linux-kernel - [PATCH] mm, memcg: prevent missed memory.low load tears

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Date:   Fri, 12 Jun 2020 18:44:37 +0100
From:   Chris Down <chris@...isdown.name>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Michal Koutný <mkoutny@...e.com>
Subject: [PATCH] mm, memcg: prevent missed memory.low load tears

Looks like one of these got missed when massaging in f86b810c2610 ("mm,
memcg: prevent memory.low load/store tearing") with other linux-mm
changes.

Reported-by: Michal Koutný <mkoutny@...e.com>
Signed-off-by: Chris Down <chris@...isdown.name>
---
 mm/memcontrol.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 0b38b6ad547d..f7cc66a80348 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6416,7 +6416,7 @@ enum mem_cgroup_protection mem_cgroup_protected(struct mem_cgroup *root,
 
 	if (parent == root) {
 		memcg->memory.emin = READ_ONCE(memcg->memory.min);
-		memcg->memory.elow = memcg->memory.low;
+		memcg->memory.elow = READ_ONCE(memcg->memory.low);
 		goto out;
 	}
 
@@ -6428,7 +6428,8 @@ enum mem_cgroup_protection mem_cgroup_protected(struct mem_cgroup *root,
 			atomic_long_read(&parent->memory.children_min_usage)));
 
 	WRITE_ONCE(memcg->memory.elow, effective_protection(usage, parent_usage,
-			memcg->memory.low, READ_ONCE(parent->memory.elow),
+			READ_ONCE(memcg->memory.low),
+			READ_ONCE(parent->memory.elow),
 			atomic_long_read(&parent->memory.children_low_usage)));
 
 out:
-- 
2.27.0