vhost: correctly pass error to caller in vhost_dev_enable_notifiers()

We override the error value r in fail_vq, this will cause the caller
can't detect the failure which may cause the caller may disable the
notifiers twice if vhost is failed to start. Fix this by using another
variable to keep track the return value of set_host_notifier().

Fixes b0b3db79559e57db340b292621c397e7a6cdbdc5 ("vhost-net: cleanup
host notifiers at last step")

Cc: qemu-stable@nongnu.org
Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
(cherry picked from commit 16617e36b02ebdc83f215d89db9ac00f7d6d6d83)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 54851b7614e1d7e434fc0b650228e5fdd2a7c759..a7858d34aa478930eb03a2173a5813137b7d3140 100644 (file)
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -921,7 +921,7 @@ int vhost_dev_enable_notifiers(struct vhost_dev *hdev, VirtIODevice *vdev)
     BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
     VirtioBusState *vbus = VIRTIO_BUS(qbus);
     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(vbus);
-    int i, r;
+    int i, r, e;
     if (!k->set_host_notifier) {
         fprintf(stderr, "binding does not support host notifiers\n");
         r = -ENOSYS;
@@ -939,12 +939,12 @@ int vhost_dev_enable_notifiers(struct vhost_dev *hdev, VirtIODevice *vdev)
     return 0;
 fail_vq:
     while (--i >= 0) {
-        r = k->set_host_notifier(qbus->parent, hdev->vq_index + i, false);
-        if (r < 0) {
+        e = k->set_host_notifier(qbus->parent, hdev->vq_index + i, false);
+        if (e < 0) {
             fprintf(stderr, "vhost VQ %d notifier cleanup error: %d\n", i, -r);
             fflush(stderr);
         }
-        assert (r >= 0);
+        assert (e >= 0);
     }
 fail:
     return r;