Hi David,

I love your patch! Perhaps something to improve:

[auto build test WARNING on linus/master]
[also build test WARNING on v5.10-rc1]
[cannot apply to tip/perf/core hch-configfs/for-next next-20201027]
[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/David-Howells/AFS-fixes/20201027-215256
base:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 4525c8781ec0701ce824e8bd379ae1b129e26568
config: powerpc-randconfig-r025-20201026 (attached as .config)
compiler: powerpc-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
        # https://github.com/0day-ci/linux/commit/5182f7848e94c4aa60f8a100b1e322cd46124efc
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review David-Howells/AFS-fixes/20201027-215256
        git checkout 5182f7848e94c4aa60f8a100b1e322cd46124efc
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=powerpc 

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

All warnings (new ones prefixed by >>):

   In file included from fs/afs/cache.c:9:
   fs/afs/internal.h: In function 'afs_page_dirty_to':
>> fs/afs/internal.h:881:15: warning: right shift count >= width of type [-Wshift-count-overflow]
     881 |  return (priv >> __AFS_PAGE_PRIV_SHIFT) & __AFS_PAGE_PRIV_MASK;
         |               ^~
   fs/afs/internal.h: In function 'afs_page_dirty':
>> fs/afs/internal.h:886:28: warning: left shift count >= width of type [-Wshift-count-overflow]
     886 |  return ((unsigned long)to << __AFS_PAGE_PRIV_SHIFT) | from;
         |                            ^~
--
   In file included from fs/afs/write.c:14:
   fs/afs/internal.h: In function 'afs_page_dirty_to':
>> fs/afs/internal.h:881:15: warning: right shift count >= width of type [-Wshift-count-overflow]
     881 |  return (priv >> __AFS_PAGE_PRIV_SHIFT) & __AFS_PAGE_PRIV_MASK;
         |               ^~
   fs/afs/internal.h: In function 'afs_page_dirty':
>> fs/afs/internal.h:886:28: warning: left shift count >= width of type [-Wshift-count-overflow]
     886 |  return ((unsigned long)to << __AFS_PAGE_PRIV_SHIFT) | from;
         |                            ^~
   In file included from <command-line>:
   fs/afs/write.c: In function 'afs_write_begin':
   include/linux/compiler_types.h:319:38: error: call to '__compiletime_assert_566' declared with attribute error: BUILD_BUG_ON failed: PAGE_SIZE > 32768 && sizeof(page->private) < 8
     319 |  _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
         |                                      ^
   include/linux/compiler_types.h:300:4: note: in definition of macro '__compiletime_assert'
     300 |    prefix ## suffix();    \
         |    ^~~~~~
   include/linux/compiler_types.h:319:2: note: in expansion of macro '_compiletime_assert'
     319 |  _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
         |  ^~~~~~~~~~~~~~~~~~~
   include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert'
      39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
         |                                     ^~~~~~~~~~~~~~~~~~
   include/linux/build_bug.h:50:2: note: in expansion of macro 'BUILD_BUG_ON_MSG'
      50 |  BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
         |  ^~~~~~~~~~~~~~~~
   fs/afs/write.c:96:2: note: in expansion of macro 'BUILD_BUG_ON'
      96 |  BUILD_BUG_ON(PAGE_SIZE > 32768 && sizeof(page->private) < 8);
         |  ^~~~~~~~~~~~

vim +881 fs/afs/internal.h

   878	
   879	static inline unsigned int afs_page_dirty_to(unsigned long priv)
   880	{
 > 881		return (priv >> __AFS_PAGE_PRIV_SHIFT) & __AFS_PAGE_PRIV_MASK;
   882	}
   883	
   884	static inline unsigned long afs_page_dirty(unsigned int from, unsigned int to)
   885	{
 > 886		return ((unsigned long)to << __AFS_PAGE_PRIV_SHIFT) | from;
   887	}
   888	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org