Re: [akpm-mm:mm-unstable 36/283] include/uapi/linux/const.h:20:25: warning: conversion from 'long long unsigned int' to 'long unsigned int' changes value from '17179869184' to '0'

[Geert Uytterhoeven <geert@linux-m68k.org>]

Hi Andrew,

On Thu, 13 Nov 2025 at 19:08, Andrew Morton <akpm@linux-foundation.org> wrote:
> On Thu, 13 Nov 2025 20:26:42 +0800 kernel test robot <lkp@intel.com> wrote:
> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-unstable
> > head:   f58b4cb6b0c11172a25c2ade23477f55596d7138
> > commit: 2f6ff71280ffddb27ad7174d24f573e2683870cd [36/283] mm: fix MAX_FOLIO_ORDER on powerpc configs with hugetlb
> > config: sh-randconfig-002-20251113 (https://download.01.org/0day-ci/archive/20251113/202511132024.tfRZgB5P-lkp@intel.com/config)
> > compiler: sh4-linux-gcc (GCC) 11.5.0
> > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251113/202511132024.tfRZgB5P-lkp@intel.com/reproduce)
> >
> > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > the same patch/commit), kindly add following tags
> > | Reported-by: kernel test robot <lkp@intel.com>
> > | Closes: https://lore.kernel.org/oe-kbuild-all/202511132024.tfRZgB5P-lkp@intel.com/
> >
> > All warnings (new ones prefixed by >>):
> >
> >    In file included from arch/sh/include/asm/bug.h:112,
> >                     from include/linux/bug.h:5,
> >                     from include/linux/mmdebug.h:5,
> >                     from include/linux/mm.h:6,
> >                     from include/linux/migrate.h:5,
> >                     from mm/migrate.c:16:
> >    mm/internal.h: In function 'folio_set_order':
> > >> include/uapi/linux/const.h:20:25: warning: conversion from 'long long unsigned int' to 'long unsigned int' changes value from '17179869184' to '0' [-Woverflow]
> >       20 | #define __AC(X,Y)       (X##Y)
> >          |                         ^~~~~~
> >    include/asm-generic/bug.h:111:32: note: in definition of macro 'WARN_ON_ONCE'
> >      111 |         int __ret_warn_on = !!(condition);                      \
> >          |                                ^~~~~~~~~
> >    mm/internal.h:758:9: note: in expansion of macro 'VM_WARN_ON_ONCE'
> >      758 |         VM_WARN_ON_ONCE(order > MAX_FOLIO_ORDER);
> >          |         ^~~~~~~~~~~~~~~
> >    include/uapi/linux/const.h:21:25: note: in expansion of macro '__AC'
> >       21 | #define _AC(X,Y)        __AC(X,Y)
> >          |                         ^~~~
> >    include/linux/sizes.h:56:41: note: in expansion of macro '_AC'
> >       56 | #define SZ_16G                          _AC(0x400000000, ULL)
> >          |                                         ^~~
> >    include/linux/mm.h:2095:43: note: in expansion of macro 'SZ_16G'
> >     2095 | #define MAX_FOLIO_ORDER         get_order(SZ_16G)
> >          |                                           ^~~~~~
> >    mm/internal.h:758:33: note: in expansion of macro 'MAX_FOLIO_ORDER'
> >      758 |         VM_WARN_ON_ONCE(order > MAX_FOLIO_ORDER);
> >          |                                 ^~~~~~~~~~~~~~~
>
> Oh gee.
>
> Here's the patch: https://lkml.kernel.org/r/20251112145632.508687-1-david@kernel.org
>
> I'll append a copy below.
>
> For a start, you have found an sh config which sets neither
> CONFIG_32BIT not CONFIG_64BIT.  Should that even be possible?

Apparently yes...

arch/sh/mm/Kconfig:

    config 29BIT
            def_bool !32BIT
            select UNCACHED_MAPPING

    config 32BIT
            bool
            default !MMU

    config PMB
            bool "Support 32-bit physical addressing through PMB"
            depends on MMU && CPU_SH4A && !CPU_SH4AL_DSP
            select 32BIT
            select UNCACHED_MAPPING
            help
              If you say Y here, physical addressing will be extended to
              32-bits through the SH-4A PMB. If this is not set, legacy
              29-bit physical addressing will be used.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds