linux-kernel - [PATCH 5.14 112/151] gve: fix gve_get

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Message-Id: <20211011134521.435783777@linuxfoundation.org>
Date:   Mon, 11 Oct 2021 15:46:24 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
        Catherine Sullivan <csully@...gle.com>,
        Sagi Shahar <sagis@...gle.com>,
        Jon Olson <jonolson@...gle.com>,
        Willem de Bruijn <willemb@...gle.com>,
        Luigi Rizzo <lrizzo@...gle.com>,
        Jeroen de Borst <jeroendb@...gle.com>,
        Tao Liu <xliutaox@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.14 112/151] gve: fix gve_get_stats()

From: Eric Dumazet <edumazet@...gle.com>

[ Upstream commit 2f57d4975fa027eabd35fdf23a49f8222ef3abf2 ]

gve_get_stats() can report wrong numbers if/when u64_stats_fetch_retry()
returns true.

What is needed here is to sample values in temporary variables,
and only use them after each loop is ended.

Fixes: f5cedc84a30d ("gve: Add transmit and receive support")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Catherine Sullivan <csully@...gle.com>
Cc: Sagi Shahar <sagis@...gle.com>
Cc: Jon Olson <jonolson@...gle.com>
Cc: Willem de Bruijn <willemb@...gle.com>
Cc: Luigi Rizzo <lrizzo@...gle.com>
Cc: Jeroen de Borst <jeroendb@...gle.com>
Cc: Tao Liu <xliutaox@...gle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/ethernet/google/gve/gve_main.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/google/gve/gve_main.c b/drivers/net/ethernet/google/gve/gve_main.c
index 29c5f994f92e..1b49e9feacac 100644
--- a/drivers/net/ethernet/google/gve/gve_main.c
+++ b/drivers/net/ethernet/google/gve/gve_main.c
@@ -41,6 +41,7 @@ static void gve_get_stats(struct net_device *dev, struct rtnl_link_stats64 *s)
 {
 	struct gve_priv *priv = netdev_priv(dev);
 	unsigned int start;
+	u64 packets, bytes;
 	int ring;
 
 	if (priv->rx) {
@@ -48,10 +49,12 @@ static void gve_get_stats(struct net_device *dev, struct rtnl_link_stats64 *s)
 			do {
 				start =
 				  u64_stats_fetch_begin(&priv->rx[ring].statss);
-				s->rx_packets += priv->rx[ring].rpackets;
-				s->rx_bytes += priv->rx[ring].rbytes;
+				packets = priv->rx[ring].rpackets;
+				bytes = priv->rx[ring].rbytes;
 			} while (u64_stats_fetch_retry(&priv->rx[ring].statss,
 						       start));
+			s->rx_packets += packets;
+			s->rx_bytes += bytes;
 		}
 	}
 	if (priv->tx) {
@@ -59,10 +62,12 @@ static void gve_get_stats(struct net_device *dev, struct rtnl_link_stats64 *s)
 			do {
 				start =
 				  u64_stats_fetch_begin(&priv->tx[ring].statss);
-				s->tx_packets += priv->tx[ring].pkt_done;
-				s->tx_bytes += priv->tx[ring].bytes_done;
+				packets = priv->tx[ring].pkt_done;
+				bytes = priv->tx[ring].bytes_done;
 			} while (u64_stats_fetch_retry(&priv->tx[ring].statss,
 						       start));
+			s->tx_packets += packets;
+			s->tx_bytes += bytes;
 		}
 	}
 }
-- 
2.33.0