Re: [RFC PATCH 00/35] user xattr support (RFC8276)

[Frank van der Linden <fllinden@amazon.com>]

On Mon, Nov 04, 2019 at 05:58:46PM -0500, Bruce Fields wrote:
> Just checking code for other filesystems quickly; if I understand right:
> 
> 	- ext4 has user_xattr and nouser_xattr options, but you get a
> 	  deprecation warning if you try to use the latter;
> 	- xfs doesn't support either option;
> 	- cifs supports both, with xattr support the default.
> 
> Not necessarily my call, but just for simplicity's sake, I'd probably
> leave out the option and see if anybody complains.

Sounds good, I'll go with that.
> 
> > Also, currently, my code does not fail the mount operation if user xattrs
> > are asked for, but the server does not support them. It just doesn't
> > set NFS_CAP_XATTR for the server, and the xattr handler entry points
> > eturn -EOPNOTSUPP, as they check for NFS_CAP_XATTR. What's the preferred
> > behavior there?
> 
> getxattr(2) under ERRORS says:
> 
> 	ENOTSUP
> 	      Extended attributes are not supported by the filesystem,
> 	      or  are disabled.
> 
> so I'm guessing just erroring out is clearest.
> 
> I also see there's an EOPNOTSUPP return in the nouser_xattr case in
> ext4_xattr_user_get.  (errno(3) says ENOTSUP and EOPNOTSUPP are the same
> value on Linux.)

Sure. So, to recap, here's what I'll do:

* Remove the CONFIG options - enable the code by default.
* Server side:
	* Remove the export file option to not export extended attributes
* Client side:
	* Always probe user xattr support, and use it when available
	  (returning EOPNOTSUPP, as expected, for all xattr syscalls if
	   it is not available).

Thanks for the feedback so far - much appreciated. I'll submit the separate
client and server patch sets this week.

- Frank