NFC: Reserve tx head and tail room

We can have the NFC core layer allocating the tx head and tail
room for the drivers and avoid 1 or more SKBs copy on write on
the Tx path.

Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

2 files changed, 11 insertions, 8 deletions

diff --git a/net/nfc/core.c b/net/nfc/core.c
index b6fd4e1f2057..284e2f6a14ff 100644
--- a/net/nfc/core.c
+++ b/net/nfc/core.c
@@ -322,7 +322,9 @@ struct nfc_dev *nfc_get_device(unsigned idx)
  * @supported_protocols: NFC protocols supported by the device
  */
 struct nfc_dev *nfc_allocate_device(struct nfc_ops *ops,
-                                        u32 supported_protocols)
+                                        u32 supported_protocols,
+                                        int tx_headroom,
+                                        int tx_tailroom)
 {
         static atomic_t dev_no = ATOMIC_INIT(0);
         struct nfc_dev *dev;
@@ -345,6 +347,8 @@ struct nfc_dev *nfc_allocate_device(struct nfc_ops *ops,
 
         dev->ops = ops;
         dev->supported_protocols = supported_protocols;
+        dev->tx_headroom = tx_headroom;
+        dev->tx_tailroom = tx_tailroom;
 
         spin_lock_init(&dev->targets_lock);
         nfc_genl_data_init(&dev->genl_data);
diff --git a/net/nfc/rawsock.c b/net/nfc/rawsock.c
index 52de84a55115..9fd652a51424 100644
--- a/net/nfc/rawsock.c
+++ b/net/nfc/rawsock.c
@@ -123,11 +123,7 @@ error:
 
 static int rawsock_add_header(struct sk_buff *skb)
 {
-
-        if (skb_cow_head(skb, 1))
-                return -ENOMEM;
-
-        *skb_push(skb, 1) = 0;
+        *skb_push(skb, NFC_HEADER_SIZE) = 0;
 
         return 0;
 }
@@ -197,6 +193,7 @@ static int rawsock_sendmsg(struct kiocb *iocb, struct socket *sock,
                                         struct msghdr *msg, size_t len)
 {
         struct sock *sk = sock->sk;
+        struct nfc_dev *dev = nfc_rawsock(sk)->dev;
         struct sk_buff *skb;
         int rc;
 
@@ -208,11 +205,13 @@ static int rawsock_sendmsg(struct kiocb *iocb, struct socket *sock,
         if (sock->state != SS_CONNECTED)
                 return -ENOTCONN;
 
-        skb = sock_alloc_send_skb(sk, len, msg->msg_flags & MSG_DONTWAIT,
-                                                                        &rc);
+        skb = sock_alloc_send_skb(sk, len + dev->tx_headroom + dev->tx_tailroom + NFC_HEADER_SIZE,
+                                        msg->msg_flags & MSG_DONTWAIT, &rc);
         if (!skb)
                 return rc;
 
+        skb_reserve(skb, dev->tx_headroom + NFC_HEADER_SIZE);
+
         rc = memcpy_fromiovec(skb_put(skb, len), msg->msg_iov, len);
         if (rc < 0) {
                 kfree_skb(skb);