On 5/14/20 1:45 AM, Vladimir Sementsov-Ogievskiy wrote:
13.05.2020 04:16, Eric Blake wrote:
Include actions for --add, --remove, --clear, --enable, --disable, and
--merge (note that --clear is a bit of fluff, because the same can be
accomplished by removing a bitmap and then adding a new one in its
place, but it matches what QMP commands exist). Listing is omitted,
because it does not require a bitmap name and because it was already
possible with 'qemu-img info'. A single command line can play one or
more bitmap commands in sequence on the same bitmap name (although all
added bitmaps share the same granularity, and and all merged bitmaps
come from the same source file). Merge defaults to other bitmaps in
the primary image, but can also be told to merge bitmaps from a
distinct image.
I'm sorry for asking it only now on v4.. But still. Why do we need it?
Ease of use.
We can instead run qemu binary (or even new qemu-storage-daemon) and
just use existing qmp commands. Is there a real benefit in developing
qemu-img, maintaining two interfaces for the same thing?
If it makes someone's life easier, and is not hard to maintain, then
yes. A command line interface that calls into QMP is not hard to
maintain. And _I_ certainly found it easier to write iotests with this
patch in place, so it already has at least one client.
Of-course, just
run qmp commands from terminal is a lot less comfortable than just a
qemu img command.. But may be we need some wrapper, which make it simple
to run one qmp command on an image?
It's simple to make a python wrapper working like
qemu-qmp block-dirty-bitmap-add '{node: self, name: bitmap0, persistent:
true}' /path/to/x.qcow2
This _IS_ such a wrapper. The whole point of this patch is that it is
now simpler to run one (or more) QMP command on an offline image from
the command line. Just because I wrote it in C instead of python, and
attached it to an existing tool instead of writing a new tool, doesn't
change the fact that it is just a wrapper around the existing QMP commands.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org