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Commit ad4ba375 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

memcg: css_id() must be called under rcu_read_lock() 



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: default avatarLi 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: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Tested-by: default avatarLi Zefan <lizf@cn.fujitsu.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
parent 1ce7e4ff

mm/memcontrol.c

+16 −5
Original line number Diff line number Diff line
@@ -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);
@@ -4038,12 +4044,17 @@ 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)) {

	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;

}