Re: [Qemu-devel] [PATCH v4 4/4] migration: Expose 'cancelling' status to user

[Eric Blake <eblake@redhat.com>]

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On 03/13/2015 04:49 AM, Paolo Bonzini wrote:
> 
> 
> On 09/03/2015 07:45, zhanghailiang wrote:
>> 'cancelling' status was introduced by commit 51cf4c1a, mainly to avoid a 
>> possible start of a new migration process while the previous one still exists.
>> But we didn't expose this status to user, instead we returned the 'active' state.
>>
>> Here, we expose it to the user (such as libvirt), 'cancelling' status only
>> occurs for a short window before the migration aborts, so for users,
>> if they cancel a migration process, it will observe 'cancelling' status
>> occasionally.
>>
>> Testing revealed that with older libvirt (anything 1.2.13 or less) will
>> print an odd error message if the state is seen, but that the migration
>> is still properly cancelled. Newer libvirt will be patched to recognize
>> the new state without the odd error message.
>>
>> Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
>> Reviewed-by: Eric Blake <eblake@redhat.com>
>> Cc: libvir-list@redhat.com
> 
> Why is this necessary?

It simplifies qemu's job of reporting migration status information (qemu
is no longer maintaining one set of states internally and a different
set of states externally), and I already have the libvirt counterpart
patch ready to go to gracefully accept the new state name.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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