From: Michal Hocko <mhocko@kernel.org>
To: Chris Down <chris@chrisdown.name>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Johannes Weiner <hannes@cmpxchg.org>, Tejun Heo <tj@kernel.org>,
Roman Gushchin <guro@fb.com>,
linux-mm@kvack.org, cgroups@vger.kernel.org,
linux-kernel@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH 3/6] mm, memcg: Prevent memory.low load/store tearing
Date: Mon, 16 Mar 2020 15:57:40 +0100 [thread overview]
Message-ID: <20200316145740.GO11482@dhcp22.suse.cz> (raw)
In-Reply-To: <448206f44b0fa7be9dad2ca2601d2bcb2c0b7844.1584034301.git.chris@chrisdown.name>
On Thu 12-03-20 17:33:01, Chris Down wrote:
> This can be set concurrently with reads, which may cause the wrong value
> to be propagated.
>
> Signed-off-by: Chris Down <chris@chrisdown.name>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Roman Gushchin <guro@fb.com>
> Cc: Tejun Heo <tj@kernel.org>
> Cc: linux-mm@kvack.org
> Cc: cgroups@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Cc: kernel-team@fb.com
Acked-by: Michal Hocko <mhocko@suse.com>
> ---
> mm/memcontrol.c | 4 ++--
> mm/page_counter.c | 9 ++++++---
> 2 files changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index aca2964ea494..c85a304fa4a1 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -6262,7 +6262,7 @@ 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 */
> @@ -6291,7 +6291,7 @@ enum mem_cgroup_protection mem_cgroup_protected(struct mem_cgroup *root,
> if (elow && parent_elow) {
> unsigned long low_usage, siblings_low_usage;
>
> - low_usage = min(usage, memcg->memory.low);
> + low_usage = min(usage, READ_ONCE(memcg->memory.low));
> siblings_low_usage = atomic_long_read(
> &parent->memory.children_low_usage);
>
> diff --git a/mm/page_counter.c b/mm/page_counter.c
> index 50184929b61f..18b7f779f2e2 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 +35,10 @@ 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;
> @@ -231,7 +234,7 @@ 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));
> --
> 2.25.1
>
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2020-03-16 14:57 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-12 17:32 [PATCH 0/6] mm, memcg: cgroup v2 tunable load/store tearing fixes Chris Down
2020-03-12 17:32 ` [PATCH 1/6] mm, memcg: Prevent memory.high load/store tearing Chris Down
2020-03-16 14:54 ` Michal Hocko
2020-03-12 17:32 ` [PATCH 2/6] mm, memcg: Prevent memory.max load tearing Chris Down
2020-03-16 14:56 ` Michal Hocko
2020-03-12 17:33 ` [PATCH 3/6] mm, memcg: Prevent memory.low load/store tearing Chris Down
2020-03-16 14:57 ` Michal Hocko [this message]
2020-06-12 17:03 ` Michal Koutný
2020-06-12 17:13 ` Chris Down
2020-03-12 17:33 ` [PATCH 4/6] mm, memcg: Prevent memory.min " Chris Down
2020-03-16 14:58 ` Michal Hocko
2020-03-12 17:33 ` [PATCH 5/6] mm, memcg: Prevent memory.swap.max load tearing Chris Down
2020-03-16 14:58 ` Michal Hocko
2020-03-12 17:33 ` [PATCH 6/6] mm, memcg: Prevent mem_cgroup_protected store tearing Chris Down
2020-03-16 14:59 ` Michal Hocko
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