Re: xattr namespace question

[Nathan Scott <nathans@sgi.com>]

On Tue, Mar 21, 2006 at 05:21:19AM -0700, Andreas Dilger wrote:
> On Mar 21, 2006  12:06 +0000, Steven Whitehouse wrote:
> > In order to remove the final ioctl() call in the GFS2 filesystem its
> > been suggested that we use xattrs as a replacement interface. Mostly
> > this is self-explanatory however there is one question that I've not
> > been able to resolve 100% satisfactorily, which is what the namespace
> > should look like.
> > 
> > We have a bunch of boolean flags, so (using the example of the journaled
> > data flag) should our xattrs be called something along the lines of

"boolean flags" sounds alot more like the lsattr/chattr inode flags
as Andreas points out.  There is already a data journalling (j) flag
there too.

> > system.gfs2.jdata (this seems to be most popular suggestion amoung those
> > I've asked privately), or perhaps system.fs.gfs2.jdata or indeed is the
> > system namespace reserved for something special so that we should use a
> > special gfs2 namespace instead?

The choice typically depends on what the permissions model for
access to the attribute needs to be.  See attr(5).

> If your extra flags can be mapped onto the EXT2_IOC_GETFLAGS equivalent,
> then you may want to (also) consider that.  This allows the flags to be
> got/set by lsattr and chattr, respectively, and have been in linux for ages.
> It also happens that ext2/ext3/reiserfs all share this same API.

And XFS, and hfsplus too from the look of it.

cheers.

-- 
Nathan