Hi Qu, Thank you for the patch! Yet something to improve: [auto build test ERROR on kdave/for-next] [also build test ERROR on next-20201209] [cannot apply to btrfs/next v5.10-rc7] [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/Qu-Wenruo/btrfs-add-read-only-su... base: https://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux.git for-next config: nds32-randconfig-r004-20201209 (attached as .config) compiler: nds32le-linux-gcc (GCC) 9.3.0 reproduce (this is a W=1 build): wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # https://github.com/0day-ci/linux/commit/e01cdf51d0d32647697616c0dd08f2cc3... git remote add linux-review https://github.com/0day-ci/linux git fetch --no-tags linux-review Qu-Wenruo/btrfs-add-read-only-support-for-subpage-sector-size/20201210-144442 git checkout e01cdf51d0d32647697616c0dd08f2cc3220bde4 # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=nds32 If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All errors (new ones prefixed by >>): nds32le-linux-ld: fs/btrfs/disk-io.o: in function `btrfs_validate_metadata_buffer': disk-io.c:(.text+0x4200): undefined reference to `__udivdi3' --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org