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Re: [Qemu-devel] CoW image commit+shrink(= make_empty) support
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] CoW image commit+shrink(= make_empty) support |
Date: |
Sun, 10 Jun 2012 18:06:58 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:12.0) Gecko/20120430 Thunderbird/12.0.1 |
Il 08/06/2012 15:19, Jeff Cody ha scritto:
>> >
>> > This means copying allocated blocks from snap1.qcow2 and writing them
>> > into vm001.img. Once this process is complete it is safe to delete
>> > snap1.qcow2 since all data is now in vm001.img.
> Yes, this is the same as what we are wanting to accomplish. The trick
> here is open vm001.img r/w, in a safe manner (by safe, I mean able to
> abort in case of error while keeping the guest running live).
>
> My thoughts on this has revolved around something similar to what was
> done in bdrv_append(), where a duplicate BDS is created, a new file-open
> performed with the appropriate access mode flags, and if successful
> swapped out for the originally opened BDS for vm001.img. If there is an
> error, the new BDS is abandoned without modifying the BDS list.
>
I haven't yet read the rest of the thread, but I'll drop here that
indeed I have a bdrv_swap in my patches for block mirroring.
A live commit of the topmost image is really just a mirroring operation,
the only thing that changes is the mechanics of opening the target and
perhaps also switching to it.
Paolo
- Re: [Qemu-devel] CoW image commit+shrink(= make_empty) support, (continued)
- Re: [Qemu-devel] CoW image commit+shrink(= make_empty) support, Stefan Hajnoczi, 2012/06/12
- Re: [Qemu-devel] CoW image commit+shrink(= make_empty) support, Supriya Kannery, 2012/06/13
- Re: [Qemu-devel] CoW image commit+shrink(= make_empty) support, Zhi Hui Li, 2012/06/14
- Re: [Qemu-devel] CoW image commit+shrink(= make_empty) support, Jeff Cody, 2012/06/14
- Re: [Qemu-devel] CoW image commit+shrink(= make_empty) support, Supriya Kannery, 2012/06/14
- Re: [Qemu-devel] CoW image commit+shrink(= make_empty) support, Supriya Kannery, 2012/06/15
- Re: [Qemu-devel] CoW image commit+shrink(= make_empty) support,
Paolo Bonzini <=
Re: [Qemu-devel] CoW image commit+shrink(= make_empty) support, Kevin Wolf, 2012/06/08