memcg, slab: clean up memcg cache initialization/destruction

Currently, we have rather a messy function set relating to per-memcg
kmem cache initialization/destruction.

Per-memcg caches are created in memcg_create_kmem_cache().  This
function calls kmem_cache_create_memcg() to allocate and initialize a
kmem cache and then "registers" the new cache in the
memcg_params::memcg_caches array of the parent cache.

During its work-flow, kmem_cache_create_memcg() executes the following
memcg-related functions:

 - memcg_alloc_cache_params(), to initialize memcg_params of the newly
   created cache;
 - memcg_cache_list_add(), to add the new cache to the memcg_slab_caches
   list.

On the other hand, kmem_cache_destroy() called on a cache destruction
only calls memcg_release_cache(), which does all the work: it cleans the
reference to the cache in its parent's memcg_params::memcg_caches,
removes the cache from the memcg_slab_caches list, and frees
memcg_params.

Such an inconsistency between destruction and initialization paths make
the code difficult to read, so let's clean this up a bit.

This patch moves all the code relating to registration of per-memcg
caches (adding to memcg list, setting the pointer to a cache from its
parent) to the newly created memcg_register_cache() and
memcg_unregister_cache() functions making the initialization and
destruction paths look symmetrical.

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Glauber Costa <glommer@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 5 deletions

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 284daff507fb..abd0113b6620 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -500,8 +500,8 @@ int memcg_cache_id(struct mem_cgroup *memcg);
 int memcg_alloc_cache_params(struct mem_cgroup *memcg, struct kmem_cache *s,
 			     struct kmem_cache *root_cache);
 void memcg_free_cache_params(struct kmem_cache *s);
-void memcg_release_cache(struct kmem_cache *cachep);
-void memcg_cache_list_add(struct mem_cgroup *memcg, struct kmem_cache *cachep);
+void memcg_register_cache(struct kmem_cache *s);
+void memcg_unregister_cache(struct kmem_cache *s);
 
 int memcg_update_cache_size(struct kmem_cache *s, int num_groups);
 void memcg_update_array_size(int num_groups);
@@ -651,12 +651,11 @@ static inline void memcg_free_cache_params(struct kmem_cache *s)
 {
 }
 
-static inline void memcg_release_cache(struct kmem_cache *cachep)
+static inline void memcg_register_cache(struct kmem_cache *s)
 {
 }
 
-static inline void memcg_cache_list_add(struct mem_cgroup *memcg,
-					struct kmem_cache *s)
+static inline void memcg_unregister_cache(struct kmem_cache *s)
 {
 }