[Qemu-block] [PATCH v5 07/11] block: Accept node-name for change-backing-file

[Kevin Wolf]

In order to remove the necessity to use BlockBackend names in the
external API, we want to allow node-names everywhere. This converts
change-backing-file 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 <address@hidden>
Reviewed-by: Eric Blake <address@hidden>
Reviewed-by: Alberto Garcia <address@hidden>
---
 blockdev.c           | 15 +++------------
 qapi/block-core.json |  3 ++-
 qmp-commands.hx      |  3 ++-
 3 files changed, 7 insertions(+), 14 deletions(-)

diff --git a/blockdev.c b/blockdev.c
index f775bbd..a42c802 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -3755,7 +3755,6 @@ void qmp_change_backing_file(const char *device,
                              const char *backing_file,
                              Error **errp)
 {
-    BlockBackend *blk;
     BlockDriverState *bs = NULL;
     AioContext *aio_context;
     BlockDriverState *image_bs = NULL;
@@ -3764,22 +3763,14 @@ void qmp_change_backing_file(const char *device,
     int open_flags;
     int ret;
 
-    blk = blk_by_name(device);
-    if (!blk) {
-        error_set(errp, ERROR_CLASS_DEVICE_NOT_FOUND,
-                  "Device '%s' not found", device);
+    bs = qmp_get_root_bs(device, errp);
+    if (!bs) {
         return;
     }
 
-    aio_context = blk_get_aio_context(blk);
+    aio_context = bdrv_get_aio_context(bs);
     aio_context_acquire(aio_context);
 
-    if (!blk_is_available(blk)) {
-        error_setg(errp, "Device '%s' has no medium", device);
-        goto out;
-    }
-    bs = blk_bs(blk);
-
     image_bs = bdrv_lookup_bs(NULL, image_node_name, &local_err);
     if (local_err) {
         error_propagate(errp, local_err);
diff --git a/qapi/block-core.json b/qapi/block-core.json
index bcb37db..d25ba46 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -998,7 +998,8 @@
 # @image-node-name: The name of the block driver state node of the
 #                   image to modify.
 #
-# @device:          The name of the device that owns image-node-name.
+# @device:          The device name or node-name of the root node that owns
+#                   image-node-name.
 #
 # @backing-file:    The string to write as the backing file.  This
 #                   string is not validated, so care should be taken
diff --git a/qmp-commands.hx b/qmp-commands.hx
index 8a53539..bd54b34 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -1806,7 +1806,8 @@ Arguments:
                         "device".
                         (json-string, optional)
 
-- "device":             The name of the device.
+- "device":             The device name or node-name of the root node that owns
+                        image-node-name.
                         (json-string)
 
 - "backing-file":       The string to write as the backing file.  This string 
is
-- 
1.8.3.1