Re: [Qemu-devel] [PATCH v3 2/8] block: add basic backup support to block driver

[Stefan Hajnoczi]

On Tue, May 21, 2013 at 06:46:39PM +0200, Paolo Bonzini wrote:
> Il 21/05/2013 18:26, Dietmar Maurer ha scritto:
> >> Hmm, right.  But do we need the bitmap at all?  We can just use
> >> > bdrv_is_allocated like bdrv_co_do_readv does.
> > Does that works with a nbd driver?
> 
> Ah, right.  That's the answer.

Yes, the target may not supported allocation info.

> > Or does that add another RPC call (slow down)?
> 
> It doesn't work at all.  Thus Stefan's patch is fine (except if you
> don't use HBitmapIter, there's no advantage in using HBitmap; you can
> use qemu/bitmap.h instead).

I chose HBitmap because bitmap.h uses the int type instead of uint64_t,
which makes it risky to use in the block layer.

Stefan