Hi Peter, [FYI, it's a private test report for your RFC patch.] [auto build test WARNING on asm-generic/master] [cannot apply to arm64/for-next/core linus/master hnaz-linux-mm/master v5.11-rc3 next-20210115] [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/arnd/asm-generic.git master config: powerpc64-randconfig-r015-20210115 (attached as .config) compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project 5b42fd8dd4e7e29125a09a41a33af7c9cb57d144) 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 powerpc64 cross compiling tool for clang build # apt-get install binutils-powerpc64-linux-gnu # https://github.com/0day-ci/linux/commit/52b3f6cd15560c697c44ecfb34fd303f9... 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/20210116-011305 git checkout 52b3f6cd15560c697c44ecfb34fd303f9cc43ae2 # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=powerpc64 If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All warnings (new ones prefixed by >>): vm_fault_t uffd_wp_handle_special(struct vm_fault *vmf) ^ mm/memory.c:4380:1: note: declare 'static' if the function is not intended to be used outside of this translation unit vm_fault_t uffd_wp_handle_special(struct vm_fault *vmf) ^ static 1 warning generated. vim +/uffd_wp_handle_special +4380 mm/memory.c 4375 4376 /* 4377 * This is actually a page-missing access, but with uffd-wp special pte 4378 * installed. It means this pte was wr-protected before being unmapped. 4379 */ 4381 { 4382 /* Careful! vmf->pte unmapped after return */ 4383 if (!pte_unmap_same(vmf)) 4384 return 0; 4385 4386 /* 4387 * Just in case there're leftover special ptes even after the region 4388 * got unregistered - we can simply clear them. 4389 */ 4390 if (unlikely(!userfaultfd_wp(vmf->vma) || vma_is_anonymous(vmf->vma))) 4391 return uffd_wp_clear_special(vmf); 4392 4393 /* 4394 * Tell all the rest of the fault code: we're handling a special pte, 4395 * always remember to arm the uffd-wp bit when intalling the new pte. 4396 */ 4397 vmf->flags |= FAULT_FLAG_UFFD_WP; 4398 4399 /* 4400 * Let's assume this is a read fault no matter what. If it is a real 4401 * write access, it'll fault again into do_wp_page() where the message 4402 * will be generated before the thread yields itself. 4403 * 4404 * Ideally we can also handle write immediately before return, but this 4405 * should be a slow path already (pte unmapped), so be simple first. 4406 */ 4407 vmf->flags &= ~FAULT_FLAG_WRITE; 4408 4409 return do_fault(vmf); 4410 } 4411 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org