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Subject[PATCH tip/core/urgent 08/10] memcg: css_id() must be called under rcu_read_lock()
Date
This patch fixes task_in_mem_cgroup(), mem_cgroup_uncharge_swapcache(),
mem_cgroup_move_swap_account(), and is_target_pte_for_mc() to protect
calls to css_id(). An additional RCU lockdep splat was reported for
memcg_oom_wake_function(), however, this function is not yet in
mainline as of 2.6.34-rc5.

Reported-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Tested-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
---
mm/memcontrol.c | 21 ++++++++++++++++-----
1 files changed, 16 insertions(+), 5 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index f4ede99..e06490d 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -811,10 +811,12 @@ int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *mem)
* enabled in "curr" and "curr" is a child of "mem" in *cgroup*
* hierarchy(even if use_hierarchy is disabled in "mem").
*/
+ rcu_read_lock();
if (mem->use_hierarchy)
ret = css_is_ancestor(&curr->css, &mem->css);
else
ret = (curr == mem);
+ rcu_read_unlock();
css_put(&curr->css);
return ret;
}
@@ -2312,7 +2314,9 @@ mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent, bool swapout)

/* record memcg information */
if (do_swap_account && swapout && memcg) {
+ rcu_read_lock();
swap_cgroup_record(ent, css_id(&memcg->css));
+ rcu_read_unlock();
mem_cgroup_get(memcg);
}
if (swapout && memcg)
@@ -2369,8 +2373,10 @@ static int mem_cgroup_move_swap_account(swp_entry_t entry,
{
unsigned short old_id, new_id;

+ rcu_read_lock();
old_id = css_id(&from->css);
new_id = css_id(&to->css);
+ rcu_read_unlock();

if (swap_cgroup_cmpxchg(entry, old_id, new_id) == old_id) {
mem_cgroup_swap_statistics(from, false);
@@ -4038,11 +4044,16 @@ static int is_target_pte_for_mc(struct vm_area_struct *vma,
put_page(page);
}
/* throught */
- if (ent.val && do_swap_account && !ret &&
- css_id(&mc.from->css) == lookup_swap_cgroup(ent)) {
- ret = MC_TARGET_SWAP;
- if (target)
- target->ent = ent;
+ if (ent.val && do_swap_account && !ret) {
+ unsigned short id;
+ rcu_read_lock();
+ id = css_id(&mc.from->css);
+ rcu_read_unlock();
+ if (id == lookup_swap_cgroup(ent)) {
+ ret = MC_TARGET_SWAP;
+ if (target)
+ target->ent = ent;
+ }
}
return ret;
}
--
1.7.0


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