Hi Mike,

I love your patch! Yet something to improve:

[auto build test ERROR on mmotm/master]
[also build test ERROR on linux/master v5.4]
[cannot apply to arm-soc/for-next linus/master next-20191208]
[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/Mike-Rapoport/mm-extend-memfd-with-ability-to-create-secret-memory/20191207-130906
base:   git://git.cmpxchg.org/linux-mmotm.git master
config: arm64-randconfig-a001-20191208 (attached as .config)
compiler: aarch64-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=arm64 

If you fix the issue, kindly add following tag
Reported-by: kbuild test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   mm/secretmem.c: In function 'secretmem_fault':
>> mm/secretmem.c:45:9: error: implicit declaration of function 'set_pages_array_uc'; did you mean 'set_page_dirty_lock'? [-Werror=implicit-function-declaration]
      err = set_pages_array_uc(&page, 1);
            ^~~~~~~~~~~~~~~~~~
            set_page_dirty_lock
   mm/secretmem.c: In function 'secretmem_close':
>> mm/secretmem.c:75:4: error: implicit declaration of function 'set_pages_array_wb'; did you mean 'set_page_dirty'? [-Werror=implicit-function-declaration]
       set_pages_array_wb(&page, 1);
       ^~~~~~~~~~~~~~~~~~
       set_page_dirty
   cc1: some warnings being treated as errors

vim +45 mm/secretmem.c

    21	
    22	static vm_fault_t secretmem_fault(struct vm_fault *vmf)
    23	{
    24		struct secretmem_state *state = vmf->vma->vm_file->private_data;
    25		struct address_space *mapping = vmf->vma->vm_file->f_mapping;
    26		pgoff_t offset = vmf->pgoff;
    27		unsigned long addr;
    28		struct page *page;
    29		int err;
    30	
    31		page = find_get_page(mapping, offset);
    32		if (!page) {
    33			page = pagecache_get_page(mapping, offset,
    34						  FGP_CREAT|FGP_FOR_MMAP,
    35						  vmf->gfp_mask);
    36			if (!page)
    37				return vmf_error(-ENOMEM);
    38	
    39			__SetPageUptodate(page);
    40		}
    41	
    42		if (state->mode == SECRETMEM_EXCLUSIVE)
    43			err = set_direct_map_invalid_noflush(page);
    44		else if (state->mode == SECRETMEM_UNCACHED)
  > 45			err = set_pages_array_uc(&page, 1);
    46		else
    47			BUG();
    48	
    49		if (err) {
    50			delete_from_page_cache(page);
    51			return vmf_error(err);
    52		}
    53	
    54		addr = (unsigned long)page_address(page);
    55		flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
    56	
    57		vmf->page = page;
    58		return  0;
    59	}
    60	
    61	static void secretmem_close(struct vm_area_struct *vma)
    62	{
    63		struct secretmem_state *state = vma->vm_file->private_data;
    64		struct address_space *mapping = vma->vm_file->f_mapping;
    65		struct page *page;
    66		pgoff_t index;
    67	
    68		xa_for_each(&mapping->i_pages, index, page) {
    69			get_page(page);
    70			lock_page(page);
    71	
    72			if (state->mode == SECRETMEM_EXCLUSIVE)
    73				set_direct_map_default_noflush(page);
    74			else if (state->mode == SECRETMEM_UNCACHED)
  > 75				set_pages_array_wb(&page, 1);
    76			else
    77				BUG();
    78	
    79			__ClearPageDirty(page);
    80			delete_from_page_cache(page);
    81	
    82			unlock_page(page);
    83			put_page(page);
    84		}
    85	}
    86	

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