Hi Chengguang,

[FYI, it's a private test report for your RFC patch.]
[auto build test WARNING on miklos-vfs/overlayfs-next]
[also build test WARNING on linus/master v5.9-rc8 next-20201009]
[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/Chengguang-Xu/implement-containerized-syncfs-for-overlayfs/20201011-071405
base:   https://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs.git overlayfs-next
config: arm-randconfig-r034-20201011 (attached as .config)
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project a8682554c6662ce01853d0069afb6c5b4ef8ab55)
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 arm cross compiling tool for clang build
        # apt-get install binutils-arm-linux-gnueabi
        # https://github.com/0day-ci/linux/commit/6a0553975f03bb63033f5c246273010a38a66ccf
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Chengguang-Xu/implement-containerized-syncfs-for-overlayfs/20201011-071405
        git checkout 6a0553975f03bb63033f5c246273010a38a66ccf
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=arm 

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 >>):

>> fs/overlayfs/super.c:393:6: warning: no previous prototype for function 'ovl_evict_inode' [-Wmissing-prototypes]
   void ovl_evict_inode(struct inode *inode)
        ^
   fs/overlayfs/super.c:393:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
   void ovl_evict_inode(struct inode *inode)
   ^
   static 
   1 warning generated.
--
   fs/overlayfs/util.c:959:7: warning: unused variable 'flags' [-Wunused-variable]
           int *flags = (int *)param;
                ^
   fs/overlayfs/util.c:958:20: warning: unused variable 'oi' [-Wunused-variable]
           struct ovl_inode *oi = container_of(nb, struct ovl_inode, mark_dirty_nb);
                             ^
>> fs/overlayfs/util.c:955:5: warning: no previous prototype for function 'ovl_inode_dirty_notify' [-Wmissing-prototypes]
   int ovl_inode_dirty_notify(struct notifier_block *nb,
       ^
   fs/overlayfs/util.c:955:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
   int ovl_inode_dirty_notify(struct notifier_block *nb,
   ^
   static 
   3 warnings generated.
--
   fs/overlayfs/util.c:958:20: warning: unused variable 'oi' [-Wunused-variable]
           struct ovl_inode *oi = container_of(nb, struct ovl_inode, mark_dirty_nb);
                             ^
   fs/overlayfs/util.c:959:7: warning: unused variable 'flags' [-Wunused-variable]
           int *flags = (int *)param;
                ^
>> fs/overlayfs/util.c:955:5: warning: no previous prototype for function 'ovl_inode_dirty_notify' [-Wmissing-prototypes]
   int ovl_inode_dirty_notify(struct notifier_block *nb,
       ^
   fs/overlayfs/util.c:955:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
   int ovl_inode_dirty_notify(struct notifier_block *nb,
   ^
   static 
   3 warnings generated.

vim +/ovl_evict_inode +393 fs/overlayfs/super.c

   392	
 > 393	void ovl_evict_inode(struct inode *inode)
   394	{
   395		struct inode *upper;
   396	
   397		upper = ovl_inode_upper(inode);
   398		if (upper)
   399			ovl_unregister_mark_dirty_notify(OVL_I(inode));
   400		clear_inode(inode);
   401	}
   402	

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