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Commit 7e97de0b authored by Kirill Tkhai's avatar Kirill Tkhai Committed by Linus Torvalds
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memcg: remove memcg_cgroup::id from IDR on mem_cgroup_css_alloc() failure 

In case of memcg_online_kmem() failure, memcg_cgroup::id remains hashed
in mem_cgroup_idr even after memcg memory is freed.  This leads to leak
of ID in mem_cgroup_idr.

This patch adds removal into mem_cgroup_css_alloc(), which fixes the
problem.  For better readability, it adds a generic helper which is used
in mem_cgroup_alloc() and mem_cgroup_id_put_many() as well.

Link: http://lkml.kernel.org/r/152354470916.22460.14397070748001974638.stgit@localhost.localdomain


Fixes 73f576c0 ("mm: memcontrol: fix cgroup creation failure after many small jobs")
Signed-off-by: default avatarKirill Tkhai <ktkhai@virtuozzo.com>
Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Acked-by: default avatarVladimir Davydov <vdavydov.dev@gmail.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent e30cb13c

mm/memcontrol.c

+11 −4
Original line number Diff line number Diff line
@@ -4037,6 +4037,14 @@ static struct cftype mem_cgroup_legacy_files[] = { 


static DEFINE_IDR(mem_cgroup_idr);



static void mem_cgroup_id_remove(struct mem_cgroup *memcg)

{

	if (memcg->id.id > 0) {

		idr_remove(&mem_cgroup_idr, memcg->id.id);

		memcg->id.id = 0;

	}

}



static void mem_cgroup_id_get_many(struct mem_cgroup *memcg, unsigned int n)

{

	VM_BUG_ON(atomic_read(&memcg->id.ref) <= 0);
@@ -4047,8 +4055,7 @@ static void mem_cgroup_id_put_many(struct mem_cgroup *memcg, unsigned int n) 
{

	VM_BUG_ON(atomic_read(&memcg->id.ref) < n);

	if (atomic_sub_and_test(n, &memcg->id.ref)) {

		idr_remove(&mem_cgroup_idr, memcg->id.id);

		memcg->id.id = 0;

		mem_cgroup_id_remove(memcg);



		/* Memcg ID pins CSS */

		css_put(&memcg->css);
@@ -4185,8 +4192,7 @@ static struct mem_cgroup *mem_cgroup_alloc(void) 
	idr_replace(&mem_cgroup_idr, memcg, memcg->id.id);

	return memcg;

fail:

	if (memcg->id.id > 0)

		idr_remove(&mem_cgroup_idr, memcg->id.id);

	mem_cgroup_id_remove(memcg);

	__mem_cgroup_free(memcg);

	return NULL;

}
@@ -4245,6 +4251,7 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css) 


	return &memcg->css;

fail:

	mem_cgroup_id_remove(memcg);

	mem_cgroup_free(memcg);

	return ERR_PTR(-ENOMEM);

}