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

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Date:   Thu, 31 Aug 2023 09:40:03 -0700
From:   Yosry Ahmed <yosryahmed@...gle.com>
To:     kernel test robot <lkp@...el.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, llvm@...ts.linux.dev,
        oe-kbuild-all@...ts.linux.dev,
        Linux Memory Management List <linux-mm@...ck.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Shakeel Butt <shakeelb@...gle.com>,
        Muchun Song <muchun.song@...ux.dev>,
        Ivan Babrou <ivan@...udflare.com>, Tejun Heo <tj@...nel.org>,
        Michal Koutný <mkoutny@...e.com>,
        Waiman Long <longman@...hat.com>, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 4/4] mm: memcg: use non-unified stats flushing for
 userspace reads

On Wed, Aug 30, 2023 at 8:08 PM kernel test robot <lkp@...el.com> wrote:
>
> 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: i386-randconfig-r013-20230831 (https://download.01.org/0day-ci/archive/20230831/202308311025.538QuXBV-lkp@intel.com/config)
> compiler: clang version 16.0.4 (https://github.com/llvm/llvm-project.git ae42196bc493ffe877a7e3dff8be32035dea4d07)
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20230831/202308311025.538QuXBV-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@...el.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202308311025.538QuXBV-lkp@intel.com/
>
> All warnings (new ones prefixed by >>):
>
> >> mm/memcontrol.c:667:6: warning: no previous prototype for function 'mem_cgroup_user_flush_stats' [-Wmissing-prototypes]
>    void mem_cgroup_user_flush_stats(struct mem_cgroup *memcg)
>         ^
>    mm/memcontrol.c:667:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
>    void mem_cgroup_user_flush_stats(struct mem_cgroup *memcg)
>    ^
>    static
>    1 warning generated.

Ah silly mistake on my end. Will send v4 after making
mem_cgroup_user_flush_stats() static.

>
>
> 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
>
> --
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests/wiki