Re: [Xen-devel] [PATCH v1 01/10] libxl: libxl-json format and internal functions to get / set it

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Thu, Jul 24, 2014 at 07:29:58PM +0100, Ian Jackson wrote:
> Wei Liu writes ("[PATCH v1 01/10] libxl: libxl-json format and internal 
> functions to get / set it"):
> > Introduce a new format in libxl userdata store called "libxl-json". This
> > file format contains JSON version of libxl_domain_config, generated by
> > libxl.
> ...
> > +int libxl__get_domain_configuration(libxl__gc *gc, uint32_t domid,
> > +                                    libxl_domain_config *d_config)
> > +{
> > +    uint8_t *data = NULL;
> > +    int rc, len;
> > +
> > +    rc = libxl_userdata_retrieve(CTX, domid, "libxl-json", &data, &len);
> ...
> > +    if (len == 0) {
> > +        LOGE(ERROR, "configuration data stream empty for domain %d", 
> > domid);
> > +        rc = ERROR_FAIL;
> 
> Reading 03/10 I notice the following issue with this:
> 
> During domain setup there is a moment where the domid exists, but the
> configuration data doesn't.  Therefore this is a possible situation,
> and does not reflect an internal error.
> 
> So, you need to treat this case differently.  It shouldn't log an
> error and it should probably return a custom error code, which all
> callers would have to handle specially.
> 
> Ultimately if an application asks for the configuration of a domain in
> this state, it is not possible to tell whether it is in the process
> being created, or is left in an anomalous (crashed) state.  So I think
> this possible but anomalous state needs to be exposed all the way up
> the stack.
> 

No problem. I can return ERROR_JSON_CONFIG_EMPTY.

Does this patch still have your ack provided I make that change?

Wei.

> Ian.

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