linux-kernel - Re: [PATCH v4] mm: Add CONFIG_PAGE_BLOCK

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Message-ID: <2513BE19-5527-45A4-8BE8-A447B53654C0@nvidia.com>
Date: Tue, 13 May 2025 12:47:51 -0400
From: Zi Yan <ziy@...dia.com>
To: Juan Yescas <jyescas@...gle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
 kernel test robot <lkp@...el.com>, linux-kernel@...r.kernel.org,
 oe-kbuild-all@...ts.linux.dev,
 Linux Memory Management List <linux-mm@...ck.org>, tjmercier@...gle.com,
 isaacmanjarres@...gle.com, surenb@...gle.com, kaleshsingh@...gle.com,
 Vlastimil Babka <vbabka@...e.cz>,
 "Liam R. Howlett" <Liam.Howlett@...cle.com>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 David Hildenbrand <david@...hat.com>, Mike Rapoport <rppt@...nel.org>,
 Minchan Kim <minchan@...nel.org>
Subject: Re: [PATCH v4] mm: Add CONFIG_PAGE_BLOCK_ORDER to select page block
 order

On 13 May 2025, at 12:41, Juan Yescas wrote:

> On Tue, May 13, 2025 at 8:08 AM Zi Yan <ziy@...dia.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@...el.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.

It seems that the Kconfig “range 1 ARCH_FORCE_MAX_ORDER if ARCH_FORCE_MAX_ORDER”
is not working. The above powerpc-allmodconfig has CONFIG_ARCH_FORCE_MAX_ORDER
set to 8 and CONFIG_PAGE_BLOCK_ORDER is set to 10, leading to the compilation
error.

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

I am not aware of any.

>
> 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


Best Regards,
Yan, Zi