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>

5 files changed, 22 insertions, 23 deletions

diff --git a/drivers/nfc/pn533.c b/drivers/nfc/pn533.c
index c77e0543e502..f81a93e5b59d 100644
--- a/drivers/nfc/pn533.c
+++ b/drivers/nfc/pn533.c
@@ -1246,7 +1246,6 @@ static int pn533_data_exchange_tx_frame(struct pn533 *dev, struct sk_buff *skb)
 {
         int payload_len = skb->len;
         struct pn533_frame *out_frame;
-        struct sk_buff *discarded;
         u8 tg;
 
         nfc_dev_dbg(&dev->interface->dev, "%s - Sending %d bytes", __func__,
@@ -1260,18 +1259,6 @@ static int pn533_data_exchange_tx_frame(struct pn533 *dev, struct sk_buff *skb)
                 return -ENOSYS;
         }
 
-        /* Reserving header space */
-        if (skb_cow_head(skb, PN533_CMD_DATAEXCH_HEAD_LEN)) {
-                nfc_dev_err(&dev->interface->dev, "Error to add header data");
-                return -ENOMEM;
-        }
-
-        /* Reserving tail space, see pn533_tx_frame_finish */
-        if (skb_cow_data(skb, PN533_FRAME_TAIL_SIZE, &discarded) < 0) {
-                nfc_dev_err(&dev->interface->dev, "Error to add tail data");
-                return -ENOMEM;
-        }
-
         skb_push(skb, PN533_CMD_DATAEXCH_HEAD_LEN);
         out_frame = (struct pn533_frame *) skb->data;
 
@@ -1536,7 +1523,9 @@ static int pn533_probe(struct usb_interface *interface,
                         | NFC_PROTO_ISO14443_MASK
                         | NFC_PROTO_NFC_DEP_MASK;
 
-        dev->nfc_dev = nfc_allocate_device(&pn533_nfc_ops, protocols);
+        dev->nfc_dev = nfc_allocate_device(&pn533_nfc_ops, protocols,
+                                           PN533_CMD_DATAEXCH_HEAD_LEN,
+                                           PN533_FRAME_TAIL_SIZE);
         if (!dev->nfc_dev)
                 goto kill_tasklet;
 
diff --git a/include/linux/nfc.h b/include/linux/nfc.h
index 330a4c5db588..c525e0b5876b 100644
--- a/include/linux/nfc.h
+++ b/include/linux/nfc.h
@@ -123,4 +123,6 @@ struct sockaddr_nfc {
 #define NFC_SOCKPROTO_RAW       0
 #define NFC_SOCKPROTO_MAX       1
 
+#define NFC_HEADER_SIZE 1
+
 #endif /*__LINUX_NFC_H */
diff --git a/include/net/nfc.h b/include/net/nfc.h
index cc0130312f70..87b51fe15b70 100644
--- a/include/net/nfc.h
+++ b/include/net/nfc.h
@@ -82,6 +82,9 @@ struct nfc_dev {
         struct nfc_genl_data genl_data;
         u32 supported_protocols;
 
+        int tx_headroom;
+        int tx_tailroom;
+
         struct nfc_ops *ops;
 };
 #define to_nfc_dev(_dev) container_of(_dev, struct nfc_dev, dev)
@@ -89,7 +92,9 @@ struct nfc_dev {
 extern struct class nfc_class;
 
 struct nfc_dev *nfc_allocate_device(struct nfc_ops *ops,
-                                        u32 supported_protocols);
+                                        u32 supported_protocols,
+                                        int tx_headroom,
+                                        int tx_tailroom);
 
 /**
  * nfc_free_device - free nfc device
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);