Re: [Xen-devel] [PATCH V5 29/32] xl: use "libxl-json" format

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Sun, 2014-06-01 at 20:07 +0100, Wei Liu wrote:
> On Tue, May 20, 2014 at 04:11:44PM +0100, Ian Jackson wrote:
> > Wei Liu writes ("[PATCH V5 29/32] xl: use "libxl-json" format"):
> > > Before this change, xl stores domain configuration in "xl" format, which
> > > is in fact a verbatim copy of user supplied domain config.
> > ...
> > > +    /* If we're doing migration, the domain name was appended with
> > > +     * "--incoming" a few lines above. So we need to remove that
> > > +     * suffix in the stored configuration.
> > > +     */
> > > +    if (migrate_fd >= 0) {
> > > +        libxl_domain_config d;
> > > +        int xlen = strlen("--incoming");
> > > +        int orig_len;
> > > +
> > > +        ret = libxl_load_domain_configuration(ctx, domid, &d);
> > 
> > Firstly, I think this editing of libxl's copy of domain config way is
> > a layering violation.
> > 
> > But it ought to be unnecessary, because either libxl_domain_rename
> > or "libxl_load_domain_configuration" should deal with it.  I would
> > much prefer the latter, as that results in the domain name being
> > stored only in one place.
> > 
> 
> Huh? I suppose to avoid "layering violation" I should make
> libxl_domain_rename manipulate the stored configuration, shouldn't I?
> But you're suggesting I make libxl_load_domain_configuration work?
> I'm confused.

He was suggesting two alternatives, not two things to both be done.

I think we need to decide if the stored configuration is the original
user provide config, which is undated by
libxl_retrieve_domain_configuration vs each libxl operation updating the
stored state so that libxl_retrieve_domain_configuration before a simple
parse and return.

Ian.


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