Re: [Qemu-block] [PATCH 07/24] qcow2: add bitmaps extension

[Max Reitz]

On 30.01.2017 08:21, Vladimir Sementsov-Ogievskiy wrote:
> 29.01.2017 00:29, Max Reitz wrote:
>> On 23.01.2017 13:10, Vladimir Sementsov-Ogievskiy wrote:
>>> Add bitmap extension as specified in docs/specs/qcow2.txt.
>>> For now, just mirror extension header into Qcow2 state and check
>>> constraints.
>>>
>>> For now, disable image resize if it has bitmaps. It will be fixed later.
>>>
>>> Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
>>> ---
>>>   block/qcow2.c | 119
>>> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
>>>   block/qcow2.h |  24 ++++++++++++
>>>   2 files changed, 141 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/block/qcow2.c b/block/qcow2.c
>>> index 96fb8a8f16..a8835988c7 100644
>>> --- a/block/qcow2.c
>>> +++ b/block/qcow2.c
>> [...]
>>
>>> @@ -185,6 +265,15 @@ static int
>>> qcow2_read_extensions(BlockDriverState *bs, uint64_t start_offset,
>>>           offset += ((ext.len + 7) & ~7);
>>>       }
>>>   +    if (need_update && !bdrv_is_root_node(bs) &&
>>> +        !(bdrv_get_flags(bs) & BDRV_O_INACTIVE))
>>> +    {
>>> +        ret = qcow2_update_header(bs);
>> Good idea, but qcow2_read_extensions() can be called pretty early in
>> qcow2_open(). Therefore, some fields in the BDRVQcow2State are not
>> necessarily set already.
>>
>> For instance, it is always called before s->snapshots_offset and
>> s->nb_snapshots are set. Thus, this will effectively always discard all
>> snapshots.
>>
>> Max
>>
> 
> So, I need to move need_update to qcow2_read_extensions parameters as
> 'bool *' and handle it later, in the end of qcow2_open. Ok?

Yes, that sounds reasonable.

Max

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