Hi Jaewon,

[FYI, it's a private test report for your RFC patch.]
[auto build test ERROR on staging/staging-testing]
[also build test ERROR on linux/master linus/master v5.6-rc7 next-20200323]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/Jaewon-Kim/meminfo_extra-introduce-meminfo-extra/20200323-174445
base:   https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git 6203da9803017701da5782998157d9826215059d
config: csky-allnoconfig (attached as .config)
compiler: csky-linux-gcc (GCC) 9.2.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        GCC_VERSION=9.2.0 make.cross ARCH=csky 

If you fix the issue, kindly add following tag
Reported-by: kbuild test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   csky-linux-ld: mm/page_alloc.o: in function `show_free_areas':
   page_alloc.c:(.text+0x32c6): undefined reference to `show_meminfo_extra'
>> csky-linux-ld: page_alloc.c:(.text+0x33e8): undefined reference to `show_meminfo_extra'

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0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org