On 2015/7/30 17:41, zhang bo wrote:
> On 2015/7/28 16:33, Ján Tomko wrote:
>
>> On Tue, Jul 28, 2015 at 04:25:13PM +0800, zhang bo wrote:
>>> static int
>>> qemuDomainDetachVirtioDiskDevice(virQEMUDriverPtr driver,
>>> virDomainObjPtr vm,
>>> virDomainDiskDefPtr detach)
>>> {
>>> .......
>>>
>>> rc = qemuDomainWaitForDeviceRemoval(vm);
>>> if (rc == 0 || rc == 1)
>>> ret = qemuDomainRemoveDiskDevice(driver, vm, detach);
>>> else
>>> ret = 0; /*the return value of 2 is dismissed here, which refers to ETIMEOUT.*/
>>> ........
>>> }
>>>
>>> ------------------------------------
>>>
>>> If it timeouts when qemu tries to del the device, the return value would be modified from 2 to 0 in
>>> function qemuDomainDetachVirtioDiskDevice(), which means that, the users would be misleaded that
>>> the device has been deleted, however, the device maybe probably failed to be detached after timeout and
>>> still in use.
>>>
>>
>> This is intentional and documented:
>> http://libvirt.org/html/libvirt-libvirt-domain.html#virDomainDetachDeviceFlags
>>
>> Unplugging a disk requires guest cooperation, so the best we can do is
>> ask qemu to unplug it and wait for a while.
>>
>>> That is to say, the function qemuDomainDetachVirtioDiskDevice()'s return value is ambiguous when it's 0,
>>> maybe successful, or timeout. Will it be better to pass ETIMEOUT to user? or any other advises? for example,
>>> let users themselves dumpxml the guest to check whether the device has been actually detached or not?
>>
>> Either dump the XML, or wait for the VIR_DOMAIN_EVENT_ID_DEVICE_REMOVED
>> event, as the API documentation suggests.
>>
>> Jan
>
>
> It seems to have fixed the problem by dumping the XML or wait for the DEVICE_REMOVED event. However, it seems to
> make nova or other apps to do more checking work, they need to dump XML or wait the event even if the device has
> already been successfully removed. which is unnecessary.
>
> I think, it's better to return ETIMEOUT and let nova to dumpxml or wait the event at this situation, rather than always
> doing that job.
>
> It maybe a better design, what's your opinion?
>
After thinking twice, it's an async job, thus returning 0 is acceptable, right?
--
Oscar
oscar.zhangbo@xxxxxxxxxx
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