xen/blkback: add accessor for xenbus backend device

Since backend_info is hidden away now.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
diff --git a/drivers/xen/blkback/common.h b/drivers/xen/blkback/common.h
index cebcc2b..0f91830 100644
--- a/drivers/xen/blkback/common.h
+++ b/drivers/xen/blkback/common.h
@@ -136,4 +136,6 @@
 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__ */
diff --git a/drivers/xen/blkback/vbd.c b/drivers/xen/blkback/vbd.c
index 0635c54..943ec23 100644
--- a/drivers/xen/blkback/vbd.c
+++ b/drivers/xen/blkback/vbd.c
@@ -123,7 +123,7 @@
 	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);
diff --git a/drivers/xen/blkback/xenbus.c b/drivers/xen/blkback/xenbus.c
index 34f8e40..c31e5c4 100644
--- a/drivers/xen/blkback/xenbus.c
+++ b/drivers/xen/blkback/xenbus.c
@@ -42,6 +42,11 @@
 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;