Extended attribute interfaces

[Andreas Gruenbacher]

Robert Watson wrote:
> [...]
>
> Open points of discussion include:
> 
> 1) Ability to retrieve list of attributes on a file or directory --
>    presumably something dirent-like, but I'd like to hear about what both
>    the SGI folk and Andreas implemented, as there are many ways to do this
>    (and I have implemented none of them :-).  Retriving is useful for
>    backups (probably only in the application namespace, see below).

I guess backing up system attributes is quite useful, too. Please
see my other posting. I've tried to address several of the issues
you are mentioning there.

> [...]
>
> 3) Namespace issues.  [...]
>    Ted also expressed concerns about exposing application
>    extended attributes to userland, and I agree that there is the
>    potential for some problems here.

I assume you mean exposing system attributes here.
What are these concerns?

>    Seperate namespaces would allow,
>    say, the Linux community to only permit system attributes and return
>    an error for application ones :-).

Entirely possible, yes.

>    That said, the Trusted IRIX
>    programmer's guide suggests a good use of application extended
>    attributes for shared spool directories.

Robert, could you please point me at that?

>    Adding an additional
>    argument for namespace control would make sense.  However, what does
>    this mean for file systems that don't currently have namespaces like
>    that (HPFS, for example).

Filesystems don't need to make a difference between user
and system attributes IMO. It's only the rest of the kernel who cares.

>    My feeling is that for backup, also,
>    backup programs should touch only the application namespace, retrieving
>    system namespace stuff through appropriate ACL, capability, etc, APIs.

I believe it's possible (and better) to handle both in a uniform
way. Please see my other posting.


Cheers,
Andreas.

------------------------------------------------------------------------
 Andreas Gruenbacher, a.gruenbacher at computer.org
 Contact information: http://www.bestbits.at/~ag/
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