linux-kernel - [PATCH net] hv_netvsc: Fix a warning of suspicious RCU usage

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Message-ID: <PU1P153MB0169AECABF6094A3E7BEE381BFD50@PU1P153MB0169.APCP153.PROD.OUTLOOK.COM>
Date:   Tue, 6 Aug 2019 05:17:44 +0000
From:   Dexuan Cui <decui@...rosoft.com>
To:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>
CC:     "sashal@...nel.org" <sashal@...nel.org>,
        KY Srinivasan <kys@...rosoft.com>,
        Michael Kelley <mikelley@...rosoft.com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "olaf@...fle.de" <olaf@...fle.de>,
        "apw@...onical.com" <apw@...onical.com>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        vkuznets <vkuznets@...hat.com>,
        "marcelo.cerri@...onical.com" <marcelo.cerri@...onical.com>
Subject: [PATCH net] hv_netvsc: Fix a warning of suspicious RCU usage


This fixes a warning of "suspicious rcu_dereference_check() usage"
when nload runs.

Signed-off-by: Stephen Hemminger <stephen@...workplumber.org>
Signed-off-by: Dexuan Cui <decui@...rosoft.com>
---
 drivers/net/hyperv/netvsc_drv.c | 44 +++++++++++++++++++--------------
 1 file changed, 26 insertions(+), 18 deletions(-)

diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index f9209594624b5..25502d335b94f 100644
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -1236,25 +1236,10 @@ static void netvsc_get_pcpu_stats(struct net_device *net,
 	}
 }
 
-static void netvsc_get_stats64(struct net_device *net,
-			       struct rtnl_link_stats64 *t)
+static void netvsc_get_per_chan_stats(struct netvsc_device *nvdev,
+				      struct rtnl_link_stats64 *t)
 {
-	struct net_device_context *ndev_ctx = netdev_priv(net);
-	struct netvsc_device *nvdev = rcu_dereference_rtnl(ndev_ctx->nvdev);
-	struct netvsc_vf_pcpu_stats vf_tot;
-	int i;
-
-	if (!nvdev)
-		return;
-
-	netdev_stats_to_stats64(t, &net->stats);
-
-	netvsc_get_vf_stats(net, &vf_tot);
-	t->rx_packets += vf_tot.rx_packets;
-	t->tx_packets += vf_tot.tx_packets;
-	t->rx_bytes   += vf_tot.rx_bytes;
-	t->tx_bytes   += vf_tot.tx_bytes;
-	t->tx_dropped += vf_tot.tx_dropped;
+	u32 i;
 
 	for (i = 0; i < nvdev->num_chn; i++) {
 		const struct netvsc_channel *nvchan = &nvdev->chan_table[i];
@@ -1286,6 +1271,29 @@ static void netvsc_get_stats64(struct net_device *net,
 	}
 }
 
+static void netvsc_get_stats64(struct net_device *net,
+			       struct rtnl_link_stats64 *t)
+{
+	struct net_device_context *ndev_ctx = netdev_priv(net);
+	struct netvsc_device *nvdev;
+	struct netvsc_vf_pcpu_stats vf_tot;
+
+	netdev_stats_to_stats64(t, &net->stats);
+
+	netvsc_get_vf_stats(net, &vf_tot);
+	t->rx_packets += vf_tot.rx_packets;
+	t->tx_packets += vf_tot.tx_packets;
+	t->rx_bytes   += vf_tot.rx_bytes;
+	t->tx_bytes   += vf_tot.tx_bytes;
+	t->tx_dropped += vf_tot.tx_dropped;
+
+	rcu_read_lock();
+	nvdev = rcu_dereference(ndev_ctx->nvdev);
+	if (nvdev)
+		netvsc_get_per_chan_stats(nvdev, t);
+	rcu_read_unlock();
+}
+
 static int netvsc_set_mac_addr(struct net_device *ndev, void *p)
 {
 	struct net_device_context *ndc = netdev_priv(ndev);