[PATCH] mm: memcontrol: fix missing wakeup polling thread

[Muchun Song]

When wen poll the memory.swap.events, we can miss being waked up when the
swap event occurs. Because we didn't notify.

Fixes: f3a53a3a1e5b ("mm, memcontrol: implement memory.swap.events")
Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
---
 include/linux/memcontrol.h | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 0f4dd7829fb2..2456cb737329 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -1071,15 +1071,29 @@ static inline void count_memcg_event_mm(struct mm_struct *mm,
 	rcu_read_unlock();
 }
 
+static inline bool is_swap_memory_event(enum memcg_memory_event event)
+{
+	return event == MEMCG_SWAP_HIGH || event == MEMCG_SWAP_MAX ||
+	       event == MEMCG_SWAP_FAIL;
+}
+
 static inline void memcg_memory_event(struct mem_cgroup *memcg,
 				      enum memcg_memory_event event)
 {
+	bool swap_event = is_swap_memory_event(event);
+	struct cgroup_file *cfile;
+
 	atomic_long_inc(&memcg->memory_events_local[event]);
-	cgroup_file_notify(&memcg->events_local_file);
+	if (swap_event) {
+		cfile = &memcg->swap_events_file;
+	} else {
+		cfile = &memcg->events_file;
+		cgroup_file_notify(&memcg->events_local_file);
+	}
 
 	do {
 		atomic_long_inc(&memcg->memory_events[event]);
-		cgroup_file_notify(&memcg->events_file);
+		cgroup_file_notify(cfile);
 
 		if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
 			break;
-- 
2.20.1