Re: [Qemu-devel] [PATCH 0/2] deal with BDRV_BLOCK_RAW

[Eric Blake]

On 8/13/19 9:31 AM, Max Reitz wrote:
> On 13.08.19 13:51, Kevin Wolf wrote:
> 
> [...]
> 
>> Hm... This is a mess. :-)
> 
> Just out of curiosity: Why?
> 
> Aren’t there only two things we really need from the block_status
> infrastructure?
> 
> (1) Whether something is allocated in the given layer of the backing chain,

(1)(a) - is it allocated in this layer
(1)(b) - is it allocated in any backing layer

> 
> (2) Whether we know that a given range reads as zeroes.
> 
> Do we really need anything else?

qemu-img map needs:

(3) What host-relative offset, if any, corresponds to a given
guest-visible offset.

I also need to find time to revisit my proposed patches on block_status
alignment - there are some cases where we want to ensure that one layer
with large granularity does not pick up mid-granularity changes in
status read from a backing layer with smaller granularity.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

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