[PATCH] memcg: fix memcg_cache_name() to use cgroup_name()

Li Zefan
2013-03-21T01:22:21Z

As cgroup supports rename, it's unsafe to dereference dentry->d_name
without proper vfs locks. Fix this by using cgroup_name().

Signed-off-by: Li Zefan <lizefan@huawei.com>
---

This patch depends on "cgroup: fix cgroup_path() vs rename() race",
which has been queued for 3.10.

---
mm/memcontrol.c | 15 +++++++--------
1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 53b8201..72be5c9 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3217,17 +3217,16 @@ void mem_cgroup_destroy_cache(struct kmem_cache *cachep)
static char *memcg_cache_name(struct mem_cgroup *memcg, struct kmem_cache *s)
{
char *name;
- struct dentry *dentry;
+
+ name = (char *)__get_free_page(GFP_TEMPORARY);
+ if (!name)
+ return NULL;

rcu_read_lock();
- dentry = rcu_dereference(memcg->css.cgroup->dentry);
+ snprintf(name, PAGE_SIZE, "%s(%d:%s)", s->name, memcg_cache_id(memcg),
+ cgroup_name(memcg->css.cgroup));
rcu_read_unlock();

- BUG_ON(dentry == NULL);
-
- name = kasprintf(GFP_KERNEL, "%s(%d:%s)", s->name,
- memcg_cache_id(memcg), dentry->d_name.name);
-
return name;
}

@@ -3247,7 +3246,7 @@ static struct kmem_cache *kmem_cache_dup(struct mem_cgroup *memcg,
if (new)
new->allocflags |= __GFP_KMEMCG;

- kfree(name);
+ free_page((unsigned long)name);
return new;
}

--
1.8.0.2

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