[Acl-Devel] What would be the 'proper' function to determine that a fs can support posix acls?

[Andreas Gruenbacher]

On Wed, 25 Apr 2001, Robert Watson wrote:

> On Mon, 23 Apr 2001, Andreas Gruenbacher wrote:
> 
> > > At first blush, (and in current Samba implementations -2.2.0) acl_init would
> > > seem like the place.  Unfortunately, acl_init(int count) takes only the
> > > parameter count to determine if the working space acl can be created.  I don't
> > > see that this has any place to check the file system.
> > > 
> > > I can see that something like acl_get_fd or acl_get_file might be a better
> > > place to accomplish such a test.
> > 
> > acl_get_{fd,file}() return a three-element ACL on filesystems that don't
> > have extended ACLs. 
> 
> Hmm.  I used to do that in the FreeBSD implementation, but after a
> discussion with Casey on the posix1e mailing list, I concluded it was
> better to do the magical permission->ACL conversion in getfacl.  This is
> derived from the following text in 23.4.16.2:
> 
>   If the argument type specifies a type of ACL that cannot be associated
>   with path_p, then the function shall fail.
> 
> I wasn't sure I entirely agreed, but it seemed to me that Casey's argument
> held water.  :-)  We now return EOPNOTSUPP from acl_get_*() if ACLs are
> not permitted on the object in question.  We also don't have the
> pathconf() feature working yet, as right now ACLs are implicitly enabled
> on file systems where the appropriate EAs are available.  I have some
> patches to make that policy driven using a file system superblock flag,
> but haven't tested/committed yet.

I did not realize I was overruled on this, but for compatibility reasons I
will change the behaviour of acl_get_{fd,file}() to match the one of Irix
+ FreeBSD.

How about acl_set_{fd,file}()? I presume your interpretation of draft 17
also means those never do the equivalent of chmod on filesystems without
ACL support?

Thanks,
--Andreas.

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