Re: [PATCH] modprobe: install default configuration

From: Lucas De Marchi <lucas.de.marchi@gmail.com>
To: Lubomir Rintel <lkundrak@v3.sk>
Cc: "De Marchi, Lucas" <lucas.demarchi@intel.com>,
	"md@Linux.IT" <md@linux.it>,
	"linux-modules@vger.kernel.org" <linux-modules@vger.kernel.org>
Subject: Re: [PATCH] modprobe: install default configuration
Date: Wed, 13 Apr 2016 01:11:47 -0300	[thread overview]
Message-ID: <CAKi4VA+VAYZ8zPGG=0qR1yMQGLfwZD5qMO8kW4kHYoqJes6KVA@mail.gmail.com> (raw)
In-Reply-To: <1459247226.25498.30.camel@v3.sk>

On Tue, Mar 29, 2016 at 7:27 AM, Lubomir Rintel <lkundrak@v3.sk> wrote:
> On Fri, 2016-03-04 at 02:02 -0300, Lucas De Marchi wrote:
>> On Wed, Mar 2, 2016 at 1:28 PM, Lubomir Rintel <lkundrak@v3.sk>
>> wrote:
>> >
>> > On Wed, 2016-03-02 at 16:07 +0000, De Marchi, Lucas wrote:
>> > >
>> > > On Wed, 2016-03-02 at 16:55 +0100, Marco d'Itri wrote:
>> > > >
>> > > >
>> > > > On Mar 02, Lubomir Rintel <lkundrak@v3.sk> wrote:
>> > > >
>> > > > >
>> > > > >
>> > > > >
>> > > > > The kernel maintainers seem opposed to fixing this in kernel
>> > > > > (despite a similar
>> > > > > thing has been done with loop block devices) [1]. Let's fix
>> > > > > this
>> > > > > my
>> > > > > overriding the
>> > > > > defaults from userspace.
>> > > > Because, guess what? This breaks userspace.
>> > > > Feel free to configure your system this way if it is what you
>> > > > want.
>> > > More context: https://github.com/systemd/systemd/pull/2778
>> > >
>> > > Marco, could you be more specific on how this breaks userspace?
>> > > It
>> > > seems already pretty much broken to me. We can even argue if
>> > > people
>> > > wants the broken system back they can equally well configure
>> > > their
>> > > system to do that (even putting on /etc to override what was set
>> > > on
>> > > /usr/lib).
>> > >
>> > > The commit message doesn't reflect the feedback from kernel
>> > > maintainers
>> > > very well IMO.  Main argument there was the compile-time option
>> > > rather
>> > > than allowing it to be in runtime like this one.
>> > I thought that this part of feedback was a bit uninformed or there
>> > has
>> > been some misunderstanding (perhaps on my side). There already are
>> > options; the kernel patch just changed defaults for the options --
>> > not
>> > hardcoding the values or anything like that; just allowing to
>> > choose
>> > different defaults at compile time.
>> >
>> > The point was that if the user merely does "make oldconfig" to
>> > update
>> > his kernel configuration the behavior wouldn't change. Thus it
>> > would be
>> > safe for anyone to install an new kernel on an old distro even if
>> > they're relying on the ancient behavior.
>> >
>> > On the other hand, it would still allow for behavior change on
>> > distro
>> > upgrades. I'm assuming it's okay to do that -- far bigger changes
>> > regularly occur and users of exotic interfaces often end up
>> > adjusting
>> > their tooling on major upgrades.
>> I would say the better patch to the kernel would be to bite the
>> bullet
>> and change the default.
>> The default is bad as shown by your example and people complaining
>> about the behavior. With a patch to kmod we are acknowledging the
>> default is bad and changing it, just like we would be if the patch to
>> the kernel was applied (i.e. people wanting the old behavior back
>> would have to change the option in kernel cmdline or /etc/modprobe.d)
>>
>> Anyway, I don't oppose to applying it here, but I'll wait some more
>> days for people to chime in.
>
> Hi, I'm wondering if this could be moved forwards or needs some more
> discussion/work?

Maybe getting an ack from kernel people involved since we still got no
feedback. Unfortunately our archives vanished and would be hard to
point them to the whole thread. Do you want to CC them here?

Lucas De Marchi