[patch -mm 7/5] oom: filter tasklist dump by mem_cgroup

[David Rientjes <rientjes@google.com>]

If an OOM was triggered as a result a cgroup's memory controller, the
tasklist shall be filtered to exclude tasks that are not a member of the
same group.

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

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

Cc: Christoph Lameter <clameter@sgi.com>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: David Rientjes <rientjes@google.com>
---
 include/linux/memcontrol.h |   16 ++++++++++++++++
 mm/oom_kill.c              |   25 ++++++++++++++-----------
 2 files changed, 30 insertions(+), 11 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -52,6 +52,16 @@ static inline void mem_cgroup_uncharge_page(struct page *page)
 	mem_cgroup_uncharge(page_get_page_cgroup(page));
 }
 
+/*
+ * Returns non-zero if the task is in the cgroup; otherwise returns zero.
+ * Call with task_lock(task) held.
+ */
+static inline int task_in_mem_cgroup(const struct task_struct *task,
+				     const struct mem_cgroup *mem)
+{
+	return mem && task->mm && mm_cgroup(task->mm) == mem;
+}
+
 #else /* CONFIG_CGROUP_MEM_CONT */
 static inline void mm_init_cgroup(struct mm_struct *mm,
 					struct task_struct *p)
@@ -103,6 +113,12 @@ static inline struct mem_cgroup *mm_cgroup(struct mm_struct *mm)
 	return NULL;
 }
 
+static inline int task_in_mem_cgroup(const struct task_struct *task,
+				     const struct mem_cgroup *mem)
+{
+	return 1;
+}
+
 #endif /* CONFIG_CGROUP_MEM_CONT */
 
 #endif /* _LINUX_MEMCONTROL_H */
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -65,13 +65,10 @@ unsigned long badness(struct task_struct *p, unsigned long uptime,
 		task_unlock(p);
 		return 0;
 	}
-
-#ifdef CONFIG_CGROUP_MEM_CONT
-	if (mem != NULL && mm->mem_cgroup != mem) {
+	if (!task_in_mem_cgroup(p, mem)) {
 		task_unlock(p);
 		return 0;
 	}
-#endif
 
 	/*
 	 * The memory size of the process is the basis for the badness.
@@ -274,9 +271,12 @@ static struct task_struct *select_bad_process(unsigned long *ppoints,
  * State information includes task's pid, uid, tgid, vm size, rss, cpu, oom_adj
  * score, and name.
  *
+ * If the actual is non-NULL, only tasks that are a member of the mem_cgroup are
+ * shown.
+ *
  * Call with tasklist_lock read-locked.
  */
-static void dump_tasks(void)
+static void dump_tasks(const struct mem_cgroup *mem)
 {
 	struct task_struct *g, *p;
 
@@ -291,6 +291,8 @@ static void dump_tasks(void)
 			continue;
 
 		task_lock(p);
+		if (!task_in_mem_cgroup(p, mem))
+			continue;
 		printk(KERN_INFO "[%5d] %5d %5d %8lu %8lu %3d     %3d %s\n",
 		       p->pid, p->uid, p->tgid, p->mm->total_vm,
 		       get_mm_rss(p->mm), (int)task_cpu(p), p->oomkilladj,
@@ -376,7 +378,8 @@ static int oom_kill_task(struct task_struct *p)
 }
 
 static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
-			    unsigned long points, const char *message)
+			    unsigned long points, struct mem_cgroup *mem,
+			    const char *message)
 {
 	struct task_struct *c;
 
@@ -387,7 +390,7 @@ static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
 		dump_stack();
 		show_mem();
 		if (sysctl_oom_dump_tasks)
-			dump_tasks();
+			dump_tasks(mem);
 	}
 
 	/*
@@ -428,7 +431,7 @@ retry:
 	if (!p)
 		p = current;
 
-	if (oom_kill_process(p, gfp_mask, 0, points,
+	if (oom_kill_process(p, gfp_mask, 0, points, mem,
 				"Memory cgroup out of memory"))
 		goto retry;
 out:
@@ -534,7 +537,7 @@ void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, int order)
 
 	switch (constraint) {
 	case CONSTRAINT_MEMORY_POLICY:
-		oom_kill_process(current, gfp_mask, order, points,
+		oom_kill_process(current, gfp_mask, order, points, NULL,
 				"No available memory (MPOL_BIND)");
 		break;
 
@@ -544,7 +547,7 @@ void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, int order)
 		/* Fall-through */
 	case CONSTRAINT_CPUSET:
 		if (sysctl_oom_kill_allocating_task) {
-			oom_kill_process(current, gfp_mask, order, points,
+			oom_kill_process(current, gfp_mask, order, points, NULL,
 					"Out of memory (oom_kill_allocating_task)");
 			break;
 		}
@@ -564,7 +567,7 @@ retry:
 			panic("Out of memory and no killable processes...\n");
 		}
 
-		if (oom_kill_process(p, points, gfp_mask, order,
+		if (oom_kill_process(p, points, gfp_mask, order, NULL,
 				     "Out of memory"))
 			goto retry;
 

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