ip_gre: Make GRE and GRETAP devices always NETIF_F_LLTX

Recently we made o_seqno atomic_t.  Stop special-casing TUNNEL_SEQ, and
always mark GRE[TAP] devices as NETIF_F_LLTX, since we no longer need
the TX lock (&txq->_xmit_lock).
Signed-off-by: Peilin Ye <peilin.ye@bytedance.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

net/ipv4/ip_gre.c

@@ -748,6 +748,7 @@ static netdev_tx_t gre_tap_xmit(struct sk_buff *skb,
 static void ipgre_link_update(struct net_device *dev, bool set_mtu)
 {
 	struct ip_tunnel *tunnel = netdev_priv(dev);
+	__be16 flags;
 	int len;
 
 	len = tunnel->tun_hlen;
@@ -763,19 +764,15 @@ static void ipgre_link_update(struct net_device *dev, bool set_mtu)
 	if (set_mtu)
 		dev->mtu = max_t(int, dev->mtu - len, 68);
 
-	if (!(tunnel->parms.o_flags & TUNNEL_SEQ)) {
-		if (!(tunnel->parms.o_flags & TUNNEL_CSUM) ||
-		    tunnel->encap.type == TUNNEL_ENCAP_NONE) {
-			dev->features |= NETIF_F_GSO_SOFTWARE;
-			dev->hw_features |= NETIF_F_GSO_SOFTWARE;
-		} else {
+	flags = tunnel->parms.o_flags;
+
+	if (flags & TUNNEL_SEQ ||
+	    (flags & TUNNEL_CSUM && tunnel->encap.type != TUNNEL_ENCAP_NONE)) {
 		dev->features &= ~NETIF_F_GSO_SOFTWARE;
 		dev->hw_features &= ~NETIF_F_GSO_SOFTWARE;
-		}
-		dev->features |= NETIF_F_LLTX;
 	} else {
-		dev->hw_features &= ~NETIF_F_GSO_SOFTWARE;
-		dev->features &= ~(NETIF_F_LLTX | NETIF_F_GSO_SOFTWARE);
+		dev->features |= NETIF_F_GSO_SOFTWARE;
+		dev->hw_features |= NETIF_F_GSO_SOFTWARE;
 	}
 }
 
@@ -949,6 +946,7 @@ static void ipgre_tunnel_setup(struct net_device *dev)
 static void __gre_tunnel_init(struct net_device *dev)
 {
 	struct ip_tunnel *tunnel;
+	__be16 flags;
 
 	tunnel = netdev_priv(dev);
 	tunnel->tun_hlen = gre_calc_hlen(tunnel->parms.o_flags);
@@ -957,25 +955,21 @@ static void __gre_tunnel_init(struct net_device *dev)
 	tunnel->hlen = tunnel->tun_hlen + tunnel->encap_hlen;
 	dev->needed_headroom = tunnel->hlen + sizeof(tunnel->parms.iph);
 
-	dev->features		|= GRE_FEATURES;
+	dev->features		|= GRE_FEATURES | NETIF_F_LLTX;
 	dev->hw_features	|= GRE_FEATURES;
 
-	if (!(tunnel->parms.o_flags & TUNNEL_SEQ)) {
-		/* TCP offload with GRE SEQ is not supported, nor
-		 * can we support 2 levels of outer headers requiring
-		 * an update.
+	flags = tunnel->parms.o_flags;
+
+	/* TCP offload with GRE SEQ is not supported, nor can we support 2
+	 * levels of outer headers requiring an update.
 	 */
-		if (!(tunnel->parms.o_flags & TUNNEL_CSUM) ||
-		    (tunnel->encap.type == TUNNEL_ENCAP_NONE)) {
+	if (flags & TUNNEL_SEQ)
+		return;
+	if (flags & TUNNEL_CSUM && tunnel->encap.type != TUNNEL_ENCAP_NONE)
+		return;
+
 	dev->features |= NETIF_F_GSO_SOFTWARE;
 	dev->hw_features |= NETIF_F_GSO_SOFTWARE;
-		}
-
-		/* Can use a lockless transmit, unless we generate
-		 * output sequences
-		 */
-		dev->features |= NETIF_F_LLTX;
-	}
 }
 
 static int ipgre_tunnel_init(struct net_device *dev)