net{back,front}: minor cleanup

- use PFN_UP() instead of open coding it
- make xennet_get_extras() static
- tighten packing of struct netbk_rx_meta
- guard GNTTABOP_unmap_and_replace by CONFIG_XEN_COMPAT check (mostly
  for documentation purposes)

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/drivers/xen/netfront/netfront.c
+++ b/drivers/xen/netfront/netfront.c
@@ -33,6 +33,7 @@
 #include <linux/module.h>
 #include <linux/version.h>
 #include <linux/kernel.h>
+#include <linux/pfn.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/string.h>
@@ -971,7 +972,7 @@ static int network_start_xmit(struct sk_
 		goto drop;
 	}
 
-	frags += (offset + len + PAGE_SIZE - 1) / PAGE_SIZE;
+	frags += PFN_UP(offset + len);
 	if (unlikely(frags > MAX_SKB_FRAGS + 1)) {
 		printk(KERN_ALERT "xennet: skb rides the rocket: %d frags\n",
 		       frags);
@@ -1102,9 +1103,8 @@ static void xennet_move_rx_slot(struct n
 	np->rx.req_prod_pvt++;
 }
 
-int xennet_get_extras(struct netfront_info *np,
-		      struct netif_extra_info *extras, RING_IDX rp)
-
+static int xennet_get_extras(struct netfront_info *np,
+			     struct netif_extra_info *extras, RING_IDX rp)
 {
 	struct netif_extra_info *extra;
 	RING_IDX cons = np->rx.rsp_cons;
--- a/drivers/xen/netback/netback.c
+++ b/drivers/xen/netback/netback.c
@@ -46,7 +46,7 @@
 
 struct netbk_rx_meta {
 	skb_frag_t frag;
-	int id;
+	u16 id;
 	u8 copy:1;
 };
 
@@ -1726,10 +1726,12 @@ static int __init netback_init(void)
 
 	netbk_copy_skb_mode = NETBK_DONT_COPY_SKB;
 	if (MODPARM_copy_skb) {
+#if CONFIG_XEN_COMPAT < 0x030200
 		if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_and_replace,
 					      NULL, 0))
 			netbk_copy_skb_mode = NETBK_ALWAYS_COPY_SKB;
 		else
+#endif
 			netbk_copy_skb_mode = NETBK_DELAYED_COPY_SKB;
 	}