[PATCH 2/3] skbuff: skb_cow_head not used in some drivers.

[PATCH 2/3] skbuff: skb_cow_head not used in some drivers.

[Dave Wiltshire]

There is a helper function skb_cow_head which checks if a skb needs to
be expanded. This was unused in some drivers. Fixing that leads to
cleaner code in the drivers.

Signed-off-by: Dave Wiltshire <david.wiltshire@gmx.com>
---
 drivers/net/ethernet/atheros/atl1c/atl1c_main.c   |    8 ++------
 drivers/net/ethernet/atheros/atl1e/atl1e_main.c   |    8 ++------
 drivers/net/ethernet/atheros/atlx/atl1.c          |    8 ++------
 drivers/net/ethernet/broadcom/tg3.c               |    3 +--
 drivers/net/ethernet/brocade/bna/bnad.c           |   11 +++--------
 drivers/net/ethernet/intel/e1000/e1000_main.c     |    8 ++------
 drivers/net/ethernet/intel/e1000e/netdev.c        |    8 ++------
 drivers/net/ethernet/intel/igb/igb_main.c         |    7 ++-----
 drivers/net/ethernet/intel/igbvf/netdev.c         |   11 +++--------
 drivers/net/ethernet/intel/ixgb/ixgb_main.c       |    8 ++------
 drivers/net/ethernet/intel/ixgbe/ixgbe_main.c     |   10 +++-------
 drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c |    7 ++-----
 drivers/net/ethernet/jme.c                        |    3 +--
 drivers/net/ethernet/qlogic/qlge/qlge_main.c      |    8 ++------
 drivers/net/wimax/i2400m/netdev.c                 |    3 +--
 15 files changed, 30 insertions(+), 81 deletions(-)

diff --git a/drivers/net/ethernet/atheros/atl1c/atl1c_main.c b/drivers/net/ethernet/atheros/atl1c/atl1c_main.c
index 786a874..8c69cda 100644
--- a/drivers/net/ethernet/atheros/atl1c/atl1c_main.c
+++ b/drivers/net/ethernet/atheros/atl1c/atl1c_main.c
@@ -1931,14 +1931,10 @@ static int atl1c_tso_csum(struct atl1c_adapter *adapter,
 	u8 hdr_len;
 	u32 real_len;
 	unsigned short offload_type;
-	int err;
 
 	if (skb_is_gso(skb)) {
-		if (skb_header_cloned(skb)) {
-			err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
-			if (unlikely(err))
-				return -1;
-		}
+		if (unlikely(skb_cow_head(skb, 0)))
+			return -1;
 		offload_type = skb_shinfo(skb)->gso_type;
 
 		if (offload_type & SKB_GSO_TCPV4) {
diff --git a/drivers/net/ethernet/atheros/atl1e/atl1e_main.c b/drivers/net/ethernet/atheros/atl1e/atl1e_main.c
index 895f537..ff10d03 100644
--- a/drivers/net/ethernet/atheros/atl1e/atl1e_main.c
+++ b/drivers/net/ethernet/atheros/atl1e/atl1e_main.c
@@ -1599,14 +1599,10 @@ static int atl1e_tso_csum(struct atl1e_adapter *adapter,
 	u8 hdr_len;
 	u32 real_len;
 	unsigned short offload_type;
-	int err;
 
 	if (skb_is_gso(skb)) {
-		if (skb_header_cloned(skb)) {
-			err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
-			if (unlikely(err))
-				return -1;
-		}
+		if (unlikely(skb_cow_head(skb, 0)))
+			return -1;
 		offload_type = skb_shinfo(skb)->gso_type;
 
 		if (offload_type & SKB_GSO_TCPV4) {
diff --git a/drivers/net/ethernet/atheros/atlx/atl1.c b/drivers/net/ethernet/atheros/atlx/atl1.c
index 538211d..da7169c 100644
--- a/drivers/net/ethernet/atheros/atlx/atl1.c
+++ b/drivers/net/ethernet/atheros/atlx/atl1.c
@@ -2115,14 +2115,10 @@ static int atl1_tso(struct atl1_adapter *adapter, struct sk_buff *skb,
 {
 	u8 hdr_len, ip_off;
 	u32 real_len;
-	int err;
 
 	if (skb_shinfo(skb)->gso_size) {
-		if (skb_header_cloned(skb)) {
-			err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
-			if (unlikely(err))
-				return -1;
-		}
+		if (unlikely(skb_cow_head(skb, 0)))
+			return -1;
 
 		if (skb->protocol == htons(ETH_P_IP)) {
 			struct iphdr *iph = ip_hdr(skb);
diff --git a/drivers/net/ethernet/broadcom/tg3.c b/drivers/net/ethernet/broadcom/tg3.c
index 28a645f..6daf8f9 100644
--- a/drivers/net/ethernet/broadcom/tg3.c
+++ b/drivers/net/ethernet/broadcom/tg3.c
@@ -7803,8 +7803,7 @@ static netdev_tx_t tg3_start_xmit(struct sk_buff *skb, struct net_device *dev)
 		struct iphdr *iph;
 		u32 tcp_opt_len, hdr_len;
 
-		if (skb_header_cloned(skb) &&
-		    pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
+		if (skb_cow_head(skb, 0))
 			goto drop;
 
 		iph = ip_hdr(skb);
diff --git a/drivers/net/ethernet/brocade/bna/bnad.c b/drivers/net/ethernet/brocade/bna/bnad.c
index b78e69e..ba5325a 100644
--- a/drivers/net/ethernet/brocade/bna/bnad.c
+++ b/drivers/net/ethernet/brocade/bna/bnad.c
@@ -2303,14 +2303,9 @@ bnad_mbox_irq_sync(struct bnad *bnad)
 static int
 bnad_tso_prepare(struct bnad *bnad, struct sk_buff *skb)
 {
-	int err;
-
-	if (skb_header_cloned(skb)) {
-		err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
-		if (err) {
-			BNAD_UPDATE_CTR(bnad, tso_err);
-			return err;
-		}
+	if (skb_cow_head(skb, 0)) {
+		BNAD_UPDATE_CTR(bnad, tso_err);
+		return -ENOMEM;
 	}
 
 	/*
diff --git a/drivers/net/ethernet/intel/e1000/e1000_main.c b/drivers/net/ethernet/intel/e1000/e1000_main.c
index 59ad007..828d850 100644
--- a/drivers/net/ethernet/intel/e1000/e1000_main.c
+++ b/drivers/net/ethernet/intel/e1000/e1000_main.c
@@ -2704,14 +2704,10 @@ static int e1000_tso(struct e1000_adapter *adapter,
 	u32 cmd_length = 0;
 	u16 ipcse = 0, tucse, mss;
 	u8 ipcss, ipcso, tucss, tucso, hdr_len;
-	int err;
 
 	if (skb_is_gso(skb)) {
-		if (skb_header_cloned(skb)) {
-			err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
-			if (err)
-				return err;
-		}
+		if (skb_cow_head(skb, 0))
+			return -ENOMEM;
 
 		hdr_len = skb_transport_offset(skb) + tcp_hdrlen(skb);
 		mss = skb_shinfo(skb)->gso_size;
diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c
index 77f81cb..da3de16 100644
--- a/drivers/net/ethernet/intel/e1000e/netdev.c
+++ b/drivers/net/ethernet/intel/e1000e/netdev.c
@@ -5070,12 +5070,8 @@ static int e1000_tso(struct e1000_ring *tx_ring, struct sk_buff *skb)
 	if (!skb_is_gso(skb))
 		return 0;
 
-	if (skb_header_cloned(skb)) {
-		int err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
-
-		if (err)
-			return err;
-	}
+	if (skb_cow_head(skb, 0))
+		return -ENOMEM;
 
 	hdr_len = skb_transport_offset(skb) + tcp_hdrlen(skb);
 	mss = skb_shinfo(skb)->gso_size;
diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index 6a0c1b6..917cacb 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -4292,11 +4292,8 @@ static int igb_tso(struct igb_ring *tx_ring,
 	if (!skb_is_gso(skb))
 		return 0;
 
-	if (skb_header_cloned(skb)) {
-		int err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
-		if (err)
-			return err;
-	}
+	if (skb_cow_head(skb, 0))
+		return -ENOMEM;
 
 	/* ADV DTYP TUCMD MKRLOC/ISCSIHEDLEN */
 	type_tucmd = E1000_ADVTXD_TUCMD_L4T_TCP;
diff --git a/drivers/net/ethernet/intel/igbvf/netdev.c b/drivers/net/ethernet/intel/igbvf/netdev.c
index 93eb7ee..5be1dc2 100644
--- a/drivers/net/ethernet/intel/igbvf/netdev.c
+++ b/drivers/net/ethernet/intel/igbvf/netdev.c
@@ -1911,19 +1911,14 @@ static int igbvf_tso(struct igbvf_adapter *adapter,
 {
 	struct e1000_adv_tx_context_desc *context_desc;
 	unsigned int i;
-	int err;
 	struct igbvf_buffer *buffer_info;
 	u32 info = 0, tu_cmd = 0;
 	u32 mss_l4len_idx, l4len;
 	*hdr_len = 0;
 
-	if (skb_header_cloned(skb)) {
-		err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
-		if (err) {
-			dev_err(&adapter->pdev->dev,
-			        "igbvf_tso returning an error\n");
-			return err;
-		}
+	if (skb_cow_head(skb, 0)) {
+		dev_err(&adapter->pdev->dev, "igbvf_tso returning an error\n");
+		return -ENOMEM;
 	}
 
 	l4len = tcp_hdrlen(skb);
diff --git a/drivers/net/ethernet/intel/ixgb/ixgb_main.c b/drivers/net/ethernet/intel/ixgb/ixgb_main.c
index fce3e92..59e768e 100644
--- a/drivers/net/ethernet/intel/ixgb/ixgb_main.c
+++ b/drivers/net/ethernet/intel/ixgb/ixgb_main.c
@@ -1226,17 +1226,13 @@ ixgb_tso(struct ixgb_adapter *adapter, struct sk_buff *skb)
 	unsigned int i;
 	u8 ipcss, ipcso, tucss, tucso, hdr_len;
 	u16 ipcse, tucse, mss;
-	int err;
 
 	if (likely(skb_is_gso(skb))) {
 		struct ixgb_buffer *buffer_info;
 		struct iphdr *iph;
 
-		if (skb_header_cloned(skb)) {
-			err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
-			if (err)
-				return err;
-		}
+		if (skb_cow_head(skb, 0))
+			return -ENOMEM;
 
 		hdr_len = skb_transport_offset(skb) + tcp_hdrlen(skb);
 		mss = skb_shinfo(skb)->gso_size;
diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
index 047ebaa..57a0c00 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
@@ -6060,11 +6060,8 @@ static int ixgbe_tso(struct ixgbe_ring *tx_ring,
 	if (!skb_is_gso(skb))
 		return 0;
 
-	if (skb_header_cloned(skb)) {
-		int err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
-		if (err)
-			return err;
-	}
+	if (skb_cow_head(skb, 0))
+		return -ENOMEM;
 
 	/* ADV DTYP TUCMD MKRLOC/ISCSIHEDLEN */
 	type_tucmd = IXGBE_ADVTXD_TUCMD_L4T_TCP;
@@ -6609,8 +6606,7 @@ netdev_tx_t ixgbe_xmit_frame_ring(struct sk_buff *skb,
 					IXGBE_TX_FLAGS_VLAN_PRIO_SHIFT;
 		if (tx_flags & IXGBE_TX_FLAGS_SW_VLAN) {
 			struct vlan_ethhdr *vhdr;
-			if (skb_header_cloned(skb) &&
-			    pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
+			if (skb_cow_head(skb, 0))
 				goto out_drop;
 			vhdr = (struct vlan_ethhdr *)skb->data;
 			vhdr->h_vlan_TCI = htons(tx_flags >>
diff --git a/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c b/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
index 1f5166a..088402e 100644
--- a/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
+++ b/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
@@ -2726,11 +2726,8 @@ static int ixgbevf_tso(struct ixgbevf_ring *tx_ring,
 	if (!skb_is_gso(skb))
 		return 0;
 
-	if (skb_header_cloned(skb)) {
-		int err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
-		if (err)
-			return err;
-	}
+	if (skb_cow_head(skb, 0))
+		return -ENOMEM;
 
 	/* ADV DTYP TUCMD MKRLOC/ISCSIHEDLEN */
 	type_tucmd = IXGBE_ADVTXD_TUCMD_L4T_TCP;
diff --git a/drivers/net/ethernet/jme.c b/drivers/net/ethernet/jme.c
index 7fbe6ab..7493db2 100644
--- a/drivers/net/ethernet/jme.c
+++ b/drivers/net/ethernet/jme.c
@@ -2057,8 +2057,7 @@ static int
 jme_expand_header(struct jme_adapter *jme, struct sk_buff *skb)
 {
 	if (unlikely(skb_shinfo(skb)->gso_size &&
-			skb_header_cloned(skb) &&
-			pskb_expand_head(skb, 0, 0, GFP_ATOMIC))) {
+		     skb_cow_head(skb, 0))) {
 		dev_kfree_skb(skb);
 		return -1;
 	}
diff --git a/drivers/net/ethernet/qlogic/qlge/qlge_main.c b/drivers/net/ethernet/qlogic/qlge/qlge_main.c
index 2553cf4..ab7e177 100644
--- a/drivers/net/ethernet/qlogic/qlge/qlge_main.c
+++ b/drivers/net/ethernet/qlogic/qlge/qlge_main.c
@@ -2496,12 +2496,8 @@ static int ql_tso(struct sk_buff *skb, struct ob_mac_tso_iocb_req *mac_iocb_ptr)
 {
 
 	if (skb_is_gso(skb)) {
-		int err;
-		if (skb_header_cloned(skb)) {
-			err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
-			if (err)
-				return err;
-		}
+		if (skb_cow_head(skb, 0))
+			return -ENOMEM;
 
 		mac_iocb_ptr->opcode = OPCODE_OB_MAC_TSO_IOCB;
 		mac_iocb_ptr->flags3 |= OB_MAC_TSO_IOCB_IC;
diff --git a/drivers/net/wimax/i2400m/netdev.c b/drivers/net/wimax/i2400m/netdev.c
index 4889613..a9970f1 100644
--- a/drivers/net/wimax/i2400m/netdev.c
+++ b/drivers/net/wimax/i2400m/netdev.c
@@ -374,8 +374,7 @@ netdev_tx_t i2400m_hard_start_xmit(struct sk_buff *skb,
 
 	d_fnstart(3, dev, "(skb %p net_dev %p)\n", skb, net_dev);
 
-	if (skb_header_cloned(skb) && 
-	    pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
+	if (skb_cow_head(skb, 0))
 		goto drop;
 
 	if (i2400m->state == I2400M_SS_IDLE)
-- 
1.7.10.4

[PATCH 3/3] skbuff: Added new helper function skb_cow_clone_head.

[Dave Wiltshire]

In a few different drivers there is a check of (skb_cloned &&
!skb_clone_writable) before then using pskb_expand_head to copy the skb
if that is required. There are already some skb_cow_* functions for
other conditions, so added this one and changed the call sites.

Signed-off-by: Dave Wiltshire <david.wiltshire-KK0ffGbhmjU@public.gmane.org>
---
 include/linux/skbuff.h    |   14 ++++++++++++++
 net/core/dev.c            |    8 ++------
 net/openvswitch/actions.c |   22 +++++++---------------
 net/sched/act_csum.c      |    8 ++------
 net/sched/act_nat.c       |   18 +++++-------------
 5 files changed, 30 insertions(+), 40 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index a7393ad..7d18541 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2154,6 +2154,20 @@ static inline int skb_cow_head(struct sk_buff *skb, unsigned int headroom)
 }
 
 /**
+ * skb_cow_clone_head
+ * @skb: buffer to cow
+ * @len: length up to which to write
+ *
+ * This function is identical to skb_cow and sb_cow_head except that we
+ * replace the skb_cloned check by skb_cloned && !skb_clone_writable.
+ *
+ */
+static inline int skb_cow_clone_head(struct sk_buff *skb, unsigned int len)
+{
+	return __skb_cow(skb, 0, skb_cloned(skb) && !skb_clone_writable(skb, len));
+}
+
+/**
  *	skb_padto	- pad an skbuff up to a minimal size
  *	@skb: buffer to pad
  *	@len: minimal length
diff --git a/net/core/dev.c b/net/core/dev.c
index fa007db..1fb1cf5 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2222,12 +2222,8 @@ int skb_checksum_help(struct sk_buff *skb)
 	offset += skb->csum_offset;
 	BUG_ON(offset + sizeof(__sum16) > skb_headlen(skb));
 
-	if (skb_cloned(skb) &&
-	    !skb_clone_writable(skb, offset + sizeof(__sum16))) {
-		ret = pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
-		if (ret)
-			goto out;
-	}
+	if (skb_cow_clone_head(skb, offset + sizeof(__sum16)))
+		goto out;
 
 	*(__sum16 *)(skb->data + offset) = csum_fold(csum);
 out_set_summed:
diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c
index 894b6cb..3d3a9d0 100644
--- a/net/openvswitch/actions.c
+++ b/net/openvswitch/actions.c
@@ -38,21 +38,13 @@
 static int do_execute_actions(struct datapath *dp, struct sk_buff *skb,
 			const struct nlattr *attr, int len, bool keep_skb);
 
-static int make_writable(struct sk_buff *skb, int write_len)
-{
-	if (!skb_cloned(skb) || skb_clone_writable(skb, write_len))
-		return 0;
-
-	return pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
-}
-
 /* remove VLAN header from packet and update csum accordingly. */
 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_cow_clone_head(skb, VLAN_ETH_HLEN);
 	if (unlikely(err))
 		return err;
 
@@ -126,7 +118,7 @@ static int set_eth_addr(struct sk_buff *skb,
 			const struct ovs_key_ethernet *eth_key)
 {
 	int err;
-	err = make_writable(skb, ETH_HLEN);
+	err = skb_cow_clone_head(skb, ETH_HLEN);
 	if (unlikely(err))
 		return err;
 
@@ -221,7 +213,7 @@ static int set_ipv4(struct sk_buff *skb, const struct ovs_key_ipv4 *ipv4_key)
 	struct iphdr *nh;
 	int err;
 
-	err = make_writable(skb, skb_network_offset(skb) +
+	err = skb_cow_clone_head(skb, skb_network_offset(skb) +
 				 sizeof(struct iphdr));
 	if (unlikely(err))
 		return err;
@@ -250,7 +242,7 @@ static int set_ipv6(struct sk_buff *skb, const struct ovs_key_ipv6 *ipv6_key)
 	__be32 *saddr;
 	__be32 *daddr;
 
-	err = make_writable(skb, skb_network_offset(skb) +
+	err = skb_cow_clone_head(skb, skb_network_offset(skb) +
 			    sizeof(struct ipv6hdr));
 	if (unlikely(err))
 		return err;
@@ -284,7 +276,7 @@ static int set_ipv6(struct sk_buff *skb, const struct ovs_key_ipv6 *ipv6_key)
 	return 0;
 }
 
-/* Must follow make_writable() since that can move the skb data. */
+/* Must follow skb_cow_clone_head() since that can move the skb data. */
 static void set_tp_port(struct sk_buff *skb, __be16 *port,
 			 __be16 new_port, __sum16 *check)
 {
@@ -313,7 +305,7 @@ static int set_udp(struct sk_buff *skb, const struct ovs_key_udp *udp_port_key)
 	struct udphdr *uh;
 	int err;
 
-	err = make_writable(skb, skb_transport_offset(skb) +
+	err = skb_cow_clone_head(skb, skb_transport_offset(skb) +
 				 sizeof(struct udphdr));
 	if (unlikely(err))
 		return err;
@@ -333,7 +325,7 @@ static int set_tcp(struct sk_buff *skb, const struct ovs_key_tcp *tcp_port_key)
 	struct tcphdr *th;
 	int err;
 
-	err = make_writable(skb, skb_transport_offset(skb) +
+	err = skb_cow_clone_head(skb, skb_transport_offset(skb) +
 				 sizeof(struct tcphdr));
 	if (unlikely(err))
 		return err;
diff --git a/net/sched/act_csum.c b/net/sched/act_csum.c
index 3a4c0ca..e7ff098 100644
--- a/net/sched/act_csum.c
+++ b/net/sched/act_csum.c
@@ -122,9 +122,7 @@ static void *tcf_csum_skb_nextlayer(struct sk_buff *skb,
 	int hl = ihl + jhl;
 
 	if (!pskb_may_pull(skb, ipl + ntkoff) || (ipl < hl) ||
-	    (skb_cloned(skb) &&
-	     !skb_clone_writable(skb, hl + ntkoff) &&
-	     pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
+	    skb_cow_clone_head(skb, hl + ntkoff))
 		return NULL;
 	else
 		return (void *)(skb_network_header(skb) + ihl);
@@ -382,9 +380,7 @@ static int tcf_csum_ipv4(struct sk_buff *skb, u32 update_flags)
 	}
 
 	if (update_flags & TCA_CSUM_UPDATE_FLAG_IPV4HDR) {
-		if (skb_cloned(skb) &&
-		    !skb_clone_writable(skb, sizeof(*iph) + ntkoff) &&
-		    pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
+		if (skb_cow_clone_head(skb, sizeof(*iph) + ntkoff))
 			goto fail;
 
 		ip_send_check(ip_hdr(skb));
diff --git a/net/sched/act_nat.c b/net/sched/act_nat.c
index 876f0ef..2b5b89c 100644
--- a/net/sched/act_nat.c
+++ b/net/sched/act_nat.c
@@ -144,9 +144,7 @@ static int tcf_nat(struct sk_buff *skb, const struct tc_action *a,
 		addr = iph->daddr;
 
 	if (!((old_addr ^ addr) & mask)) {
-		if (skb_cloned(skb) &&
-		    !skb_clone_writable(skb, sizeof(*iph) + noff) &&
-		    pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
+		if (skb_cow_clone_head(skb, sizeof(*iph) + noff))
 			goto drop;
 
 		new_addr &= mask;
@@ -174,9 +172,7 @@ static int tcf_nat(struct sk_buff *skb, const struct tc_action *a,
 		struct tcphdr *tcph;
 
 		if (!pskb_may_pull(skb, ihl + sizeof(*tcph) + noff) ||
-		    (skb_cloned(skb) &&
-		     !skb_clone_writable(skb, ihl + sizeof(*tcph) + noff) &&
-		     pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
+		    skb_cow_clone_head(skb, ihl + sizeof(*tcph) + noff))
 			goto drop;
 
 		tcph = (void *)(skb_network_header(skb) + ihl);
@@ -188,9 +184,7 @@ static int tcf_nat(struct sk_buff *skb, const struct tc_action *a,
 		struct udphdr *udph;
 
 		if (!pskb_may_pull(skb, ihl + sizeof(*udph) + noff) ||
-		    (skb_cloned(skb) &&
-		     !skb_clone_writable(skb, ihl + sizeof(*udph) + noff) &&
-		     pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
+		    skb_cow_clone_head(skb, ihl + sizeof(*udph) + noff))
 			goto drop;
 
 		udph = (void *)(skb_network_header(skb) + ihl);
@@ -230,10 +224,8 @@ static int tcf_nat(struct sk_buff *skb, const struct tc_action *a,
 		if ((old_addr ^ addr) & mask)
 			break;
 
-		if (skb_cloned(skb) &&
-		    !skb_clone_writable(skb, ihl + sizeof(*icmph) +
-					     sizeof(*iph) + noff) &&
-		    pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
+		if (skb_cow_clone_head(skb, ihl + sizeof(*icmph) +
+					    sizeof(*iph) + noff))
 			goto drop;
 
 		icmph = (void *)(skb_network_header(skb) + ihl);
-- 
1.7.10.4

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Re: [PATCH 3/3] skbuff: Added new helper function skb_cow_clone_head.

[Ben Hutchings]

On Wed, 2013-06-12 at 22:40 +1000, Dave Wiltshire wrote:
> In a few different drivers there is a check of (skb_cloned &&
> !skb_clone_writable) before then using pskb_expand_head to copy the skb
> if that is required. There are already some skb_cow_* functions for
> other conditions, so added this one and changed the call sites.
> 
> Signed-off-by: Dave Wiltshire <david.wiltshire@gmx.com>
> ---
>  include/linux/skbuff.h    |   14 ++++++++++++++
>  net/core/dev.c            |    8 ++------
>  net/openvswitch/actions.c |   22 +++++++---------------
>  net/sched/act_csum.c      |    8 ++------
>  net/sched/act_nat.c       |   18 +++++-------------
>  5 files changed, 30 insertions(+), 40 deletions(-)
> 
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index a7393ad..7d18541 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -2154,6 +2154,20 @@ static inline int skb_cow_head(struct sk_buff *skb, unsigned int headroom)
>  }
>  
>  /**
> + * skb_cow_clone_head

This is a missing a short description after the name.

Ben.

> + * @skb: buffer to cow
> + * @len: length up to which to write
> + *
> + * This function is identical to skb_cow and sb_cow_head except that we
> + * replace the skb_cloned check by skb_cloned && !skb_clone_writable.
> + *
> + */
> +static inline int skb_cow_clone_head(struct sk_buff *skb, unsigned int len)
> +{
> +	return __skb_cow(skb, 0, skb_cloned(skb) && !skb_clone_writable(skb, len));
> +}
[...]

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.