From 8ef892f0023b2badf6b303e14ef531ef44b83b8c Mon Sep 17 00:00:00 2001 From: Chris Down Date: Wed, 1 Apr 2020 21:07:27 -0700 Subject: [PATCH 2158/2944] mm, memcg: prevent memory.min load/store tearing task #31315199 commit c3d532008661da197997fc6d8098190eef9344ad upstream This can be set concurrently with reads, which may cause the wrong value to be propagated. Signed-off-by: Chris Down Signed-off-by: Andrew Morton Acked-by: Michal Hocko Cc: Johannes Weiner Cc: Roman Gushchin Cc: Tejun Heo Link: http://lkml.kernel.org/r/e809b4e6b0c1626dac6945970de06409a180ee65.1584034301.git.chris@chrisdown.name Signed-off-by: Linus Torvalds Signed-off-by: zhongjiang-ali Reviewed-by: Xunlei Pang --- mm/memcontrol.c | 2 +- mm/page_counter.c | 9 +++++---- 2 files changed, 6 insertions(+), 5 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 68182d4..4e6bdb3 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -7266,7 +7266,7 @@ enum mem_cgroup_protection mem_cgroup_protected(struct mem_cgroup *root, if (!usage) return MEMCG_PROT_NONE; - emin = memcg->memory.min; + emin = READ_ONCE(memcg->memory.min); elow = READ_ONCE(memcg->memory.low); parent = parent_mem_cgroup(memcg); diff --git a/mm/page_counter.c b/mm/page_counter.c index 3a13668..04d2cab 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)) { - if (usage <= c->min) + min = READ_ONCE(c->min); + if (min || atomic_long_read(&c->min_usage)) { + if (usage <= min) protected = usage; else protected = 0; @@ -215,7 +216,7 @@ 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)); -- 1.8.3.1