Re: [fuse-devel] [RFC] fuse: Support posix ACLs

[Seth Forshee <seth.forshee@canonical.com>]

On Wed, Jun 29, 2016 at 03:18:24PM -0500, Eric W. Biederman wrote:
> "Michael j Theall" <mtheall@us.ibm.com> writes:
> 
> > Going by the patch I posted a couple of years ago:
> > https://sourceforge.net/p/fuse/mailman/message/33033653/
> >
> > The only hole I see in your patch is that in setattr() you are not
> > updating the cached acl if the ATTR_MODE is updated. The other major
> > difference is that my version uses the get_acl/set_acl inode
> > operations but you use that plus the xattr handlers. I'm not
> > up-to-speed on the kernel so I'm not sure if you actually need to
> > implement both.
> 
> That makes an interesting question.  Is it desirable to keep
> inode->i_mode in sync with the posix acls in fuse or should a filesystem
> that supports posix acls worry about that?

My first blush opinion is that the kernel should take care of this, not
the filesystems. Then a fuse filesystem which supports xattrs gets acl
support for free. Otherwise if a filesystem supports xattrs but not acls
internally, we have no way of knowing that in the kernel and they get
out of sync.

However if some filesystems are already doing this internally then we
have redundancy. Presumably this would be harmless aside from the wasted
effort.

Seth