Re: [EXT4 set 4][PATCH 1/5] i_version:64 bit inode version

["J. Bruce Fields" <bfields@fieldses.org>]

On Tue, Jul 03, 2007 at 05:32:00PM -0600, Andreas Dilger wrote:
> On Jul 03, 2007  18:15 -0400, J. Bruce Fields wrote:
> > How will nfsd tell whether it can really on a given filesystem's
> > i_version, or whether it should fall back on ctime?
> 
> Good question.

Well, we don't need anything particularly complicated--just a one-bit
flag on the superblock would be enough.

> > So what's the motivation for the "noversion" mount option?
> 
> Lustre needs to be able to control the version number directly (version
> number needs to be ordered between all inodes, is set by Lustre to be a
> transaction number).  Instead of trying to incorporate this unused code
> into ext4 we just turn off the ext4 version code and let Lustre control
> this directly.  It may even be that NFSv4 will need to control the version
> numbers itself...

I can't think of any reason we would need to in the near future, but
maybe I'm insufficiently creative.

The use of a mount option means the change attribute could be
inconsistent across mounts.  If we really need this, wouldn't it make
more sense for it to be a persistent feature of the filesystem, set at
mkfs time?

--b.