block: Accept node-name for block-stream

In order to remove the necessity to use BlockBackend names in the
external API, we want to allow node-names everywhere. This converts
block-stream to accept a node-name without lifting the restriction that
we're operating at a root node.

In case of an invalid device name, the command returns the GenericError
error class now instead of DeviceNotFound, because this is what
qmp_get_root_bs() returns.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/block/block-backend.c b/block/block-backend.c
index effa038924..dc2bc60b9e 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -410,6 +410,22 @@ bool bdrv_has_blk(BlockDriverState *bs)
 }
 
 /*
+ * Returns true if @bs has only BlockBackends as parents.
+ */
+bool bdrv_is_root_node(BlockDriverState *bs)
+{
+    BdrvChild *c;
+
+    QLIST_FOREACH(c, &bs->parents, next_parent) {
+        if (c->role != &child_root) {
+            return false;
+        }
+    }
+
+    return true;
+}
+
+/*
  * Return @blk's DriveInfo if any, else null.
  */
 DriveInfo *blk_legacy_dinfo(BlockBackend *blk)