error: Use error_prepend() where it makes obvious sense

Done with this Coccinelle semantic patch

    @@
    expression FMT, E1, E2;
    expression list ARGS;
    @@
    -    error_setg(E1, FMT, ARGS, error_get_pretty(E2));
    +    error_propagate(E1, E2);/*###*/
    +    error_prepend(E1, FMT/*@@@*/, ARGS);

followed by manual cleanup, first because I can't figure out how to
make Coccinelle transform strings, and second to get rid of now
superfluous error_propagate().

We now use or propagate the original error whole instead of just its
message obtained with error_get_pretty().  This avoids suppressing its
hint (see commit 50b7b00), but I can't see how the errors touched in
this commit could come with hints.  It also improves the message
printed with &error_abort when we screw up (see commit 1e9b65b).

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>

3 files changed, 7 insertions, 13 deletions

diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
index a2529b2..b8ce6cd 100644
--- a/hw/block/dataplane/virtio-blk.c
+++ b/hw/block/dataplane/virtio-blk.c
@@ -142,7 +142,6 @@ void virtio_blk_data_plane_create(VirtIODevice *vdev, VirtIOBlkConf *conf,
                                   Error **errp)
 {
     VirtIOBlockDataPlane *s;
-    Error *local_err = NULL;
     BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
 
@@ -163,11 +162,8 @@ void virtio_blk_data_plane_create(VirtIODevice *vdev, VirtIOBlkConf *conf,
     /* If dataplane is (re-)enabled while the guest is running there could be
      * block jobs that can conflict.
      */
-    if (blk_op_is_blocked(conf->conf.blk, BLOCK_OP_TYPE_DATAPLANE,
-                          &local_err)) {
-        error_setg(errp, "cannot start dataplane thread: %s",
-                   error_get_pretty(local_err));
-        error_free(local_err);
+    if (blk_op_is_blocked(conf->conf.blk, BLOCK_OP_TYPE_DATAPLANE, errp)) {
+        error_prepend(errp, "cannot start dataplane thread: ");
         return;
     }
 
diff --git a/hw/scsi/vhost-scsi.c b/hw/scsi/vhost-scsi.c
index 00cdac6..7bc8288 100644
--- a/hw/scsi/vhost-scsi.c
+++ b/hw/scsi/vhost-scsi.c
@@ -217,11 +217,9 @@ static void vhost_scsi_realize(DeviceState *dev, Error **errp)
     }
 
     if (vs->conf.vhostfd) {
-        vhostfd = monitor_fd_param(cur_mon, vs->conf.vhostfd, &err);
+        vhostfd = monitor_fd_param(cur_mon, vs->conf.vhostfd, errp);
         if (vhostfd == -1) {
-            error_setg(errp, "vhost-scsi: unable to parse vhostfd: %s",
-                       error_get_pretty(err));
-            error_free(err);
+            error_prepend(errp, "vhost-scsi: unable to parse vhostfd: ");
             return;
         }
     } else {
diff --git a/hw/usb/bus.c b/hw/usb/bus.c
index 26ab67f..1bbe930 100644
--- a/hw/usb/bus.c
+++ b/hw/usb/bus.c
@@ -329,9 +329,9 @@ static USBDevice *usb_try_create_simple(USBBus *bus, const char *name,
     }
     object_property_set_bool(OBJECT(dev), true, "realized", &err);
     if (err) {
-        error_setg(errp, "Failed to initialize USB device '%s': %s",
-                   name, error_get_pretty(err));
-        error_free(err);
+        error_propagate(errp, err);
+        error_prepend(errp, "Failed to initialize USB device '%s': ",
+                      name);
         object_unparent(OBJECT(dev));
         return NULL;
     }