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Re: [Qemu-block] [Qemu-devel] [PATCH 11/34] block: Allow references for
From: |
Kevin Wolf |
Subject: |
Re: [Qemu-block] [Qemu-devel] [PATCH 11/34] block: Allow references for backing files |
Date: |
Wed, 27 May 2015 14:31:18 +0200 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
Am 21.05.2015 um 07:47 hat Wen Congyang geschrieben:
> On 05/09/2015 01:21 AM, Kevin Wolf wrote:
> > For bs->file, using references to existing BDSes has been possible for a
> > while already. This patch enables the same for bs->backing_hd.
>
> 1. We reference to an existing BDSes, and some disk uses this blk. Do
> we allow this?
Currently yes. If it breaks, you get to keep both pieces.
As long as your guest device is read-only, it should just work. It would
be a very bad idea, though, to write to a backing file.
Op blockers should eventually prevent this from happening (Jeff, you may
want to take a note ;-))
> 2. bs->backing_hd->blk can be not NULL now? If we do an active commit
> to this backing file(use mirror job), we will call bdrv_swap() in
> mirror_exit(), and the function bdrv_swap() doesn't allow that
> new_bs->blk(here is bs->backing_hd) is not NULL.
You're right.
I can remove this patch from the series for now, but of course that
doesn't solve the problem. I'm not sure what to do about it. Making
bdrv_swap() work with BDSes that have BB attached is probably another
item in the list of "dynamic reconfiguration" problems.
Markus, any ideas?
Kevin
- Re: [Qemu-block] [Qemu-devel] [PATCH 10/34] block: Fix reopen flag inheritance, (continued)
- [Qemu-block] [PATCH 08/34] block: Add list of children to BlockDriverState, Kevin Wolf, 2015/05/08
- [Qemu-block] [PATCH 11/34] block: Allow references for backing files, Kevin Wolf, 2015/05/08
- Re: [Qemu-block] [PATCH 11/34] block: Allow references for backing files, Max Reitz, 2015/05/11
- Re: [Qemu-block] [Qemu-devel] [PATCH 11/34] block: Allow references for backing files, Eric Blake, 2015/05/12
- Re: [Qemu-block] [Qemu-devel] [PATCH 11/34] block: Allow references for backing files, Wen Congyang, 2015/05/21
- Re: [Qemu-block] [Qemu-devel] [PATCH 11/34] block: Allow references for backing files, Wen Congyang, 2015/05/27
- Re: [Qemu-block] [Qemu-devel] [PATCH 11/34] block: Allow references for backing files, Kevin Wolf, 2015/05/28
- Re: [Qemu-block] [Qemu-devel] [PATCH 11/34] block: Allow references for backing files, Wen Congyang, 2015/05/28
- Re: [Qemu-block] [Qemu-devel] [PATCH 11/34] block: Allow references for backing files, Wen Congyang, 2015/05/31
[Qemu-block] [PATCH 13/34] qemu-io: Add command 'reopen', Kevin Wolf, 2015/05/08