igb: fix stats handling

There are currently some problems with igb.

- On 32bit arches, maintaining 64bit counters without proper
synchronization between writers and readers.

- Stats updated every two seconds, as reported by Jesper.
   (Jesper provided a patch for this)

- Potential problem between worker thread and ethtool -S

This patch uses u64_stats_sync, and convert everything to be 64bit safe,
SMP safe, even on 32bit arches. It integrates Jesper idea of providing
accurate stats at the time user reads them.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Tested-by: Emil Tantilov <emil.s.tantilov@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/igb/igb.h

@@ -159,6 +159,7 @@ struct igb_tx_queue_stats {
 	u64 packets;
 	u64 bytes;
 	u64 restart_queue;
+	u64 restart_queue2;
 };
 
 struct igb_rx_queue_stats {
@@ -210,11 +211,14 @@ struct igb_ring {
 		/* TX */
 		struct {
 			struct igb_tx_queue_stats tx_stats;
+			struct u64_stats_sync tx_syncp;
+			struct u64_stats_sync tx_syncp2;
 			bool detect_tx_hung;
 		};
 		/* RX */
 		struct {
 			struct igb_rx_queue_stats rx_stats;
+			struct u64_stats_sync rx_syncp;
 			u32 rx_buffer_len;
 		};
 	};
@@ -288,6 +292,9 @@ struct igb_adapter {
 	struct timecompare compare;
 	struct hwtstamp_config hwtstamp_config;
 
+	spinlock_t stats64_lock;
+	struct rtnl_link_stats64 stats64;
+
 	/* structs defined in e1000_hw.h */
 	struct e1000_hw hw;
 	struct e1000_hw_stats stats;
@@ -357,7 +364,7 @@ extern netdev_tx_t igb_xmit_frame_ring_adv(struct sk_buff *, struct igb_ring *);
 extern void igb_unmap_and_free_tx_resource(struct igb_ring *,
 					   struct igb_buffer *);
 extern void igb_alloc_rx_buffers_adv(struct igb_ring *, int);
-extern void igb_update_stats(struct igb_adapter *);
+extern void igb_update_stats(struct igb_adapter *, struct rtnl_link_stats64 *);
 extern bool igb_has_link(struct igb_adapter *adapter);
 extern void igb_set_ethtool_ops(struct net_device *);
 extern void igb_power_up_link(struct igb_adapter *);

drivers/net/igb/igb_ethtool.c

@@ -90,8 +90,8 @@ static const struct igb_stats igb_gstrings_stats[] = {
 
 #define IGB_NETDEV_STAT(_net_stat) { \
 	.stat_string = __stringify(_net_stat), \
-	.sizeof_stat = FIELD_SIZEOF(struct net_device_stats, _net_stat), \
-	.stat_offset = offsetof(struct net_device_stats, _net_stat) \
+	.sizeof_stat = FIELD_SIZEOF(struct rtnl_link_stats64, _net_stat), \
+	.stat_offset = offsetof(struct rtnl_link_stats64, _net_stat) \
 }
 static const struct igb_stats igb_gstrings_net_stats[] = {
 	IGB_NETDEV_STAT(rx_errors),
@@ -111,8 +111,9 @@ static const struct igb_stats igb_gstrings_net_stats[] = {
 	(sizeof(igb_gstrings_net_stats) / sizeof(struct igb_stats))
 #define IGB_RX_QUEUE_STATS_LEN \
 	(sizeof(struct igb_rx_queue_stats) / sizeof(u64))
-#define IGB_TX_QUEUE_STATS_LEN \
-	(sizeof(struct igb_tx_queue_stats) / sizeof(u64))
+
+#define IGB_TX_QUEUE_STATS_LEN 3 /* packets, bytes, restart_queue */
+
 #define IGB_QUEUE_STATS_LEN \
 	((((struct igb_adapter *)netdev_priv(netdev))->num_rx_queues * \
 	  IGB_RX_QUEUE_STATS_LEN) + \
@@ -2070,12 +2071,14 @@ static void igb_get_ethtool_stats(struct net_device *netdev,
 				  struct ethtool_stats *stats, u64 *data)
 {
 	struct igb_adapter *adapter = netdev_priv(netdev);
-	struct net_device_stats *net_stats = &netdev->stats;
-	u64 *queue_stat;
-	int i, j, k;
+	struct rtnl_link_stats64 *net_stats = &adapter->stats64;
+	unsigned int start;
+	struct igb_ring *ring;
+	int i, j;
 	char *p;
 
-	igb_update_stats(adapter);
+	spin_lock(&adapter->stats64_lock);
+	igb_update_stats(adapter, net_stats);
 
 	for (i = 0; i < IGB_GLOBAL_STATS_LEN; i++) {
 		p = (char *)adapter + igb_gstrings_stats[i].stat_offset;
@@ -2088,15 +2091,36 @@ static void igb_get_ethtool_stats(struct net_device *netdev,
 			sizeof(u64)) ? *(u64 *)p : *(u32 *)p;
 	}
 	for (j = 0; j < adapter->num_tx_queues; j++) {
-		queue_stat = (u64 *)&adapter->tx_ring[j]->tx_stats;
-		for (k = 0; k < IGB_TX_QUEUE_STATS_LEN; k++, i++)
-			data[i] = queue_stat[k];
+		u64	restart2;
+
+		ring = adapter->tx_ring[j];
+		do {
+			start = u64_stats_fetch_begin_bh(&ring->tx_syncp);
+			data[i]   = ring->tx_stats.packets;
+			data[i+1] = ring->tx_stats.bytes;
+			data[i+2] = ring->tx_stats.restart_queue;
+		} while (u64_stats_fetch_retry_bh(&ring->tx_syncp, start));
+		do {
+			start = u64_stats_fetch_begin_bh(&ring->tx_syncp2);
+			restart2  = ring->tx_stats.restart_queue2;
+		} while (u64_stats_fetch_retry_bh(&ring->tx_syncp2, start));
+		data[i+2] += restart2;
+
+		i += IGB_TX_QUEUE_STATS_LEN;
 	}
 	for (j = 0; j < adapter->num_rx_queues; j++) {
-		queue_stat = (u64 *)&adapter->rx_ring[j]->rx_stats;
-		for (k = 0; k < IGB_RX_QUEUE_STATS_LEN; k++, i++)
-			data[i] = queue_stat[k];
+		ring = adapter->rx_ring[j];
+		do {
+			start = u64_stats_fetch_begin_bh(&ring->rx_syncp);
+			data[i]   = ring->rx_stats.packets;
+			data[i+1] = ring->rx_stats.bytes;
+			data[i+2] = ring->rx_stats.drops;
+			data[i+3] = ring->rx_stats.csum_err;
+			data[i+4] = ring->rx_stats.alloc_failed;
+		} while (u64_stats_fetch_retry_bh(&ring->rx_syncp, start));
+		i += IGB_RX_QUEUE_STATS_LEN;
 	}
+	spin_unlock(&adapter->stats64_lock);
 }
 
 static void igb_get_strings(struct net_device *netdev, u32 stringset, u8 *data)