Re: [linux-next:master 12342/12641] mm/vmscan.c:205:7: error: implicit declaration of function 'memcg_expand_shrinker_maps'; did you mean 'memcg_set_shrinker_bit'?

[Randy Dunlap <rdunlap@infradead.org>]

On 7/5/19 2:20 PM, Andrew Morton wrote:
> On Fri, 5 Jul 2019 21:09:24 +0800 kbuild test robot <lkp@intel.com> wrote:
> 
>> tree:   https://kernel.googlesource.com/pub/scm/linux/kernel/git/next/linux-next.git master
>> head:   22c45ec32b4a9fa8c48ef4f5bf9b189b307aae12
>> commit: 8236f517d69e2217f5200d7f700e8b18b01c94c8 [12342/12641] mm: shrinker: make shrinker not depend on memcg kmem
>> config: x86_64-randconfig-s2-07051907 (attached as .config)
>> compiler: gcc-7 (Debian 7.4.0-9) 7.4.0
>> reproduce:
>>         git checkout 8236f517d69e2217f5200d7f700e8b18b01c94c8
>>         # save the attached .config to linux build tree
>>         make ARCH=x86_64 
>>
>> If you fix the issue, kindly add following tag
>> Reported-by: kbuild test robot <lkp@intel.com>
>>
>> All error/warnings (new ones prefixed by >>):
>>
>>    mm/vmscan.c: In function 'prealloc_memcg_shrinker':
>>>> mm/vmscan.c:205:7: error: implicit declaration of function 'memcg_expand_shrinker_maps'; did you mean 'memcg_set_shrinker_bit'? [-Werror=implicit-function-declaration]
>>       if (memcg_expand_shrinker_maps(id)) {
>>           ^~~~~~~~~~~~~~~~~~~~~~~~~~
>>           memcg_set_shrinker_bit
>>    In file included from include/linux/rbtree.h:22:0,
>>                     from include/linux/mm_types.h:10,
>>                     from include/linux/mmzone.h:21,
>>                     from include/linux/gfp.h:6,
>>                     from include/linux/mm.h:10,
>>                     from mm/vmscan.c:17:
>>    mm/vmscan.c: In function 'shrink_slab_memcg':
>>>> mm/vmscan.c:593:54: error: 'struct mem_cgroup_per_node' has no member named 'shrinker_map'
> 
> This?
> 
> --- a/include/linux/memcontrol.h~mm-shrinker-make-shrinker-not-depend-on-memcg-kmem-fix
> +++ a/include/linux/memcontrol.h
> @@ -128,7 +128,7 @@ struct mem_cgroup_per_node {
>  
>  	struct mem_cgroup_reclaim_iter	iter[DEF_PRIORITY + 1];
>  
> -#ifdef CONFIG_MEMCG_KMEM
> +#ifdef CONFIG_MEMCG
>  	struct memcg_shrinker_map __rcu	*shrinker_map;
>  #endif
>  	struct rb_node		tree_node;	/* RB tree node */
> @@ -1272,6 +1272,7 @@ static inline bool mem_cgroup_under_sock
>  
>  struct kmem_cache *memcg_kmem_get_cache(struct kmem_cache *cachep);
>  void memcg_kmem_put_cache(struct kmem_cache *cachep);
> +extern int memcg_expand_shrinker_maps(int new_id);
>  
>  #ifdef CONFIG_MEMCG_KMEM
>  int __memcg_kmem_charge(struct page *page, gfp_t gfp, int order);
> @@ -1339,8 +1340,6 @@ static inline int memcg_cache_id(struct
>  	return memcg ? memcg->kmemcg_id : -1;
>  }
>  
> -extern int memcg_expand_shrinker_maps(int new_id);
> -
>  extern void memcg_set_shrinker_bit(struct mem_cgroup *memcg,
>  				   int nid, int shrinker_id);
>  #else
> _
> 

I suggest that someone drop these patches until they are better.

E.g., in include/linux/memcontrol.h:

65: #ifdef CONFIG_MEMCG
131: #ifdef CONFIG_MEMCG
133: #endif
802: #else /* CONFIG_MEMCG */
1138: #endif /* CONFIG_MEMCG */

so lines 131 & 133 are redundant.

-- 
~Randy