Re: [PATCH 05/14] xfs: repair free space btrees

[Dave Chinner <david@fromorbit.com>]

On Sat, Aug 11, 2018 at 08:50:49AM -0400, Brian Foster wrote:
> On Fri, Aug 10, 2018 at 12:36:51PM -0700, Darrick J. Wong wrote:
> > Technically we're not supposed to have flag days, but otoh this is a
> > xfs-only ioctl for a feature that's still experimental, so perhaps it's
> > not crucial to maintain compatibility with old kernels where the feature
> > is incomplete and experimental?
> > 
> 
> In my mind, I kind of take the experimental status as all bits/interface
> may explode and are otherwise subject to change or disappear. Perhaps
> others feel differently, it does seem we've kind of hinted towards the
> contrary recently with respect to the per-inode dax bits and then now in
> this discussion, but IMO that's kind of an inherent risk of doing
> incremental work on complex features upstream.

I've always considered that the experimental tag covers the
user/ioctl interfaces as much as it does the functionality and
on-disk format. i.e. like the on-disk format, the ioctl interfaces
are subject to change until we clear the exp. tag, at which point
they are essentially fixed forever. We /try/ not to have to change
them after the initial merge, but sometimes we screw up and need to
fix them before we commit to long term support.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com