[PATCH] bnx2x: fix occasional statistics off-by-4GB error

["Maciej Żenczykowski" <zenczykowski@gmail.com>]

From: Maciej Żenczykowski <maze@google.com>

The UPDATE_QSTAT function introduced on February 15, 2012
in commit 1355b704b9ba "bnx2x: consistent statistics after
internal driver reload" incorrectly fails to handle overflow
during addition of the lower 32-bit field of a stat.

This bug is present since 3.4-rc1 and should thus be considered
a candidate for stable 3.4+ releases.

Google-Bug-Id: 8374428
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Cc: Mintz Yuval <yuvalmin@broadcom.com>
---
 drivers/net/ethernet/broadcom/bnx2x/bnx2x_stats.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/broadcom/bnx2x/bnx2x_stats.h b/drivers/net/ethernet/broadcom/bnx2x/bnx2x_stats.h
index 364e37ecbc5c..198f6f1c9ad5 100644
--- a/drivers/net/ethernet/broadcom/bnx2x/bnx2x_stats.h
+++ b/drivers/net/ethernet/broadcom/bnx2x/bnx2x_stats.h
@@ -459,8 +459,9 @@ struct bnx2x_fw_port_stats_old {
 
 #define UPDATE_QSTAT(s, t) \
 	do { \
-		qstats->t##_hi = qstats_old->t##_hi + le32_to_cpu(s.hi); \
 		qstats->t##_lo = qstats_old->t##_lo + le32_to_cpu(s.lo); \
+		qstats->t##_hi = qstats_old->t##_hi + le32_to_cpu(s.hi) \
+			+ ((qstats->t##_lo < qstats_old->t##_lo) ? 1 : 0); \
 	} while (0)
 
 #define UPDATE_QSTAT_OLD(f) \
-- 
1.8.1.3