memcontrol: move oom task exclusion to tasklist scan

Creates a helper function to return non-zero if a task is a member of a
memory controller:

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

When the OOM killer is constrained by the memory controller, the exclusion
of tasks that are not a member of that controller was previously misplaced
and appeared in the badness scoring function.  It should be excluded
during the tasklist scan in select_bad_process() instead.

[akpm@linux-foundation.org: build fix]
Cc: Christoph Lameter <clameter@sgi.com>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 12 insertions, 7 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index f6cdbf755ed3..2fadd4896a14 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -170,6 +170,16 @@ static void __mem_cgroup_move_lists(struct page_cgroup *pc, bool active)
                 list_move(&pc->lru, &pc->mem_cgroup->inactive_list);
 }
 
+int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *mem)
+{
+        int ret;
+
+        task_lock(task);
+        ret = task->mm && mm_cgroup(task->mm) == mem;
+        task_unlock(task);
+        return ret;
+}
+
 /*
  * This routine assumes that the appropriate zone's lru lock is already held
  */
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 64751dc9d997..ef5084dbc793 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -65,13 +65,6 @@ unsigned long badness(struct task_struct *p, unsigned long uptime,
                 return 0;
         }
 
-#ifdef CONFIG_CGROUP_MEM_CONT
-        if (mem != NULL && mm->mem_cgroup != mem) {
-                task_unlock(p);
-                return 0;
-        }
-#endif
-
         /*
          * The memory size of the process is the basis for the badness.
          */
@@ -223,6 +216,8 @@ static struct task_struct *select_bad_process(unsigned long *ppoints,
                 /* skip the init task */
                 if (is_global_init(p))
                         continue;
+                if (mem && !task_in_mem_cgroup(p, mem))
+                        continue;
 
                 /*
                  * This task already has access to memory reserves and is