linux-kernel - [PATCH 2/6] memcg: root_cgroup cannot reach mem_cgroup_move

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1350480648-10905-3-git-send-email-mhocko@suse.cz>
Date:	Wed, 17 Oct 2012 15:30:44 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	linux-mm@...ck.org
Cc:	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
	Tejun Heo <tj@...nel.org>, Li Zefan <lizefan@...wei.com>,
	Johannes Weiner <hannes@...xchg.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Balbir Singh <bsingharora@...il.com>
Subject: [PATCH 2/6] memcg: root_cgroup cannot reach mem_cgroup_move_parent

The root cgroup cannot be destroyed so we never hit it idown the
mem_cgroup_pre_destroy path and mem_cgroup_force_empty_write shouldn't
even try to do anything if called for the root.

This means that mem_cgroup_move_parent doesn't have to bother with the
root cgroup and it can assume it can always move charges upwards.

Signed-off-by: Michal Hocko <mhocko@...e.cz>
---
 mm/memcontrol.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index f25e9c0..9ce24b7 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2709,9 +2709,7 @@ static int mem_cgroup_move_parent(struct page *page,
 	unsigned long uninitialized_var(flags);
 	int ret;
 
-	/* Is ROOT ? */
-	if (mem_cgroup_is_root(child))
-		return -EINVAL;
+	VM_BUG_ON(mem_cgroup_is_root(child));
 
 	ret = -EBUSY;
 	if (!get_page_unless_zero(page))
@@ -3817,6 +3815,8 @@ static int mem_cgroup_force_empty_write(struct cgroup *cont, unsigned int event)
 	struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
 	int ret;
 
+	if (mem_cgroup_is_root(memcg))
+		return -EINVAL;
 	css_get(&memcg->css);
 	ret = mem_cgroup_force_empty(memcg);
 	css_put(&memcg->css);
-- 
1.7.10.4

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/