Hi Qu, Thank you for the patch! Yet something to improve: [auto build test ERROR on v5.9-rc5] [also build test ERROR on next-20200915] [cannot apply to kdave/for-next btrfs/next] [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: 856deb866d16e29bd65952e0289066f6078af773 config: nds32-randconfig-r003-20200916 (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 # 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 `btree_readpage_end_io_hook': nds32le-linux-ld: nds32le-linux-ld: DWARF error: found dwarf version '36812', this reader only handles version 2, 3, 4 and 5 information fs/btrfs/extent_io.o: in function `release_extent_buffer': extent_io.c:(.text+0x6b08): undefined reference to `__udivdi3' nds32le-linux-ld: extent_io.c:(.text+0x6b0c): undefined reference to `__udivdi3' nds32le-linux-ld: fs/btrfs/extent_io.o: in function `find_extent_buffer': extent_io.c:(.text+0x6d1a): undefined reference to `__udivdi3' nds32le-linux-ld: fs/btrfs/extent_io.o:extent_io.c:(.text+0x6d1e): more undefined references to `__udivdi3' follow --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org