linux-kernel - [PATCH 5.9 174/255] mm: memcontrol: fix missing wakeup polling thread

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Date:   Tue, 17 Nov 2020 14:05:14 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Muchun Song <songmuchun@...edance.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Shakeel Butt <shakeelb@...gle.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Roman Gushchin <guro@...com>, Michal Hocko <mhocko@...e.com>,
        Yafang Shao <laoar.shao@...il.com>,
        Chris Down <chris@...isdown.name>, Tejun Heo <tj@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.9 174/255] mm: memcontrol: fix missing wakeup polling thread

From: Muchun Song <songmuchun@...edance.com>

[ Upstream commit 8b21ca0218d29cc6bb7028125c7e5a10dfb4730c ]

When we poll the swap.events, we can miss being woken 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@...edance.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Reviewed-by: Shakeel Butt <shakeelb@...gle.com>
Acked-by: Johannes Weiner <hannes@...xchg.org>
Cc: Roman Gushchin <guro@...com>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Yafang Shao <laoar.shao@...il.com>
Cc: Chris Down <chris@...isdown.name>
Cc: Tejun Heo <tj@...nel.org>
Link: https://lkml.kernel.org/r/20201105161936.98312-1-songmuchun@bytedance.com
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 include/linux/memcontrol.h | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index d0b036123c6ab..fa635207fe96d 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -897,12 +897,19 @@ static inline void count_memcg_event_mm(struct mm_struct *mm,
 static inline void memcg_memory_event(struct mem_cgroup *memcg,
 				      enum memcg_memory_event event)
 {
+	bool swap_event = event == MEMCG_SWAP_HIGH || event == MEMCG_SWAP_MAX ||
+			  event == MEMCG_SWAP_FAIL;
+
 	atomic_long_inc(&memcg->memory_events_local[event]);
-	cgroup_file_notify(&memcg->events_local_file);
+	if (!swap_event)
+		cgroup_file_notify(&memcg->events_local_file);
 
 	do {
 		atomic_long_inc(&memcg->memory_events[event]);
-		cgroup_file_notify(&memcg->events_file);
+		if (swap_event)
+			cgroup_file_notify(&memcg->swap_events_file);
+		else
+			cgroup_file_notify(&memcg->events_file);
 
 		if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
 			break;
-- 
2.27.0