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: David Rientjes <rientjes@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 4 deletions

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index d6183f06d8c1..7b4d9d79570b 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -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,
                                   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 *mem_cgroup_from_task(struct task_struct *p);
@@ -273,10 +274,10 @@ static inline bool mm_match_cgroup(struct mm_struct *mm,
         return true;
 }
 
-static inline int task_in_mem_cgroup(struct task_struct *task,
-                                     const struct mem_cgroup *memcg)
+static inline bool task_in_mem_cgroup(struct task_struct *task,
+                                      const struct mem_cgroup *memcg)
 {
-        return 1;
+        return true;
 }
 
 static inline struct cgroup_subsys_state