Re: [PATCH 0/4] Make qemu-img dd more flexible

[Eric Blake]

On Thu, Feb 10, 2022 at 02:31:19PM +0100, Fabian Ebner wrote:
> Adds support for reading from stdin and writing to stdout (when raw
> format is used), as well as overriding the size of the output and
> input image/stream.
> 
> Additionally, the options -n for skipping output image creation and -l
> for loading a snapshot are made available like for convert.

Without looking at the series itself, I want to refer back to earlier
times that someone proposed improving 'qemu-img dd':

https://lists.gnu.org/archive/html/qemu-devel/2021-02/msg00636.html
https://lists.gnu.org/archive/html/qemu-devel/2018-08/msg02618.html

As well as the observation that when we originally allowed 'qemu-img
dd' to be added, the end goal was that if 'qemu-img dd' can't operate
as a thin wrapper around 'qemu-img convert', then 'qemu-img convert'
needs to be made more powerful first.  Every time we diverge on what
the two uses can do, rather than keeping dd as a thin wrapper, we add
to our maintenance burden.

Sadly, there is a lot of technical debt in this area ('qemu-img dd
skip= count=' is STILL broken, more than 4 years after I first
proposed a potential patch), where no one has spent the necessary time
to improve the situation.

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