From c3d532008661da197997fc6d8098190eef9344ad Mon Sep 17 00:00:00 2001
From: Chris Down <chris@chrisdown.name>
Date: Wed, 1 Apr 2020 21:07:27 -0700
Subject: [PATCH] mm, memcg: prevent memory.min load/store tearing
This can be set concurrently with reads, which may cause the wrong value
to be propagated.
Signed-off-by: Chris Down <chris@chrisdown.name>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Tejun Heo <tj@kernel.org>
Link: http://lkml.kernel.org/r/e809b4e6b0c1626dac6945970de06409a180ee65.1584034301.git.chris@chrisdown.name
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
mm/memcontrol.c | 5 +++--
mm/page_counter.c | 9 +++++----
2 files changed, 8 insertions(+), 6 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index f7af5aea005405..dc28afa149ef6b 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6389,7 +6389,7 @@ enum mem_cgroup_protection mem_cgroup_protected(struct mem_cgroup *root,
return MEMCG_PROT_NONE;
if (parent == root) {
- memcg->memory.emin = memcg->memory.min;
+ memcg->memory.emin = READ_ONCE(memcg->memory.min);
memcg->memory.elow = memcg->memory.low;
goto out;
}
@@ -6397,7 +6397,8 @@ enum mem_cgroup_protection mem_cgroup_protected(struct mem_cgroup *root,
parent_usage = page_counter_read(&parent->memory);
memcg->memory.emin = effective_protection(usage, parent_usage,
- memcg->memory.min, READ_ONCE(parent->memory.emin),
+ READ_ONCE(memcg->memory.min),
+ READ_ONCE(parent->memory.emin),
atomic_long_read(&parent->memory.children_min_usage));
memcg->memory.elow = effective_protection(usage, parent_usage,
diff --git a/mm/page_counter.c b/mm/page_counter.c
index 509143f232d803..c56db2d5e15924 100644
--- a/mm/page_counter.c
+++ b/mm/page_counter.c
@@ -17,14 +17,15 @@ static void propagate_protected_usage(struct page_counter *c,
unsigned long usage)
{
unsigned long protected, old_protected;
- unsigned long low;
+ unsigned long low, min;
long delta;
if (!c->parent)
return;
- if (c->min || atomic_long_read(&c->min_usage)) {
- protected = min(usage, c->min);
+ min = READ_ONCE(c->min);
+ if (min || atomic_long_read(&c->min_usage)) {
+ protected = min(usage, min);
old_protected = atomic_long_xchg(&c->min_usage, protected);
delta = protected - old_protected;
if (delta)
@@ -207,7 +208,7 @@ void page_counter_set_min(struct page_counter *counter, unsigned long nr_pages)
{
struct page_counter *c;
- counter->min = nr_pages;
+ WRITE_ONCE(counter->min, nr_pages);
for (c = counter; c; c = c->parent)
propagate_protected_usage(c, atomic_long_read(&c->usage));
--
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