Re: [Qemu-devel] [PATCH 3/6] bloc/qcow2: drop dirty_bitmaps_loaded state variable

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

10.07.2018 02:25, John Snow wrote:
>
> On 06/26/2018 09:50 AM, Vladimir Sementsov-Ogievskiy wrote:
>> This variable doesn't work as it should, because it is actually cleared
>> in qcow2_co_invalidate_cache() by memset(). Drop it, as the following
>> patch will introduce new behavior.
>>
>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>> ---
>>   block/qcow2.h |  1 -
>>   block/qcow2.c | 19 ++-----------------
>>   2 files changed, 2 insertions(+), 18 deletions(-)
>>
>> diff --git a/block/qcow2.h b/block/qcow2.h
>> index 01b5250415..c9df19b6e6 100644
>> --- a/block/qcow2.h
>> +++ b/block/qcow2.h
>> @@ -294,7 +294,6 @@ typedef struct BDRVQcow2State {
>>       uint32_t nb_bitmaps;
>>       uint64_t bitmap_directory_size;
>>       uint64_t bitmap_directory_offset;
>> -    bool dirty_bitmaps_loaded;
>>   
>>       int flags;
>>       int qcow_version;
>> diff --git a/block/qcow2.c b/block/qcow2.c
>> index 46194a33ca..0044ff58e7 100644
>> --- a/block/qcow2.c
>> +++ b/block/qcow2.c
>> @@ -1149,7 +1149,6 @@ static int coroutine_fn qcow2_do_open(BlockDriverState *bs, QDict *options,
>>       uint64_t ext_end;
>>       uint64_t l1_vm_state_index;
>>       bool update_header = false;
>> -    bool header_updated = false;
>>   
>>       ret = bdrv_pread(bs->file, 0, &header, sizeof(header));
>>       if (ret < 0) {
>> @@ -1488,23 +1487,9 @@ static int coroutine_fn qcow2_do_open(BlockDriverState *bs, QDict *options,
>>           s->autoclear_features &= QCOW2_AUTOCLEAR_MASK;
>>       }
>>   
>> -    if (s->dirty_bitmaps_loaded) {
>> -        /* It's some kind of reopen. There are no known cases where we need to
>> -         * reload bitmaps in such a situation, so it's safer to skip them.
>> -         *
>> -         * Moreover, if we have some readonly bitmaps and we are reopening for
>> -         * rw we should reopen bitmaps correspondingly.
>> -         */
>> -        if (bdrv_has_readonly_bitmaps(bs) &&
>> -            !bdrv_is_read_only(bs) && !(bdrv_get_flags(bs) & BDRV_O_INACTIVE))
>> -        {
>> -            qcow2_reopen_bitmaps_rw_hint(bs, &header_updated, &local_err);
>> -        }
>> -    } else {
>> -        header_updated = qcow2_load_dirty_bitmaps(bs, &local_err);
>> -        s->dirty_bitmaps_loaded = true;
>> +    if (qcow2_load_dirty_bitmaps(bs, &local_err)) {
>> +        update_header = false;
>>       }
>> -    update_header = update_header && !header_updated;
>>       if (local_err != NULL) {
>>           error_propagate(errp, local_err);
>>           ret = -EINVAL;
>>
> Usually I'd like to see the new behavior introduced before removing the
> old, imperfect solution... (it doesn't make any tests fail!? ...)
>
> At this point in the series I just have to trust that you will fix it to
> be better :)

As I understand, this field is actually always false, so it's safe to 
drop it.

>
> --js


-- 
Best regards,
Vladimir