Re: [PATCH net-next 5/5] ifb: convert to 64 bit stats

[Eric Dumazet <eric.dumazet@gmail.com>]

From: Stephen Hemminger <shemminger@vyatta.com>


Le lundi 20 juin 2011 à 14:38 -0700, Stephen Hemminger a écrit :
> On Mon, 20 Jun 2011 23:27:01 +0200
> Eric Dumazet <eric.dumazet@gmail.com> wrote:
> 
> > Le lundi 20 juin 2011 à 23:23 +0200, Eric Dumazet a écrit :
> > > Le lundi 20 juin 2011 à 14:12 -0700, Stephen Hemminger a écrit :
> > > > Convert input functional block device to use 64 bit stats.
> > > > 
> > > > Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
> > > > 
> > > > ---
> > > > v2 - add stats_sync
> > > > 
> > > 
> > > Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
> > > 
> > 
> > Ah well, I am wondering if ri_tasklet() & ifb_xmit() could run
> > concurrently
> > 
> > If so, we need two separate syncp, one for each function.
> 
> For the normal case that isn't possible but
> someone could be perverse and put an address on the ifb device and
> try and use like loopback?

Hmm, this can occur on normal case I think, on SMP.

Here is an updated patch

[PATCH net-next v3] ifb: convert to 64 bit stats

Convert input functional block device to use 64 bit stats.

[Eric Dumazet]: Use two different synchronization points for rx and tx.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
---
v2 - add stats_sync
v3 - must use two different sync

 drivers/net/ifb.c |   58 +++++++++++++++++++++++++++++++++++++-------
 1 file changed, 49 insertions(+), 9 deletions(-)

diff --git a/drivers/net/ifb.c b/drivers/net/ifb.c
index ce53f4a..2443e90 100644
--- a/drivers/net/ifb.c
+++ b/drivers/net/ifb.c
@@ -41,8 +41,16 @@
 struct ifb_private {
 	struct tasklet_struct   ifb_tasklet;
 	int     tasklet_pending;
+
 	struct sk_buff_head     rq;
+	u64			rx_packets;
+	u64			rx_bytes;
+	struct u64_stats_sync	stats_rx_sync;
+
 	struct sk_buff_head     tq;
+	u64			tx_packets;
+	u64			tx_bytes;
+	struct u64_stats_sync	stats_tx_sync;
 };
 
 static int numifbs = 2;
@@ -54,10 +62,8 @@ static int ifb_close(struct net_device *dev);
 
 static void ri_tasklet(unsigned long dev)
 {
-
 	struct net_device *_dev = (struct net_device *)dev;
 	struct ifb_private *dp = netdev_priv(_dev);
-	struct net_device_stats *stats = &_dev->stats;
 	struct netdev_queue *txq;
 	struct sk_buff *skb;
 
@@ -77,15 +83,18 @@ static void ri_tasklet(unsigned long dev)
 
 		skb->tc_verd = 0;
 		skb->tc_verd = SET_TC_NCLS(skb->tc_verd);
-		stats->tx_packets++;
-		stats->tx_bytes +=skb->len;
+
+		u64_stats_update_begin(&dp->stats_tx_sync);
+		dp->tx_packets++;
+		dp->tx_bytes += skb->len;
+		u64_stats_update_end(&dp->stats_tx_sync);
 
 		rcu_read_lock();
 		skb->dev = dev_get_by_index_rcu(&init_net, skb->skb_iif);
 		if (!skb->dev) {
 			rcu_read_unlock();
 			dev_kfree_skb(skb);
-			stats->tx_dropped++;
+			_dev->stats.tx_dropped++;
 			if (skb_queue_len(&dp->tq) != 0)
 				goto resched;
 			break;
@@ -120,9 +129,39 @@ resched:
 
 }
 
+static struct rtnl_link_stats64 *ifb_stats64(struct net_device *dev,
+					     struct rtnl_link_stats64 *stats)
+{
+	const struct ifb_private *dp = netdev_priv(dev);
+	unsigned int start;
+
+	do {
+		start = u64_stats_fetch_begin_bh(&dp->stats_rx_sync);
+
+		stats->rx_packets = dp->rx_packets;
+		stats->rx_bytes = dp->rx_bytes;
+
+	} while (u64_stats_fetch_retry_bh(&dp->stats_rx_sync, start));
+
+	do {
+		start = u64_stats_fetch_begin_bh(&dp->stats_tx_sync);
+
+		stats->tx_packets = dp->tx_packets;
+		stats->tx_bytes = dp->tx_bytes;
+
+	} while (u64_stats_fetch_retry_bh(&dp->stats_tx_sync, start));
+
+	stats->rx_dropped = dev->stats.rx_dropped;
+	stats->tx_dropped = dev->stats.tx_dropped;
+
+	return stats;
+}
+
+
 static const struct net_device_ops ifb_netdev_ops = {
 	.ndo_open	= ifb_open,
 	.ndo_stop	= ifb_close,
+	.ndo_get_stats64 = ifb_stats64,
 	.ndo_start_xmit	= ifb_xmit,
 	.ndo_validate_addr = eth_validate_addr,
 };
@@ -153,15 +192,16 @@ static void ifb_setup(struct net_device *dev)
 static netdev_tx_t ifb_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	struct ifb_private *dp = netdev_priv(dev);
-	struct net_device_stats *stats = &dev->stats;
 	u32 from = G_TC_FROM(skb->tc_verd);
 
-	stats->rx_packets++;
-	stats->rx_bytes+=skb->len;
+	u64_stats_update_begin(&dp->stats_rx_sync);
+	dp->rx_packets++;
+	dp->rx_bytes += skb->len;
+	u64_stats_update_end(&dp->stats_rx_sync);
 
 	if (!(from & (AT_INGRESS|AT_EGRESS)) || !skb->skb_iif) {
 		dev_kfree_skb(skb);
-		stats->rx_dropped++;
+		dev->stats.rx_dropped++;
 		return NETDEV_TX_OK;
 	}