Commit ffbdccf5 authored by David Rientjes's avatar David Rientjes Committed by Linus Torvalds
Browse files

mm, memcg: don't take task_lock in task_in_mem_cgroup 



For processes that have detached their mm's, task_in_mem_cgroup()
unnecessarily takes task_lock() when rcu_read_lock() is all that is
necessary to call mem_cgroup_from_task().

While we're here, switch task_in_mem_cgroup() to return bool.

Signed-off-by: default avatarDavid Rientjes <rientjes@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: default avatarMichal Hocko <mhocko@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 541c237c

include/linux/memcontrol.h

+5 −4
Original line number Original line Diff line number Diff line
@@ -77,7 +77,8 @@ extern void mem_cgroup_uncharge_cache_page(struct page *page); 




bool __mem_cgroup_same_or_subtree(const struct mem_cgroup *root_memcg,

bool __mem_cgroup_same_or_subtree(const struct mem_cgroup *root_memcg,

				  struct mem_cgroup *memcg);

				  struct mem_cgroup *memcg);

int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *memcg);

bool task_in_mem_cgroup(struct task_struct *task,

			const struct mem_cgroup *memcg);





extern struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page);

extern struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page);

extern struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p);

extern struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p);
@@ -273,10 +274,10 @@ static inline bool mm_match_cgroup(struct mm_struct *mm, 
	return true;

	return true;

}

}





static inline int task_in_mem_cgroup(struct task_struct *task,

static inline bool task_in_mem_cgroup(struct task_struct *task,

				      const struct mem_cgroup *memcg)

				      const struct mem_cgroup *memcg)

{

{

	return 1;

	return true;

}

}





static inline struct cgroup_subsys_state

static inline struct cgroup_subsys_state

mm/memcontrol.c

+6 −5
Original line number Original line Diff line number Diff line
@@ -1448,11 +1448,12 @@ static bool mem_cgroup_same_or_subtree(const struct mem_cgroup *root_memcg, 
	return ret;

	return ret;

}

}





int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *memcg)

bool task_in_mem_cgroup(struct task_struct *task,

			const struct mem_cgroup *memcg)

{

{

	int ret;

	struct mem_cgroup *curr = NULL;

	struct mem_cgroup *curr = NULL;

	struct task_struct *p;

	struct task_struct *p;

	bool ret;





	p = find_lock_task_mm(task);

	p = find_lock_task_mm(task);

	if (p) {

	if (p) {
@@ -1464,14 +1465,14 @@ int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *memcg) 
		 * killer still needs to detect if they have already been oom

		 * killer still needs to detect if they have already been oom

		 * killed to prevent needlessly killing additional tasks.

		 * killed to prevent needlessly killing additional tasks.

		 */

		 */

		task_lock(task);

		rcu_read_lock();

		curr = mem_cgroup_from_task(task);

		curr = mem_cgroup_from_task(task);

		if (curr)

		if (curr)

			css_get(&curr->css);

			css_get(&curr->css);

		task_unlock(task);

		rcu_read_unlock();

	}

	}

	if (!curr)

	if (!curr)

		return 0;

		return false;

	/*

	/*

	 * We should check use_hierarchy of "memcg" not "curr". Because checking

	 * We should check use_hierarchy of "memcg" not "curr". Because checking

	 * use_hierarchy of "curr" here make this function true if hierarchy is

	 * use_hierarchy of "curr" here make this function true if hierarchy is

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