[patch 23/87] xen/blkfront: allow xenbus state transition to Closing->Closed when not Connected

[Greg KH]

2.6.29-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Ian Campbell <ian.campbell@xxxxxxxxxx>

commit 28afea5b2ffaa48f4f43d22ae8edcc384c05df80 upstream.

This situation can occur when attempting to attach a block device whose
backend is an empty physical CD-ROM driver. The backend in this case
will go directly from the Initialising state to Closing->Closed.
Previously this would result in a NULL pointer deref on info->gd
(xenbus_dev_fatal does not return as a1a15ac5 seems to expect)

Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
Acked-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
Signed-off-by: Jens Axboe <jens.axboe@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 drivers/block/xen-blkfront.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -977,8 +977,10 @@ static void backend_changed(struct xenbu
 		break;
 
 	case XenbusStateClosing:
-		if (info->gd == NULL)
-			xenbus_dev_fatal(dev, -ENODEV, "gd is NULL");
+		if (info->gd == NULL) {
+			xenbus_frontend_closed(dev);
+			break;
+		}
 		bd = bdget_disk(info->gd, 0);
 		if (bd == NULL)
 			xenbus_dev_fatal(dev, -ENODEV, "bdget failed");


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