netdev - [PATCH net-next 5/6] net: ethtool: implement lockless ETHTOOL

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Date: Thu, 20 Jun 2024 11:47:10 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: Ziwei Xiao <ziweixiao@...gle.com>, Praveen Kaligineedi <pkaligineedi@...gle.com>, 
	Harshitha Ramamurthy <hramamurthy@...gle.com>, Willem de Bruijn <willemb@...gle.com>, 
	Jeroen de Borst <jeroendb@...gle.com>, Shailend Chand <shailend@...gle.com>, netdev@...r.kernel.org, 
	eric.dumazet@...il.com, Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 5/6] net: ethtool: implement lockless ETHTOOL_GFLAGS

ETHTOOL_GFLAGS only reads dev->features, there is no need for RTNL protection.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/ethtool/ioctl.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
index d0c9d2ad9c3d0acb1be00eb4970d3a1ef9da030a..56b959495698c7cd0dfda995be7232e7cbb314a2 100644
--- a/net/ethtool/ioctl.c
+++ b/net/ethtool/ioctl.c
@@ -291,17 +291,18 @@ static int ethtool_set_one_feature(struct net_device *dev,
 
 static u32 __ethtool_get_flags(struct net_device *dev)
 {
+	netdev_features_t features = READ_ONCE(dev->features);
 	u32 flags = 0;
 
-	if (dev->features & NETIF_F_LRO)
+	if (features & NETIF_F_LRO)
 		flags |= ETH_FLAG_LRO;
-	if (dev->features & NETIF_F_HW_VLAN_CTAG_RX)
+	if (features & NETIF_F_HW_VLAN_CTAG_RX)
 		flags |= ETH_FLAG_RXVLAN;
-	if (dev->features & NETIF_F_HW_VLAN_CTAG_TX)
+	if (features & NETIF_F_HW_VLAN_CTAG_TX)
 		flags |= ETH_FLAG_TXVLAN;
-	if (dev->features & NETIF_F_NTUPLE)
+	if (features & NETIF_F_NTUPLE)
 		flags |= ETH_FLAG_NTUPLE;
-	if (dev->features & NETIF_F_RXHASH)
+	if (features & NETIF_F_RXHASH)
 		flags |= ETH_FLAG_RXHASH;
 
 	return flags;
@@ -2993,10 +2994,6 @@ __dev_ethtool(struct net_device *dev, struct ifreq *ifr,
 	case ETHTOOL_GPERMADDR:
 		rc = ethtool_get_perm_addr(dev, useraddr);
 		break;
-	case ETHTOOL_GFLAGS:
-		rc = ethtool_get_value(dev, useraddr, ethcmd,
-					__ethtool_get_flags);
-		break;
 	case ETHTOOL_SFLAGS:
 		rc = ethtool_set_value(dev, useraddr, __ethtool_set_flags);
 		break;
@@ -3179,6 +3176,10 @@ int dev_ethtool(struct net *net, struct ifreq *ifr, void __user *useraddr)
 	case ETHTOOL_GGRO:
 		rc = ethtool_get_one_feature(dev, useraddr, ethcmd);
 		break;
+	case ETHTOOL_GFLAGS:
+		rc = ethtool_get_value(dev, useraddr, ethcmd,
+					__ethtool_get_flags);
+		break;
 	default:
 		rtnl_lock();
 		rc = __dev_ethtool(dev, ifr, useraddr, ethcmd, sub_cmd, state);
-- 
2.45.2.627.g7a2c4fd464-goog