memcg: use css_get/put when charging/uncharging kmem

static void memcg_kmem_mark_dead(struct mem_cgroup *memcg)

{

	/*

	 * Our caller must use css_get() first, because memcg_uncharge_kmem()

	 * will call css_put() if it sees the memcg is dead.

	 */

	smp_wmb();

	if (test_bit(KMEM_ACCOUNTED_ACTIVE, &memcg->kmem_account_flags))

		set_bit(KMEM_ACCOUNTED_DEAD, &memcg->kmem_account_flags);

}

	if (res_counter_uncharge(&memcg->kmem, size))

		return;

	/*

	 * Releases a reference taken in kmem_cgroup_css_offline in case

	 * this last uncharge is racing with the offlining code or it is

	 * outliving the memcg existence.

	 *

	 * The memory barrier imposed by test&clear is paired with the

	 * explicit one in memcg_kmem_mark_dead().

	 */

	if (memcg_kmem_test_and_clear_dead(memcg))

		mem_cgroup_put(memcg);

		css_put(&memcg->css);

}

void memcg_cache_list_add(struct mem_cgroup *memcg, struct kmem_cache *cachep)

		 * starts accounting before all call sites are patched

		 */

		memcg_kmem_set_active(memcg);

		/*

		 * kmem charges can outlive the cgroup. In the case of slab

		 * pages, for instance, a page contain objects from various

		 * processes, so it is unfeasible to migrate them away. We

		 * need to reference count the memcg because of that.

		 */

		mem_cgroup_get(memcg);

	} else

		ret = res_counter_set_limit(&memcg->kmem, val);

out:

		goto out;

	/*

	 * destroy(), called if we fail, will issue static_key_slow_inc() and

	 * mem_cgroup_put() if kmem is enabled. We have to either call them

	 * unconditionally, or clear the KMEM_ACTIVE flag. I personally find

	 * this more consistent, since it always leads to the same destroy path

	 * __mem_cgroup_free() will issue static_key_slow_dec() because this

	 * memcg is active already. If the later initialization fails then the

	 * cgroup core triggers the cleanup so we do not have to do it here.

	 */

	mem_cgroup_get(memcg);

	static_key_slow_inc(&memcg_kmem_enabled_key);

	mutex_lock(&set_limit_mutex);

	return mem_cgroup_sockets_init(memcg, ss);

}

static void kmem_cgroup_destroy(struct mem_cgroup *memcg)

static void memcg_destroy_kmem(struct mem_cgroup *memcg)

{

	mem_cgroup_sockets_destroy(memcg);

}

static void kmem_cgroup_css_offline(struct mem_cgroup *memcg)

{

	if (!memcg_kmem_is_active(memcg))

		return;

	/*

	 * kmem charges can outlive the cgroup. In the case of slab

	 * pages, for instance, a page contain objects from various

	 * processes. As we prevent from taking a reference for every

	 * such allocation we have to be careful when doing uncharge

	 * (see memcg_uncharge_kmem) and here during offlining.

	 *

	 * The idea is that that only the _last_ uncharge which sees

	 * the dead memcg will drop the last reference. An additional

	 * reference is taken here before the group is marked dead

	 * which is then paired with css_put during uncharge resp. here.

	 *

	 * Although this might sound strange as this path is called from

	 * css_offline() when the referencemight have dropped down to 0

	 * and shouldn't be incremented anymore (css_tryget would fail)

	 * we do not have other options because of the kmem allocations

	 * lifetime.

	 */

	css_get(&memcg->css);

	memcg_kmem_mark_dead(memcg);

	if (res_counter_read_u64(&memcg->kmem, RES_USAGE) != 0)

		return;

	/*

	 * Charges already down to 0, undo mem_cgroup_get() done in the charge

	 * path here, being careful not to race with memcg_uncharge_kmem: it is

	 * possible that the charges went down to 0 between mark_dead and the

	 * res_counter read, so in that case, we don't need the put

	 */

	if (memcg_kmem_test_and_clear_dead(memcg))

		mem_cgroup_put(memcg);

		css_put(&memcg->css);

}

#else

static int memcg_init_kmem(struct mem_cgroup *memcg, struct cgroup_subsys *ss)

	return 0;

}

static void kmem_cgroup_destroy(struct mem_cgroup *memcg)

static void memcg_destroy_kmem(struct mem_cgroup *memcg)

{

}

static void kmem_cgroup_css_offline(struct mem_cgroup *memcg)

{

}

#endif

{

	struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);

	kmem_cgroup_css_offline(memcg);

	mem_cgroup_invalidate_reclaim_iterators(memcg);

	mem_cgroup_reparent_charges(memcg);

	mem_cgroup_destroy_all_caches(memcg);

{

	struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);

	kmem_cgroup_destroy(memcg);

	mem_cgroup_put(memcg);

	memcg_destroy_kmem(memcg);

	__mem_cgroup_free(memcg);

}

#ifdef CONFIG_MMU