RE: [PATCH] Fail XS_DIRECTORY for paths with no children

[Owen Smith <owen.smith@xxxxxxxxxx>]

> -----Original Message-----
> From: win-pv-devel <win-pv-devel-bounces@xxxxxxxxxxxxxxxxxxxx> On Behalf Of
> Paul Durrant
> Sent: 11 January 2021 08:13
> To: 'Marek Marczykowski-Górecki' <marmarek@xxxxxxxxxxxxxxxxxxxxxx>; Owen
> Smith <owen.smith@xxxxxxxxxx>
> Cc: win-pv-devel@xxxxxxxxxxxxxxxxxxxx
> Subject: RE: [PATCH] Fail XS_DIRECTORY for paths with no children
> 
> [CAUTION - EXTERNAL EMAIL] DO NOT reply, click links, or open attachments
> unless you have verified the sender and know the content is safe.
> 
> > -----Original Message-----
> > From: win-pv-devel <win-pv-devel-bounces@xxxxxxxxxxxxxxxxxxxx> On
> > Behalf Of Marek Marczykowski-Górecki
> > Sent: 10 January 2021 12:35
> > To: Owen Smith <owen.smith@xxxxxxxxxx>
> > Cc: win-pv-devel@xxxxxxxxxxxxxxxxxxxx
> > Subject: Re: [PATCH] Fail XS_DIRECTORY for paths with no children
> >
> > On Wed, Jan 06, 2021 at 04:17:50PM +0000, Owen Smith wrote:
> > > When a xenstore path has no children, a response is generated which
> > > contians only the double null terminator. Detect a 0-length response
> > > payload and return STATUS_OBJECT_PATH_NOT_FOUND to indicate that
> > > this path does not have any children
> >
> > Is it really the right thing to do? I think it may confuse empty
> > directory with non-existing directory. But I may be missing some
> > context here.
> 
> For Directory I think ENOENT (aka STATUS_OBJECT_PATH_NOT_FOUND) is the
> most useful thing to hand back in both the empty and non-existent cases. If it
> becomes necessary to distinguish between the two then a Read can be issued
> which would succeed in the former case but fail in the latter.
> 
>   Paul

STATUS_OBJECT_PATH_NOT_FOUND and STATUS_OBJECT_NAME_NOT_FOUND could be used to 
disambiguate between "path doesn’t exist" and "path has no children".

ENOENT is mapped to STATUS_OBJECT_NAME_NOT_FOUND

Owen

> 
> >
> > --
> > Best Regards,
> > Marek Marczykowski-Górecki
> > Invisible Things Lab
> > A: Because it messes up the order in which people normally read text.
> > Q: Why is top-posting such a bad thing?
>