xen-block: treat XenbusStateUnknown the same as XenbusStateClosed

When a frontend gracefully disconnects from an offline backend, it will
set its own state to XenbusStateClosed. The code in xen-block.c correctly
deals with this and sets the backend into XenbusStateClosed. Unfortunately
it is possible for toolstack to actually delete the frontend area
before the state key has been read, leading to an apparent frontend state
of XenbusStateUnknown. This prevents the backend state from transitioning
to XenbusStateClosed and hence leaves it limbo.

This patch simply treats a frontend state of XenbusStateUnknown the same
as XenbusStateClosed, which will unblock the backend in these circumstances.

Reported-by: Mark Syms <mark.syms@citrix.com>
Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Acked-by: Anthony PERARD <anthony.perard@citrix.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Message-Id: <20190918115702.38959-1-paul.durrant@citrix.com>
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>

diff --git a/hw/block/xen-block.c b/hw/block/xen-block.c
index f77343db6064f8b8af433cc21e65932e88a74707..879fc310a4c5dfa4a7d8936f7d8ee76acacf988b 100644 (file)
--- a/hw/block/xen-block.c
+++ b/hw/block/xen-block.c
@@ -313,6 +313,7 @@ static void xen_block_frontend_changed(XenDevice *xendev,
         break;
 
     case XenbusStateClosed:
+    case XenbusStateUnknown:
         xen_block_disconnect(xendev, &local_err);
         if (local_err) {
             error_propagate(errp, local_err);