[PATCH v4] Print the memcg's name when system-wide OOM happened

[ufo19890607 <ufo19890607@gmail.com>]

From: yuzhoujian <yuzhoujian@didichuxing.com>

The dump_header does not print the memcg's name when the system
oom happened. So users cannot locate the certain container which
contains the task that has been killed by the oom killer.

System oom report will print the memcg's name after this patch,
so users can get the memcg's path from the oom report and check
the certain container more quickly.

Changes since v3:
- rename the helper's name to mem_cgroup_print_oom_memcg_name.
- add the rcu lock held to the helper.
- remove the print info of memcg's name in mem_cgroup_print_oom_info.

Changes since v2:
- add the mem_cgroup_print_memcg_name helper to print the memcg's
  name which contains the task that will be killed by the oom-killer.

Changes since v1:
- replace adding mem_cgroup_print_oom_info with printing the memcg's
  name only.

Signed-off-by: yuzhoujian <yuzhoujian@didichuxing.com>
---
 include/linux/memcontrol.h |  9 +++++++++
 mm/memcontrol.c            | 27 +++++++++++++++++++--------
 mm/oom_kill.c              |  1 +
 3 files changed, 29 insertions(+), 8 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index d99b71bc2c66..5fc58beae368 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -464,6 +464,9 @@ void mem_cgroup_handle_over_high(void);
 
 unsigned long mem_cgroup_get_limit(struct mem_cgroup *memcg);
 
+void mem_cgroup_print_oom_memcg_name(struct mem_cgroup *memcg,
+				struct task_struct *p);
+
 void mem_cgroup_print_oom_info(struct mem_cgroup *memcg,
 				struct task_struct *p);
 
@@ -858,6 +861,12 @@ static inline unsigned long mem_cgroup_get_limit(struct mem_cgroup *memcg)
 	return 0;
 }
 
+static inline void
+mem_cgroup_print_oom_memcg_name(struct mem_cgroup *memcg,
+					struct task_struct *p)
+{
+}
+
 static inline void
 mem_cgroup_print_oom_info(struct mem_cgroup *memcg, struct task_struct *p)
 {
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 2bd3df3d101a..138a11edfacb 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1118,19 +1118,15 @@ static const char *const memcg1_stat_names[] = {
 };
 
 #define K(x) ((x) << (PAGE_SHIFT-10))
+
 /**
- * mem_cgroup_print_oom_info: Print OOM information relevant to memory controller.
+ * mem_cgroup_print_oom_memcg_name: Print the memcg's name which contains the
+ * task that will be killed by the oom-killer.
  * @memcg: The memory cgroup that went over limit
  * @p: Task that is going to be killed
- *
- * NOTE: @memcg and @p's mem_cgroup can be different when hierarchy is
- * enabled
  */
-void mem_cgroup_print_oom_info(struct mem_cgroup *memcg, struct task_struct *p)
+void mem_cgroup_print_oom_memcg_name(struct mem_cgroup *memcg, struct task_struct *p)
 {
-	struct mem_cgroup *iter;
-	unsigned int i;
-
 	rcu_read_lock();
 
 	if (p) {
@@ -1145,7 +1141,22 @@ void mem_cgroup_print_oom_info(struct mem_cgroup *memcg, struct task_struct *p)
 	pr_cont("\n");
 
 	rcu_read_unlock();
+}
+
+/**
+ * mem_cgroup_print_oom_info: Print OOM information relevant to memory controller.
+ * @memcg: The memory cgroup that went over limit
+ * @p: Task that is going to be killed
+ *
+ * NOTE: @memcg and @p's mem_cgroup can be different when hierarchy is
+ * enabled
+ */
+void mem_cgroup_print_oom_info(struct mem_cgroup *memcg, struct task_struct *p)
+{
+	struct mem_cgroup *iter;
+	unsigned int i;
 
+	mem_cgroup_print_oom_memcg_name(memcg, p);
 	pr_info("memory: usage %llukB, limit %llukB, failcnt %lu\n",
 		K((u64)page_counter_read(&memcg->memory)),
 		K((u64)memcg->memory.limit), memcg->memory.failcnt);
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 8ba6cb88cf58..3e0b725fb877 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -433,6 +433,7 @@ static void dump_header(struct oom_control *oc, struct task_struct *p)
 	if (is_memcg_oom(oc))
 		mem_cgroup_print_oom_info(oc->memcg, p);
 	else {
+		mem_cgroup_print_oom_memcg_name(oc->memcg, p);
 		show_mem(SHOW_MEM_FILTER_NODES, oc->nodemask);
 		if (is_dump_unreclaim_slabs())
 			dump_unreclaimable_slab();
-- 
2.14.1