Hi Muchun, Thank you for the patch! Yet something to improve: [auto build test ERROR on hnaz-mm/master] [also build test ERROR on next-20220225] [cannot apply to mcgrof/sysctl-next linus/master v5.17-rc6] [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] url: https://github.com/0day-ci/linux/commits/Muchun-Song/add-hugetlb_free_vmemmap-sysctl/20220228-151303 base: https://github.com/hnaz/linux-mm master config: x86_64-randconfig-c022 (https://download.01.org/0day-ci/archive/20220301/202203010141.TqyZvdm5-lkp@xxxxxxxxx/config) compiler: gcc-9 (Debian 9.3.0-22) 9.3.0 reproduce (this is a W=1 build): # https://github.com/0day-ci/linux/commit/a2a3193fd949ff24ed0c138ef495e67373839483 git remote add linux-review https://github.com/0day-ci/linux git fetch --no-tags linux-review Muchun-Song/add-hugetlb_free_vmemmap-sysctl/20220228-151303 git checkout a2a3193fd949ff24ed0c138ef495e67373839483 # save the config file to linux build tree mkdir build_dir make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp@xxxxxxxxx> All errors (new ones prefixed by >>): mm/hugetlb_vmemmap.c: In function 'hugetlb_vmemmap_sysctl_handler': >> mm/hugetlb_vmemmap.c:156:55: error: 'memmap_on_memory' undeclared (first use in this function) 156 | if (write && (!is_power_of_2(sizeof(struct page)) || memmap_on_memory)) | ^~~~~~~~~~~~~~~~ mm/hugetlb_vmemmap.c:156:55: note: each undeclared identifier is reported only once for each function it appears in vim +/memmap_on_memory +156 mm/hugetlb_vmemmap.c 148 149 int hugetlb_vmemmap_sysctl_handler(struct ctl_table *table, int write, 150 void *buffer, size_t *length, loff_t *ppos) 151 { 152 /* 153 * The vmemmap pages cannot be optimized if a "struct page" crosses page 154 * boundaries or memory_hotplug.memmap_on_memory is enabled. 155 */ > 156 if (write && (!is_power_of_2(sizeof(struct page)) || memmap_on_memory)) --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@xxxxxxxxxxxx