net: move make_writable helper into common code

note that skb_make_writable already exists in net/netfilter/core.c
but does something slightly different.
Suggested-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Acked-by: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/skbuff.h

@@ -2678,6 +2678,7 @@ void skb_scrub_packet(struct sk_buff *skb, bool xnet);
 unsigned int skb_gso_transport_seglen(const struct sk_buff *skb);
 struct sk_buff *skb_segment(struct sk_buff *skb, netdev_features_t features);
 struct sk_buff *skb_vlan_untag(struct sk_buff *skb);
+int skb_ensure_writable(struct sk_buff *skb, int write_len);
 
 struct skb_checksum_ops {
 	__wsum (*update)(const void *mem, int len, __wsum wsum);

net/core/skbuff.c

@@ -4151,6 +4151,18 @@ struct sk_buff *skb_vlan_untag(struct sk_buff *skb)
 }
 EXPORT_SYMBOL(skb_vlan_untag);
 
+int skb_ensure_writable(struct sk_buff *skb, int write_len)
+{
+	if (!pskb_may_pull(skb, write_len))
+		return -ENOMEM;
+
+	if (!skb_cloned(skb) || skb_clone_writable(skb, write_len))
+		return 0;
+
+	return pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
+}
+EXPORT_SYMBOL(skb_ensure_writable);
+
 /**
  * alloc_skb_with_frags - allocate skb with page frags
  *

net/openvswitch/actions.c

@@ -119,17 +119,6 @@ static bool is_flow_key_valid(const struct sw_flow_key *key)
 	return !!key->eth.type;
 }
 
-static int make_writable(struct sk_buff *skb, int write_len)
-{
-	if (!pskb_may_pull(skb, write_len))
-		return -ENOMEM;
-
-	if (!skb_cloned(skb) || skb_clone_writable(skb, write_len))
-		return 0;
-
-	return pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
-}
-
 static int push_mpls(struct sk_buff *skb, struct sw_flow_key *key,
 		     const struct ovs_action_push_mpls *mpls)
 {
@@ -171,7 +160,7 @@ static int pop_mpls(struct sk_buff *skb, struct sw_flow_key *key,
 	struct ethhdr *hdr;
 	int err;
 
-	err = make_writable(skb, skb->mac_len + MPLS_HLEN);
+	err = skb_ensure_writable(skb, skb->mac_len + MPLS_HLEN);
 	if (unlikely(err))
 		return err;
 
@@ -201,7 +190,7 @@ static int set_mpls(struct sk_buff *skb, struct sw_flow_key *key,
 	__be32 *stack;
 	int err;
 
-	err = make_writable(skb, skb->mac_len + MPLS_HLEN);
+	err = skb_ensure_writable(skb, skb->mac_len + MPLS_HLEN);
 	if (unlikely(err))
 		return err;
 
@@ -223,7 +212,7 @@ static int __pop_vlan_tci(struct sk_buff *skb, __be16 *current_tci)
 	struct vlan_hdr *vhdr;
 	int err;
 
-	err = make_writable(skb, VLAN_ETH_HLEN);
+	err = skb_ensure_writable(skb, VLAN_ETH_HLEN);
 	if (unlikely(err))
 		return err;
 
@@ -310,7 +299,7 @@ static int set_eth_addr(struct sk_buff *skb, struct sw_flow_key *key,
 			const struct ovs_key_ethernet *eth_key)
 {
 	int err;
-	err = make_writable(skb, ETH_HLEN);
+	err = skb_ensure_writable(skb, ETH_HLEN);
 	if (unlikely(err))
 		return err;
 
@@ -412,8 +401,8 @@ static int set_ipv4(struct sk_buff *skb, struct sw_flow_key *key,
 	struct iphdr *nh;
 	int err;
 
-	err = make_writable(skb, skb_network_offset(skb) +
-				 sizeof(struct iphdr));
+	err = skb_ensure_writable(skb, skb_network_offset(skb) +
+				  sizeof(struct iphdr));
 	if (unlikely(err))
 		return err;
 
@@ -450,8 +439,8 @@ static int set_ipv6(struct sk_buff *skb, struct sw_flow_key *key,
 	__be32 *saddr;
 	__be32 *daddr;
 
-	err = make_writable(skb, skb_network_offset(skb) +
-			    sizeof(struct ipv6hdr));
+	err = skb_ensure_writable(skb, skb_network_offset(skb) +
+				  sizeof(struct ipv6hdr));
 	if (unlikely(err))
 		return err;
 
@@ -493,7 +482,7 @@ static int set_ipv6(struct sk_buff *skb, struct sw_flow_key *key,
 	return 0;
 }
 
-/* Must follow make_writable() since that can move the skb data. */
+/* Must follow skb_ensure_writable() since that can move the skb data. */
 static void set_tp_port(struct sk_buff *skb, __be16 *port,
 			 __be16 new_port, __sum16 *check)
 {
@@ -523,8 +512,8 @@ static int set_udp(struct sk_buff *skb, struct sw_flow_key *key,
 	struct udphdr *uh;
 	int err;
 
-	err = make_writable(skb, skb_transport_offset(skb) +
-				 sizeof(struct udphdr));
+	err = skb_ensure_writable(skb, skb_transport_offset(skb) +
+				  sizeof(struct udphdr));
 	if (unlikely(err))
 		return err;
 
@@ -548,8 +537,8 @@ static int set_tcp(struct sk_buff *skb, struct sw_flow_key *key,
 	struct tcphdr *th;
 	int err;
 
-	err = make_writable(skb, skb_transport_offset(skb) +
-				 sizeof(struct tcphdr));
+	err = skb_ensure_writable(skb, skb_transport_offset(skb) +
+				  sizeof(struct tcphdr));
 	if (unlikely(err))
 		return err;
 
@@ -574,7 +563,7 @@ static int set_sctp(struct sk_buff *skb, struct sw_flow_key *key,
 	int err;
 	unsigned int sctphoff = skb_transport_offset(skb);
 
-	err = make_writable(skb, sctphoff + sizeof(struct sctphdr));
+	err = skb_ensure_writable(skb, sctphoff + sizeof(struct sctphdr));
 	if (unlikely(err))
 		return err;