[PATCH] Prevent vbd frontend from oopsing if the underlying device doesn't exist

[Horms <horms@verge.net.au>]

Prevent vbd frontend from oopsing if the underlying device doesn't exist.

connect() in blkfront.c was not checking the return value of xlvbd_add().
In my case xlvbd_alloc_gendisk() was failing in xlvbd_add(), and the
subsequent call to kick_pending_request_queues() barfed because info->rq
was unitinialised.

Signed-Off-By: Horms <horms@verge.net.au>

diff -r e3b95be182e2 -r 9c36c9568da0 linux-2.6-xen-sparse/drivers/xen/blkfront/blkfront.c
--- a/linux-2.6-xen-sparse/drivers/xen/blkfront/blkfront.c	Thu Dec 22 03:30:14 2005
+++ b/linux-2.6-xen-sparse/drivers/xen/blkfront/blkfront.c	Mon Dec 26 08:52:20 2005
@@ -338,7 +338,12 @@
 		return;
 	}
 
-        xlvbd_add(sectors, info->vdevice, binfo, sector_size, info);
+        err = xlvbd_add(sectors, info->vdevice, binfo, sector_size, info);
+	if (err) {
+		xenbus_dev_fatal(info->xbdev, err, "xlvbd_add at %s",
+				 info->xbdev->otherend);
+		return;
+	}
 
 	(void)xenbus_switch_state(info->xbdev, NULL, XenbusStateConnected);