On Fri, Jul 10, 2015 at 11:46:49AM +0800, Fam Zheng wrote:
>  static BlockErrorAction backup_error_action(BackupBlockJob *job,
> @@ -444,7 +462,7 @@ static void coroutine_fn backup_run(void *opaque)
>      qemu_co_rwlock_wrlock(&job->flush_rwlock);
>      qemu_co_rwlock_unlock(&job->flush_rwlock);
>  
> -    if (job->sync_bitmap) {
> +    if (!job->common.txn && job->sync_bitmap) {
>          backup_handle_dirty_bitmap(job, ret);
>      }
>      hbitmap_free(job->bitmap);

It would be nice if the core blockjob code called commit/abort even when
there is no txn object.  That way we can avoid special case code

> diff --git a/qapi/block-core.json b/qapi/block-core.json
> index 7b2efb8..d5e33fd 100644
> --- a/qapi/block-core.json
> +++ b/qapi/block-core.json
> @@ -736,6 +736,10 @@
>  #                   default 'report' (no limitations, since this applies to
>  #                   a different block device than @device).
>  #
> +# @transactional-cancel: #optional whether failure or cancellation of other
> +#                        block jobs with @transactional-cancel true causes the
> +#                        whole group to cancel.
> +#
>  # Note that @on-source-error and @on-target-error only affect background I/O.
>  # If an error occurs during a guest write request, the device's rerror/werror
>  # actions will be used.
> @@ -747,7 +751,8 @@
>              'sync': 'MirrorSyncMode', '*mode': 'NewImageMode',
>              '*speed': 'int', '*bitmap': 'str',
>              '*on-source-error': 'BlockdevOnError',
> -            '*on-target-error': 'BlockdevOnError' } }
> +            '*on-target-error': 'BlockdevOnError',
> +            '*transactional-cancel': 'bool' } }
>  
>  ##
>  # @BlockdevBackup
> @@ -771,6 +776,10 @@
>  #                   default 'report' (no limitations, since this applies to
>  #                   a different block device than @device).
>  #
> +# @transactional-cancel: #optional whether failure or cancellation of other
> +#                        block jobs with @transactional-cancel true causes the
> +#                        whole group to cancel.
> +#
>  # Note that @on-source-error and @on-target-error only affect background I/O.
>  # If an error occurs during a guest write request, the device's rerror/werror
>  # actions will be used.
> @@ -782,7 +791,8 @@
>              'sync': 'MirrorSyncMode',
>              '*speed': 'int',
>              '*on-source-error': 'BlockdevOnError',
> -            '*on-target-error': 'BlockdevOnError' } }
> +            '*on-target-error': 'BlockdevOnError',
> +            '*transactional-cancel': 'bool' } }

The doc comments are missing (Since: 2.5).  My fault, sorry!