xen-blkfront: handle backend CLOSED without CLOSING

Backend drivers shouldn't transistion to CLOSED unless the frontend is
CLOSED.  If a backend does transition to CLOSED too soon then the
frontend may not see the CLOSING state and will not properly shutdown.

So, treat an unexpected backend CLOSED state the same as CLOSING.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: stable@vger.kernel.org
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 7d09dfc9735c163554ad2df070569af73daeb3ef..76e5c0b265b17d7576826a00ebae7c437fae5ccd 100644 (file)
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -1904,13 +1904,16 @@ static void blkback_changed(struct xenbus_device *dev,
        case XenbusStateReconfiguring:
        case XenbusStateReconfigured:
        case XenbusStateUnknown:
-       case XenbusStateClosed:
                break;
 
        case XenbusStateConnected:
                blkfront_connect(info);
                break;
 
+       case XenbusStateClosed:
+               if (dev->state == XenbusStateClosed)
+                       break;
+               /* Missed the backend's Closing state -- fallthrough */
        case XenbusStateClosing:
                blkfront_closing(info);
                break;