From 1793bc1dd7393760a8e60ed6e0c819d349470fb8 Mon Sep 17 00:00:00 2001 From: Chris Down Date: Wed, 1 Apr 2020 21:07:24 -0700 Subject: [PATCH 2157/2944] mm, memcg: prevent memory.low load/store tearing task #31315199 commit f86b810c2610b08afc82218068d1dfeef02dd0a1 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/448206f44b0fa7be9dad2ca2601d2bcb2c0b7844.1584034301.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 | 8 +++++--- 2 files changed, 6 insertions(+), 4 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index dd294a9..68182d4 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -7267,7 +7267,7 @@ enum mem_cgroup_protection mem_cgroup_protected(struct mem_cgroup *root, return MEMCG_PROT_NONE; emin = memcg->memory.min; - elow = memcg->memory.low; + elow = READ_ONCE(memcg->memory.low); parent = parent_mem_cgroup(memcg); /* No parent means a non-hierarchical mode on v1 memcg */ diff --git a/mm/page_counter.c b/mm/page_counter.c index ee480e6..3a13668 100644 --- a/mm/page_counter.c +++ b/mm/page_counter.c @@ -17,6 +17,7 @@ static void propagate_protected_usage(struct page_counter *c, unsigned long usage) { unsigned long protected, old_protected; + unsigned long low; long delta; if (!c->parent) @@ -34,8 +35,9 @@ static void propagate_protected_usage(struct page_counter *c, atomic_long_add(delta, &c->parent->children_min_usage); } - if (c->low || atomic_long_read(&c->low_usage)) { - if (usage <= c->low) + low = READ_ONCE(c->low); + if (low || atomic_long_read(&c->low_usage)) { + if (usage <= low) protected = usage; else protected = 0; @@ -230,7 +232,7 @@ void page_counter_set_low(struct page_counter *counter, unsigned long nr_pages) { struct page_counter *c; - counter->low = nr_pages; + WRITE_ONCE(counter->low, nr_pages); for (c = counter; c; c = c->parent) propagate_protected_usage(c, atomic_long_read(&c->usage)); -- 1.8.3.1