Re: [Qemu-devel] [PATCH 4/7] qemu-img: Add print_amend_option_help()

[Eric Blake <eblake@redhat.com>]

On 04/21/2018 11:54 AM, Max Reitz wrote:
> The more generic print_block_option_help() function is not really
> suitable for qemu-img amend, for a couple of reasons:
> (1) We do not need to append the protocol-level options, as amendment
>      happens only on one node and does not descend downwards to its
>      children.
> (2) print_block_option_help() says those options are "supported".  For
>      option amendment, we do not really know that.  So this new function
>      explicitly says that those options are the creation options, and not
>      all of them may be supported.
> (3) If the driver does not support option amendment, we should not print
>      anything (except for an error message that amendment is not
>      supported).
> 
> Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1537956
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
>   qemu-img.c                 | 30 ++++++++++++++++++++++++++++--
>   tests/qemu-iotests/082.out | 44 +++++++++++++++++++++++++++-----------------
>   2 files changed, 55 insertions(+), 19 deletions(-)
> 

> diff --git a/qemu-img.c b/qemu-img.c
> index 6dd8e95bb2..45e243cc80 100644
> --- a/qemu-img.c
> +++ b/qemu-img.c
> @@ -3578,6 +3578,32 @@ static void amend_status_cb(BlockDriverState *bs,
>       qemu_progress_print(100.f * offset / total_work_size, 0);
>   }
>   
> +static int print_amend_option_help(const char *format)
> +{
> +    BlockDriver *drv;
> +
> +    /* Find driver and parse its options */
> +    drv = bdrv_find_format(format);
> +    if (!drv) {
> +        error_report("Unknown file format '%s'", format);
> +        return 1;
> +    }

Not your fault; I'd love it if this file consistently used EXIT_FAILURE 
instead of 1 (since that's a bit more obvious why we are returning a 
positive value instead of our more usual negative-on-error - we expect 
the caller to feed our return value to exit()), but that's a separate 
cleanup.

But the new output is definitely nicer.

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org