Re: librbd discard bug problems -> i got it

[Stefan Priebe <s.priebe@profihost.ag>]

Hi Josh,

i don't get it. Every debug line i print is a prositive fine value. BUt 
rbd_aio_bh_cb get's called with these values. As you can see that are 
not much values i copied all values < 0 from log for discarding a whole 
30GB device.

Stefan

Am 20.11.2012 00:47, schrieb Josh Durgin:
> On 11/19/2012 03:42 PM, Stefan Priebe wrote:
>> Am 20.11.2012 00:33, schrieb Josh Durgin:
>>> On 11/19/2012 03:16 PM, Stefan Priebe wrote:
>>>> mhm qemu rbd block driver. Get's always these errors back. As
>>>> rbd_aio_bh_cb is directly called from librbd the problem must be there.
>>>> Strangely i can't find where rbd_aio_bh_cb get's called with -512.
>>>>
>>>> ANy further ideas?
>>>
>>> Two ideas:
>>>
>>> 1) Is rbd_finish_aiocb getting this same return value?
>> Will check this tomorrow.
>>
>>
>>> 2) Perhaps it's an issue with the return value wrapping around with
>>> very large discards. Adding some logging of the return values of each
>>> rados operation in AioCompletion::complete_request() might give us a
>>> clue. These large negative return values are suspicious.
>>
>> Good idea. As r and rval is int it is limited. But
>> AioCompletion::complete_request is adding more and more stuff to rval.
>> What could be a solution? Bump rval to int64? Or wrap to around to start
>> at 0 again?
>
> The final return value is limited to int at a few levels. Probably it's
> best to make discard alway return 0 on success. aio_discard should
> already be doing this, but perhaps it's not in this case.
>
> Josh
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