Re: [PATCH v3 04/10] hbitmap: drop meta bitmaps as they are unused

[Eric Blake]

On 1/20/20 11:28 AM, Vladimir Sementsov-Ogievskiy wrote:

> > > I'm a bit not follow what you mean. I can just note, that dirty-bitmap.c
> > > part of meta bitmaps was recently removed, and hbitmap.c part I forgot to
> > > remove...
> >
> > Yes, but who used that dirty-bitmap.c interface?  As far as I can tell,
> > nobody.
>
> Yes, as far as I know, nobody and never.
>
> > > Meta bitmaps were intended to control live migration of bitmaps and to
> > > implement something like partial sync of bitmaps (write to qcow2 only
> > > changed part of bitmap), but migration implemented in other way
> > > (postcopy) and the second thing was not implemented.
> >
> > OK.  I was wondering why they were implemented without ever having been
> > used (as far as I can tell).
>
> It was too optimistic preparatory series.

Matches my recollection (we had several ideas about how to tackle it; 
meta-bitmaps was proposed as one idea and this code landed, but we never 
actually finished that idea before a better one was actually coded, so 
this has always been dead code).

> (I can never finally understand, series - who a they or what is it?
>    Plural or singular?

English is funny; "series" is one of the few words that works as both 
singular and plural (another example is "sheep").

> They were too optimistic series? Sounds weird..

My spin: "The original series was too optimistic."

>    And if one series is series, than what about several serieses?
>    OK, let's say, it was too optimistic preparatory patch set :)

--
Eric Blake, Principal Software Engineer
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