memcg: rename some cache id related variables

memcg_limited_groups_array_size, which defines the size of memcg_caches
arrays, sounds rather cumbersome.  Also it doesn't point anyhow that
it's related to kmem/caches stuff.  So let's rename it to
memcg_nr_cache_ids.  It's concise and points us directly to
memcg_cache_id.

Also, rename kmem_limited_groups to memcg_cache_ida.

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Greg Thelen <gthelen@google.com>
Cc: Glauber Costa <glommer@gmail.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/memcontrol.h

@@ -398,7 +398,7 @@ static inline void sock_release_memcg(struct sock *sk)
 #ifdef CONFIG_MEMCG_KMEM
 extern struct static_key memcg_kmem_enabled_key;
 
-extern int memcg_limited_groups_array_size;
+extern int memcg_nr_cache_ids;
 
 /*
  * Helper macro to loop through all memcg-specific caches. Callers must still
@@ -406,7 +406,7 @@ extern int memcg_limited_groups_array_size;
  * the slab_mutex must be held when looping through those caches
  */
 #define for_each_memcg_cache_index(_idx)	\
-	for ((_idx) = 0; (_idx) < memcg_limited_groups_array_size; (_idx)++)
+	for ((_idx) = 0; (_idx) < memcg_nr_cache_ids; (_idx)++)
 
 static inline bool memcg_kmem_enabled(void)
 {

mm/memcontrol.c

@@ -538,12 +538,11 @@ static void disarm_sock_keys(struct mem_cgroup *memcg)
  *  memcgs, and none but the 200th is kmem-limited, we'd have to have a
  *  200 entry array for that.
  *
- * The current size of the caches array is stored in
- * memcg_limited_groups_array_size.  It will double each time we have to
- * increase it.
+ * The current size of the caches array is stored in memcg_nr_cache_ids. It
+ * will double each time we have to increase it.
  */
-static DEFINE_IDA(kmem_limited_groups);
-int memcg_limited_groups_array_size;
+static DEFINE_IDA(memcg_cache_ida);
+int memcg_nr_cache_ids;
 
 /*
  * MIN_SIZE is different than 1, because we would like to avoid going through
@@ -2538,12 +2537,12 @@ static int memcg_alloc_cache_id(void)
 	int id, size;
 	int err;
 
-	id = ida_simple_get(&kmem_limited_groups,
+	id = ida_simple_get(&memcg_cache_ida,
 			    0, MEMCG_CACHES_MAX_SIZE, GFP_KERNEL);
 	if (id < 0)
 		return id;
 
-	if (id < memcg_limited_groups_array_size)
+	if (id < memcg_nr_cache_ids)
 		return id;
 
 	/*
@@ -2559,7 +2558,7 @@ static int memcg_alloc_cache_id(void)
 
 	err = memcg_update_all_caches(size);
 	if (err) {
-		ida_simple_remove(&kmem_limited_groups, id);
+		ida_simple_remove(&memcg_cache_ida, id);
 		return err;
 	}
 	return id;
@@ -2567,7 +2566,7 @@ static int memcg_alloc_cache_id(void)
 
 static void memcg_free_cache_id(int id)
 {
-	ida_simple_remove(&kmem_limited_groups, id);
+	ida_simple_remove(&memcg_cache_ida, id);
 }
 
 /*
@@ -2577,7 +2576,7 @@ static void memcg_free_cache_id(int id)
  */
 void memcg_update_array_size(int num)
 {
-	memcg_limited_groups_array_size = num;
+	memcg_nr_cache_ids = num;
 }
 
 struct memcg_kmem_cache_create_work {

mm/slab_common.c

@@ -116,7 +116,7 @@ static int memcg_alloc_cache_params(struct mem_cgroup *memcg,
 
 	if (!memcg) {
 		size = offsetof(struct memcg_cache_params, memcg_caches);
-		size += memcg_limited_groups_array_size * sizeof(void *);
+		size += memcg_nr_cache_ids * sizeof(void *);
 	} else
 		size = sizeof(struct memcg_cache_params);
 
@@ -154,7 +154,7 @@ static int memcg_update_cache_params(struct kmem_cache *s, int num_memcgs)
 
 	cur_params = s->memcg_params;
 	memcpy(new_params->memcg_caches, cur_params->memcg_caches,
-	       memcg_limited_groups_array_size * sizeof(void *));
+	       memcg_nr_cache_ids * sizeof(void *));
 
 	new_params->is_root_cache = true;