[for-6.1 1/4] virtio-blk: Fix rollback path in virtio_blk_data_plane_start()

[Greg Kurz <groug@kaod.org>]

When dataplane multiqueue support was added in QEMU 2.7, the path
that would rollback guest notifiers assignment in case of error
simply got dropped.

Later on, when Error was added to blk_set_aio_context() in QEMU 4.1,
another error path was introduced, but it ommits to rollback both
host and guest notifiers.

It seems cleaner to fix the rollback path in one go. The patch is
simple enough that it can be adjusted if backported to a pre-4.1
QEMU.

Fixes: 51b04ac5c6a6 ("virtio-blk: dataplane multiqueue support")
Cc: stefanha@redhat.com
Fixes: 97896a4887a0 ("block: Add Error to blk_set_aio_context()")
Cc: kwolf@redhat.com
Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 hw/block/dataplane/virtio-blk.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
index e9050c8987e7..d7b5c95d26d9 100644
--- a/hw/block/dataplane/virtio-blk.c
+++ b/hw/block/dataplane/virtio-blk.c
@@ -207,7 +207,7 @@ int virtio_blk_data_plane_start(VirtIODevice *vdev)
                 virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), i, false);
                 virtio_bus_cleanup_host_notifier(VIRTIO_BUS(qbus), i);
             }
-            goto fail_guest_notifiers;
+            goto fail_host_notifiers;
         }
     }
 
@@ -221,7 +221,7 @@ int virtio_blk_data_plane_start(VirtIODevice *vdev)
     aio_context_release(old_context);
     if (r < 0) {
         error_report_err(local_err);
-        goto fail_guest_notifiers;
+        goto fail_aio_context;
     }
 
     /* Process queued requests before the ones in vring */
@@ -245,6 +245,13 @@ int virtio_blk_data_plane_start(VirtIODevice *vdev)
     aio_context_release(s->ctx);
     return 0;
 
+  fail_aio_context:
+    for (i = 0; i < nvqs; i++) {
+        virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), i, false);
+        virtio_bus_cleanup_host_notifier(VIRTIO_BUS(qbus), i);
+    }
+  fail_host_notifiers:
+    k->set_guest_notifiers(qbus->parent, nvqs, false);
   fail_guest_notifiers:
     /*
      * If we failed to set up the guest notifiers queued requests will be
-- 
2.26.3