Re: [Qemu-devel] [PATCH 5/7] block: allow migration to work with image files (v2)

[Juan Quintela]

Anthony Liguori <address@hidden> wrote:
> On 11/14/2011 07:11 AM, Juan Quintela wrote:
>>
>>> diff --git a/cpus.c b/cpus.c
>>> index 82530c4..ae5ec99 100644
>>> --- a/cpus.c
>>> +++ b/cpus.c
>>> @@ -398,6 +398,7 @@ static void do_vm_stop(RunState state)
>>>           vm_state_notify(0, state);
>>>           qemu_aio_flush();
>>>           bdrv_flush_all();
>>> +        bdrv_invalidate_cache_all();
>>>           monitor_protocol_event(QEVENT_STOP, NULL);
>>>       }
>>
>> This is too much. Reopening all qcow2 images each time that we stop the
>> vm looks excesive, no?
>
> This general code came in via:
>
> http://mid.gmane.org/address@hidden
>
> That series made migration stable after issuing a stop operation.  I
> believe the justification was for debugging purposes or something like
> that.
>
> At any rate, invalidating the cache is part of what's required to make
> things stable.  If you look at something like cache=unsafe, the only
> way the metadata will get flushed if via a bdrv_close since bdrv_flush
> is a nop.
>
> So this is needed as long as we care about supporting this use-case.

Then we need a "proper" qcow2 invalidate call.  Doing in qemu toplevel:

(qemu)stop

And now all your qcow2 block devices are closed, or perhaps failing to
re-open() looks too much to me (TM).

Kevin?

Later, Juan.