Re: [PATCH] xfs: stop advertising SB_I_VERSION

["Darrick J. Wong" <djwong@kernel.org>]

On Thu, Feb 29, 2024 at 10:55:22AM +1100, Dave Chinner wrote:
> On Wed, Feb 28, 2024 at 08:08:48AM -0800, Darrick J. Wong wrote:
> > On Wed, Feb 28, 2024 at 03:28:59PM +1100, Dave Chinner wrote:
> > > From: Dave Chinner <dchinner@redhat.com>
> > > 
> > > The redefinition of how NFS wants inode->i_version to be updated is
> > > incomaptible with the XFS i_version mechanism. The VFS now wants
> > > inode->i_version to only change when ctime changes (i.e. it has
> > > become a ctime change counter, not an inode change counter). XFS has
> > > fine grained timestamps, so it can just use ctime for the NFS change
> > > cookie like it still does for V4 XFS filesystems.
> > > 
> > > We still want XFS to update the inode change counter as it currently
> > > does, so convert all the code that checks SB_I_VERSION to check for
> > > v5 format support. Then we can remove the SB_I_VERSION flag from the
> > > VFS superblock to indicate that inode->i_version is not a valid
> > > change counter and should not be used as such.
> > > 
> > > Signed-off-by: Dave Chinner <dchinner@redhat.com>
> > 
> > Seeing as NFS and XFS' definition of i_version have diverged, I suppose
> > divorce is the only option.  But please, let's get rid of all the
> > *iversion() calls in the codebase.
> > 
> > With my paranoia hat on: let's add an i_changecounter to xfs_inode and
> > completely stop using the inode.i_version to prevent the vfs from
> > messing with us.
> 
> Ok, I'll do that in a new patch rather than try to do everything in
> a single complicated patch.

Sounds good!

--D

> Cheers,
> 
> Dave.
> -- 
> Dave Chinner
> david@fromorbit.com
>