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Date: Tue, 02 Jul 2013 16:44:55 +0200
From: Laszlo Ersek <lersek@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v4 08/10] qemu-ga: call Windows VSS
 requester in fsfreeze command handler
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To: Luiz Capitulino <lcapitulino@redhat.com>
Cc: "libaiqing@huawei.com" <libaiqing@huawei.com>, "stefanha@gmail.com" <stefanha@gmail.com>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, "mdroth@linux.vnet.ibm.com" <mdroth@linux.vnet.ibm.com>, "vrozenfe@redhat.com" <vrozenfe@redhat.com>, Tomoki Sekiyama <tomoki.sekiyama@hds.com>, "pbonzini@redhat.com" <pbonzini@redhat.com>, Seiji Aguchi <seiji.aguchi@hds.com>, "areis@redhat.com" <areis@redhat.com>

On 07/02/13 16:09, Luiz Capitulino wrote:
> On Tue, 02 Jul 2013 08:36:11 +0200
> Laszlo Ersek <lersek@redhat.com> wrote:
> 
>> On 07/01/13 19:59, Tomoki Sekiyama wrote:
>>> On 7/1/13 9:29 , "Laszlo Ersek" <lersek@redhat.com> wrote:
>>>
>>>>> +error:
>>>>> +    qmp_guest_fsfreeze_thaw(NULL);
>>>>
>>>> Passing NULL here as "errp" concerns me slightly. I've been assuming
>>>> that "errp" is never NULL due to the outermost QMP layer always wanting
>>>> to receive errors and to serialize them.
>>>>
>>>> Specifically, a NULL "errp" would turn all error_set*(errp, ...) calls
>>>> into no-ops under qmp_guest_fsfreeze_thaw(), and all error_is_set(errp)
>>>> questions would answer with false. That said, nothing seems to be
>>>> affected right now.
>>>>
>>>> Maybe a dummy local variable would be more future-proof... OTOH it would
>>>> be stylistically questionable :)
>>>
>>> OK, then it should be:
>>>     Error *local_err = NULL;
>>> ...
>>> error:
>>>     qmp_guest_fsfreeze_thaw(&local_err);
>>>     if (error_is_set(&local_err)) {
>>>         error_free(local_err);
>>>     }
>>
>> I think so, yes.
>>
>> You could also log it before freeing it I guess:
>>
>>     g_debug("cleanup thaw: %s", error_get_pretty(local_err));
>>
>> or some such, but it's probably not important.
> 
> I'd rather do something like that, otherwise it doesn't seem to
> make sense to pass Error as qmp_guest_fsfreeze_thaw() does
> use a local Error.

No, the win32 version of qmp_guest_fsfreeze_thaw() being added by this
patch doesn't.

Thanks,
Laszlo