memcg, kmem: use cache_from_memcg_idx instead of hard code

Signed-off-by: Qiang Huang <h.huangqiang@huawei.com>
Reviewed-by: Pekka Enberg <penberg@kernel.org>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Glauber Costa <glommer@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memcontrol.c

@@ -2956,7 +2956,7 @@ static struct kmem_cache *memcg_params_to_cache(struct memcg_cache_params *p)
 
 	VM_BUG_ON(p->is_root_cache);
 	cachep = p->root_cache;
-	return cachep->memcg_params->memcg_caches[memcg_cache_id(p->memcg)];
+	return cache_from_memcg_idx(cachep, memcg_cache_id(p->memcg));
 }
 
 #ifdef CONFIG_SLABINFO
@@ -3393,7 +3393,7 @@ static struct kmem_cache *memcg_create_kmem_cache(struct mem_cgroup *memcg,
 	idx = memcg_cache_id(memcg);
 
 	mutex_lock(&memcg_cache_mutex);
-	new_cachep = cachep->memcg_params->memcg_caches[idx];
+	new_cachep = cache_from_memcg_idx(cachep, idx);
 	if (new_cachep) {
 		css_put(&memcg->css);
 		goto out;
@@ -3439,8 +3439,8 @@ void kmem_cache_destroy_memcg_children(struct kmem_cache *s)
 	 * we'll take the set_limit_mutex to protect ourselves against this.
 	 */
 	mutex_lock(&set_limit_mutex);
-	for (i = 0; i < memcg_limited_groups_array_size; i++) {
-		c = s->memcg_params->memcg_caches[i];
+	for_each_memcg_cache_index(i) {
+		c = cache_from_memcg_idx(s, i);
 		if (!c)
 			continue;
 
@@ -3573,8 +3573,8 @@ struct kmem_cache *__memcg_kmem_get_cache(struct kmem_cache *cachep,
 	 * code updating memcg_caches will issue a write barrier to match this.
 	 */
 	read_barrier_depends();
-	if (likely(cachep->memcg_params->memcg_caches[idx])) {
-		cachep = cachep->memcg_params->memcg_caches[idx];
+	if (likely(cache_from_memcg_idx(cachep, idx))) {
+		cachep = cache_from_memcg_idx(cachep, idx);
 		goto out;
 	}