On Thu 17 Mar 2016 02:22:40 AM CET, Wen Congyang <we...@cn.fujitsu.com> wrote:
>>>>> @@ -81,6 +82,8 @@ typedef struct BDRVQuorumState {
>>>>> bool rewrite_corrupted;/* true if the driver must rewrite-on-read
>>>>> corrupted
>>>>> * block if Quorum is reached.
>>>>> */
>>>>> + unsigned long *index_bitmap;
>>>
>>> Hi Berto
>>>
>>> *NOTE*, In the old version, we just used "bs->node_name", but in the
>>> lastest one, as Kevin suggested we introduce
>>> "child->child_name"(formart as "children.xxx"), this is the key cause
>>> why we need this two functions here.
>>
>> I'm sorry I missed this discussion earlier. Your code seems technically
>> correct but I have several questions:
>>
>> - I read that one of the reasons for this change is that "In theory, the
>> same node could be attached twice to the same parent in different
>> roles.". Is there any example of that? What's the use case?
>
> Kevin may know the case.
Kevin, do you have an example?
>> - How do you obtain the child name?
>
> IIRC, the answer is no now. I think we can improve 'info block' output
Okay, but then we should extend that first, otherwise this API cannot be
used.
>> - I see that if you have children.0 and children.1 (let's say hd0.qcow2
>> and hd1.qcow2), then you remove children.0 and add it again, it will
>> keep the 'children.0' name (that's what the bitmap is for if I'm
>> understanding it correctly). However the position in the s->children
>> array will change because you do memmove() when you remove children.0
>> and then add it again to the end of the array.
>>
>> Initial status:
>>
>> s->children[0] <--> "children.0" (hd0.qcow2)
>> s->children[1] <--> "children.1" (hd1.qcow2)
>>
>> children.0 (hd0.qcow2) is removed:
>>
>> s->children[0] <--> "children.1" (hd1.qcow2)
>>
>> children.0 (hd0.qcow2) is added again:
>>
>> s->children[0] <--> "children.1" (hd1.qcow2)
>> s->children[1] <--> "children.0" (hd0.qcow2)
>
> Yes, it is correct.
>
>>
>> Is this correct? Is this the indented behavior? Since you are reading
>> in FIFO mode, now hd1.qcow2 will always be read first, so if
>> children.1 was the secondary disk, it has just become the primary.
>
> Yes.
And don't you need a way to control the order in which the disks must be
read for COLO?
Berto
