Re: [akpm-mm:mm-unstable 313/322] include/linux/huge_mm.h:274:23: error: variably modified 'stats' at file scope

[Barry Song <21cnbao@gmail.com>]

On Sun, Apr 7, 2024 at 12:52 PM Barry Song <21cnbao@gmail.com> wrote:
>
> >
> >
> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-unstable
> > head:   f43b3aae94511d62174c3b29239da0dd22d0eeb3
> > commit: d4358ee0a075e232114dfec0cd162860cfa2771b [313/322] mm: add per-order mTHP anon_alloc and anon_alloc_fallback counters
> > config: powerpc-allmodconfig (https://download.01.org/0day-ci/archive/20240406/202404061627.ungVloow-lkp@intel.com/config)
> > compiler: powerpc64-linux-gcc (GCC) 13.2.0
> > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240406/202404061627.ungVloow-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/202404061627.ungVloow-lkp@intel.com/
>
> > All errors (new ones prefixed by >>):
> >
> >    In file included from include/linux/mm.h:1115,
> >                     from include/linux/mman.h:5,
> >                     from arch/powerpc/kernel/asm-offsets.c:19:
> >>> include/linux/huge_mm.h:274:23: error: variably modified 'stats' at file scope
> >      274 |         unsigned long stats[PMD_ORDER + 1][__MTHP_STAT_COUNT];
> >          |                       ^~~~~
> >    make[3]: *** [scripts/Makefile.build:117: arch/powerpc/kernel/asm-offsets.s] Error 1
>
> Should have been fixed by:
>
> From 573aa50dbebcd4b2650d477374b28aa53c21b968 Mon Sep 17 00:00:00 2001
> From: Barry Song <v-songbaohua@oppo.com>
> Date: Sun, 7 Apr 2024 12:23:35 +1200
> Subject: [PATCH] mm: fix powerpc build issue
>
> Signed-off-by: Barry Song <v-songbaohua@oppo.com>
> ---
>  include/linux/huge_mm.h |  9 ++++-----
>  mm/huge_memory.c        | 13 +++++++++++--
>  2 files changed, 15 insertions(+), 7 deletions(-)
>
> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> index c5d33017a4dd..0717063dc5e7 100644
> --- a/include/linux/huge_mm.h
> +++ b/include/linux/huge_mm.h
> @@ -271,16 +271,15 @@ enum mthp_stat_item {
>  };
>
>  struct mthp_stat {
> -       unsigned long stats[PMD_ORDER + 1][__MTHP_STAT_COUNT];
> +       unsigned long stats[0][__MTHP_STAT_COUNT];
>  };
>
> -DECLARE_PER_CPU(struct mthp_stat, mthp_stats);
> +extern struct mthp_stat __percpu *mthp_stats;
>
>  static inline void count_mthp_stat(int order, enum mthp_stat_item item)
>  {
> -       if (unlikely(order > PMD_ORDER))
> -               return;
> -       this_cpu_inc(mthp_stats.stats[order][item]);
> +       if (likely(order <= PMD_ORDER))
> +               raw_cpu_ptr(mthp_stats)->stats[order][item]++;
>  }
>
>  #define transparent_hugepage_use_zero_page()                           \
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 5b875f0fc923..10bc3f54cb81 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -526,7 +526,7 @@ static const struct kobj_type thpsize_ktype = {
>         .sysfs_ops = &kobj_sysfs_ops,
>  };
>
> -DEFINE_PER_CPU(struct mthp_stat, mthp_stats) = {{{0}}};
> +struct mthp_stat __percpu *mthp_stats;
>
>  static unsigned long sum_mthp_stat(int order, enum mthp_stat_item item)
>  {
> @@ -534,7 +534,7 @@ static unsigned long sum_mthp_stat(int order, enum mthp_stat_item item)
>         int cpu;
>
>         for_each_online_cpu(cpu) {
> -               struct mthp_stat *this = &per_cpu(mthp_stats, cpu);
> +               struct mthp_stat *this = per_cpu_ptr(mthp_stats, cpu);
>
>                 sum += this->stats[order][item];
>         }
> @@ -602,6 +602,7 @@ static struct thpsize *thpsize_create(int order, struct kobject *parent)
>  static void thpsize_release(struct kobject *kobj)
>  {
>         kfree(to_thpsize(kobj));
> +       free_percpu(mthp_stats);
>  }
>
>  static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
> @@ -636,6 +637,13 @@ static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
>                 goto remove_hp_group;
>         }
>
> +       mthp_stats = (struct mthp_stat __percpu *)alloc_percpu((PMD_ORDER + 1) *
> +                                       sizeof(sizeof(mthp_stats->stats[0])));

sorry. I made the wrong allocation size. please change the above two
lines to the below when you
test the patch:

+       mthp_stats = __alloc_percpu((PMD_ORDER + 1) *
sizeof(mthp_stats->stats[0]),
+                       sizeof(unsigned long));

> +       if (!mthp_stats) {
> +               err = -ENOMEM;
> +               goto remove_hp_group;
> +       }
> +
>         orders = THP_ORDERS_ALL_ANON;
>         order = highest_order(orders);
>         while (orders) {
> @@ -673,6 +681,7 @@ static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
>         sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
>         sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
>         kobject_put(hugepage_kobj);
> +       free_percpu(mthp_stats);
>  }
>  #else
>  static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
> --
> 2.34.1
>

Thanks
Barry