linux-kernel - [PATCH v3 6/8] memcg: fail to create cgroup if the cgroup id is too big

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Date:	Mon, 29 Jul 2013 15:09:08 +0800
From:	Li Zefan <lizefan@...wei.com>
To:	Tejun Heo <tj@...nel.org>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Glauber Costa <glommer@...allels.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Michal Hocko <mhocko@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Cgroups <cgroups@...r.kernel.org>, <linux-mm@...ck.org>
Subject: [PATCH v3 6/8] memcg: fail to create cgroup if the cgroup id is too
 big

memcg requires the cgroup id to be smaller than 65536.

This is a preparation to kill css id.

Signed-off-by: Li Zefan <lizefan@...wei.com>
Acked-by: Michal Hocko <mhocko@...e.cz>
---
 mm/memcontrol.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 62541f5..ad7d7c9 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -512,6 +512,12 @@ static inline bool mem_cgroup_is_root(struct mem_cgroup *memcg)
 	return (memcg == root_mem_cgroup);
 }
 
+/*
+ * We restrict the id in the range of [1, 65535], so it can fit into
+ * an unsigned short.
+ */
+#define MEM_CGROUP_ID_MAX	USHRT_MAX
+
 static inline unsigned short mem_cgroup_id(struct mem_cgroup *memcg)
 {
 	/*
@@ -6248,6 +6254,9 @@ mem_cgroup_css_alloc(struct cgroup *cont)
 	long error = -ENOMEM;
 	int node;
 
+	if (cont->id > MEM_CGROUP_ID_MAX)
+		return ERR_PTR(-ENOSPC);
+
 	memcg = mem_cgroup_alloc();
 	if (!memcg)
 		return ERR_PTR(error);
-- 
1.8.0.2

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