net: xen-netback: use API provided by xenbus module to map rings

The xenbus module provides xenbus_map_ring_valloc() and
xenbus_map_ring_vfree().  Use these to map the Tx and Rx ring pages
granted by the frontend.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
index 161f207..94b79c3 100644
--- a/drivers/net/xen-netback/common.h
+++ b/drivers/net/xen-netback/common.h
@@ -58,10 +58,6 @@
 	u8               fe_dev_addr[6];
 
 	/* Physical parameters of the comms window. */
-	grant_handle_t   tx_shmem_handle;
-	grant_ref_t      tx_shmem_ref;
-	grant_handle_t   rx_shmem_handle;
-	grant_ref_t      rx_shmem_ref;
 	unsigned int     irq;
 
 	/* List of frontends to notify after a batch of frames sent. */
@@ -70,8 +66,6 @@
 	/* The shared rings and indexes. */
 	struct xen_netif_tx_back_ring tx;
 	struct xen_netif_rx_back_ring rx;
-	struct vm_struct *tx_comms_area;
-	struct vm_struct *rx_comms_area;
 
 	/* Frontend feature information. */
 	u8 can_sg:1;
@@ -106,6 +100,11 @@
 	wait_queue_head_t waiting_to_free;
 };
 
+static inline struct xenbus_device *xenvif_to_xenbus_device(struct xenvif *vif)
+{
+	return to_xenbus_device(vif->dev->dev.parent);
+}
+
 #define XEN_NETIF_TX_RING_SIZE __CONST_RING_SIZE(xen_netif_tx, PAGE_SIZE)
 #define XEN_NETIF_RX_RING_SIZE __CONST_RING_SIZE(xen_netif_rx, PAGE_SIZE)