Merge branch 'dsa-tagger-simplification'

Vivien Didelot says:

====================
net: dsa: tagger simplification

This series clarifies the hot path, removes the labels in tagging
implementations, and frees the original SKB in the xmit caller.

Changes in v3:
  - drop removal of usused rcv arguments because they will be used later
  - include the new ksz tagging implementation
  - add reviewers' tags

Changes in v2:
  - do not remove tagger function copies
  - document hot path requirements
  - make netdev_uses_dsa simpler
  - add reviewers' tags
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/dsa.h

@@ -127,6 +127,8 @@ struct dsa_switch_tree {
 	 * protocol to use.
 	 */
 	struct net_device	*master_netdev;
+
+	/* Copy of tag_ops->rcv for faster access in hot path */
 	struct sk_buff *	(*rcv)(struct sk_buff *skb,
 				       struct net_device *dev,
 				       struct packet_type *pt,
@@ -465,16 +467,11 @@ struct mii_bus *dsa_host_dev_to_mii_bus(struct device *dev);
 
 struct net_device *dsa_dev_to_net_device(struct device *dev);
 
-static inline bool dsa_uses_tagged_protocol(struct dsa_switch_tree *dst)
-{
-	return dst->rcv != NULL;
-}
-
+/* Keep inline for faster access in hot path */
 static inline bool netdev_uses_dsa(struct net_device *dev)
 {
 #if IS_ENABLED(CONFIG_NET_DSA)
-	if (dev->dsa_ptr != NULL)
-		return dsa_uses_tagged_protocol(dev->dsa_ptr);
+	return dev->dsa_ptr && dev->dsa_ptr->rcv;
 #endif
 	return false;
 }

net/dsa/dsa2.c

@@ -454,7 +454,7 @@ static int dsa_dst_apply(struct dsa_switch_tree *dst)
 	 * sent to the tag format's receive function.
 	 */
 	wmb();
-	dst->master_netdev->dsa_ptr = (void *)dst;
+	dst->master_netdev->dsa_ptr = dst;
 	dst->applied = true;
 
 	return 0;

net/dsa/dsa_priv.h

@@ -73,6 +73,7 @@ struct dsa_device_ops {
 };
 
 struct dsa_slave_priv {
+	/* Copy of dp->ds->dst->tag_ops->xmit for faster access in hot path */
 	struct sk_buff *	(*xmit)(struct sk_buff *skb,
 					struct net_device *dev);
 

net/dsa/legacy.c

@@ -651,7 +651,7 @@ static int dsa_setup_dst(struct dsa_switch_tree *dst, struct net_device *dev,
 	 * sent to the tag format's receive function.
 	 */
 	wmb();
-	dev->dsa_ptr = (void *)dst;
+	dev->dsa_ptr = dst;
 
 	return 0;
 }

net/dsa/slave.c

@@ -357,10 +357,14 @@ static netdev_tx_t dsa_slave_xmit(struct sk_buff *skb, struct net_device *dev)
 	dev->stats.tx_packets++;
 	dev->stats.tx_bytes += skb->len;
 
-	/* Transmit function may have to reallocate the original SKB */
+	/* Transmit function may have to reallocate the original SKB,
+	 * in which case it must have freed it. Only free it here on error.
+	 */
 	nskb = p->xmit(skb, dev);
-	if (!nskb)
+	if (!nskb) {
+		kfree_skb(skb);
 		return NETDEV_TX_OK;
+	}
 
 	/* SKB for netpoll still need to be mangled with the protocol-specific
 	 * tag to be successfully transmitted

net/dsa/tag_brcm.c

@@ -65,7 +65,7 @@ static struct sk_buff *brcm_tag_xmit(struct sk_buff *skb, struct net_device *dev
 	u8 *brcm_tag;
 
 	if (skb_cow_head(skb, BRCM_TAG_LEN) < 0)
-		goto out_free;
+		return NULL;
 
 	skb_push(skb, BRCM_TAG_LEN);
 
@@ -86,10 +86,6 @@ static struct sk_buff *brcm_tag_xmit(struct sk_buff *skb, struct net_device *dev
 	brcm_tag[3] = (1 << p->dp->index) & BRCM_IG_DSTMAP1_MASK;
 
 	return skb;
-
-out_free:
-	kfree_skb(skb);
-	return NULL;
 }
 
 static struct sk_buff *brcm_tag_rcv(struct sk_buff *skb, struct net_device *dev,
@@ -104,27 +100,27 @@ static struct sk_buff *brcm_tag_rcv(struct sk_buff *skb, struct net_device *dev,
 	ds = dst->cpu_dp->ds;
 
 	if (unlikely(!pskb_may_pull(skb, BRCM_TAG_LEN)))
-		goto out_drop;
+		return NULL;
 
 	/* skb->data points to the EtherType, the tag is right before it */
 	brcm_tag = skb->data - 2;
 
 	/* The opcode should never be different than 0b000 */
 	if (unlikely((brcm_tag[0] >> BRCM_OPCODE_SHIFT) & BRCM_OPCODE_MASK))
-		goto out_drop;
+		return NULL;
 
 	/* We should never see a reserved reason code without knowing how to
 	 * handle it
 	 */
 	if (unlikely(brcm_tag[2] & BRCM_EG_RC_RSVD))
-		goto out_drop;
+		return NULL;
 
 	/* Locate which port this is coming from */
 	source_port = brcm_tag[3] & BRCM_EG_PID_MASK;
 
 	/* Validate port against switch setup, either the port is totally */
 	if (source_port >= ds->num_ports || !ds->ports[source_port].netdev)
-		goto out_drop;
+		return NULL;
 
 	/* Remove Broadcom tag and update checksum */
 	skb_pull_rcsum(skb, BRCM_TAG_LEN);
@@ -137,9 +133,6 @@ static struct sk_buff *brcm_tag_rcv(struct sk_buff *skb, struct net_device *dev,
 	skb->dev = ds->ports[source_port].netdev;
 
 	return skb;
-
-out_drop:
-	return NULL;
 }
 
 const struct dsa_device_ops brcm_netdev_ops = {

net/dsa/tag_dsa.c

@@ -28,7 +28,7 @@ static struct sk_buff *dsa_xmit(struct sk_buff *skb, struct net_device *dev)
 	 */
 	if (skb->protocol == htons(ETH_P_8021Q)) {
 		if (skb_cow_head(skb, 0) < 0)
-			goto out_free;
+			return NULL;
 
 		/*
 		 * Construct tagged FROM_CPU DSA tag from 802.1q tag.
@@ -46,7 +46,7 @@ static struct sk_buff *dsa_xmit(struct sk_buff *skb, struct net_device *dev)
 		}
 	} else {
 		if (skb_cow_head(skb, DSA_HLEN) < 0)
-			goto out_free;
+			return NULL;
 		skb_push(skb, DSA_HLEN);
 
 		memmove(skb->data, skb->data + DSA_HLEN, 2 * ETH_ALEN);
@@ -62,10 +62,6 @@ static struct sk_buff *dsa_xmit(struct sk_buff *skb, struct net_device *dev)
 	}
 
 	return skb;
-
-out_free:
-	kfree_skb(skb);
-	return NULL;
 }
 
 static struct sk_buff *dsa_rcv(struct sk_buff *skb, struct net_device *dev,
@@ -79,7 +75,7 @@ static struct sk_buff *dsa_rcv(struct sk_buff *skb, struct net_device *dev,
 	int source_port;
 
 	if (unlikely(!pskb_may_pull(skb, DSA_HLEN)))
-		goto out_drop;
+		return NULL;
 
 	/*
 	 * The ethertype field is part of the DSA header.
@@ -90,7 +86,7 @@ static struct sk_buff *dsa_rcv(struct sk_buff *skb, struct net_device *dev,
 	 * Check that frame type is either TO_CPU or FORWARD.
 	 */
 	if ((dsa_header[0] & 0xc0) != 0x00 && (dsa_header[0] & 0xc0) != 0xc0)
-		goto out_drop;
+		return NULL;
 
 	/*
 	 * Determine source device and port.
@@ -103,14 +99,14 @@ static struct sk_buff *dsa_rcv(struct sk_buff *skb, struct net_device *dev,
 	 * port is a registered DSA port.
 	 */
 	if (source_device >= DSA_MAX_SWITCHES)
-		goto out_drop;
+		return NULL;
 
 	ds = dst->ds[source_device];
 	if (!ds)
-		goto out_drop;
+		return NULL;
 
 	if (source_port >= ds->num_ports || !ds->ports[source_port].netdev)
-		goto out_drop;
+		return NULL;
 
 	/*
 	 * Convert the DSA header to an 802.1q header if the 'tagged'
@@ -161,9 +157,6 @@ static struct sk_buff *dsa_rcv(struct sk_buff *skb, struct net_device *dev,
 	skb->dev = ds->ports[source_port].netdev;
 
 	return skb;
-
-out_drop:
-	return NULL;
 }
 
 const struct dsa_device_ops dsa_netdev_ops = {

net/dsa/tag_edsa.c

@@ -30,7 +30,7 @@ static struct sk_buff *edsa_xmit(struct sk_buff *skb, struct net_device *dev)
 	 */
 	if (skb->protocol == htons(ETH_P_8021Q)) {
 		if (skb_cow_head(skb, DSA_HLEN) < 0)
-			goto out_free;
+			return NULL;
 		skb_push(skb, DSA_HLEN);
 
 		memmove(skb->data, skb->data + DSA_HLEN, 2 * ETH_ALEN);
@@ -55,7 +55,7 @@ static struct sk_buff *edsa_xmit(struct sk_buff *skb, struct net_device *dev)
 		}
 	} else {
 		if (skb_cow_head(skb, EDSA_HLEN) < 0)
-			goto out_free;
+			return NULL;
 		skb_push(skb, EDSA_HLEN);
 
 		memmove(skb->data, skb->data + EDSA_HLEN, 2 * ETH_ALEN);
@@ -75,10 +75,6 @@ static struct sk_buff *edsa_xmit(struct sk_buff *skb, struct net_device *dev)
 	}
 
 	return skb;
-
-out_free:
-	kfree_skb(skb);
-	return NULL;
 }
 
 static struct sk_buff *edsa_rcv(struct sk_buff *skb, struct net_device *dev,
@@ -92,7 +88,7 @@ static struct sk_buff *edsa_rcv(struct sk_buff *skb, struct net_device *dev,
 	int source_port;
 
 	if (unlikely(!pskb_may_pull(skb, EDSA_HLEN)))
-		goto out_drop;
+		return NULL;
 
 	/*
 	 * Skip the two null bytes after the ethertype.
@@ -103,7 +99,7 @@ static struct sk_buff *edsa_rcv(struct sk_buff *skb, struct net_device *dev,
 	 * Check that frame type is either TO_CPU or FORWARD.
 	 */
 	if ((edsa_header[0] & 0xc0) != 0x00 && (edsa_header[0] & 0xc0) != 0xc0)
-		goto out_drop;
+		return NULL;
 
 	/*
 	 * Determine source device and port.
@@ -116,14 +112,14 @@ static struct sk_buff *edsa_rcv(struct sk_buff *skb, struct net_device *dev,
 	 * port is a registered DSA port.
 	 */
 	if (source_device >= DSA_MAX_SWITCHES)
-		goto out_drop;
+		return NULL;
 
 	ds = dst->ds[source_device];
 	if (!ds)
-		goto out_drop;
+		return NULL;
 
 	if (source_port >= ds->num_ports || !ds->ports[source_port].netdev)
-		goto out_drop;
+		return NULL;
 
 	/*
 	 * If the 'tagged' bit is set, convert the DSA tag to a 802.1q
@@ -180,9 +176,6 @@ static struct sk_buff *edsa_rcv(struct sk_buff *skb, struct net_device *dev,
 	skb->dev = ds->ports[source_port].netdev;
 
 	return skb;
-
-out_drop:
-	return NULL;
 }
 
 const struct dsa_device_ops edsa_netdev_ops = {

net/dsa/tag_ksz.c

@@ -46,10 +46,8 @@ static struct sk_buff *ksz_xmit(struct sk_buff *skb, struct net_device *dev)
 	} else {
 		nskb = alloc_skb(NET_IP_ALIGN + skb->len +
 				 padlen + KSZ_INGRESS_TAG_LEN, GFP_ATOMIC);
-		if (!nskb) {
-			kfree_skb(skb);
+		if (!nskb)
 			return NULL;
-		}
 		skb_reserve(nskb, NET_IP_ALIGN);
 
 		skb_reset_mac_header(nskb);

net/dsa/tag_lan9303.c

@@ -52,7 +52,7 @@ static struct sk_buff *lan9303_xmit(struct sk_buff *skb, struct net_device *dev)
 	if (skb_cow_head(skb, LAN9303_TAG_LEN) < 0) {
 		dev_dbg(&dev->dev,
 			"Cannot make room for the special tag. Dropping packet\n");
-		goto out_free;
+		return NULL;
 	}
 
 	/* provide 'LAN9303_TAG_LEN' bytes additional space */
@@ -66,9 +66,6 @@ static struct sk_buff *lan9303_xmit(struct sk_buff *skb, struct net_device *dev)
 	lan9303_tag[1] = htons(p->dp->index | BIT(4));
 
 	return skb;
-out_free:
-	kfree_skb(skb);
-	return NULL;
 }
 
 static struct sk_buff *lan9303_rcv(struct sk_buff *skb, struct net_device *dev,

net/dsa/tag_mtk.c

@@ -27,7 +27,7 @@ static struct sk_buff *mtk_tag_xmit(struct sk_buff *skb,
 	u8 *mtk_tag;
 
 	if (skb_cow_head(skb, MTK_HDR_LEN) < 0)
-		goto out_free;
+		return NULL;
 
 	skb_push(skb, MTK_HDR_LEN);
 
@@ -41,10 +41,6 @@ static struct sk_buff *mtk_tag_xmit(struct sk_buff *skb,
 	mtk_tag[3] = 0;
 
 	return skb;
-
-out_free:
-	kfree_skb(skb);
-	return NULL;
 }
 
 static struct sk_buff *mtk_tag_rcv(struct sk_buff *skb, struct net_device *dev,
@@ -57,7 +53,7 @@ static struct sk_buff *mtk_tag_rcv(struct sk_buff *skb, struct net_device *dev,
 	__be16 *phdr, hdr;
 
 	if (unlikely(!pskb_may_pull(skb, MTK_HDR_LEN)))
-		goto out_drop;
+		return NULL;
 
 	/* The MTK header is added by the switch between src addr
 	 * and ethertype at this point, skb->data points to 2 bytes
@@ -79,19 +75,16 @@ static struct sk_buff *mtk_tag_rcv(struct sk_buff *skb, struct net_device *dev,
 	 */
 	ds = dst->ds[0];
 	if (!ds)
-		goto out_drop;
+		return NULL;
 
 	/* Get source port information */
 	port = (hdr & MTK_HDR_RECV_SOURCE_PORT_MASK);
 	if (!ds->ports[port].netdev)
-		goto out_drop;
+		return NULL;
 
 	skb->dev = ds->ports[port].netdev;
 
 	return skb;
-
-out_drop:
-	return NULL;
 }
 
 const struct dsa_device_ops mtk_netdev_ops = {

net/dsa/tag_qca.c

@@ -45,7 +45,7 @@ static struct sk_buff *qca_tag_xmit(struct sk_buff *skb, struct net_device *dev)
 	dev->stats.tx_bytes += skb->len;
 
 	if (skb_cow_head(skb, 0) < 0)
-		goto out_free;
+		return NULL;
 
 	skb_push(skb, QCA_HDR_LEN);
 
@@ -60,10 +60,6 @@ static struct sk_buff *qca_tag_xmit(struct sk_buff *skb, struct net_device *dev)
 	*phdr = htons(hdr);
 
 	return skb;
-
-out_free:
-	kfree_skb(skb);
-	return NULL;
 }
 
 static struct sk_buff *qca_tag_rcv(struct sk_buff *skb, struct net_device *dev,
@@ -77,7 +73,7 @@ static struct sk_buff *qca_tag_rcv(struct sk_buff *skb, struct net_device *dev,
 	__be16 *phdr, hdr;
 
 	if (unlikely(!pskb_may_pull(skb, QCA_HDR_LEN)))
-		goto out_drop;
+		return NULL;
 
 	/* The QCA header is added by the switch between src addr and Ethertype
 	 * At this point, skb->data points to ethertype so header should be
@@ -89,7 +85,7 @@ static struct sk_buff *qca_tag_rcv(struct sk_buff *skb, struct net_device *dev,
 	/* Make sure the version is correct */
 	ver = (hdr & QCA_HDR_RECV_VERSION_MASK) >> QCA_HDR_RECV_VERSION_S;
 	if (unlikely(ver != QCA_HDR_VERSION))
-		goto out_drop;
+		return NULL;
 
 	/* Remove QCA tag and recalculate checksum */
 	skb_pull_rcsum(skb, QCA_HDR_LEN);
@@ -101,20 +97,17 @@ static struct sk_buff *qca_tag_rcv(struct sk_buff *skb, struct net_device *dev,
 	 */
 	ds = dst->cpu_dp->ds;
 	if (!ds)
-		goto out_drop;
+		return NULL;
 
 	/* Get source port information */
 	port = (hdr & QCA_HDR_RECV_SOURCE_PORT_MASK);
 	if (!ds->ports[port].netdev)
-		goto out_drop;
+		return NULL;
 
 	/* Update skb & forward the frame accordingly */
 	skb->dev = ds->ports[port].netdev;
 
 	return skb;
-
-out_drop:
-	return NULL;
 }
 
 const struct dsa_device_ops qca_netdev_ops = {

net/dsa/tag_trailer.c

@@ -32,10 +32,8 @@ static struct sk_buff *trailer_xmit(struct sk_buff *skb, struct net_device *dev)
 		padlen = 60 - skb->len;
 
 	nskb = alloc_skb(NET_IP_ALIGN + skb->len + padlen + 4, GFP_ATOMIC);
-	if (nskb == NULL) {
-		kfree_skb(skb);
+	if (!nskb)
 		return NULL;
-	}
 	skb_reserve(nskb, NET_IP_ALIGN);
 
 	skb_reset_mac_header(nskb);
@@ -70,25 +68,22 @@ static struct sk_buff *trailer_rcv(struct sk_buff *skb, struct net_device *dev,
 	ds = dst->cpu_dp->ds;
 
 	if (skb_linearize(skb))
-		goto out_drop;
+		return NULL;
 
 	trailer = skb_tail_pointer(skb) - 4;
 	if (trailer[0] != 0x80 || (trailer[1] & 0xf8) != 0x00 ||
 	    (trailer[2] & 0xef) != 0x00 || trailer[3] != 0x00)
-		goto out_drop;
+		return NULL;
 
 	source_port = trailer[1] & 7;
 	if (source_port >= ds->num_ports || !ds->ports[source_port].netdev)
-		goto out_drop;
+		return NULL;
 
 	pskb_trim_rcsum(skb, skb->len - 4);
 
 	skb->dev = ds->ports[source_port].netdev;
 
 	return skb;
-
-out_drop:
-	return NULL;
 }
 
 const struct dsa_device_ops trailer_netdev_ops = {