[SK_BUFF]: Introduce skb_copy_to_linear_data{_offset}

To clearly state the intent of copying to linear sk_buffs, _offset being a
overly long variant but interesting for the sake of saving some bytes.

Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
diff --git a/net/atm/mpc.c b/net/atm/mpc.c
index 4d2592c..813e08d 100644
--- a/net/atm/mpc.c
+++ b/net/atm/mpc.c
@@ -504,11 +504,13 @@
 		tagged_llc_snap_hdr.tag = entry->ctrl_info.tag;
 		skb_pull(skb, ETH_HLEN);                       /* get rid of Eth header */
 		skb_push(skb, sizeof(tagged_llc_snap_hdr));    /* add LLC/SNAP header   */
-		memcpy(skb->data, &tagged_llc_snap_hdr, sizeof(tagged_llc_snap_hdr));
+		skb_copy_to_linear_data(skb, &tagged_llc_snap_hdr,
+					sizeof(tagged_llc_snap_hdr));
 	} else {
 		skb_pull(skb, ETH_HLEN);                        /* get rid of Eth header */
 		skb_push(skb, sizeof(struct llc_snap_hdr));     /* add LLC/SNAP header + tag  */
-		memcpy(skb->data, &llc_snap_mpoa_data, sizeof(struct llc_snap_hdr));
+		skb_copy_to_linear_data(skb, &llc_snap_mpoa_data,
+					sizeof(struct llc_snap_hdr));
 	}
 
 	atomic_add(skb->truesize, &sk_atm(entry->shortcut)->sk_wmem_alloc);
@@ -711,7 +713,8 @@
 		return;
 	}
 	skb_push(new_skb, eg->ctrl_info.DH_length);     /* add MAC header */
-	memcpy(new_skb->data, eg->ctrl_info.DLL_header, eg->ctrl_info.DH_length);
+	skb_copy_to_linear_data(new_skb, eg->ctrl_info.DLL_header,
+				eg->ctrl_info.DH_length);
 	new_skb->protocol = eth_type_trans(new_skb, dev);
 	skb_reset_network_header(new_skb);
 
@@ -936,7 +939,7 @@
 	if (skb == NULL)
 		return -ENOMEM;
 	skb_put(skb, sizeof(struct k_message));
-	memcpy(skb->data, mesg, sizeof(struct k_message));
+	skb_copy_to_linear_data(skb, mesg, sizeof(*mesg));
 	atm_force_charge(mpc->mpoad_vcc, skb->truesize);
 
 	sk = sk_atm(mpc->mpoad_vcc);