Re: [Qemu-devel] [PATCH 23/24] qcow2: add .bdrv_remove_persistent_dirty_bitmap

[Max Reitz]

On 01.02.2017 15:23, Vladimir Sementsov-Ogievskiy wrote:
> 01.02.2017 16:57, Vladimir Sementsov-Ogievskiy wrote:
>> 01.02.2017 02:20, Max Reitz wrote:
>>> On 23.01.2017 13:10, Vladimir Sementsov-Ogievskiy wrote:
>>>> Realize .bdrv_remove_persistent_dirty_bitmap interface.
>>>>
>>>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com>
>>>> ---
>>>>   block/qcow2-bitmap.c | 40 ++++++++++++++++++++++++++++++++++++++++
>>>>   block/qcow2.c        |  1 +
>>>>   block/qcow2.h        |  3 +++
>>>>   3 files changed, 44 insertions(+)
>>>>
>>>> diff --git a/block/qcow2-bitmap.c b/block/qcow2-bitmap.c
>>>> index 2687a3acd5..be026fc80e 100644
>>>> --- a/block/qcow2-bitmap.c
>>>> +++ b/block/qcow2-bitmap.c
>>>> @@ -1064,6 +1064,46 @@ static Qcow2Bitmap
>>>> *find_bitmap_by_name(Qcow2BitmapList *bm_list,
>>>>       return NULL;
>>>>   }
>>>>   +void qcow2_remove_persistent_dirty_bitmap(BlockDriverState *bs,
>>>> +                                          const char *name,
>>>> +                                          Error **errp)
>>>> +{
>>>> +    int ret;
>>>> +    BDRVQcow2State *s = bs->opaque;
>>>> +    Qcow2Bitmap *bm;
>>>> +    Qcow2BitmapList *bm_list;
>>>> +
>>>> +    if (s->nb_bitmaps == 0) {
>>>> +        /* No bitmaps - nothing to do */
>>> Shouldn't it be an error? I.e. "bitmap not found"?
>>>
>>>> +        return;
>>>> +    }
>>>> +
>>>> +    bm_list = bitmap_list_load(bs, s->bitmap_directory_offset,
>>>> +                               s->bitmap_directory_size, errp);
>>>> +    if (bm_list == NULL) {
>>>> +        return;
>>>> +    }
>>>> +
>>>> +    bm = find_bitmap_by_name(bm_list, name);
>>>> +    if (bm == NULL) {
>>>> +        goto fail;
>>> What about setting errp? Or do you not consider this an error?
>>>
>>> I think it should be an error.
>>
>> Hmm. The following scenery should not be an error:
>> 1. qmp create dirty bitmap with persistent = true (bitmap not exists
>> and not created  in the storage, it will be saved only on storage close)
>> 2. qmp remove dirty bitmap. persistent = true, so we will try to
>> remove it from storage..
>>
>> So, I see following variants:
>> 1. as is, just add comment "remove if exists"
>> 2. add return value to this function, return ENOENT if bitmap not
>> found and ignore this ENOENT in qmp_remove_bitmap
>> 3. add additional bool field 'exist_in_storage' to BdrvDirtyBitmap.
> 
> Also, I can call remove_persistent...() from
> bdrv_dirty_bitmap_set_persistance( ..., false), and use this function in
> qmp block-remove-dirty-bitmap

Right, that would make sense.

Max

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