[PATCH net-next v2 7/9] xen-netback: Add stat counters for frag_list skbs

[Zoltan Kiss <zoltan.kiss@citrix.com>]

These counters help determine how often the guest sends a packet with more
than MAX_SKB_FRAGS frags.

Signed-off-by: Zoltan Kiss <zoltan.kiss@citrix.com>
---
 drivers/net/xen-netback/common.h    |    1 +
 drivers/net/xen-netback/interface.c |    7 +++++++
 drivers/net/xen-netback/netback.c   |    1 +
 3 files changed, 9 insertions(+)

diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
index e3c28ff..c037efb 100644
--- a/drivers/net/xen-netback/common.h
+++ b/drivers/net/xen-netback/common.h
@@ -158,6 +158,7 @@ struct xenvif {
 	unsigned long tx_zerocopy_sent;
 	unsigned long tx_zerocopy_success;
 	unsigned long tx_zerocopy_fail;
+	unsigned long tx_frag_overflow;
 
 	/* Miscellaneous private stuff. */
 	struct net_device *dev;
diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
index ac27af3..b7daf8d 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -254,6 +254,13 @@ static const struct xenvif_stat {
 		"tx_zerocopy_fail",
 		offsetof(struct xenvif, tx_zerocopy_fail)
 	},
+	/* Number of packets exceeding MAX_SKB_FRAG slots. You should use
+	 * a guest with the same MAX_SKB_FRAG
+	 */
+	{
+		"tx_frag_overflow",
+		offsetof(struct xenvif, tx_frag_overflow)
+	},
 };
 
 static int xenvif_get_sset_count(struct net_device *dev, int string_set)
diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 9841429..4305965 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -1656,6 +1656,7 @@ static int xenvif_tx_submit(struct xenvif *vif, int budget)
 			skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
 			skb_shinfo(nskb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
 			vif->tx_zerocopy_sent += 2;
+			vif->tx_frag_overflow++;
 			nskb = skb;
 
 			skb = skb_copy_expand(skb, 0, 0, GFP_ATOMIC | __GFP_NOWARN);