memcg: move memcg_update_cache_size() to slab_common.c

`While growing per memcg caches arrays, we jump between memcontrol.c and
slab_common.c in a weird way:

  memcg_alloc_cache_id - memcontrol.c
    memcg_update_all_caches - slab_common.c
      memcg_update_cache_size - memcontrol.c

There's absolutely no reason why memcg_update_cache_size can't live on the
slab's side though.  So let's move it there and settle it comfortably amid
per-memcg cache allocation functions.

Besides, this patch cleans this function up a bit, removing all the
useless comments from it, and renames it to memcg_update_cache_params to
conform to memcg_alloc/free_cache_params, which we already have in
slab_common.c.

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: Glauber Costa <glommer@gmail.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 28 insertions, 2 deletions

diff --git a/mm/slab_common.c b/mm/slab_common.c
index c2a8661f8b81..3a6e0cfdf03a 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -148,6 +148,33 @@ static void memcg_free_cache_params(struct kmem_cache *s)
         kfree(s->memcg_params);
 }
 
+static int memcg_update_cache_params(struct kmem_cache *s, int num_memcgs)
+{
+        int size;
+        struct memcg_cache_params *new_params, *cur_params;
+
+        BUG_ON(!is_root_cache(s));
+
+        size = offsetof(struct memcg_cache_params, memcg_caches);
+        size += num_memcgs * sizeof(void *);
+
+        new_params = kzalloc(size, GFP_KERNEL);
+        if (!new_params)
+                return -ENOMEM;
+
+        cur_params = s->memcg_params;
+        memcpy(new_params->memcg_caches, cur_params->memcg_caches,
+               memcg_limited_groups_array_size * sizeof(void *));
+
+        new_params->is_root_cache = true;
+
+        rcu_assign_pointer(s->memcg_params, new_params);
+        if (cur_params)
+                kfree_rcu(cur_params, rcu_head);
+
+        return 0;
+}
+
 int memcg_update_all_caches(int num_memcgs)
 {
         struct kmem_cache *s;
@@ -158,9 +185,8 @@ int memcg_update_all_caches(int num_memcgs)
                 if (!is_root_cache(s))
                         continue;
 
-                ret = memcg_update_cache_size(s, num_memcgs);
+                ret = memcg_update_cache_params(s, num_memcgs);
                 /*
-                 * See comment in memcontrol.c, memcg_update_cache_size:
                  * Instead of freeing the memory, we'll just leave the caches
                  * up to this point in an updated state.
                  */