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>

1 files changed, 2 insertions, 6 deletions

diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
index a2529b2242..b8ce6cd5f3 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;
     }