[PATCH] openvswitch: make for_each_node loops work with sparse numa systems

[Chris J Arges <chris.j.arges@canonical.com>]

Some architectures like POWER can have a NUMA node_possible_map that
contains sparse entries. This causes memory corruption with openvswitch
since it allocates flow_cache with a multiple of num_possible_nodes() and
assumes the node variable returned by for_each_node will index into
flow->stats[node].

For example, if node_possible_map is 0x30003, this patch will map node to
node_cnt as follows:
    0,1,16,17 => 0,1,2,3

The crash was noticed after 3af229f2 was applied as it changed the
node_possible_map to match node_online_map on boot.
Fixes: 3af229f2071f5b5cb31664be6109561fbe19c861

Signed-off-by: Chris J Arges <chris.j.arges@canonical.com>
---
 net/openvswitch/flow.c       | 10 ++++++----
 net/openvswitch/flow_table.c | 18 +++++++++++-------
 2 files changed, 17 insertions(+), 11 deletions(-)

diff --git a/net/openvswitch/flow.c b/net/openvswitch/flow.c
index bc7b0ab..425d45d 100644
--- a/net/openvswitch/flow.c
+++ b/net/openvswitch/flow.c
@@ -134,14 +134,14 @@ void ovs_flow_stats_get(const struct sw_flow *flow,
 			struct ovs_flow_stats *ovs_stats,
 			unsigned long *used, __be16 *tcp_flags)
 {
-	int node;
+	int node, node_cnt = 0;
 
 	*used = 0;
 	*tcp_flags = 0;
 	memset(ovs_stats, 0, sizeof(*ovs_stats));
 
 	for_each_node(node) {
-		struct flow_stats *stats = rcu_dereference_ovsl(flow->stats[node]);
+		struct flow_stats *stats = rcu_dereference_ovsl(flow->stats[node_cnt]);
 
 		if (stats) {
 			/* Local CPU may write on non-local stats, so we must
@@ -155,16 +155,17 @@ void ovs_flow_stats_get(const struct sw_flow *flow,
 			ovs_stats->n_bytes += stats->byte_count;
 			spin_unlock_bh(&stats->lock);
 		}
+		node_cnt++;
 	}
 }
 
 /* Called with ovs_mutex. */
 void ovs_flow_stats_clear(struct sw_flow *flow)
 {
-	int node;
+	int node, node_cnt = 0;
 
 	for_each_node(node) {
-		struct flow_stats *stats = ovsl_dereference(flow->stats[node]);
+		struct flow_stats *stats = ovsl_dereference(flow->stats[node_cnt]);
 
 		if (stats) {
 			spin_lock_bh(&stats->lock);
@@ -174,6 +175,7 @@ void ovs_flow_stats_clear(struct sw_flow *flow)
 			stats->tcp_flags = 0;
 			spin_unlock_bh(&stats->lock);
 		}
+		node_cnt++;
 	}
 }
 
diff --git a/net/openvswitch/flow_table.c b/net/openvswitch/flow_table.c
index 4613df8..5d10c54 100644
--- a/net/openvswitch/flow_table.c
+++ b/net/openvswitch/flow_table.c
@@ -77,7 +77,7 @@ struct sw_flow *ovs_flow_alloc(void)
 {
 	struct sw_flow *flow;
 	struct flow_stats *stats;
-	int node;
+	int node, node_cnt = 0;
 
 	flow = kmem_cache_alloc(flow_cache, GFP_KERNEL);
 	if (!flow)
@@ -99,9 +99,11 @@ struct sw_flow *ovs_flow_alloc(void)
 
 	RCU_INIT_POINTER(flow->stats[0], stats);
 
-	for_each_node(node)
+	for_each_node(node) {
 		if (node != 0)
-			RCU_INIT_POINTER(flow->stats[node], NULL);
+			RCU_INIT_POINTER(flow->stats[node_cnt], NULL);
+		node_cnt++;
+	}
 
 	return flow;
 err:
@@ -139,15 +141,17 @@ static struct flex_array *alloc_buckets(unsigned int n_buckets)
 
 static void flow_free(struct sw_flow *flow)
 {
-	int node;
+	int node, node_cnt = 0;
 
 	if (ovs_identifier_is_key(&flow->id))
 		kfree(flow->id.unmasked_key);
 	kfree((struct sw_flow_actions __force *)flow->sf_acts);
-	for_each_node(node)
-		if (flow->stats[node])
+	for_each_node(node) {
+		if (flow->stats[node_cnt])
 			kmem_cache_free(flow_stats_cache,
-					(struct flow_stats __force *)flow->stats[node]);
+					(struct flow_stats __force *)flow->stats[node_cnt]);
+		node_cnt++;
+	}
 	kmem_cache_free(flow_cache, flow);
 }
 
-- 
1.9.1