net: Add sysfs value to determine queue traffic class

Add a sysfs attribute for a Tx queue that allows us to determine the
traffic class for a given queue.  This will allow us to more easily
determine this in the future.  It is needed as XPS will take the traffic
class for a group of queues into account in order to avoid pulling traffic
from one traffic class into another.
Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netdevice.h

@@ -1920,6 +1920,7 @@ int netdev_set_prio_tc_map(struct net_device *dev, u8 prio, u8 tc)
 	return 0;
 }
 
+int netdev_txq_to_tc(struct net_device *dev, unsigned int txq);
 void netdev_reset_tc(struct net_device *dev);
 int netdev_set_tc_queue(struct net_device *dev, u8 tc, u16 count, u16 offset);
 int netdev_set_num_tc(struct net_device *dev, u8 num_tc);

net/core/dev.c

@@ -1948,6 +1948,23 @@ static void netif_setup_tc(struct net_device *dev, unsigned int txq)
 	}
 }
 
+int netdev_txq_to_tc(struct net_device *dev, unsigned int txq)
+{
+	if (dev->num_tc) {
+		struct netdev_tc_txq *tc = &dev->tc_to_txq[0];
+		int i;
+
+		for (i = 0; i < TC_MAX_QUEUE; i++, tc++) {
+			if ((txq - tc->offset) < tc->count)
+				return i;
+		}
+
+		return -1;
+	}
+
+	return 0;
+}
+
 #ifdef CONFIG_XPS
 static DEFINE_MUTEX(xps_map_mutex);
 #define xmap_dereference(P)		\

net/core/net-sysfs.c

@@ -1024,7 +1024,6 @@ static ssize_t show_trans_timeout(struct netdev_queue *queue,
 	return sprintf(buf, "%lu", trans_timeout);
 }
 
-#ifdef CONFIG_XPS
 static unsigned int get_netdev_queue_index(struct netdev_queue *queue)
 {
 	struct net_device *dev = queue->dev;
@@ -1036,6 +1035,21 @@ static unsigned int get_netdev_queue_index(struct netdev_queue *queue)
 	return i;
 }
 
+static ssize_t show_traffic_class(struct netdev_queue *queue,
+				  struct netdev_queue_attribute *attribute,
+				  char *buf)
+{
+	struct net_device *dev = queue->dev;
+	int index = get_netdev_queue_index(queue);
+	int tc = netdev_txq_to_tc(dev, index);
+
+	if (tc < 0)
+		return -EINVAL;
+
+	return sprintf(buf, "%u\n", tc);
+}
+
+#ifdef CONFIG_XPS
 static ssize_t show_tx_maxrate(struct netdev_queue *queue,
 			       struct netdev_queue_attribute *attribute,
 			       char *buf)
@@ -1078,6 +1092,9 @@ static struct netdev_queue_attribute queue_tx_maxrate =
 static struct netdev_queue_attribute queue_trans_timeout =
 	__ATTR(tx_timeout, S_IRUGO, show_trans_timeout, NULL);
 
+static struct netdev_queue_attribute queue_traffic_class =
+	__ATTR(traffic_class, S_IRUGO, show_traffic_class, NULL);
+
 #ifdef CONFIG_BQL
 /*
  * Byte queue limits sysfs structures and functions.
@@ -1263,6 +1280,7 @@ static struct netdev_queue_attribute xps_cpus_attribute =
 
 static struct attribute *netdev_queue_default_attrs[] = {
 	&queue_trans_timeout.attr,
+	&queue_traffic_class.attr,
 #ifdef CONFIG_XPS
 	&xps_cpus_attribute.attr,
 	&queue_tx_maxrate.attr,