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Date:   Fri, 1 Mar 2019 12:41:00 -0800
From:   Andrew Morton <>
To:     Guillaume Tucker <>
Cc:     Dan Williams <>,
        Michal Hocko <>,
        Mark Brown <>,
        Tomeu Vizoso <>,
        Matt Hart <>,
        Stephen Rothwell <>,,, Nicholas Piggin <>,
        Dominik Brodowski <>,
        Masahiro Yamada <>,
        Kees Cook <>,
        Adrian Reber <>,
        Linux Kernel Mailing List <>,
        Johannes Weiner <>,
        Linux MM <>,
        Mathieu Desnoyers <>,
        Richard Guy Briggs <>,
        "Peter Zijlstra (Intel)" <>,
Subject: Re: next/master boot bisection: next-20190215 on beaglebone-black

On Fri, 1 Mar 2019 09:25:24 +0100 Guillaume Tucker <> wrote:

> >>> Michal had asked if the free space accounting fix up addressed this
> >>> boot regression? I was awaiting word on that.
> >>
> >> hm, does actually read emails?  Let's try info@ as well..
> is not person, it's a send-only account for
> automated reports.  So no, it doesn't read emails.
> I guess the tricky point here is that the authors of the commits
> found by bisections may not always have the hardware needed to
> reproduce the problem.  So it needs to be dealt with on a
> case-by-case basis: sometimes they do have the hardware,
> sometimes someone else on the list or on CC does, and sometimes
> it's better for the people who have access to the test lab which
> ran the KernelCI test to deal with it.
> This case seems to fall into the last category.  As I have access
> to the Collabora lab, I can do some quick checks to confirm
> whether the proposed patch does fix the issue.  I hadn't realised
> that someone was waiting for this to happen, especially as the
> BeagleBone Black is a very common platform.  Sorry about that,
> I'll take a look today.
> It may be a nice feature to be able to give access to the
> KernelCI test infrastructure to anyone who wants to debug an
> issue reported by KernelCI or verify a fix, so they won't need to
> have the hardware locally.  Something to think about for the
> future.

Thanks, that all sounds good.

> >> Is it possible to determine whether this regression is still present in
> >> current linux-next?
> I'll try to re-apply the patch that caused the issue, then see if
> the suggested change fixes it.  As far as the current linux-next
> master branch is concerned, KernelCI boot tests are passing fine
> on that platform.

They would, because I dropped
mm-shuffle-default-enable-all-shuffling.patch, so your tests presumably
now have shuffling disabled.

Is it possible to add the below to linux-next and try again?

Or I can re-add this to linux-next.  Where should we go to determine
the results of such a change?  There are a heck of a lot of results on and entering "beaglebone-black" doesn't get
me anything.


From: Dan Williams <>
Subject: mm/shuffle: default enable all shuffling

Per Andrew's request arrange for all memory allocation shuffling code to
be enabled by default.

The page_alloc.shuffle command line parameter can still be used to disable
shuffling at boot, but the kernel will default enable the shuffling if the
command line option is not specified.

Signed-off-by: Dan Williams <>
Cc: Kees Cook <>
Cc: Michal Hocko <>
Cc: Dave Hansen <>
Cc: Keith Busch <>

Signed-off-by: Andrew Morton <>

 init/Kconfig |    4 ++--
 mm/shuffle.c |    4 ++--
 mm/shuffle.h |    2 +-
 3 files changed, 5 insertions(+), 5 deletions(-)

--- a/init/Kconfig~mm-shuffle-default-enable-all-shuffling
+++ a/init/Kconfig
@@ -1709,7 +1709,7 @@ config SLAB_MERGE_DEFAULT
 	  command line.
-	default n
+	default y
 	depends on SLAB || SLUB
 	bool "SLAB freelist randomization"
@@ -1728,7 +1728,7 @@ config SLAB_FREELIST_HARDENED
 	bool "Page allocator randomization"
+	default y
 	  Randomization of the page allocator improves the average
 	  utilization of a direct-mapped memory-side-cache. See section
--- a/mm/shuffle.c~mm-shuffle-default-enable-all-shuffling
+++ a/mm/shuffle.c
@@ -9,8 +9,8 @@
 #include "internal.h"
 #include "shuffle.h"
-static unsigned long shuffle_state __ro_after_init;
+static unsigned long shuffle_state __ro_after_init = 1 << SHUFFLE_ENABLE;
  * Depending on the architecture, module parameter parsing may run
--- a/mm/shuffle.h~mm-shuffle-default-enable-all-shuffling
+++ a/mm/shuffle.h
@@ -19,7 +19,7 @@ enum mm_shuffle_ctl {
 extern void page_alloc_shuffle(enum mm_shuffle_ctl ctl);
 extern void __shuffle_free_memory(pg_data_t *pgdat);
 static inline void shuffle_free_memory(pg_data_t *pgdat)

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