block: Accept node-name for block-commit

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

As libvirt makes use of the DeviceNotFound error class, we must add
explicit code to retain this behaviour because qmp_get_root_bs() only
returns GenericErrors.

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

blockdev.c

@@ -3068,7 +3068,6 @@ void qmp_block_commit(bool has_job_id, const char *job_id, const char *device,
                       bool has_speed, int64_t speed,
                       Error **errp)
 {
-    BlockBackend *blk;
     BlockDriverState *bs;
     BlockDriverState *base_bs, *top_bs;
     AioContext *aio_context;
@@ -3087,22 +3086,22 @@ void qmp_block_commit(bool has_job_id, const char *job_id, const char *device,
      *  live commit feature versions; for this to work, we must make sure to
      *  perform the device lookup before any generic errors that may occur in a
      *  scenario in which all optional arguments are omitted. */
-    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, &local_err);
+    if (!bs) {
+        bs = bdrv_lookup_bs(device, device, NULL);
+        if (!bs) {
+            error_free(local_err);
+            error_set(errp, ERROR_CLASS_DEVICE_NOT_FOUND,
+                      "Device '%s' not found", device);
+        } else {
+            error_propagate(errp, local_err);
+        }
         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);
-
     if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_COMMIT_SOURCE, errp)) {
         goto out;
     }

qapi/block-core.json

@@ -1020,7 +1020,7 @@
 # @job-id: #optional identifier for the newly-created block job. If
 #          omitted, the device name will be used. (Since 2.7)
 #
-# @device:  the name of the device
+# @device:  the device name or node-name of a root node
 #
 # @base:   #optional The file name of the backing image to write data into.
 #                    If not specified, this is the deepest backing image

qmp-commands.hx

@@ -1166,7 +1166,7 @@ Arguments:
 
 - "job-id": Identifier for the newly-created block job. If omitted,
             the device name will be used. (json-string, optional)
-- "device": The device's ID, must be unique (json-string)
+- "device": The device name or node-name of a root node (json-string)
 - "base": The file name of the backing image to write data into.
           If not specified, this is the deepest backing image
           (json-string, optional)