Hi Vivek, I love your patch! Yet something to improve: [auto build test ERROR on dm/for-next] [also build test ERROR on s390/features xfs-linux/for-next linus/master linux-nvdimm/libnvdimm-for-next v5.5 next-20200203] [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/Vivek-Goyal/dax-pmem-Provide-a-dax-operation-to-zero-range-of-memory/20200204-082750 base: https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git for-next config: s390-alldefconfig (attached as .config) compiler: s390-linux-gcc (GCC) 7.5.0 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=7.5.0 make.cross ARCH=s390 If you fix the issue, kindly add following tag Reported-by: kbuild test robot All errors (new ones prefixed by >>): >> drivers/s390/block/dcssblk.c:65:21: error: 'dcssblk_dax_zero_page_range' undeclared here (not in a function); did you mean 'generic_dax_zero_page_range'? .zero_page_range = dcssblk_dax_zero_page_range, ^~~~~~~~~~~~~~~~~~~~~~~~~~~ generic_dax_zero_page_range drivers/s390/block/dcssblk.c:945:12: warning: 'dcssblk_dax_zero_page_range' defined but not used [-Wunused-function] static int dcssblk_dax_zero_page_range(struct dax_device *dax_dev,pgoff_t pgoff, ^~~~~~~~~~~~~~~~~~~~~~~~~~~ vim +65 drivers/s390/block/dcssblk.c b3a9a0c36e1f7b Dan Williams 2018-05-02 59 7a2765f6e82063 Dan Williams 2017-01-26 60 static const struct dax_operations dcssblk_dax_ops = { 7a2765f6e82063 Dan Williams 2017-01-26 61 .direct_access = dcssblk_dax_direct_access, 7bf7eac8d64805 Dan Williams 2019-05-16 62 .dax_supported = generic_fsdax_supported, 5d61e43b3975c0 Dan Williams 2017-06-27 63 .copy_from_iter = dcssblk_dax_copy_from_iter, b3a9a0c36e1f7b Dan Williams 2018-05-02 64 .copy_to_iter = dcssblk_dax_copy_to_iter, c5cb636194a0d8 Vivek Goyal 2020-02-03 @65 .zero_page_range = dcssblk_dax_zero_page_range, ^1da177e4c3f41 Linus Torvalds 2005-04-16 66 }; ^1da177e4c3f41 Linus Torvalds 2005-04-16 67 :::::: The code at line 65 was first introduced by commit :::::: c5cb636194a0d8d33d549903c92189385db48406 s390,dax: Add dax zero_page_range operation to dcssblk driver :::::: TO: Vivek Goyal :::::: CC: 0day robot --- 0-DAY kernel test infrastructure Open Source Technology Center https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org Intel Corporation