Commit 20f05310 authored Jul 08, 2013 by Li Zefan Committed by Linus Torvalds Jul 09, 2013

memcg: don't use mem_cgroup_get() when creating a kmemcg cache



Use css_get()/css_put() instead of mem_cgroup_get()/mem_cgroup_put().

There are two things being done in the current code:

First, we acquired a css_ref to make sure that the underlying cgroup
would not go away.  That is a short lived reference, and it is put as
soon as the cache is created.

At this point, we acquire a long-lived per-cache memcg reference count
to guarantee that the memcg will still be alive.

so it is:

  enqueue: css_get
  create : memcg_get, css_put
  destroy: memcg_put

So we only need to get rid of the memcg_get, change the memcg_put to
css_put, and get rid of the now extra css_put.

(This changelog is mostly written by Glauber)

Signed-off-by: Li Zefan <lizefan@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Glauber Costa <glommer@openvz.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 5347e5ae

mm/memcontrol.c

+5 −5

Original line number	Diff line number	Diff line
		@@ -3242,7 +3242,7 @@ void memcg_release_cache(struct kmem_cache *s)
		list_del(&s->memcg_params->list);
		mutex_unlock(&memcg->slab_caches_mutex);

		mem_cgroup_put(memcg);
		css_put(&memcg->css);
		out:
		kfree(s->memcg_params);
		}
		@@ -3402,16 +3402,18 @@ static struct kmem_cache memcg_create_kmem_cache(struct mem_cgroup memcg,

		mutex_lock(&memcg_cache_mutex);
		new_cachep = cachep->memcg_params->memcg_caches[idx];
		if (new_cachep)
		if (new_cachep) {
		css_put(&memcg->css);
		goto out;
		}

		new_cachep = kmem_cache_dup(memcg, cachep);
		if (new_cachep == NULL) {
		new_cachep = cachep;
		css_put(&memcg->css);
		goto out;
		}

		mem_cgroup_get(memcg);
		atomic_set(&new_cachep->memcg_params->nr_pages , 0);

		cachep->memcg_params->memcg_caches[idx] = new_cachep;
		@@ -3499,8 +3501,6 @@ static void memcg_create_cache_work_func(struct work_struct *w)

		cw = container_of(w, struct create_work, work);
		memcg_create_kmem_cache(cw->memcg, cw->cachep);
		/* Drop the reference gotten when we enqueued. */
		css_put(&cw->memcg->css);
		kfree(cw);
		}