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Re: [Qemu-devel] [PATCH 11/34] block: Allow references for backing files
From: |
Wen Congyang |
Subject: |
Re: [Qemu-devel] [PATCH 11/34] block: Allow references for backing files |
Date: |
Thu, 28 May 2015 08:59:02 +0800 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 |
On 05/27/2015 08:31 PM, Kevin Wolf wrote:
> 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.
What does "dynamic reconfiguration" mean? Allow to change drive's option
when guest is running?
Thanks
Wen Congyang
>
> Markus, any ideas?
>
> Kevin
> .
>
- Re: [Qemu-devel] [PATCH 08/34] block: Add list of children to BlockDriverState, (continued)
- [Qemu-devel] [PATCH 11/34] block: Allow references for backing files, Kevin Wolf, 2015/05/08
- Re: [Qemu-devel] [PATCH 11/34] block: Allow references for backing files, Max Reitz, 2015/05/11
- Re: [Qemu-devel] [PATCH 11/34] block: Allow references for backing files, Eric Blake, 2015/05/12
- Re: [Qemu-devel] [PATCH 11/34] block: Allow references for backing files, Wen Congyang, 2015/05/21
- Re: [Qemu-devel] [PATCH 11/34] block: Allow references for backing files,
Wen Congyang <=
- Re: [Qemu-devel] [PATCH 11/34] block: Allow references for backing files, Kevin Wolf, 2015/05/28
- Re: [Qemu-devel] [PATCH 11/34] block: Allow references for backing files, Wen Congyang, 2015/05/28
- Re: [Qemu-devel] [PATCH 11/34] block: Allow references for backing files, Wen Congyang, 2015/05/31
[Qemu-devel] [PATCH 13/34] qemu-io: Add command 'reopen', Kevin Wolf, 2015/05/08
[Qemu-devel] [PATCH 12/34] block: Allow specifying driver-specific options to reopen, Kevin Wolf, 2015/05/08