tree:   https://github.com/amir73il/linux ovl-watch
head:   854541356b2eb98d7779c0f548d5cfb51f80f358
commit: e8140137d1b0304da823ba9954324acae62fb3e1 [18/27] ovl: introduce an fsnotify watch
config: powerpc-allyesconfig (attached as .config)
compiler: powerpc64-linux-gcc (GCC) 11.2.0
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/amir73il/linux/commit/e8140137d1b0304da823ba9954324acae62fb3e1
        git remote add amir73il https://github.com/amir73il/linux
        git fetch --no-tags amir73il ovl-watch
        git checkout e8140137d1b0304da823ba9954324acae62fb3e1
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 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 >>):

>> fs/overlayfs/super.c:2164:6: warning: no previous prototype for 'ovl_kill_super' [-Wmissing-prototypes]
    2164 | void ovl_kill_super(struct super_block *sb)
         |      ^~~~~~~~~~~~~~


vim +/ovl_kill_super +2164 fs/overlayfs/super.c

  2163	
> 2164	void ovl_kill_super(struct super_block *sb)
  2165	{
  2166		/*
  2167		 * We need to destroy the fsnotify group and wait on all pending events
  2168		 * *before* shutting down super block, because event handler is
  2169		 * derefernecing this sb from group->private.
  2170		 */
  2171		if (sb->s_root)
  2172			ovl_free_watch(sb->s_fs_info);
  2173		kill_anon_super(sb);
  2174	}
  2175	

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