net: remove NETIF_F_NO_CSUM feature bit

Only distinct use is checking if NETIF_F_NOCACHE_COPY should be
enabled by default. The check heuristics is altered a bit here,
so it hits other people than before. The default shouldn't be
trusted for performance-critical cases anyway.

For all other uses NETIF_F_NO_CSUM is equivalent to NETIF_F_HW_CSUM.

Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/bridge/br_device.c b/net/bridge/br_device.c
index 772bad3..a3754ac 100644
--- a/net/bridge/br_device.c
+++ b/net/bridge/br_device.c
@@ -342,10 +342,10 @@
 	dev->priv_flags = IFF_EBRIDGE;
 
 	dev->features = NETIF_F_SG | NETIF_F_FRAGLIST | NETIF_F_HIGHDMA |
-			NETIF_F_GSO_MASK | NETIF_F_NO_CSUM | NETIF_F_LLTX |
+			NETIF_F_GSO_MASK | NETIF_F_HW_CSUM | NETIF_F_LLTX |
 			NETIF_F_NETNS_LOCAL | NETIF_F_HW_VLAN_TX;
 	dev->hw_features = NETIF_F_SG | NETIF_F_FRAGLIST | NETIF_F_HIGHDMA |
-			   NETIF_F_GSO_MASK | NETIF_F_NO_CSUM |
+			   NETIF_F_GSO_MASK | NETIF_F_HW_CSUM |
 			   NETIF_F_HW_VLAN_TX;
 
 	br->dev = dev;
diff --git a/net/core/dev.c b/net/core/dev.c
index f1cca59..26c49d5 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5362,12 +5362,6 @@
 		features &= ~(NETIF_F_IP_CSUM|NETIF_F_IPV6_CSUM);
 	}
 
-	if ((features & NETIF_F_NO_CSUM) &&
-	    (features & (NETIF_F_HW_CSUM|NETIF_F_IP_CSUM|NETIF_F_IPV6_CSUM))) {
-		netdev_warn(dev, "mixed no checksumming and other settings.\n");
-		features &= ~(NETIF_F_IP_CSUM|NETIF_F_IPV6_CSUM|NETIF_F_HW_CSUM);
-	}
-
 	/* Fix illegal SG+CSUM combinations. */
 	if ((features & NETIF_F_SG) &&
 	    !(features & NETIF_F_ALL_CSUM)) {
@@ -5624,11 +5618,12 @@
 	dev->wanted_features = dev->features & dev->hw_features;
 
 	/* Turn on no cache copy if HW is doing checksum */
-	dev->hw_features |= NETIF_F_NOCACHE_COPY;
-	if ((dev->features & NETIF_F_ALL_CSUM) &&
-	    !(dev->features & NETIF_F_NO_CSUM)) {
-		dev->wanted_features |= NETIF_F_NOCACHE_COPY;
-		dev->features |= NETIF_F_NOCACHE_COPY;
+	if (!(dev->flags & IFF_LOOPBACK)) {
+		dev->hw_features |= NETIF_F_NOCACHE_COPY;
+		if (dev->features & NETIF_F_ALL_CSUM) {
+			dev->wanted_features |= NETIF_F_NOCACHE_COPY;
+			dev->features |= NETIF_F_NOCACHE_COPY;
+		}
 	}
 
 	/* Make NETIF_F_HIGHDMA inheritable to VLAN devices.
@@ -6374,10 +6369,6 @@
 	all |= one & (NETIF_F_ONE_FOR_ALL|NETIF_F_ALL_CSUM) & mask;
 	all &= one | ~NETIF_F_ALL_FOR_ALL;
 
-	/* If device needs checksumming, downgrade to it. */
-	if (all & (NETIF_F_ALL_CSUM & ~NETIF_F_NO_CSUM))
-		all &= ~NETIF_F_NO_CSUM;
-
 	/* If one device supports hw checksumming, set for all. */
 	if (all & NETIF_F_GEN_CSUM)
 		all &= ~(NETIF_F_ALL_CSUM & ~NETIF_F_GEN_CSUM);
diff --git a/net/core/ethtool.c b/net/core/ethtool.c
index bbf84fe..d2eff9e 100644
--- a/net/core/ethtool.c
+++ b/net/core/ethtool.c
@@ -43,7 +43,6 @@
 static const char netdev_features_strings[NETDEV_FEATURE_COUNT][ETH_GSTRING_LEN] = {
 	[NETIF_F_SG_BIT] =               "tx-scatter-gather",
 	[NETIF_F_IP_CSUM_BIT] =          "tx-checksum-ipv4",
-	[NETIF_F_NO_CSUM_BIT] =          "tx-checksum-unneeded",
 	[NETIF_F_HW_CSUM_BIT] =          "tx-checksum-ip-generic",
 	[NETIF_F_IPV6_CSUM_BIT] =        "tx-checksum-ipv6",
 	[NETIF_F_HIGHDMA_BIT] =          "highdma",