pcnt holds address of the
- * real (percpu) counter.  On !SMP, its just the packet count,
- * so nothing needs to be done there.
- *
- * xt_percpu_counter_alloc returns the address of the percpu
- * counter, or 0 on !SMP. We force an alignment of 16 bytes
- * so that bytes/packets share a common cache line.
- *
- * Hence caller must use IS_ERR_VALUE to check for error, this
- * allows us to return 0 for single core systems without forcing
- * callers to deal with SMP vs. NONSMP issues.
- */
-static inline unsigned long xt_percpu_counter_alloc(void)
-{
-	if (nr_cpu_ids > 1) {
-		void __percpu *res = __alloc_percpu(sizeof(struct xt_counters),
-						    sizeof(struct xt_counters));
-
-		if (res == NULL)
-			return -ENOMEM;
-
-		return (__force unsigned long) res;
-	}
-
-	return 0;
-}
+bool xt_percpu_counter_alloc(struct xt_counters *counters);
 void xt_percpu_counter_free(struct xt_counters *cnt);
 
 static inline struct xt_counters *
diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
index a2be65c..eb08438 100644
--- a/net/ipv4/netfilter/arp_tables.c
+++ b/net/ipv4/netfilter/arp_tables.c
@@ -436,13 +436,10 @@ find_check_entry(struct arpt_entry *e, const char *name, unsigned int size)
 {
 	struct xt_entry_target *t;
 	struct xt_target *target;
-	unsigned long pcnt;
 	int ret;
 
-	pcnt = xt_percpu_counter_alloc();
-	if (IS_ERR_VALUE(pcnt))
+	if (!xt_percpu_counter_alloc(&e->counters))
 		return -ENOMEM;
-	e->counters.pcnt = pcnt;
 
 	t = arpt_get_target(e);
 	target = xt_request_find_target(NFPROTO_ARP, t->u.user.name,
diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
index 7c25dd4..9bef9e2 100644
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -560,12 +560,9 @@ find_check_entry(struct ipt_entry *e, struct net *net, const char *name,
 	unsigned int j;
 	struct xt_mtchk_param mtpar;
 	struct xt_entry_match *ematch;
-	unsigned long pcnt;
 
-	pcnt = xt_percpu_counter_alloc();
-	if (IS_ERR_VALUE(pcnt))
+	if (!xt_percpu_counter_alloc(&e->counters))
 		return -ENOMEM;
-	e->counters.pcnt = pcnt;
 
 	j = 0;
 	mtpar.net	= net;
diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c
index 862e20f..e871415 100644
--- a/net/ipv6/netfilter/ip6_tables.c
+++ b/net/ipv6/netfilter/ip6_tables.c
@@ -591,12 +591,9 @@ find_check_entry(struct ip6t_entry *e, struct net *net, const char *name,
 	unsigned int j;
 	struct xt_mtchk_param mtpar;
 	struct xt_entry_match *ematch;
-	unsigned long pcnt;
 
-	pcnt = xt_percpu_counter_alloc();
-	if (IS_ERR_VALUE(pcnt))
+	if (!xt_percpu_counter_alloc(&e->counters))
 		return -ENOMEM;
-	e->counters.pcnt = pcnt;
 
 	j = 0;
 	mtpar.net	= net;
diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index 93703c9..812dee9 100644
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -1615,6 +1615,36 @@ void xt_proto_fini(struct net *net, u_int8_t af)
 }
 EXPORT_SYMBOL_GPL(xt_proto_fini);
 
+/**
+ * xt_percpu_counter_alloc - allocate x_tables rule counter
+ *
+ * @counter: pointer to counter struct inside the ip(6)/arpt_entry struct
+ *
+ * On SMP, the packet counter [ ip(6)t_entry->counters.pcnt ] will then
+ * contain the address of the real (percpu) counter.
+ *
+ * Rule evaluation needs to use xt_get_this_cpu_counter() helper
+ * to fetch the real percpu counter.
+ *
+ * returns false on error.
+ */
+bool xt_percpu_counter_alloc(struct xt_counters *counter)
+{
+	void __percpu *res;
+
+	if (nr_cpu_ids <= 1)
+		return true;
+
+	res = __alloc_percpu(sizeof(struct xt_counters),
+			     sizeof(struct xt_counters));
+	if (!res)
+		return false;
+
+	counter->pcnt = (__force unsigned long)res;
+	return true;
+}
+EXPORT_SYMBOL_GPL(xt_percpu_counter_alloc);
+
 void xt_percpu_counter_free(struct xt_counters *counters)
 {
 	unsigned long pcnt = counters->pcnt;
-- 
2.7.4