Re: [Qemu-devel] [PATCH v5 13/15] block: add support for partial streaming

[Marcelo Tosatti]

On Tue, Jan 17, 2012 at 02:27:04PM +0100, Kevin Wolf wrote:
> Am 13.01.2012 14:14, schrieb Stefan Hajnoczi:
> > From: Marcelo Tosatti <address@hidden>
> > 
> > Add support for streaming data from an intermediate section of the
> > image chain (see patch and documentation for details).
> > 
> > Signed-off-by: Marcelo Tosatti <address@hidden>
> > Signed-off-by: Stefan Hajnoczi <address@hidden>
> 
> I'm afraid that in the review for the previous version I couldn't see
> the wood for the trees... This does limit the COR requests issued by
> image streaming, but not those issued by the guest. Am I missing
> something? This is not what we want, is it?

What you mean "limit the COR requests"? 

bdrv_co_is_allocated_base (or its new name) relies on
bbdrv_co_is_allocated being synchronous.

Sectors are only allocated in the top image, and in that case the
situation regaring synchronicity is the same as without shared base
option, that is, the serialization in bdrv_aio_read/bdrv_aio_write level
is responsible for correctness.