block: Handle null backing link

Instead of converting all "backing": null instances into "backing": "",
handle a null value directly in bdrv_open_inherit().

This enables explicitly null backing links for json:{} filenames.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Message-Id: <20180224154033.29559-7-mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: rebase to qobject_to() parameter order and qapi headers split]
Signed-off-by: Eric Blake <eblake@redhat.com>

1 files changed, 0 insertions, 14 deletions

diff --git a/blockdev.c b/blockdev.c
index 6067792e41..5048e73aba 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -4045,7 +4045,6 @@ void qmp_blockdev_add(BlockdevOptions *options, Error **errp)
     QObject *obj;
     Visitor *v = qobject_output_visitor_new(&obj);
     QDict *qdict;
-    const QDictEntry *ent;
     Error *local_err = NULL;
 
     visit_type_BlockdevOptions(v, NULL, &options, &local_err);
@@ -4059,19 +4058,6 @@ void qmp_blockdev_add(BlockdevOptions *options, Error **errp)
 
     qdict_flatten(qdict);
 
-    /*
-     * Rewrite "backing": null to "backing": ""
-     * TODO Rewrite "" to null instead, and perhaps not even here
-     */
-    for (ent = qdict_first(qdict); ent; ent = qdict_next(qdict, ent)) {
-        char *dot = strrchr(ent->key, '.');
-
-        if (!strcmp(dot ? dot + 1 : ent->key, "backing")
-            && qobject_type(ent->value) == QTYPE_QNULL) {
-            qdict_put(qdict, ent->key, qstring_new());
-        }
-    }
-
     if (!qdict_get_try_str(qdict, "node-name")) {
         error_setg(errp, "'node-name' must be specified for the root node");
         goto fail;