Re: [Qemu-block] [PATCH v2 3/9] blockjob: Don't set iostatus of target

[Max Reitz]

On 06.05.2016 16:12, Kevin Wolf wrote:
> Am 06.05.2016 um 15:40 hat Max Reitz geschrieben:
>> On 06.05.2016 15:31, Kevin Wolf wrote:
>>> Am 06.05.2016 um 14:32 hat Max Reitz geschrieben:
>>>> On 06.05.2016 14:01, Max Reitz wrote:
>>>>> On 27.04.2016 15:20, Kevin Wolf wrote:
>>>>>> When block job errors were introduced, we assigned the iostatus of the
>>>>>> target BDS "just in case". The field has never been accessible for the
>>>>>> user because the target isn't listed in query-block.
>>>>>>
>>>>>> Before we can allow the user to have a second BlockBackend on the
>>>>>> target, we need to clean this up. If anything, we would want to set the
>>>>>> iostatus for the internal BB of the job (which we can always do later),
>>>>>> but certainly not for a separate BB which the job doesn't even use.
>>>>>>
>>>>>> As a nice side effect, this gets us rid of another bs->blk use.
>>>>>>
>>>>>> Signed-off-by: Kevin Wolf <address@hidden>
>>>>>> ---
>>>>>>  block/backup.c           | 8 ++++----
>>>>>>  block/mirror.c           | 8 ++++----
>>>>>>  block/stream.c           | 3 +--
>>>>>>  blockjob.c               | 6 +-----
>>>>>>  include/block/blockjob.h | 4 +---
>>>>>>  5 files changed, 11 insertions(+), 18 deletions(-)
>>>>>
>>>>> Reviewed-by: Max Reitz <address@hidden>
>>>>
>>>> Maybe I need to take that back. Using e.g. blockdev-backup, you can
>>>> indeed see the target in query-block.
>>>>
>>>> e.g.:
>>>>
>>>> (echo "{'execute':'qmp_capabilities'}
>>>>        {'execute':'blockdev-backup',
>>>>         'arguments':{'device':'src','target':'dst',
>>>>         'sync':'full','on-target-error':'enospc'}}";
>>>>  sleep 1;
>>>>  echo "{'execute':'query-block'}") | \
>>>>    x86_64-softmmu/qemu-system-x86_64 \
>>>>        -drive if=none,id=src,file=test.qcow2 \
>>>>        -drive if=none,id=dst,file=mnt/out.qcow2 \
>>>>        -qmp-pretty stdio -nodefaults
>>>>
>>>> Where mnt is a file system and test.qcow2 is large enough such that an
>>>> ENOSPC will occur.
>>>
>>> Hm... Let's pretend we didn't notice. In fact, I don't think this
>>> behaviour is documented and it also doesn't make a lot of sense.
>>>
>>> I would be surprised if libvirt made use of it, as there is still the
>>> job iostatus which works in drive-* cases, too.
>>>
>>> (Eric?)
>>>
>>>> Before this patch, you can see "io-status": "nospace" in query-block for
>>>> dst. After it, it says "io-status": "ok", and after the next it doesn't
>>>> say anything about the status at all anymore.
>>>
>>> Simply letting the field disappear sounds like a nice solution.
>>
>> I'm not sure I completely agree with that because the iostatus appears
>> to be the only way of obtaining the information whether the block job
>> stopped because of an ENOSPC or because of something different (the
>> BLOCK_JOB_ERROR doesn't tell you).
>>
>> I don't know whether anyone actually needs that information, though, and
>> if you think dropping this is fine, then I guess it's fine with me, too,
>> and my R-b stands.
> 
> But you don't have this information with the drive-* commands either.
> 
> I would be okay with reintroducing this information, but in the right
> place. Modifying the guest device iostatus for block jobs certainly
> isn't right.

As discussed on IRC, that sounds right to me. Thus, have an explicit

Reviewed-by: Max Reitz <address@hidden>

> Anyway, we need Eric's input to confirm that libvirt doesn't depend on
> this.
> 
> Kevin
>

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