Re: [PATCH 2/2] mkfs: remove notion of config "type"

[Dave Chinner <david@fromorbit.com>]

On Thu, Jun 14, 2018 at 09:45:49PM -0500, Eric Sandeen wrote:
> 
> 
> On 6/14/18 9:33 PM, Dave Chinner wrote:
> > On Thu, Jun 14, 2018 at 07:10:09PM -0700, Luis R. Rodriguez wrote:
> >> Silly mobile gmail interface not letting me bottom-post... What if we treat
> >> no version being present as version 0?
> > 
> > We haven't released anything yet so we should put it in there from
> > the start rather than having to work around the lack of a version
> > field later.
> 
> So, pretend I'm dumb ('cause I often am) and spell it out for me, what would
> we do with a version?
> 
> If a config file contains a section or token that some version of mkfs doesn't
> understand, it'll fail.
> 
> If we try to read a config file with a too-new version, we'd ... fail?

Fail with a useful error message, rather than do something
unexpected or incorrect.

Let's face it - the config file is a persistent, on-disk structure
that we have to handle in both forwards and backwards compatible
manners for many, many years. It's no different to the on-disk
format in that respect. Why wouldn't we apply the same guards for
format changes we apply to syscalls, ioctls, on-disk formats, etc
that all have the same long term compatibility requirements?

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com