From: AMEET M. PARANJAPE <aparanja@redhat.com>
Date: Thu, 8 Jan 2009 11:31:23 -0500
Subject: [net] s2io: flush statistics when changing the MTU
Message-id: 20090108163024.28975.42566.sendpatchset@squad5-lp1.lab.bos.redhat.com
O-Subject: [PATCH RHEL5.4 BZ459514] s2io flushs statistics when changing the MTU
Bugzilla: 459514
RH-Acked-by: Andy Gospodarek <gospo@redhat.com>
RH-Acked-by: David Miller <davem@redhat.com>
RH-Acked-by: Neil Horman <nhorman@redhat.com>
RH-Acked-by: David Howells <dhowells@redhat.com>

RHBZ#:
======
https://bugzilla.redhat.com/show_bug.cgi?id=459514

Description:
===========
This patch prevents s2io device driver from flushing the packet
statistics information when the Maximum Transmission Unit(MTU) is changed.

RHEL Version Found:
================
RHEL 5.3

kABI Status:
============
No symbols were harmed.

Brew:
=====
Built on all platforms.
http://brewweb.devel.redhat.com/brew/taskinfo?taskID=1641905

Upstream Status:
================
commit dc56e634c807c6be69be8af919f20a746197b87d

Test Status:
============
Testcase is in the Bugzilla as well.

# rmmod s2io
# modprobe s2io
# ifconfig eth11 192.168.200.2 netmask 255.255.255.0 up
# ping -f -c1000 192.168.200.3
# ifconfig eth11 | grep -E '(R|T)X'
 Notice RX and TX are non-zero
# ifconfig eth11 mtu 1600
# ifconfig eth11 | grep -E '(R|T)X'
 Without this patch the RX and TX values are zero and this is not
seen with patch applied.

===============================================================
Ameet Paranjape 978-392-3903 ext 23903
IBM on-site partner

Proposed Patch:
===============

diff --git a/drivers/net/s2io.c b/drivers/net/s2io.c
index bd5d336..4f4124b 100644
--- a/drivers/net/s2io.c
+++ b/drivers/net/s2io.c
@@ -3446,9 +3446,9 @@ static void s2io_reset(struct s2io_nic * sp)
 		writeq(BIT(62), &bar0->txpic_int_reg);
 	}
 
-	/* Reset device statistics maintained by OS */
-	memset(&sp->stats, 0, sizeof (struct net_device_stats));
-	
+	/* Reset device statistics buffer */
+	memset(&sp->stats_buffer, 0, sizeof (struct s2io_stats_buffer));
+
 	up_cnt = sp->mac_control.stats_info->sw_stat.link_up_cnt;
 	down_cnt = sp->mac_control.stats_info->sw_stat.link_down_cnt;
 	up_time = sp->mac_control.stats_info->sw_stat.link_up_time;
@@ -4355,23 +4355,44 @@ static struct net_device_stats *s2io_get_stats(struct net_device *dev)
 	struct mac_info *mac_control;
 	struct config_param *config;
 
-
 	mac_control = &sp->mac_control;
 	config = &sp->config;
 
 	/* Configure Stats for immediate updt */
 	s2io_updt_stats(sp);
 
-	sp->stats.tx_packets =
-		le32_to_cpu(mac_control->stats_info->tmac_frms);
-	sp->stats.tx_errors =
-		le32_to_cpu(mac_control->stats_info->tmac_any_err_frms);
-	sp->stats.rx_errors =
-		le64_to_cpu(mac_control->stats_info->rmac_drop_frms);
-	sp->stats.multicast =
-		le32_to_cpu(mac_control->stats_info->rmac_vld_mcst_frms);
-	sp->stats.rx_length_errors =
-		le64_to_cpu(mac_control->stats_info->rmac_long_frms);
+	/* Calculate the changes in the device statistics since the last call, 
+	 * and add them to the statistics maintained by the OS.
+	 *
+	 * The amount of changes to be added equals to the distance between the 
+	 * s2io statistics buffer (which holds the device statistics when 
+	 * this function was previously called) towards the current values of the
+	 * device statistics.
+	 *
+	 * Normally the current device statistics are always greater or equal to 
+	 * the old statistics stored in the buffer, unless the 32bit device 
+	 * registers cycle back to zero due to overflow. This fact is taken into 
+	 * account for calculating the correct amount of increment to be added to 
+	 * the OS statistics.
+	 */
+
+#define UPDATE_STATS(FIELD, DEVFIELD) \
+{ \
+	u32 dev_stat = le32_to_cpu(mac_control->stats_info->DEVFIELD); \
+	if (dev_stat >= sp->stats_buffer.FIELD) \
+		sp->stats.FIELD += dev_stat - sp->stats_buffer.FIELD; \
+	else \
+		sp->stats.FIELD += ((u32) -1) - sp->stats_buffer.FIELD + dev_stat; \
+	sp->stats_buffer.FIELD = dev_stat; \
+}
+
+	UPDATE_STATS(tx_packets, tmac_frms);
+	UPDATE_STATS(tx_errors, tmac_any_err_frms);
+	UPDATE_STATS(rx_errors, rmac_drop_frms);
+	UPDATE_STATS(multicast, rmac_vld_mcst_frms);
+	UPDATE_STATS(rx_length_errors, rmac_long_frms);
+
+#undef UPDATE_STATS
 
 	return (&sp->stats);
 }
diff --git a/drivers/net/s2io.h b/drivers/net/s2io.h
index 8e52954..6436e28 100644
--- a/drivers/net/s2io.h
+++ b/drivers/net/s2io.h
@@ -777,6 +777,17 @@ struct lro {
 	u8		saw_ts;
 };
 
+/* Network private statistics. */
+struct s2io_stats_buffer {
+
+	unsigned long   tx_packets;             /* packets transmitted    */
+	unsigned long   rx_errors;              /* bad packets received         */
+	unsigned long   tx_errors;              /* packet transmit problems     */
+	unsigned long   multicast;              /* multicast packets received   */
+	unsigned long   rx_length_errors;
+
+};
+
 /* Structure representing one instance of the NIC */
 struct s2io_nic {
 	int rxd_mode;
@@ -786,6 +797,7 @@ struct s2io_nic {
 	 */
 	int pkts_to_process;
 	struct net_device *dev;
+	struct s2io_stats_buffer stats_buffer;
 	struct mac_info mac_control;
 	struct config_param config;
 	struct pci_dev *pdev;