Re: [Xen-devel] [PATCH for-4.5 1/2] libxl: continue when encounter ERROR_JSON_CONFIG_EMPTY

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Fri, Nov 14, 2014 at 11:19:56AM +0000, Ian Campbell wrote:
> On Fri, 2014-11-14 at 11:10 +0000, Wei Liu wrote:
> > On Fri, Nov 14, 2014 at 10:55:35AM +0000, Ian Campbell wrote:
> > > On Fri, 2014-11-14 at 10:52 +0000, Ian Campbell wrote:
> > > > On Wed, 2014-11-12 at 17:04 +0000, Wei Liu wrote:
> > > > > Continue when libxl_retrieve_domain_configuration encounters
> > > > > ERROR_JSON_CONFIG_EMPTY, as caller might be interested in the partial
> > > > > configuration pulled from xenstore.  In this case
> > > > > ERROR_JSON_CONFIG_EMPTY is used as return value as before, if no other
> > > > > error happens along the way.
> > > > > 
> > > > > Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
> > > > > Cc: Zhigang Wang <zhigang.x.wang@xxxxxxxxxx>
> > > > 
> > > > Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> > > 
> > > On second thoughts, I think this really needs an update to libxl.h to
> > > describe the semantics of this function, i.e. to what extent the output
> > > is valid for various error codes, especially ERROR_JSON_CONFIG_EMPTY.
> > > 
> > 
> > Any non-zero return code means the output is invalid (as in "Is this
> > output valid to rebuild a domain?").
> 
> But your second patch prints it as if it is at least somewhat
> meaningful, if not entirely valid. According to what you just said it
> shouldn't do so.
> 
> You effectively have three return states now: Fully valid, domain exists
> but it's configuration is unsure or somehow incomplete (~= JSON EMPTY),
> some sort of error occurred.
> 
> It might even be a good idea to have some new externally visible error
> code for the middle state, since JSON_EMPTY may not be the only reason
> for being in that state (at least in theory).
> 
> Anyway, since this is all more subtle than the existing 0 is good,
> non-zero is completely bad it should be written down.
> 

I'm not very keen on rushing to get ERROR_JSON_CONFIG_EMPTY special
meaning at this point of a release. I think we can deal with this in
next release.

Wei.

> Ian.

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel