On 03/17/2016 05:10 PM, Alberto Garcia wrote:
> 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?
I think in fifo mode, we should read the disk first that is added earlier.
We don't need a way to control the order now.
Thanks
Wen Congyang
>
> Berto
>
>
> .
>
