xen/usbfront: use xenbus_setup_ring() and xenbus_teardown_ring()

Simplify xen-hcd's ring creation and removal via xenbus_setup_ring()
and xenbus_teardown_ring().
Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juergen Gross <jgross@suse.com>

drivers/usb/host/xen-hcd.c

@@ -1098,19 +1098,10 @@ static void xenhcd_destroy_rings(struct xenhcd_info *info)
 		unbind_from_irqhandler(info->irq, info);
 	info->irq = 0;
 
-	if (info->urb_ring_ref != INVALID_GRANT_REF) {
-		gnttab_end_foreign_access(info->urb_ring_ref,
-					  (unsigned long)info->urb_ring.sring);
-		info->urb_ring_ref = INVALID_GRANT_REF;
-	}
-	info->urb_ring.sring = NULL;
-
-	if (info->conn_ring_ref != INVALID_GRANT_REF) {
-		gnttab_end_foreign_access(info->conn_ring_ref,
-					  (unsigned long)info->conn_ring.sring);
-		info->conn_ring_ref = INVALID_GRANT_REF;
-	}
-	info->conn_ring.sring = NULL;
+	xenbus_teardown_ring((void **)&info->urb_ring.sring, 1,
+			     &info->urb_ring_ref);
+	xenbus_teardown_ring((void **)&info->conn_ring.sring, 1,
+			     &info->conn_ring_ref);
 }
 
 static int xenhcd_setup_rings(struct xenbus_device *dev,
@@ -1118,46 +1109,24 @@ static int xenhcd_setup_rings(struct xenbus_device *dev,
 {
 	struct xenusb_urb_sring *urb_sring;
 	struct xenusb_conn_sring *conn_sring;
-	grant_ref_t gref;
 	int err;
 
-	info->urb_ring_ref = INVALID_GRANT_REF;
 	info->conn_ring_ref = INVALID_GRANT_REF;
-
-	urb_sring = (struct xenusb_urb_sring *)get_zeroed_page(
-							GFP_NOIO | __GFP_HIGH);
-	if (!urb_sring) {
-		xenbus_dev_fatal(dev, -ENOMEM, "allocating urb ring");
-		return -ENOMEM;
-	}
-	SHARED_RING_INIT(urb_sring);
-	FRONT_RING_INIT(&info->urb_ring, urb_sring, PAGE_SIZE);
-
-	err = xenbus_grant_ring(dev, urb_sring, 1, &gref);
-	if (err < 0) {
-		free_page((unsigned long)urb_sring);
-		info->urb_ring.sring = NULL;
-		goto fail;
-	}
-	info->urb_ring_ref = gref;
-
-	conn_sring = (struct xenusb_conn_sring *)get_zeroed_page(
-							GFP_NOIO | __GFP_HIGH);
-	if (!conn_sring) {
-		xenbus_dev_fatal(dev, -ENOMEM, "allocating conn ring");
-		err = -ENOMEM;
-		goto fail;
+	err = xenbus_setup_ring(dev, GFP_NOIO | __GFP_HIGH,
+				(void **)&urb_sring, 1, &info->urb_ring_ref);
+	if (err) {
+		xenbus_dev_fatal(dev, err, "allocating urb ring");
+		return err;
 	}
-	SHARED_RING_INIT(conn_sring);
-	FRONT_RING_INIT(&info->conn_ring, conn_sring, PAGE_SIZE);
+	XEN_FRONT_RING_INIT(&info->urb_ring, urb_sring, PAGE_SIZE);
 
-	err = xenbus_grant_ring(dev, conn_sring, 1, &gref);
-	if (err < 0) {
-		free_page((unsigned long)conn_sring);
-		info->conn_ring.sring = NULL;
+	err = xenbus_setup_ring(dev, GFP_NOIO | __GFP_HIGH,
+				(void **)&conn_sring, 1, &info->conn_ring_ref);
+	if (err) {
+		xenbus_dev_fatal(dev, err, "allocating conn ring");
 		goto fail;
 	}
-	info->conn_ring_ref = gref;
+	XEN_FRONT_RING_INIT(&info->conn_ring, conn_sring, PAGE_SIZE);
 
 	err = xenbus_alloc_evtchn(dev, &info->evtchn);
 	if (err) {