block: use bdrv_get_device_or_node_name() in error messages

There are several error messages that identify a BlockDriverState by
its device name. However those errors can be produced in nodes that
don't have a device name associated.

In those cases we should use bdrv_get_device_or_node_name() to fall
back to the node name and produce a more meaningful message. The
messages are also updated to use the more generic term 'node' instead
of 'device'.

Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 9823a1f0514fdb0692e92868661c38a9e00a12d6.1428485266.git.berto@igalia.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/block/snapshot.c b/block/snapshot.c
index 698e1a1..50ae610 100644
--- a/block/snapshot.c
+++ b/block/snapshot.c
@@ -246,9 +246,9 @@
     if (bs->file) {
         return bdrv_snapshot_delete(bs->file, snapshot_id, name, errp);
     }
-    error_set(errp, QERR_BLOCK_FORMAT_FEATURE_NOT_SUPPORTED,
-              drv->format_name, bdrv_get_device_name(bs),
-              "internal snapshot deletion");
+    error_setg(errp, "Block format '%s' used by device '%s' "
+               "does not support internal snapshot deletion",
+               drv->format_name, bdrv_get_device_name(bs));
     return -ENOTSUP;
 }
 
@@ -329,9 +329,9 @@
     if (drv->bdrv_snapshot_load_tmp) {
         return drv->bdrv_snapshot_load_tmp(bs, snapshot_id, name, errp);
     }
-    error_set(errp, QERR_BLOCK_FORMAT_FEATURE_NOT_SUPPORTED,
-              drv->format_name, bdrv_get_device_name(bs),
-              "temporarily load internal snapshot");
+    error_setg(errp, "Block format '%s' used by device '%s' "
+               "does not support temporarily loading internal snapshots",
+               drv->format_name, bdrv_get_device_name(bs));
     return -ENOTSUP;
 }