xen/blkback: add accessor for xenbus backend device

Since backend_info is hidden away now.
Signed-off-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

drivers/xen/blkback/common.h

@@ -136,4 +136,6 @@ int blkif_schedule(void *arg);
 int blkback_barrier(struct xenbus_transaction xbt,
 		    struct backend_info *be, int state);
 
+struct xenbus_device *blkback_xenbus(struct backend_info *be);
+
 #endif /* __BLKIF__BACKEND__COMMON_H__ */

drivers/xen/blkback/vbd.c

@@ -123,7 +123,7 @@ void vbd_resize(blkif_t *blkif)
 	struct vbd *vbd = &blkif->vbd;
 	struct xenbus_transaction xbt;
 	int err;
-	struct xenbus_device *dev = blkif->be->dev;
+	struct xenbus_device *dev = blkback_xenbus(blkif->be);
 	unsigned long long new_size = vbd_size(vbd);
 
 	printk(KERN_INFO "VBD Resize: new size %Lu\n", new_size);

drivers/xen/blkback/xenbus.c

@@ -42,6 +42,11 @@ static int connect_ring(struct backend_info *);
 static void backend_changed(struct xenbus_watch *, const char **,
 			    unsigned int);
 
+struct xenbus_device *blkback_xenbus(struct backend_info *be)
+{
+	return be->dev;
+}
+
 static int blkback_name(blkif_t *blkif, char *buf)
 {
 	char *devpath, *devname;