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Date: Thu, 26 Feb 2015 19:43:43 +0000
From: Ben Hutchings <ben.hutchings@...ethink.co.uk>
To: Oliver Neukum <oliver@...kum.org>, netdev@...r.kernel.org
Cc: ct-linux-kernel <linux-kernel@...ethink.co.uk>,
linux-usb@...r.kernel.org
Subject: [RFC][PATCH] usbnet: Fix tx_bytes statistic running backward in
cdc_ncm
cdc_ncm disagrees with usbnet about how much framing overhead should
be counted in the tx_bytes statistics, and tries 'fix' this by
decrementing tx_bytes on the transmit path. But statistics must never
be decremented except due to roll-over; this will thoroughly confuse
user-space. Also, tx_bytes is only incremented by usbnet in the
completion path.
Fix this by requiring drivers that set FLAG_MULTI_FRAME to set a
tx_bytes delta along with the tx_packets count.
Signed-off-by: Ben Hutchings <ben.hutchings@...ethink.co.uk>
---
I noticed this bug while trying to fix the tx_packets statistic in asix.
It depends on the patch I just sent for that. I don't have any hardware
to test this with, or any need to make it work. If you want this fix,
please test and re-submit it yoursef.
Ben.
drivers/net/usb/asix_common.c | 2 +-
drivers/net/usb/cdc_ncm.c | 7 +++----
drivers/net/usb/sr9800.c | 2 +-
drivers/net/usb/usbnet.c | 16 +++++++++++++---
include/linux/usb/usbnet.h | 6 ++++--
5 files changed, 22 insertions(+), 11 deletions(-)
diff --git a/drivers/net/usb/asix_common.c b/drivers/net/usb/asix_common.c
index 724a9b50df7a..75d6f26729a3 100644
--- a/drivers/net/usb/asix_common.c
+++ b/drivers/net/usb/asix_common.c
@@ -189,7 +189,7 @@ struct sk_buff *asix_tx_fixup(struct usbnet *dev, struct sk_buff *skb,
skb_put(skb, sizeof(padbytes));
}
- usbnet_set_skb_tx_stats(skb, 1);
+ usbnet_set_skb_tx_stats(skb, 1, 0);
return skb;
}
diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
index 70cbea551139..c3e4da9e79ca 100644
--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c
@@ -1177,13 +1177,12 @@ cdc_ncm_fill_tx_frame(struct usbnet *dev, struct sk_buff *skb, __le32 sign)
ctx->tx_overhead += skb_out->len - ctx->tx_curr_frame_payload;
ctx->tx_ntbs++;
- /* usbnet has already counted all the framing overhead.
+ /* usbnet will count all the framing overhead by default.
* Adjust the stats so that the tx_bytes counter show real
* payload data instead.
*/
- dev->net->stats.tx_bytes -= skb_out->len - ctx->tx_curr_frame_payload;
-
- usbnet_set_skb_tx_stats(skb_out, n);
+ usbnet_set_skb_tx_stats(skb_out, n,
+ ctx->tx_curr_frame_payload - skb_out->len);
return skb_out;
diff --git a/drivers/net/usb/sr9800.c b/drivers/net/usb/sr9800.c
index 7650cdc8fe6b..953de13267df 100644
--- a/drivers/net/usb/sr9800.c
+++ b/drivers/net/usb/sr9800.c
@@ -144,7 +144,7 @@ static struct sk_buff *sr_tx_fixup(struct usbnet *dev, struct sk_buff *skb,
skb_put(skb, sizeof(padbytes));
}
- usbnet_set_skb_tx_stats(skb, 1);
+ usbnet_set_skb_tx_stats(skb, 1, 0);
return skb;
}
diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
index 0f3ff285f6a1..777757ae1973 100644
--- a/drivers/net/usb/usbnet.c
+++ b/drivers/net/usb/usbnet.c
@@ -1346,9 +1346,19 @@ netdev_tx_t usbnet_start_xmit (struct sk_buff *skb,
} else
urb->transfer_flags |= URB_ZERO_PACKET;
}
- entry->length = urb->transfer_buffer_length = length;
- if (!(info->flags & FLAG_MULTI_PACKET))
- usbnet_set_skb_tx_stats(skb, 1);
+ urb->transfer_buffer_length = length;
+
+ if (info->flags & FLAG_MULTI_PACKET) {
+ /* Driver has set number of packets and a length delta.
+ * Calculate the complete length and ensure that it's
+ * positive.
+ */
+ entry->length += length;
+ if (WARN_ON_ONCE(entry->length <= 0))
+ entry->length = length;
+ } else {
+ usbnet_set_skb_tx_stats(skb, 1, length);
+ }
spin_lock_irqsave(&dev->txq.lock, flags);
retval = usb_autopm_get_interface_async(dev->intf);
diff --git a/include/linux/usb/usbnet.h b/include/linux/usb/usbnet.h
index ff3fb2bd0e90..6e0ce8c7b8cb 100644
--- a/include/linux/usb/usbnet.h
+++ b/include/linux/usb/usbnet.h
@@ -227,7 +227,7 @@ struct skb_data { /* skb->cb is one of these */
struct urb *urb;
struct usbnet *dev;
enum skb_state state;
- size_t length;
+ long length;
unsigned long packets;
};
@@ -235,11 +235,13 @@ struct skb_data { /* skb->cb is one of these */
* tx_fixup method before returning an skb.
*/
static inline void
-usbnet_set_skb_tx_stats(struct sk_buff *skb, unsigned long packets)
+usbnet_set_skb_tx_stats(struct sk_buff *skb,
+ unsigned long packets, long bytes_delta)
{
struct skb_data *entry = (struct skb_data *) skb->cb;
entry->packets = packets;
+ entry->length = bytes_delta;
}
extern int usbnet_open(struct net_device *net);
--
1.7.10.4
--
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