Re: [Qemu-devel] [RFC V6 24/33] qcow2: Integrate deduplication in qcow2_co_writev loop.

[Stefan Hajnoczi]

On Wed, Feb 27, 2013 at 03:31:48PM +0100, Benoît Canet wrote:
> > I find this expression hard to understand.
> > 
> > We only get here if ds.nb_undedupable_sectors > 0.  In other words, we
> > tried to dedup but failed, so we must write data into the image file.
> > 
> > Can we ensure that ds.nb_undedupable_sectors is limited to at most
> > remaining_sectors?  Then the expression becomes clearer:
> 
> ds.nb_undedupable_sectors can be bigger than remaining_sectors if
> dedup_cluster_data was completed at its begining and/or at its ending in case 
> of
> an unaligned write.
> 
> Maybe I could grow/replace qiov at the begining of writev to ingest the
> completed data and increase remaining_sectors so its will be alway >=
> ds.nb_undedupable_sectors ?
> 
> What do you think about this solution ?

Sure, if the semantics of the rest of this function can cope with
extending qiov.

Stefan