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From: Kirill Tkhai <ktkhai@virtuozzo.com>
To: akpm@linux-foundation.org, hannes@cmpxchg.org, mhocko@kernel.org,
	vdavydov.dev@gmail.com, cgroups@vger.kernel.org,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: [PATCH] memcg: Remove memcg_cgroup::id from IDR on mem_cgroup_css_alloc() failure
Date: Thu, 12 Apr 2018 17:52:04 +0300
Message-ID: <152354470916.22460.14397070748001974638.stgit@localhost.localdomain> (raw)

In case of memcg_online_kmem() fail, 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 removing into mem_cgroup_css_alloc(), which fixes
the problem. For better readability, it adds generic helper, which
will be used in mem_cgroup_alloc() and mem_cgroup_id_put_many() too.

Fixes 73f576c04b94 "mm: memcontrol: fix cgroup creation failure after many small jobs"
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
---
 mm/memcontrol.c |   15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 3e7942c301a8..448db08d97a0 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4263,6 +4263,14 @@ 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);
@@ -4273,8 +4281,7 @@ 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);
@@ -4411,8 +4418,7 @@ 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;
 }
@@ -4471,6 +4477,7 @@ 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);
 }

             reply index

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-12 14:52 Kirill Tkhai [this message]
2018-04-13  8:55 ` Michal Hocko
2018-04-13  9:35   ` Kirill Tkhai
2018-04-13 11:02     ` Michal Hocko
2018-04-13 11:06       ` Kirill Tkhai
2018-04-13 11:20         ` Michal Hocko
2018-04-13 11:29           ` Kirill Tkhai
2018-04-13 11:38             ` Michal Hocko
2018-04-13 11:49               ` Kirill Tkhai
2018-04-13 11:54                 ` Michal Hocko
2018-04-13 12:07                   ` Kirill Tkhai
2018-04-13 12:14                     ` Michal Hocko
2018-04-13 12:51                       ` Michal Hocko
2018-07-26 23:25                         ` Andrew Morton
2018-07-27 19:31                           ` Johannes Weiner
2018-07-29 19:26                             ` Vladimir Davydov
2018-07-30 15:31                               ` Johannes Weiner
2018-07-31 23:39                                 ` Andrew Morton
2018-08-01 15:55                                   ` Johannes Weiner
2018-08-01 16:22                                     ` Vladimir Davydov
2018-08-02  8:03                                       ` Kirill Tkhai
2018-08-02  8:13                                         ` [PATCH] memcg: Add comment to mem_cgroup_css_online() Kirill Tkhai
2018-08-01 16:16                                 ` [PATCH] memcg: Remove memcg_cgroup::id from IDR on mem_cgroup_css_alloc() failure Vladimir Davydov

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