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Re: [libvirt] Correct a check for capacity arg of storageVolumeResize()



On Fri, Feb 24, 2012 at 8:58 PM, Eric Blake <eblake redhat com> wrote:
> On 02/23/2012 08:00 PM, Zeeshan Ali (Khattak) wrote:
>> From: "Zeeshan Ali (Khattak)" <zeeshanak gnome org>
>>
>> ---
>>  src/storage/storage_driver.c |    2 +-
>>  1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/src/storage/storage_driver.c b/src/storage/storage_driver.c
>> index df0e291..641944d 100644
>> --- a/src/storage/storage_driver.c
>> +++ b/src/storage/storage_driver.c
>> @@ -1758,7 +1758,7 @@ storageVolumeResize(virStorageVolPtr obj,
>>          goto out;
>>      }
>>
>> -    if (abs_capacity > vol->allocation + pool->def->available) {
>> +    if (abs_capacity > vol->capacity + pool->def->available) {
>
> I'm not sure this is right.  If you allow for sparse files and
> over-commitment of capacity, then sparsely resizing to something that
> has too much capacity but still fits within allocation limits would be a
> reasonable that should not be rejected.  I think it is more likely that
> we have several bugs in this area, in being too lax about which values
> we are actually checking.  In fact, is the only reason we are checking
> for overflow is to avoid wasting time doing a partial allocation just to
> learn at the end that we would hit ENOSPACE?
>
> Adding to your commit message with the actual scenario you used to
> trigger the problem, and why your fix is correct, will go a long way in
> convincing me that this is needed.

I got a volume with '1G' allocation and '10G' capacity. The available
space in the parent pool is '5G'. With the current check for
overcapacity, I can only try to resize to <= '6G'. You see the
problem?

>>          virStorageReportError(VIR_ERR_INVALID_ARG,
>
> Meanwhile, I just noticed this error code is wrong - the argument was
> syntactically valid, so the real problem is that we are out of space,
> which fits better as VIR_ERR_OPERATION_FAILED, or possibly a new error
> message specific to out-of-space errors.

K, i'll submit a fix for that.

-- 
Regards,

Zeeshan Ali (Khattak)
FSF member#5124


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