Subject: Re: [vserver] COW Hardlinks, Hashify and NILFS2
From: Herbert Poetzl <herbert@13thfloor.at>
Date: Thu, 26 Aug 2010 04:37:51 +0200

On Wed, Aug 25, 2010 at 01:15:11PM +0100, Gordan Bobic wrote:
> I've been looking through the VS patches, and I notice that they
> modify fs driver code. I'm guessing to implement hashify support. 
> If that guess is correct, what file systems are supported for 
> hashify with COW hardlinks?

CoW requires that the filesystem supports xattrs and is
patched to allow for a special immutable linkage invert
(IXUNLINK) flag which basically markes 'normal' hard
links as CoW links ...

currently ext2/3/4, jfs, reiserfs, xfs, btrfs, ocfs2
and gfs2 are supported ...

> I'm thinking about using nilfs2, but not if that would sacrifice 
> the hashify feature.

shouldn't be too hard to add the required flags and the
Linux-VServer support to set them ... the rest will
happen automagically ...

best,
Herbert

> TIA.
> Gordan