linux-kernel - Re: [RFC 00/12] module: avoid userspace pressure on unwanted allocations

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Date:   Mon, 20 Mar 2023 14:23:36 -0700
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     David Hildenbrand <david@...hat.com>,
        Adam Manzanares <a.manzanares@...sung.com>
Cc:     linux-modules@...r.kernel.org, linux-kernel@...r.kernel.org,
        pmladek@...e.com, petr.pavlu@...e.com, prarit@...hat.com,
        christophe.leroy@...roup.eu, song@...nel.org,
        torvalds@...ux-foundation.org
Subject: Re: [RFC 00/12] module: avoid userspace pressure on unwanted
 allocations

On Mon, Mar 20, 2023 at 10:15:23PM +0100, David Hildenbrand wrote:
> On 20.03.23 22:09, Luis Chamberlain wrote:
> > On Mon, Mar 20, 2023 at 08:40:07PM +0100, David Hildenbrand wrote:
> > > On 20.03.23 10:38, David Hildenbrand wrote:
> > > > On 18.03.23 01:11, Luis Chamberlain wrote:
> > > > > On Thu, Mar 16, 2023 at 04:56:56PM -0700, Luis Chamberlain wrote:
> > > > > > On Thu, Mar 16, 2023 at 04:55:31PM -0700, Luis Chamberlain wrote:
> > > > > > > On Wed, Mar 15, 2023 at 05:41:53PM +0100, David Hildenbrand wrote:
> > > > > > > > I expect to have a machine (with a crazy number of CPUs/devices) available
> > > > > > > > in a couple of days (1-2), so no need to rush.
> > > > > > > > 
> > > > > > > > The original machine I was able to reproduce with is blocked for a little
> > > > > > > > bit longer; so I hope the alternative I looked up will similarly trigger the
> > > > > > > > issue easily.
> > > > > > > 
> > > > > > > OK give this a spin:
> > > > > > > 
> > > > > > > https://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux.git/log/?h=20230316-module-alloc-opts
> > > > > 
> > > > > Today I am up to here:
> > > > > 
> > > > > https://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux.git/log/?h=20230317-module-alloc-opts
> > > > > 
> > > > > The last patch really would have no justification yet at all unless it
> > > > > does help your case.
> > > > 
> > > > Still waiting on the system (the replacement system I was able to grab
> > > > broke ...).
> > > > 
> > > > I'll let you know once I succeeded in reproducing + testing your fixes.
> > > 
> > > Okay, I have a system where I can reproduce.
> > > 
> > > Should I give
> > > 
> > > https://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux.git/log/?h=20230319-module-alloc-opts
> > > 
> > > from yesterday a churn?
> > 
> > Yes please give that a run.
> 
> Reproduced with v6.3.0-rc1 (on 1st try)

By reproduced, you mean it fails to boot?

> Not able to reproduce with 20230319-module-alloc-opts so far (2 tries).

Oh wow, so to clarify, it boots OK?

> > Please collect systemd-analyze given lack of any other tool to evaluate
> > any deltas. Can't think of anything else to gather other than seeing if
> > it booted.
> 
> Issue is that some services (kdump, tuned) seem to take sometimes ages on
> that system to start for some reason, 

How about disabling that?

> and systemd-analyze refuses to do
> something reasonable while the system is still booting up.

I see.

> I'll see if I can come up with some data.

Thanks!

> > If that boots works then try removing the last patch "module: add a
> > sanity check prior to allowing kernel module auto-loading" to see if
> > that last patch helped or was just noise. As it stands I'm not convinced
> > yet if it did help, if it *does* help we probably need to rethink some
> > finit_module() allocations things.
> 
> Okay, will try without the last patch tomorrow.

Thanks!!

  Luis