Hi,

On Tue, Dec 11, 2001 at 12:41:15PM +1100, Nathan Scott wrote:
> On Mon, Dec 10, 2001 at 11:52:09AM +0000, Stephen C. Tweedie wrote:

> > Unfortunately, if there are many filesystems wanting to use posix
> > ACLs, then standardising the API is still desirable.
 
> Yes, absolutely.  That is in fact a large driving force behind
> this effort to get a common EA and POSIX ACL API, and we are now
> for the first time at a point where we have multiple filesystems
> (xfs, ext2, and ext3) sharing the same API.  The history went a
> bit like this:

Yep, I know the history: I've been following this for a long time. :)

> - Andreas made attempt #1 to get a system call interface agreed on
> over a year ago now.  He incorporated several peoples suggestions,
> but eventually the discussion got sidetracked, died and nothing
> further happened;

Yep, and I brought up all these points last time, too.

> > But the ACL encoding is still hobbled: ...
> 
> I have been on the acl-devel mailing list for a long time now,
> and while these features all sound like good ideas or interesting
> projects, I have never seen anyone post a patch or request any
> specific changes to Andreas' ACL encoding in that time.

It was proposed over a year ago on fsdevel-list.  I've attached the
main proposal email, and I've posted the mailbox containing the
discussion at

	http://people.redhat.com/sct/ACL/ACL.mailbox.gz

Warning, it uncompresses to over 600k!

> It seems to me that the relatively simple implementation which
> Andreas has done is a good starting point (it has been used in
> production for a long time now).
> 
> His POSIX ACL encoding has a version field in it

Umm, and where in the EA man pages is this described?  How does an
application use the EA API?  That's what I'm concerned about.  

The EA API is fine, as far as it goes.  However, it doesn't talk _at
all_ about extending semantics.  It doesn't even say if it is legal to
use system EAs for POSIX ACLs.  Right now, system EAs are just a magic
way of stuffing undefined bits into undefined filesystems.  What if I
want to add non-user-modifiable EAs to a file for user-space reasons?
Eg. what if my backup tool wants to write a backup timestamp which the
user can't modify?  How do I do that?  The EA spec doesn't actually
say whether it is legal for applications to store their own data in
system EAs, and if so, which set of system EAs must be reserved for
system internal use.

> so if/when some
> people step forward to implement these features you've described,
> and if they require changes to the format, then there should be no
> reason they can't do it cleanly and in a filesystem-independent
> manner, right?

What format?  There _is_ no defined format.  There's some existing
practice, but no rules whatever right now.

Cheers,
 Stephen