block: Accept node-name for drive-backup

In order to remove the necessity to use BlockBackend names in the
external API, we want to allow node-names everywhere. This converts
drive-backup and the corresponding transaction action 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: Eric Blake <eblake@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>

blockdev.c

@@ -1856,30 +1856,23 @@ static void do_drive_backup(const char *job_id, const char *device,
 static void drive_backup_prepare(BlkActionState *common, Error **errp)
 {
     DriveBackupState *state = DO_UPCAST(DriveBackupState, common, common);
-    BlockBackend *blk;
+    BlockDriverState *bs;
     DriveBackup *backup;
     Error *local_err = NULL;
 
     assert(common->action->type == TRANSACTION_ACTION_KIND_DRIVE_BACKUP);
     backup = common->action->u.drive_backup.data;
 
-    blk = blk_by_name(backup->device);
-    if (!blk) {
-        error_set(errp, ERROR_CLASS_DEVICE_NOT_FOUND,
-                  "Device '%s' not found", backup->device);
-        return;
-    }
-
-    if (!blk_is_available(blk)) {
-        error_setg(errp, QERR_DEVICE_HAS_NO_MEDIUM, backup->device);
+    bs = qmp_get_root_bs(backup->device, errp);
+    if (!bs) {
         return;
     }
 
     /* AioContext is released in .clean() */
-    state->aio_context = blk_get_aio_context(blk);
+    state->aio_context = bdrv_get_aio_context(bs);
     aio_context_acquire(state->aio_context);
-    bdrv_drained_begin(blk_bs(blk));
-    state->bs = blk_bs(blk);
+    bdrv_drained_begin(bs);
+    state->bs = bs;
 
     do_drive_backup(backup->has_job_id ? backup->job_id : NULL,
                     backup->device, backup->target,
@@ -3153,7 +3146,6 @@ static void do_drive_backup(const char *job_id, const char *device,
                             BlockdevOnError on_target_error,
                             BlockJobTxn *txn, Error **errp)
 {
-    BlockBackend *blk;
     BlockDriverState *bs;
     BlockDriverState *target_bs;
     BlockDriverState *source = NULL;
@@ -3177,24 +3169,14 @@ static void do_drive_backup(const char *job_id, const char *device,
         mode = NEW_IMAGE_MODE_ABSOLUTE_PATHS;
     }
 
-    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);
 
-    /* Although backup_run has this check too, we need to use bs->drv below, so
-     * do an early check redundantly. */
-    if (!blk_is_available(blk)) {
-        error_setg(errp, QERR_DEVICE_HAS_NO_MEDIUM, device);
-        goto out;
-    }
-    bs = blk_bs(blk);
-
     if (!has_format) {
         format = mode == NEW_IMAGE_MODE_EXISTING ? NULL : bs->drv->format_name;
     }

qapi/block-core.json

@@ -876,7 +876,7 @@
 # @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 which should be copied.
+# @device: the device name or node-name of a root node which should be copied.
 #
 # @target: the target of the new image. If the file exists, or if it
 #          is a device, the existing file/device will be used as the new
@@ -1087,7 +1087,7 @@
 # For the arguments, see the documentation of DriveBackup.
 #
 # Returns: nothing on success
-#          If @device is not a valid block device, DeviceNotFound
+#          If @device is not a valid block device, GenericError
 #
 # Since 1.6
 ##

qmp-commands.hx

@@ -1235,7 +1235,7 @@ Arguments:
 
 - "job-id": Identifier for the newly-created block job. If omitted,
             the device name will be used. (json-string, optional)
-- "device": the name of the device which should be copied.
+- "device": the device name or node-name of a root node which should be copied.
             (json-string)
 - "target": the target of the new image. If the file exists, or if it is a
             device, the existing file/device will be used as the new

tests/qemu-iotests/055

@@ -134,10 +134,7 @@ class TestSingleDrive(iotests.QMPTestCase):
 
     def do_test_device_not_found(self, cmd, **args):
         result = self.vm.qmp(cmd, **args)
-        if cmd == 'drive-backup':
-            self.assert_qmp(result, 'error/class', 'DeviceNotFound')
-        else:
-            self.assert_qmp(result, 'error/class', 'GenericError')
+        self.assert_qmp(result, 'error/class', 'GenericError')
 
     def test_device_not_found(self):
         self.do_test_device_not_found('drive-backup', device='nonexistent',
@@ -371,7 +368,7 @@ class TestSingleTransaction(iotests.QMPTestCase):
                           'sync': 'full' },
             }
         ])
-        self.assert_qmp(result, 'error/class', 'DeviceNotFound')
+        self.assert_qmp(result, 'error/class', 'GenericError')
 
         result = self.vm.qmp('transaction', actions=[{
                 'type': 'blockdev-backup',