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Commit 10d5ebf4 authored by Li Zefan's avatar Li Zefan Committed by Linus Torvalds
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memcg: use css_get/put when charging/uncharging kmem 



Use css_get/put instead of mem_cgroup_get/put.

We can't do a simple replacement, because here mem_cgroup_put() is
called during mem_cgroup_css_free(), while mem_cgroup_css_free() won't
be called until css refcnt goes down to 0.

Instead we increment css refcnt in mem_cgroup_css_offline(), and then
check if there's still kmem charges.  If not, css refcnt will be
decremented immediately, otherwise the refcnt will be released after the
last kmem allocation is uncahred.

[akpm@linux-foundation.org: tweak comment]
Signed-off-by: default avatarLi Zefan <lizefan@huawei.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.cz>
Acked-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: default avatarTejun Heo <tj@kernel.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Glauber Costa <glommer@openvz.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 20f05310

mm/memcontrol.c

+54 −26
Original line number Diff line number Diff line
@@ -406,6 +406,11 @@ static void memcg_kmem_clear_activated(struct mem_cgroup *memcg) 


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);

}
@@ -3050,8 +3055,16 @@ static void memcg_uncharge_kmem(struct mem_cgroup *memcg, u64 size) 
	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)
@@ -5183,14 +5196,6 @@ static int memcg_update_kmem_limit(struct cgroup *cont, u64 val) 
		 * 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:
@@ -5223,12 +5228,10 @@ static int memcg_propagate_kmem(struct mem_cgroup *memcg) 
		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);
@@ -5913,23 +5916,43 @@ static int memcg_init_kmem(struct mem_cgroup *memcg, struct cgroup_subsys *ss) 
	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)
@@ -5937,7 +5960,11 @@ 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
@@ -6370,6 +6397,8 @@ static void mem_cgroup_css_offline(struct cgroup *cont) 
{

	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);
@@ -6379,9 +6408,8 @@ static void mem_cgroup_css_free(struct cgroup *cont) 
{

	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