xen/front: Propagate changed size of VBDs

Support dynamic resizing of virtual block devices. This patch supports
both file backed block devices as well as physical devices that can be
dynamically resized on the host side.
Signed-off-by: NK. Y. Srinivasan <ksrinivasan@novell.com>
Signed-off-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

drivers/block/xen-blkfront.c

@@ -930,9 +930,24 @@ static void blkfront_connect(struct blkfront_info *info)
 	unsigned int binfo;
 	int err;
 
-	if ((info->connected == BLKIF_STATE_CONNECTED) ||
-	    (info->connected == BLKIF_STATE_SUSPENDED) )
+	switch (info->connected) {
+	case BLKIF_STATE_CONNECTED:
+		/*
+		 * Potentially, the back-end may be signalling
+		 * a capacity change; update the capacity.
+		 */
+		err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
+				   "sectors", "%Lu", &sectors);
+		if (XENBUS_EXIST_ERR(err))
 			return;
+		printk(KERN_INFO "Setting capacity to %Lu\n",
+		       sectors);
+		set_capacity(info->gd, sectors);
+
+		/* fall through */
+	case BLKIF_STATE_SUSPENDED:
+		return;
+	}
 
 	dev_dbg(&info->xbdev->dev, "%s:%s.\n",
 		__func__, info->xbdev->otherend);