On 22.02.19 16:38, Kevin Wolf wrote:
> Am 22.02.2019 um 15:12 hat Max Reitz geschrieben:
>> On 19.02.19 09:51, Kevin Wolf wrote:
>>> Am 19.02.2019 um 00:57 hat Max Reitz geschrieben:
>>>> On 31.01.19 18:55, Kevin Wolf wrote:
>>>>> This adds a .bdrv_open option to specify the external data file node.
>>>>>
>>>>> Signed-off-by: Kevin Wolf <kw...@redhat.com>
>>>>> ---
>>>>> qapi/block-core.json | 3 ++-
>>>>> block/qcow2.h | 4 +++-
>>>>> block/qcow2.c | 25 +++++++++++++++++++++++--
>>>>> 3 files changed, 28 insertions(+), 4 deletions(-)
>>>>
>>>> [...]
>>>>
>>>>> diff --git a/block/qcow2.h b/block/qcow2.h
>>>>> index c161970882..e2114900b4 100644
>>>>> --- a/block/qcow2.h
>>>>> +++ b/block/qcow2.h
>>>>
>>>> [...]
>>>>
>>>>> @@ -205,7 +206,8 @@ enum {
>>>>> QCOW2_INCOMPAT_DATA_FILE = 1 <<
>>>>> QCOW2_INCOMPAT_DATA_FILE_BITNR,
>>>>>
>>>>> QCOW2_INCOMPAT_MASK = QCOW2_INCOMPAT_DIRTY
>>>>> - | QCOW2_INCOMPAT_CORRUPT,
>>>>> + | QCOW2_INCOMPAT_CORRUPT
>>>>> + | QCOW2_INCOMPAT_DATA_FILE,
>>>>
>>>> This hunk seems to belong somewhere else.
>>>
>>> Isn't this the first patch that actually allows opening images that have
>>> QCOW2_INCOMPAT_DATA_FILE set in their header?
>>
>> Oh, sorry. I thought the mask was the mask of all incompatible
>> features, but it's actually the mask of supported incompatible features.
>> Yep, then it's correct here.
>>
>>>>> };
>>>>>
>>>>> /* Compatible feature bits */
>>>>> diff --git a/block/qcow2.c b/block/qcow2.c
>>>>> index ac9934b3ed..376232d3f0 100644
>>>>> --- a/block/qcow2.c
>>>>> +++ b/block/qcow2.c
>>>>> @@ -1441,8 +1441,22 @@ static int coroutine_fn
>>>>> qcow2_do_open(BlockDriverState *bs, QDict *options,
>>>>> goto fail;
>>>>> }
>>>>>
>>>>> - /* TODO Open external data file */
>>>>> - s->data_file = bs->file;
>>>>> + /* Open external data file */
>>>>> + if (s->incompatible_features & QCOW2_INCOMPAT_DATA_FILE) {
>>>>> + s->data_file = bdrv_open_child(NULL, options, "data-file", bs,
>>>>> + &child_file, false, errp);
>>>>> + if (!s->data_file) {
>>>>> + ret = -EINVAL;
>>>>> + goto fail;
>>>>> + }
>>>>> + } else if (qdict_get(options, QCOW2_OPT_DATA_FILE)) {
>>>>
>>>> I get the idea, but this isn't crumpled so this key may not exist (but
>>>> data-file.driver and data-file.filename may). Of course the fact that
>>>> these options remain unused will be caught by the block layer, but that
>>>> makes the error message below a bit less useful.
>>>
>>> Hmm, good point... So you'd just leave out the check and always let the
>>> block layer complain (with a less than helpful message)? Or are you
>>> suggesting I should try and catch all cases somehow, even if that makes
>>> things quite a bit more complicated?
>>
>> I don't mind either way. Nice error messages are nice as long as
>> they're not too much trouble. It's just that this current state feels a
>> bit half-baked.
>
> I think catching everything is just not worth the effort. So I
> considered dropping the check. But then I thought that this half baked
> check will make sure that we'll get full coverage once qcow2 is
> converted to a QAPI-based open interface instead of forgetting to bring
> the check back. So I'm leaning towards just leaving it as it is now. If
> you like, I can add a comment that we know this is half baked."Once"... :-) Seems reasonable to me. Max
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