Re: [akpm-mm:mm-unstable 333/334] include/linux/mmzone.h:1816:8: warning: left shift count is negative

[Philip Li <philip.li@intel.com>]

On Fri, May 09, 2025 at 01:43:33PM -0700, Juan Yescas wrote:
> On Fri, May 9, 2025 at 12:49 AM kernel test robot <lkp@intel.com> wrote:
> >
> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-unstable
> > head:   930c125f685d7e8eef566fcd563390b76a28d824
> > commit: 16994f2b09a22523885d371caa59f17999686805 [333/334] mm: add CONFIG_PAGE_BLOCK_ORDER to select page block order
> > config: powerpc64-randconfig-003-20250509 (https://download.01.org/0day-ci/archive/20250509/202505091548.FuKO4b4v-lkp@intel.com/config)
> > compiler: powerpc64-linux-gcc (GCC) 10.5.0
> > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250509/202505091548.FuKO4b4v-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/202505091548.FuKO4b4v-lkp@intel.com/
> >
> > All warnings (new ones prefixed by >>):
> >
> >    In file included from include/vdso/const.h:5,
> >                     from include/linux/const.h:4,
> >                     from include/linux/bits.h:5,
> >                     from include/linux/ratelimit_types.h:5,
> >                     from include/linux/printk.h:9,
> >                     from include/asm-generic/bug.h:22,
> >                     from arch/powerpc/include/asm/bug.h:116,
> >                     from include/linux/bug.h:5,
> >                     from include/linux/mmdebug.h:5,
> >                     from include/linux/mm.h:6,
> >                     from mm/sparse.c:5:
> >    mm/sparse.c: In function 'usemap_size':
> > >> include/linux/mmzone.h:1816:8: warning: left shift count is negative [-Wshift-count-negative]
> >     1816 |  ((1UL << (PFN_SECTION_SHIFT - pageblock_order)) * NR_PAGEBLOCK_BITS)
> >          |        ^~
> >    include/uapi/linux/const.h:51:40: note: in definition of macro '__KERNEL_DIV_ROUND_UP'
> >       51 | #define __KERNEL_DIV_ROUND_UP(n, d) (((n) + (d) - 1) / (d))
> >          |                                        ^
> >    mm/sparse.c:301:9: note: in expansion of macro 'BITS_TO_LONGS'
> >      301 |  return BITS_TO_LONGS(SECTION_BLOCKFLAGS_BITS) * sizeof(unsigned long);
> >          |         ^~~~~~~~~~~~~
> >    mm/sparse.c:301:23: note: in expansion of macro 'SECTION_BLOCKFLAGS_BITS'
> >      301 |  return BITS_TO_LONGS(SECTION_BLOCKFLAGS_BITS) * sizeof(unsigned long);
> >          |                       ^~~~~~~~~~~~~~~~~~~~~~~
> >
> >
> > vim +1816 include/linux/mmzone.h
> >
> > d41dee369bff3b Andy Whitcroft 2005-06-23  1814
> > 835c134ec4dd75 Mel Gorman     2007-10-16  1815  #define SECTION_BLOCKFLAGS_BITS \
> > d9c2340052278d Mel Gorman     2007-10-16 @1816          ((1UL << (PFN_SECTION_SHIFT - pageblock_order)) * NR_PAGEBLOCK_BITS)
> > 835c134ec4dd75 Mel Gorman     2007-10-16  1817
> >
> 
> Thanks for testing,
> 
> The reason for the warning is because CONFIG_PAGE_BLOCK_ORDER >
> CONFIG_ARCH_FORCE_MAX_ORDER.
> 
> This config: powerpc64-randconfig-003-20250509
> (https://download.01.org/0day-ci/archive/20250509/202505091548.FuKO4b4v-lkp@intel.com/config)
> 
> is not respecting the range config below. Should the test make sure
> that the ranges are valid?

Thanks for the information, I will check the bot side to resolve the problem.

Sorry for the false positive.

> 
> config PAGE_BLOCK_ORDER
> int "Page Block Order"
> range 1 10 if !ARCH_FORCE_MAX_ORDER
> default 10 if !ARCH_FORCE_MAX_ORDER
> range 1 ARCH_FORCE_MAX_ORDER if ARCH_FORCE_MAX_ORDER
> default ARCH_FORCE_MAX_ORDER if ARCH_FORCE_MAX_ORDER
> 
> I can add a check in include/linux/pageblock-flags.h
> 
> /*
>  * The PAGE_BLOCK_ORDER, which defines the order for the number of pages
>  * that can have a migrate type, must be less or equal to the MAX_PAGE_ORDER,
>  * which defines the max order of pages to be allocated by the buddy allocator.
>  */
> BUILD_BUG_ON_MSG(PAGE_BLOCK_ORDER > MAX_PAGE_ORDER,
>         "MAX_PAGE_ORDER must be >= PAGE_BLOCK_ORDER");
> 
> Is there any preference?
> 
> > :::::: The code at line 1816 was first introduced by commit
> > :::::: d9c2340052278d8eb2ffb16b0484f8f794def4de Do not depend on MAX_ORDER when grouping pages by mobility
> >
> > :::::: TO: Mel Gorman <mel@csn.ul.ie>
> > :::::: CC: Linus Torvalds <torvalds@woody.linux-foundation.org>
> >
> > --
> > 0-DAY CI Kernel Test Service
> > https://github.com/intel/lkp-tests/wiki
>