net: annotate accesses to dev->gso_max_segs

dev->gso_max_segs is written under RTNL protection, or when the device is
not yet visible, but is read locklessly.

Add netif_set_gso_max_segs() helper.

Add the READ_ONCE()/WRITE_ONCE() pairs, and use netif_set_gso_max_segs()
where we can to better document what is going on.
Signed-off-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/bonding/bond_main.c

@@ -1460,7 +1460,7 @@ static void bond_compute_features(struct bonding *bond)
 	bond_dev->hw_enc_features |= xfrm_features;
 #endif /* CONFIG_XFRM_OFFLOAD */
 	bond_dev->mpls_features = mpls_features;
-	bond_dev->gso_max_segs = gso_max_segs;
+	netif_set_gso_max_segs(bond_dev, gso_max_segs);
 	netif_set_gso_max_size(bond_dev, gso_max_size);
 
 	bond_dev->priv_flags &= ~IFF_XMIT_DST_RELEASE;

drivers/net/ethernet/freescale/fec_main.c

@@ -3558,7 +3558,7 @@ static int fec_enet_init(struct net_device *ndev)
 		ndev->features |= NETIF_F_HW_VLAN_CTAG_RX;
 
 	if (fep->quirks & FEC_QUIRK_HAS_CSUM) {
-		ndev->gso_max_segs = FEC_MAX_TSO_SEGS;
+		netif_set_gso_max_segs(ndev, FEC_MAX_TSO_SEGS);
 
 		/* enable hw accelerator */
 		ndev->features |= (NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM

drivers/net/ethernet/marvell/mv643xx_eth.c

@@ -3201,7 +3201,7 @@ static int mv643xx_eth_probe(struct platform_device *pdev)
 	dev->hw_features = dev->features;
 
 	dev->priv_flags |= IFF_UNICAST_FLT;
-	dev->gso_max_segs = MV643XX_MAX_TSO_SEGS;
+	netif_set_gso_max_segs(dev, MV643XX_MAX_TSO_SEGS);
 
 	/* MTU range: 64 - 9500 */
 	dev->min_mtu = 64;

drivers/net/ethernet/marvell/mvneta.c

@@ -5335,7 +5335,7 @@ static int mvneta_probe(struct platform_device *pdev)
 	dev->hw_features |= dev->features;
 	dev->vlan_features |= dev->features;
 	dev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
-	dev->gso_max_segs = MVNETA_MAX_TSO_SEGS;
+	netif_set_gso_max_segs(dev, MVNETA_MAX_TSO_SEGS);
 
 	/* MTU range: 68 - 9676 */
 	dev->min_mtu = ETH_MIN_MTU;

drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c

@@ -6857,7 +6857,7 @@ static int mvpp2_port_probe(struct platform_device *pdev,
 		mvpp2_set_hw_csum(port, port->pool_long->id);
 
 	dev->vlan_features |= features;
-	dev->gso_max_segs = MVPP2_MAX_TSO_SEGS;
+	netif_set_gso_max_segs(dev, MVPP2_MAX_TSO_SEGS);
 	dev->priv_flags |= IFF_UNICAST_FLT;
 
 	/* MTU range: 68 - 9704 */

drivers/net/ethernet/marvell/octeontx2/nic/otx2_pf.c

@@ -2741,7 +2741,7 @@ static int otx2_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 
 	netdev->hw_features |= NETIF_F_LOOPBACK | NETIF_F_RXALL;
 
-	netdev->gso_max_segs = OTX2_MAX_GSO_SEGS;
+	netif_set_gso_max_segs(netdev, OTX2_MAX_GSO_SEGS);
 	netdev->watchdog_timeo = OTX2_TX_TIMEOUT;
 
 	netdev->netdev_ops = &otx2_netdev_ops;

drivers/net/ethernet/marvell/octeontx2/nic/otx2_vf.c

@@ -663,7 +663,7 @@ static int otx2vf_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 	netdev->hw_features |= NETIF_F_NTUPLE;
 	netdev->hw_features |= NETIF_F_RXALL;
 
-	netdev->gso_max_segs = OTX2_MAX_GSO_SEGS;
+	netif_set_gso_max_segs(netdev, OTX2_MAX_GSO_SEGS);
 	netdev->watchdog_timeo = OTX2_TX_TIMEOUT;
 
 	netdev->netdev_ops = &otx2vf_netdev_ops;

drivers/net/ethernet/netronome/nfp/nfp_net_common.c

@@ -4097,7 +4097,7 @@ static void nfp_net_netdev_init(struct nfp_net *nn)
 	netdev->min_mtu = ETH_MIN_MTU;
 	netdev->max_mtu = nn->max_mtu;
 
-	netdev->gso_max_segs = NFP_NET_LSO_MAX_SEGS;
+	netif_set_gso_max_segs(netdev, NFP_NET_LSO_MAX_SEGS);
 
 	netif_carrier_off(netdev);
 

drivers/net/ethernet/netronome/nfp/nfp_net_repr.c

@@ -287,7 +287,7 @@ nfp_repr_transfer_features(struct net_device *netdev, struct net_device *lower)
 		return;
 
 	netif_set_gso_max_size(netdev, lower->gso_max_size);
-	netdev->gso_max_segs = lower->gso_max_segs;
+	netif_set_gso_max_segs(netdev, lower->gso_max_segs);
 
 	netdev_update_features(netdev);
 }
@@ -381,7 +381,7 @@ int nfp_repr_init(struct nfp_app *app, struct net_device *netdev,
 
 	/* Advertise but disable TSO by default. */
 	netdev->features &= ~(NETIF_F_TSO | NETIF_F_TSO6);
-	netdev->gso_max_segs = NFP_NET_LSO_MAX_SEGS;
+	netif_set_gso_max_segs(netdev, NFP_NET_LSO_MAX_SEGS);
 
 	netdev->priv_flags |= IFF_NO_QUEUE | IFF_DISABLE_NETPOLL;
 	netdev->features |= NETIF_F_LLTX;

drivers/net/ethernet/realtek/r8169_main.c

@@ -5391,11 +5391,11 @@ static int rtl_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 	if (rtl_chip_supports_csum_v2(tp)) {
 		dev->hw_features |= NETIF_F_SG | NETIF_F_TSO | NETIF_F_TSO6;
 		netif_set_gso_max_size(dev, RTL_GSO_MAX_SIZE_V2);
-		dev->gso_max_segs = RTL_GSO_MAX_SEGS_V2;
+		netif_set_gso_max_segs(dev, RTL_GSO_MAX_SEGS_V2);
 	} else {
 		dev->hw_features |= NETIF_F_SG | NETIF_F_TSO;
 		netif_set_gso_max_size(dev, RTL_GSO_MAX_SIZE_V1);
-		dev->gso_max_segs = RTL_GSO_MAX_SEGS_V1;
+		netif_set_gso_max_segs(dev, RTL_GSO_MAX_SEGS_V1);
 	}
 
 	dev->hw_features |= NETIF_F_RXALL;

drivers/net/ethernet/sfc/ef100_nic.c

@@ -997,7 +997,7 @@ static int ef100_process_design_param(struct efx_nic *efx,
 		return 0;
 	case ESE_EF100_DP_GZ_TSO_MAX_PAYLOAD_NUM_SEGS:
 		nic_data->tso_max_payload_num_segs = min_t(u64, reader->value, 0xffff);
-		efx->net_dev->gso_max_segs = nic_data->tso_max_payload_num_segs;
+		netif_set_gso_max_segs(efx->net_dev, nic_data->tso_max_payload_num_segs);
 		return 0;
 	case ESE_EF100_DP_GZ_TSO_MAX_NUM_FRAMES:
 		nic_data->tso_max_frames = min_t(u64, reader->value, 0xffff);
@@ -1122,7 +1122,7 @@ static int ef100_probe_main(struct efx_nic *efx)
 	nic_data->tso_max_frames = ESE_EF100_DP_GZ_TSO_MAX_NUM_FRAMES_DEFAULT;
 	nic_data->tso_max_payload_num_segs = ESE_EF100_DP_GZ_TSO_MAX_PAYLOAD_NUM_SEGS_DEFAULT;
 	nic_data->tso_max_payload_len = ESE_EF100_DP_GZ_TSO_MAX_PAYLOAD_LEN_DEFAULT;
-	net_dev->gso_max_segs = ESE_EF100_DP_GZ_TSO_MAX_HDR_NUM_SEGS_DEFAULT;
+	netif_set_gso_max_segs(net_dev, ESE_EF100_DP_GZ_TSO_MAX_HDR_NUM_SEGS_DEFAULT);
 	/* Read design parameters */
 	rc = ef100_check_design_params(efx);
 	if (rc) {

drivers/net/ethernet/sfc/efx.c

@@ -709,7 +709,7 @@ static int efx_register_netdev(struct efx_nic *efx)
 	if (efx_nic_rev(efx) >= EFX_REV_HUNT_A0)
 		net_dev->priv_flags |= IFF_UNICAST_FLT;
 	net_dev->ethtool_ops = &efx_ethtool_ops;
-	net_dev->gso_max_segs = EFX_TSO_MAX_SEGS;
+	netif_set_gso_max_segs(net_dev, EFX_TSO_MAX_SEGS);
 	net_dev->min_mtu = EFX_MIN_MTU;
 	net_dev->max_mtu = EFX_MAX_MTU;
 

drivers/net/ethernet/sfc/falcon/efx.c

@@ -2267,7 +2267,7 @@ static int ef4_register_netdev(struct ef4_nic *efx)
 	net_dev->irq = efx->pci_dev->irq;
 	net_dev->netdev_ops = &ef4_netdev_ops;
 	net_dev->ethtool_ops = &ef4_ethtool_ops;
-	net_dev->gso_max_segs = EF4_TSO_MAX_SEGS;
+	netif_set_gso_max_segs(net_dev, EF4_TSO_MAX_SEGS);
 	net_dev->min_mtu = EF4_MIN_MTU;
 	net_dev->max_mtu = EF4_MAX_MTU;
 

drivers/net/ipvlan/ipvlan_main.c

@@ -141,7 +141,7 @@ static int ipvlan_init(struct net_device *dev)
 	dev->vlan_features |= IPVLAN_ALWAYS_ON_OFLOADS;
 	dev->hw_enc_features |= dev->features;
 	netif_set_gso_max_size(dev, phy_dev->gso_max_size);
-	dev->gso_max_segs = phy_dev->gso_max_segs;
+	netif_set_gso_max_segs(dev, phy_dev->gso_max_segs);
 	dev->hard_header_len = phy_dev->hard_header_len;
 
 	netdev_lockdep_set_classes(dev);
@@ -764,7 +764,7 @@ static int ipvlan_device_event(struct notifier_block *unused,
 	case NETDEV_FEAT_CHANGE:
 		list_for_each_entry(ipvlan, &port->ipvlans, pnode) {
 			netif_set_gso_max_size(ipvlan->dev, dev->gso_max_size);
-			ipvlan->dev->gso_max_segs = dev->gso_max_segs;
+			netif_set_gso_max_segs(ipvlan->dev, dev->gso_max_segs);
 			netdev_update_features(ipvlan->dev);
 		}
 		break;

drivers/net/macvlan.c

@@ -901,7 +901,7 @@ static int macvlan_init(struct net_device *dev)
 	dev->vlan_features	|= ALWAYS_ON_OFFLOADS;
 	dev->hw_enc_features    |= dev->features;
 	netif_set_gso_max_size(dev, lowerdev->gso_max_size);
-	dev->gso_max_segs	= lowerdev->gso_max_segs;
+	netif_set_gso_max_segs(dev, lowerdev->gso_max_segs);
 	dev->hard_header_len	= lowerdev->hard_header_len;
 	macvlan_set_lockdep_class(dev);
 
@@ -1749,7 +1749,7 @@ static int macvlan_device_event(struct notifier_block *unused,
 	case NETDEV_FEAT_CHANGE:
 		list_for_each_entry(vlan, &port->vlans, list) {
 			netif_set_gso_max_size(vlan->dev, dev->gso_max_size);
-			vlan->dev->gso_max_segs = dev->gso_max_segs;
+			netif_set_gso_max_segs(vlan->dev, dev->gso_max_segs);
 			netdev_update_features(vlan->dev);
 		}
 		break;

drivers/net/veth.c

@@ -1690,7 +1690,7 @@ static int veth_newlink(struct net *src_net, struct net_device *dev,
 		peer->ifindex = ifmp->ifi_index;
 
 	netif_set_gso_max_size(peer, dev->gso_max_size);
-	peer->gso_max_segs = dev->gso_max_segs;
+	netif_set_gso_max_segs(peer, dev->gso_max_segs);
 
 	err = register_netdevice(peer);
 	put_net(net);

drivers/net/vxlan.c

@@ -3812,7 +3812,7 @@ static void vxlan_config_apply(struct net_device *dev,
 		dst->remote_ifindex = conf->remote_ifindex;
 
 		netif_set_gso_max_size(dev, lowerdev->gso_max_size);
-		dev->gso_max_segs = lowerdev->gso_max_segs;
+		netif_set_gso_max_segs(dev, lowerdev->gso_max_segs);
 
 		needed_headroom = lowerdev->hard_header_len;
 		needed_headroom += lowerdev->needed_headroom;

include/linux/netdevice.h

@@ -4735,6 +4735,13 @@ static inline void netif_set_gso_max_size(struct net_device *dev,
 	WRITE_ONCE(dev->gso_max_size, size);
 }
 
+static inline void netif_set_gso_max_segs(struct net_device *dev,
+					  unsigned int segs)
+{
+	/* dev->gso_max_segs is read locklessly from sk_setup_caps() */
+	WRITE_ONCE(dev->gso_max_segs, segs);
+}
+
 static inline void skb_gso_error_unwind(struct sk_buff *skb, __be16 protocol,
 					int pulled_hlen, u16 mac_offset,
 					int mac_len)

net/8021q/vlan.c

@@ -323,7 +323,7 @@ static void vlan_transfer_features(struct net_device *dev,
 	struct vlan_dev_priv *vlan = vlan_dev_priv(vlandev);
 
 	netif_set_gso_max_size(vlandev, dev->gso_max_size);
-	vlandev->gso_max_segs = dev->gso_max_segs;
+	netif_set_gso_max_segs(vlandev, dev->gso_max_segs);
 
 	if (vlan_hw_offload_capable(dev->features, vlan->vlan_proto))
 		vlandev->hard_header_len = dev->hard_header_len;

net/8021q/vlan_dev.c

@@ -574,7 +574,7 @@ static int vlan_dev_init(struct net_device *dev)
 
 	dev->features |= dev->hw_features | NETIF_F_LLTX;
 	netif_set_gso_max_size(dev, real_dev->gso_max_size);
-	dev->gso_max_segs = real_dev->gso_max_segs;
+	netif_set_gso_max_segs(dev, real_dev->gso_max_segs);
 	if (dev->features & NETIF_F_VLAN_FEATURES)
 		netdev_warn(real_dev, "VLAN features are set incorrectly.  Q-in-Q configurations may not work correctly.\n");
 

net/bridge/br_if.c

@@ -526,7 +526,7 @@ static void br_set_gso_limits(struct net_bridge *br)
 		gso_max_segs = min(gso_max_segs, p->dev->gso_max_segs);
 	}
 	netif_set_gso_max_size(br->dev, gso_max_size);
-	br->dev->gso_max_segs = gso_max_segs;
+	netif_set_gso_max_segs(br->dev, gso_max_segs);
 }
 
 /*

net/core/dev.c

@@ -3396,7 +3396,7 @@ static netdev_features_t gso_features_check(const struct sk_buff *skb,
 {
 	u16 gso_segs = skb_shinfo(skb)->gso_segs;
 
-	if (gso_segs > dev->gso_max_segs)
+	if (gso_segs > READ_ONCE(dev->gso_max_segs))
 		return features & ~NETIF_F_GSO_MASK;
 
 	if (!skb_shinfo(skb)->gso_type) {

net/core/rtnetlink.c

@@ -2768,7 +2768,7 @@ static int do_setlink(const struct sk_buff *skb,
 		}
 
 		if (dev->gso_max_segs ^ max_segs) {
-			dev->gso_max_segs = max_segs;
+			netif_set_gso_max_segs(dev, max_segs);
 			status |= DO_SETLINK_MODIFIED;
 		}
 	}
@@ -3222,7 +3222,7 @@ struct net_device *rtnl_create_link(struct net *net, const char *ifname,
 	if (tb[IFLA_GSO_MAX_SIZE])
 		netif_set_gso_max_size(dev, nla_get_u32(tb[IFLA_GSO_MAX_SIZE]));
 	if (tb[IFLA_GSO_MAX_SEGS])
-		dev->gso_max_segs = nla_get_u32(tb[IFLA_GSO_MAX_SEGS]);
+		netif_set_gso_max_segs(dev, nla_get_u32(tb[IFLA_GSO_MAX_SEGS]));
 
 	return dev;
 }

net/core/sock.c

@@ -2259,7 +2259,8 @@ void sk_setup_caps(struct sock *sk, struct dst_entry *dst)
 			sk->sk_route_caps |= NETIF_F_SG | NETIF_F_HW_CSUM;
 			/* pairs with the WRITE_ONCE() in netif_set_gso_max_size() */
 			sk->sk_gso_max_size = READ_ONCE(dst->dev->gso_max_size);
-			max_segs = max_t(u32, dst->dev->gso_max_segs, 1);
+			/* pairs with the WRITE_ONCE() in netif_set_gso_max_segs() */
+			max_segs = max_t(u32, READ_ONCE(dst->dev->gso_max_segs), 1);
 		}
 	}
 	sk->sk_gso_max_segs = max_segs;