Re: [Qemu-block] [PATCH 4/8] block/backup: hoist bitmap check into QMP interface

[John Snow]

On 7/10/19 12:11 PM, Max Reitz wrote:
> On 10.07.19 03:05, John Snow wrote:
>> This is nicer to do in the unified QMP interface that we have now,
>> because it lets us use the right terminology back at the user.
>>
>> Signed-off-by: John Snow <address@hidden>
>> ---
>>  block/backup.c | 13 ++++---------
>>  blockdev.c     | 10 ++++++++++
>>  2 files changed, 14 insertions(+), 9 deletions(-)
>>
>> diff --git a/block/backup.c b/block/backup.c
>> index e2729cf6fa..a64b768e24 100644
>> --- a/block/backup.c
>> +++ b/block/backup.c
>> @@ -566,6 +566,10 @@ BlockJob *backup_job_create(const char *job_id, 
>> BlockDriverState *bs,
>>      assert(bs);
>>      assert(target);
>>  
>> +    /* QMP interface protects us from these cases */
>> +    assert(sync_mode != MIRROR_SYNC_MODE_INCREMENTAL);
>> +    assert(sync_bitmap || sync_mode != MIRROR_SYNC_MODE_BITMAP);
> 
> Implication would be a nice operator sometimes.
> 
> ("assert(sync_mode == MIRROR_SYNC_MODE_BITMAP -> sync_bitmap)")
> 
> (Can you do that in C++?  No, you can’t overload bool’s operators, right?)
> 
> Reviewed-by: Max Reitz <address@hidden>
> 

Yes, I also find this assertion kind of hard to read personally, but it
feels somewhat clunky to write:

if (antecedent) {
    assert(condition);
}

I suppose we can also phrase this as:

assert(sync_mode == MIRROR_SYNC_MODE_BITMAP ? sync_bitmap : true);

Which might honestly be pretty good. Mind if I change it to this?

--js