[libvirt] [PATCH v2] test_driver: implement virDomainGetDiskErrors

[Michal Privoznik]

On 5/15/19 11:49 AM, Ilias Stamatis wrote:
> On Wed, May 15, 2019 at 10:14 AM Michal Privoznik <mprivozn at redhat.com> wrote:
>>
>> On 5/14/19 5:24 PM, Ilias Stamatis wrote:
>>> On Tue, May 14, 2019 at 5:04 PM Michal Privoznik <mprivozn at redhat.com> wrote:
>>>>
>>>> On 5/14/19 12:50 PM, Ilias Stamatis wrote:
>>>>> On Tue, May 14, 2019 at 12:40 PM John Ferlan <jferlan at redhat.com> wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>> On 5/13/19 9:04 AM, Ilias Stamatis wrote:
>>>>>>> On Mon, May 13, 2019 at 2:38 PM Michal Privoznik <mprivozn at redhat.com> wrote:
>>>>>>>>
>>>>>>>> On 5/13/19 1:26 AM, Ilias Stamatis wrote:
>>>>>>>>> Return the number of disks present in the configuration of the test
>>>>>>>>> domain when called with @errors as NULL and @maxerrors as 0.
>>>>>>>>>
>>>>>>>>> Otherwise report an error for every second disk, assigning available
>>>>>>>>> error codes in a cyclic order.
>>>>>>>>>
>>>>>>>>> Signed-off-by: Ilias Stamatis <stamatis.iliass at gmail.com>
>>>>>>>>> ---
>>>>>>>>>      src/test/test_driver.c | 42 ++++++++++++++++++++++++++++++++++++++++++
>>>>>>>>>      1 file changed, 42 insertions(+)
>>>>>>>>>
>>>>>>>>> diff --git a/src/test/test_driver.c b/src/test/test_driver.c
>>>>>>>>> index a06d1fc402..527c2f5d3b 100644
>>>>>>>>> --- a/src/test/test_driver.c
>>>>>>>>> +++ b/src/test/test_driver.c
>>>>>>>>> @@ -3046,6 +3046,47 @@ static int testDomainSetAutostart(virDomainPtr domain,
>>>>>>>>>          return 0;
>>>>>>>>>      }
>>>>>>>>>
>>>>>>>>> +static int testDomainGetDiskErrors(virDomainPtr dom,
>>>>>>>>> +                                   virDomainDiskErrorPtr errors,
>>>>>>>>> +                                   unsigned int maxerrors,
>>>>>>>>> +                                   unsigned int flags)
>>>>>>>>> +{
>>>>>>
>>>>>> [...]
>>>>>>
>>>>>>>>> +            n++;
>>>>>>>>> +        }
>>>>>>>>> +        ret = n;
>>>>>>>>> +    }
>>>>>>>>> +
>>>>>>>>> + cleanup:
>>>>>>>>> +    virDomainObjEndAPI(&vm);
>>>>>>>>> +    if (ret < 0) {
>>>>>>>>> +        for (i = 0; i < n; i++)
>>>>>>>>> +            VIR_FREE(errors[i].disk);
>>>>>>>>> +    }
>>>>>>
>>>>>> The above got changed to :
>>>>>>
>>>>>> + cleanup:
>>>>>> +    virDomainObjEndAPI(&vm);
>>>>>> +    if (ret < 0) {
>>>>>> +        for (i = 0; i < MIN(vm->def->ndisks, maxerrors); i++)
>>>>>> +            VIR_FREE(errors[i].disk);
>>>>>> +    }
>>>>>
>>>>> I think this change is incorrect and a bug lies in here.
>>>>>
>>>>> If VIR_STRDUP fails above, memory for less than MIN(vm->def->ndisks,
>>>>> maxerrors) will have been allocated, and then in the cleanup code
>>>>> we'll call VIR_FREE with pointers that haven't been previously
>>>>> allocated.
>>>>
>>>> That isn't a problem. User has to passed an array that we can touch. If
>>>> they store some data in it, well, their fault - how are we supposed to
>>>> return anything if we can't touch the array?
>>>
>>> I'm not sure I understand exactly what you mean.
>>>
>>> We can touch the array of course.
>>>
>>> What I'm saying is that we allocate memory with VIR_STRDUP for each
>>> errors[i].disk, but if the call fails we free this memory on our own.
>>>
>>> However how it is implemented now we might call VIR_FREE on pointers
>>> for which we have *not* allocated any memory.
>>>
>>> Because in the first loop, VIR_STRDUP might fail and send us to
>>> "cleanup". But then on cleanup we iterate over the whole errors array.
>>>
>>> Isn't this incorrect? Do I understand something wrong?
>>
>>
>> Ah, now I get it. If user passes an array that is not zeroed out then we
>> might end up passing a random pointer to free(). How about this then?
>>
>>       if (ret < 0) {
>>           while (i > 0)
>>               VIR_FREE(errors[i--].disk);
>>       }
>>
> 
> Yes, this would work I think. And then the other changes in the
> cleanup etc are not needed.
> 
> Ie it can be again:
> 
>      if (!(vm = testDomObjFromDomain(dom)))
>          goto cleanup;
> 
> instead of "return -1" which is more consistent with the rest of the code.

This is done in 1/2. Or what do you mean?

> 
> However the code now returns errors for all disks. I thought we wanted
> to report errors only for some of them?

Doesn't matter really.

Michal