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Re: [Qemu-devel] [PATCH v3 2/2] qapi: Change BlockDirtyInfo to list
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [PATCH v3 2/2] qapi: Change BlockDirtyInfo to list |
Date: |
Wed, 13 Nov 2013 13:37:23 -0700 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.1.0 |
On 11/13/2013 07:19 AM, Kevin Wolf wrote:
>> #
>> -# @dirty: #optional dirty bitmap information (only present if the dirty
>> -# bitmap is enabled)
>> +# @dirty-bitmaps: #optional dirty bitmaps information (only present if the
>> +# driver has one or more dirty bitmaps)
>> #
>> # @io-status: #optional @BlockDeviceIoStatus. Only present if the device
>> # supports it and the VM is configured to stop on errors
>> @@ -963,7 +963,7 @@
>> 'data': {'device': 'str', 'type': 'str', 'removable': 'bool',
>> 'locked': 'bool', '*inserted': 'BlockDeviceInfo',
>> '*tray_open': 'bool', '*io-status': 'BlockDeviceIoStatus',
>> - '*dirty': 'BlockDirtyInfo' } }
>> + '*dirty-bitmaps': ['BlockDirtyInfo'] } }
>>
>> ##
>> # @query-block:
>
> I believe this is of limited use; if you ever have more than one dirty
> bitmap, we're lacking information to associate it with the job it
> belongs to. One option would be to extend BlockDirtyInfo to indicate
> this, but another might be to actually extend other commands like
> query-block-jobs to return information on the dirty bitmap associated
> with a specific job.
>
> I've applied it to block-next anyway, we still have some time to
> reconsider for 1.8.
Indeed, expanding the per-job query output to list a single dirty bitmap
tied to that job is probably more useful than listing all dirty bitmaps
without context here. Since it's output-only, and marked optional, we
can still withdraw this output even after 1.8 if we decide we don't like
it and no one has reported wanting to use it.
I was going to suggest _always_ outputting dirty-bitmaps, even if it is
an empty array, if that makes it easier to detect that yes, this is a
version of qemu new enough to have per-job dirty bitmaps but there are
no jobs at the moment; on the other hand, doing that would mean the
field is not marked optional, and then we would always have to output it
for back-compat reasons. So keeping the field marked optional makes sense.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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Re: [Qemu-devel] [PATCH v3 2/2] qapi: Change BlockDirtyInfo to list, Wenchao Xia, 2013/11/13