Re: [Qemu-block] [Qemu-devel] [PATCH v3 6/7] block/dirty-bitmaps: disallow busy bitmaps as merge source

[Eric Blake]

On 3/6/19 9:24 AM, John Snow wrote:

>>>
>>> We could always split it back out later, but in basic terms for
>>> permissions and user perspective, "in use" seems robust enough of a
>>> resolution. (It might be safe to read, it might not be, who knows --
>>> it's in use.)
>>
>> I think, if we need some kind of sharing busy bitmaps, it should be two
>> busy states: one, which allows reads for other users and one that doesn't.
>>

Indeed, similar to flock having shared (multiple read-only users) and
exclusive (single writer) locks.  So it's nice to know we have a
technical plan for growth, if we have a reason to use that plan.

> 
> I think that's... hopefully premature. We don't need this NOW do we?

No, we don't need it now.

> 
> I think this is OK as-is.

It sounds like we are in violent agreement ;)

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

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