Hi Peter, Thank you for the patch! Yet something to improve: [auto build test ERROR on linus/master] [also build test ERROR on v5.14-rc1 next-20210714] [cannot apply to hnaz-linux-mm/master asm-generic/master linux/master] [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/Peter-Xu/userfaultfd-wp-Support-... base: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 8096acd7442e613fad0354fc8dfdb2003cceea0b config: x86_64-randconfig-r021-20210714 (attached as .config) compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project 0e49c54a8cbd3e779e5526a5888c683c01cc3c50) 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 # install x86_64 cross compiling tool for clang build # apt-get install binutils-x86-64-linux-gnu # https://github.com/0day-ci/linux/commit/8b3e70f40b8333a803e642ed5c8cce738... git remote add linux-review https://github.com/0day-ci/linux git fetch --no-tags linux-review Peter-Xu/userfaultfd-wp-Support-shmem-and-hugetlbfs/20210715-062718 git checkout 8b3e70f40b8333a803e642ed5c8cce738985881c # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64 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 >>): >> mm/memory.c:4167:6: error: implicit declaration of function 'uffd_disable_fault_around' [-Werror,-Wimplicit-function-declaration] if (uffd_disable_fault_around(vmf->vma)) ^ 1 error generated. vim +/uffd_disable_fault_around +4167 mm/memory.c 4159 4160 /* Return true if we should do read fault-around, false otherwise */ 4161 static inline bool should_fault_around(struct vm_fault *vmf) 4162 { 4163 /* No ->map_pages? No way to fault around... */ 4164 if (!vmf->vma->vm_ops->map_pages) 4165 return false; 4166 > 4167 if (uffd_disable_fault_around(vmf->vma)) 4168 return false; 4169 4170 return fault_around_bytes >> PAGE_SHIFT > 1; 4171 } 4172 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org