linux-kernel - Re: [PATCH] kconfig: remove EXPERT from CHECKPOINT

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Date:   Fri, 13 Jul 2018 16:20:22 +0200
From:   Adrian Reber <adrian@...as.de>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     Pavel Emelyanov <xemul@...tuozzo.com>,
        linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Oleg Nesterov <oleg@...hat.com>,
        Andrei Vagin <avagin@...tuozzo.com>,
        Hendrik Brueckner <brueckner@...ux.vnet.ibm.com>,
        Cyrill Gorcunov <gorcunov@...nvz.org>,
        Kees Cook <keescook@...omium.org>,
        Linux Containers <containers@...ts.linux-foundation.org>
Subject: Re: [PATCH] kconfig: remove EXPERT from CHECKPOINT_RESTORE

On Fri, Jul 13, 2018 at 08:46:25AM -0500, Eric W. Biederman wrote:
> Pavel Emelyanov <xemul@...tuozzo.com> writes:
> 
> > On 07/12/2018 07:33 PM, Eric W. Biederman wrote:
> >> 
> >> Adrian Reber <adrian@...as.de> writes:
> >> 
> >>> The CHECKPOINT_RESTORE configuration option was introduced in 2012 and
> >>> combined with EXPERT. CHECKPOINT_RESTORE is already enabled in many
> >>> distribution kernels and also part of the defconfigs of various
> >>> architectures.
> >>>
> >>> To make it easier for distributions to enable CHECKPOINT_RESTORE this
> >>> removes EXPERT and moves the configuration option out of the EXPERT
> >>> block.
> >> 
> >> I think we should change the help text at the same time, to match
> >> our improve understanding of the situation.
> >> 
> >> Does anyone remember why this option was added at all?
> >
> > Sure! Quoting Andrew's ~7 years ago akpm branch merge e-mail:
> >
> >    However I'm less confident than the developers that it will all
> >    eventually work! So what I'm asking them to do is to wrap each piece
> >    of new code inside CONFIG_CHECKPOINT_RESTORE.  So if it all
> >    eventually comes to tears and the project as a whole fails, it should
> >    be a simple matter to go through and delete all trace of it.
> >
> > the best link with full e-mail I googled for is
> > https://gitlab.imag.fr/kaunetem/linux-kaunetem/commit/099469502f62fbe0d7e4f0b83a2f22538367f734
> 
> Good explanation.  Thank you.
> 
> At this point we even have not CRIU users of some of the pieces.
> The project as a whole has not failed.
> 
> The code is old enough an common enough (enabled in some distros) that
> we need to do the whole watch out for regressions if we remove any part
> of it.
> 
> Which is a long way of saying the original justifiction for
> CONFIG_CHECKPOINT_RESTORE is gone.  So please let's remove the entire
> config option and simplify everyone's lives who has to test this stuff.

Sounds good.

> Unless someone can come up with a justification for keeping some of this
> behind a config option.

I can provide a patch removing CONFIG_CHECKPOINT_RESTORE if there are no
further objections against it.

		Adrian