Re: [PATCH v4] mm: Add CONFIG_PAGE_BLOCK_ORDER to select page block order

[Juan Yescas <jyescas@google.com>]

On Tue, May 13, 2025 at 8:08 AM Zi Yan <ziy@nvidia.com> wrote:
>
> On 10 May 2025, at 13:16, kernel test robot wrote:
>
> > Hi Juan,
> >
> > kernel test robot noticed the following build errors:
> >
> > [auto build test ERROR on linus/master]
> > [also build test ERROR on v6.15-rc5]
> > [cannot apply to akpm-mm/mm-everything next-20250509]
> > [If your patch is applied to the wrong git tree, kindly drop us a note.
> > And when submitting patch, we suggest to use '--base' as documented in
> > https://git-scm.com/docs/git-format-patch#_base_tree_information]
> >
> > url:    https://github.com/intel-lab-lkp/linux/commits/Juan-Yescas/mm-Add-CONFIG_PAGE_BLOCK_ORDER-to-select-page-block-order/20250510-090501
> > base:   linus/master
> > patch link:    https://lore.kernel.org/r/20250510010338.3978696-1-jyescas%40google.com
> > patch subject: [PATCH v4] mm: Add CONFIG_PAGE_BLOCK_ORDER to select page block order
> > config: powerpc-allmodconfig (https://download.01.org/0day-ci/archive/20250511/202505110035.wtOWnL8o-lkp@intel.com/config)
> > compiler: powerpc64-linux-gcc (GCC) 14.2.0
> > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250511/202505110035.wtOWnL8o-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/202505110035.wtOWnL8o-lkp@intel.com/
> >
> > All errors (new ones prefixed by >>):
> >
> >    In file included from include/linux/gfp.h:7,
> >                     from include/linux/xarray.h:16,
> >                     from include/linux/list_lru.h:14,
> >                     from include/linux/fs.h:14,
> >                     from include/linux/compat.h:17,
> >                     from arch/powerpc/kernel/asm-offsets.c:12:
> >>> include/linux/mmzone.h:53:2: error: #error MAX_PAGE_ORDER must be >= PAGE_BLOCK_ORDER
> >       53 | #error MAX_PAGE_ORDER must be >= PAGE_BLOCK_ORDER
> >          |  ^~~~~
> >    make[3]: *** [scripts/Makefile.build:98: arch/powerpc/kernel/asm-offsets.s] Error 1
>
> In this config, CONFIG_ARCH_FORCE_MAX_ORDER is set to 8, lower than
> the default PAGE_BLOCK_ORDER value, 10. I wonder if the error should
> be changed to ignore CONFIG_PAGE_BLOCK_ORDER when MAX_PAGE_ORDER is
> set by CONFIG_ARCH_FORCE_MAX_ORDER and give a warning instead.

In ARMv8, MAX_PAGE_ORDER is set up by CONFIG_ARCH_FORCE_MAX_ORDER
and CONFIG_PAGE_BLOCK_ORDER is also set up, so we need to take into account
CONFIG_PAGE_BLOCK_ORDER. For other architectures, the default will be:
CONFIG_ARCH_FORCE_MAX_ORDER = CONFIG_PAGE_BLOCK_ORDER.

Is there any valid case where the MAX_PAGE_ORDER needs to be smaller than
the page block order?

Thanks
Juan
>
> >    make[3]: Target 'prepare' not remade because of errors.
> >    make[2]: *** [Makefile:1275: prepare0] Error 2
> >    make[2]: Target 'prepare' not remade because of errors.
> >    make[1]: *** [Makefile:248: __sub-make] Error 2
> >    make[1]: Target 'prepare' not remade because of errors.
> >    make: *** [Makefile:248: __sub-make] Error 2
> >    make: Target 'prepare' not remade because of errors.
> >
> >
> > vim +53 include/linux/mmzone.h
> >
> >     46
> >     47        /*
> >     48         * The MAX_PAGE_ORDER, which defines the max order of pages to be allocated
> >     49         * by the buddy allocator, has to be larger or equal to the PAGE_BLOCK_ORDER,
> >     50         * which defines the order for the number of pages that can have a migrate type
> >     51         */
> >     52        #if (PAGE_BLOCK_ORDER > MAX_PAGE_ORDER)
> >   > 53        #error MAX_PAGE_ORDER must be >= PAGE_BLOCK_ORDER
> >     54        #endif
> >     55
> >
> > --
> > 0-DAY CI Kernel Test Service
> > https://github.com/intel/lkp-tests/wiki
>
>
> Best Regards,
> Yan, Zi