[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-block] QCOW2 runtime options and json: backing file strings
From: |
Max Reitz |
Subject: |
Re: [Qemu-block] QCOW2 runtime options and json: backing file strings |
Date: |
Tue, 26 Apr 2016 19:39:16 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.7.2 |
On 26.04.2016 13:32, Alberto Garcia wrote:
> Hi,
>
> I was away for a few days but I just came back. There's a ton of
> patches that I'll try to review these days but I also have a question.
>
> Let's create a QCOW2 image and pass a runtime option such as
> l2-cache-size:
>
> $ qemu -drive if=virtio,file=hd0.qcow2,l2-cache-size=10M
>
> Now we make a snapshot:
>
> (qemu) snapshot_blkdev virtio0 hd1.qcow2
>
> And here's the backing file string of hd1.qcow2:
>
> $ qemu-img info hd1.qcow2 | grep backing
> backing file: json:{"driver": "qcow2", "l2-cache-size": "10M", "file":
> {"driver": "file", "filename": "hd0.qcow2"}}
> backing file format: qcow2
>
> The problem is that this QCOW2 image cannot be opened with older
> versions of QEMU (because of the "json:" syntax), although there's
> nothing in the image itself that would prevent that.
>
> Is this something we should deal with?
Yes, we do.
Yes, the problem is known.
Yes, I have patches for it.
No, I have no clue why I haven't sent them out yet. I literally have a
series lying around, including its cover letter, from last November. But
for some reason I forgot to send it. Thanks for remining me. :-)
Max
signature.asc
Description: OpenPGP digital signature