Re: [Qemu-block] [Qemu-devel] [PATCH v3 1/2] block: sync bdrv_co_get_block_status_above() with bdrv_is_allocated_above()

[Eric Blake]

On 09/18/2016 11:37 PM, Denis V. Lunev wrote:
> On 09/19/2016 04:21 AM, Fam Zheng wrote:
>> On Thu, 09/15 19:34, Denis V. Lunev wrote:
>>> They should work very similar, covering same areas if backing store is
>>> shorter than the image. This change is necessary for the followup patch
>>> switching to bdrv_get_block_status_above() in mirror to avoid assert
>>> in check_block.
>>>
>>> This change should be made very carefully. Let us assume that we have
>>> top image and 2 backing stores L0->L1->L2.
>> Stupid question: which one is top and which are backing?
> L0 is top, L2 is at bottom.

I typically write this as:

L2 <- L1 <- L0

(read "L2 backs L1, which in turn backs L0") with the active on the
right.  So I understand the confusion in Fam's question where you were
using the opposite direction.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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