State of ZFS xattr support in FreeBSD

[Martin von Gagern]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Hi!

I'm trying to work out whether or not, or rather to what extend,
xattrs are supported in FreeBSD using ZFS. I've read some conflicting
information.

1. zfs get xattr lists it as on (default) for /, /usr and /var,
   but as off (temporary) for all other datasets, including children
   of those mentioned above.
2. Running zfs set xattr=on zroot/usr/home I get the message
   “property 'xattr' not supported on FreeBSD: permission denied.”
3. This agrees with the zfs man page:
   “The xattr property is currently not supported on FreeBSD.”
4. setextattr, getextattr and lsextattr seem to work well enough.
5. I also managed to save and restore a device file node using
   “rsync --fake-super”, and could see its data using lsextattr and
   getextattr.
6. Wikipedia has some discussion in the xattr talk page. Apparently
   there once was a claim that ZFS supports xattr since FreeBSD 8, but
   that was removed later on, with reference to the manpage (see 3.).

Currently I get the impression that extended attributes on zfs work in
practice, but that the xattr property which would control their use
does not work as it would in other zfs distributions. But I'd like to
hear that confirmed (or corrected) before I trust large amounts of
backup data to an rsync --fake-super running on such a machine. I'd
rather not lose all my metadata due to known xattr problems.

If it matters, this is a very fresh FreeBSD 10.2 install I just set
up, with ZFS set up by the installer.

I posted this question in other places before:
http://unix.stackexchange.com/q/266913/20807 (currently with a bounty)
https://forums.freebsd.org/threads/55418/
Feel free to cross-post your answers to these. If you don't, I'll
probably post a summary myself.

Thank you very much,
 Martin von Gagern
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2

iEYEARECAAYFAlbkX24ACgkQRhp6o4m9dFtzQACaAkCbCR2Yi1PyicZ61PLM4Ad+
2pUAn0P8YzEQ3rOMfdD8MVnLP1PQ2CLu
=Bazu
-----END PGP SIGNATURE-----