[Intel-wired-lan] [net-next PATCH v2 3/4] net: Refactor removal of queues from XPS map and apply on num_tc changes

[Alexander Duyck]

This patch updates the code for removing queues from the XPS map and makes
it so that we can apply the code any time we change either the number of
traffic classes or the mapping of a given block of queues.  This way we
avoid having queues pulling traffic from a foreign traffic class.

Signed-off-by: Alexander Duyck <alexander.h.duyck at intel.com>
---

v2: Replaced do/while with for loop
    Changed order for remove_xps_queue_cpu loop
    Updated i to reflect count, j to be temporary offset
    Updated test to check for i < 0 instead of i < offset

 net/core/dev.c |   73 ++++++++++++++++++++++++++++++++++++++------------------
 1 file changed, 50 insertions(+), 23 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 08ed625..fea7061 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1970,32 +1970,50 @@ int netdev_txq_to_tc(struct net_device *dev, unsigned int txq)
 #define xmap_dereference(P)		\
 	rcu_dereference_protected((P), lockdep_is_held(&xps_map_mutex))
 
-static struct xps_map *remove_xps_queue(struct xps_dev_maps *dev_maps,
-					int cpu, u16 index)
+static bool remove_xps_queue(struct xps_dev_maps *dev_maps,
+			     int tci, u16 index)
 {
 	struct xps_map *map = NULL;
 	int pos;
 
 	if (dev_maps)
-		map = xmap_dereference(dev_maps->cpu_map[cpu]);
+		map = xmap_dereference(dev_maps->cpu_map[tci]);
+	if (!map)
+		return false;
 
-	for (pos = 0; map && pos < map->len; pos++) {
-		if (map->queues[pos] == index) {
-			if (map->len > 1) {
-				map->queues[pos] = map->queues[--map->len];
-			} else {
-				RCU_INIT_POINTER(dev_maps->cpu_map[cpu], NULL);
-				kfree_rcu(map, rcu);
-				map = NULL;
-			}
+	for (pos = map->len; pos--;) {
+		if (map->queues[pos] != index)
+			continue;
+
+		if (map->len > 1) {
+			map->queues[pos] = map->queues[--map->len];
 			break;
 		}
+
+		RCU_INIT_POINTER(dev_maps->cpu_map[tci], NULL);
+		kfree_rcu(map, rcu);
+		return false;
 	}
 
-	return map;
+	return true;
 }
 
-static void netif_reset_xps_queues_gt(struct net_device *dev, u16 index)
+static bool remove_xps_queue_cpu(struct net_device *dev,
+				 struct xps_dev_maps *dev_maps,
+				 int cpu, u16 offset, u16 count)
+{
+	int i, j;
+
+	for (i = count, j = offset; i--; j++) {
+		if (!remove_xps_queue(dev_maps, cpu, j))
+			break;
+	}
+
+	return i < 0;
+}
+
+static void netif_reset_xps_queues(struct net_device *dev, u16 offset,
+				   u16 count)
 {
 	struct xps_dev_maps *dev_maps;
 	int cpu, i;
@@ -2007,21 +2025,16 @@ static void netif_reset_xps_queues_gt(struct net_device *dev, u16 index)
 	if (!dev_maps)
 		goto out_no_maps;
 
-	for_each_possible_cpu(cpu) {
-		for (i = index; i < dev->num_tx_queues; i++) {
-			if (!remove_xps_queue(dev_maps, cpu, i))
-				break;
-		}
-		if (i == dev->num_tx_queues)
-			active = true;
-	}
+	for_each_possible_cpu(cpu)
+		active |= remove_xps_queue_cpu(dev, dev_maps, cpu,
+					       offset, count);
 
 	if (!active) {
 		RCU_INIT_POINTER(dev->xps_maps, NULL);
 		kfree_rcu(dev_maps, rcu);
 	}
 
-	for (i = index; i < dev->num_tx_queues; i++)
+	for (i = offset + (count - 1); count--; i--)
 		netdev_queue_numa_node_write(netdev_get_tx_queue(dev, i),
 					     NUMA_NO_NODE);
 
@@ -2029,6 +2042,11 @@ static void netif_reset_xps_queues_gt(struct net_device *dev, u16 index)
 	mutex_unlock(&xps_map_mutex);
 }
 
+static void netif_reset_xps_queues_gt(struct net_device *dev, u16 index)
+{
+	netif_reset_xps_queues(dev, index, dev->num_tx_queues - index);
+}
+
 static struct xps_map *expand_xps_map(struct xps_map *map,
 				      int cpu, u16 index)
 {
@@ -2192,6 +2210,9 @@ int netif_set_xps_queue(struct net_device *dev, const struct cpumask *mask,
 #endif
 void netdev_reset_tc(struct net_device *dev)
 {
+#ifdef CONFIG_XPS
+	netif_reset_xps_queues_gt(dev, 0);
+#endif
 	dev->num_tc = 0;
 	memset(dev->tc_to_txq, 0, sizeof(dev->tc_to_txq));
 	memset(dev->prio_tc_map, 0, sizeof(dev->prio_tc_map));
@@ -2203,6 +2224,9 @@ int netdev_set_tc_queue(struct net_device *dev, u8 tc, u16 count, u16 offset)
 	if (tc >= dev->num_tc)
 		return -EINVAL;
 
+#ifdef CONFIG_XPS
+	netif_reset_xps_queues(dev, offset, count);
+#endif
 	dev->tc_to_txq[tc].count = count;
 	dev->tc_to_txq[tc].offset = offset;
 	return 0;
@@ -2214,6 +2238,9 @@ int netdev_set_num_tc(struct net_device *dev, u8 num_tc)
 	if (num_tc > TC_MAX_QUEUE)
 		return -EINVAL;
 
+#ifdef CONFIG_XPS
+	netif_reset_xps_queues_gt(dev, 0);
+#endif
 	dev->num_tc = num_tc;
 	return 0;
 }