Re: [PATCH v3 4/4] mm: memcg: use non-unified stats flushing for userspace reads

[kernel test robot <lkp@intel.com>]

Hi Yosry,

kernel test robot noticed the following build warnings:

[auto build test WARNING on akpm-mm/mm-everything]
[also build test WARNING on linus/master next-20230830]
[cannot apply to v6.5]
[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#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Yosry-Ahmed/mm-memcg-properly-name-and-document-unified-stats-flushing/20230831-015518
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20230830175335.1536008-5-yosryahmed%40google.com
patch subject: [PATCH v3 4/4] mm: memcg: use non-unified stats flushing for userspace reads
config: m68k-randconfig-r016-20230831 (https://download.01.org/0day-ci/archive/20230831/202308310858.19VshX68-lkp@intel.com/config)
compiler: m68k-linux-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20230831/202308310858.19VshX68-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202308310858.19VshX68-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> mm/memcontrol.c:667:6: warning: no previous prototype for 'mem_cgroup_user_flush_stats' [-Wmissing-prototypes]
     667 | void mem_cgroup_user_flush_stats(struct mem_cgroup *memcg)
         |      ^~~~~~~~~~~~~~~~~~~~~~~~~~~


vim +/mem_cgroup_user_flush_stats +667 mm/memcontrol.c

   658	
   659	/*
   660	 * mem_cgroup_user_flush_stats - do a stats flush for a user read
   661	 * @memcg: memory cgroup to flush
   662	 *
   663	 * Flush the subtree of @memcg. A mutex is used for userspace readers to gate
   664	 * the global rstat spinlock. This protects in-kernel flushers from userspace
   665	 * readers hogging the lock.
   666	 */
 > 667	void mem_cgroup_user_flush_stats(struct mem_cgroup *memcg)
   668	{
   669		mutex_lock(&stats_user_flush_mutex);
   670		do_stats_flush(memcg);
   671		mutex_unlock(&stats_user_flush_mutex);
   672	}
   673	

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