From f6f989c5cebcc38b2d28c5b5f045d9a0a2082a9b Mon Sep 17 00:00:00 2001
From: Chris Down <chris@chrisdown.name>
Date: Wed, 1 Apr 2020 21:07:17 -0700
Subject: [PATCH] mm, memcg: prevent memory.high load/store tearing
A mem_cgroup's high attribute can be concurrently set at the same time as
we are trying to read it -- for example, if we are in memory_high_write at
the same time as we are trying to do high reclaim.
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/2f66f7038ed1d4688e59de72b627ae0ea52efa83.1584034301.git.chris@chrisdown.name
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
mm/memcontrol.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index badd043d58ac6b..b1bb62485622b0 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2242,7 +2242,7 @@ static void reclaim_high(struct mem_cgroup *memcg,
gfp_t gfp_mask)
{
do {
- if (page_counter_read(&memcg->memory) <= memcg->high)
+ if (page_counter_read(&memcg->memory) <= READ_ONCE(memcg->high))
continue;
memcg_memory_event(memcg, MEMCG_HIGH);
try_to_free_mem_cgroup_pages(memcg, nr_pages, gfp_mask, true);
@@ -2582,7 +2582,7 @@ done_restock:
* reclaim, the cost of mismatch is negligible.
*/
do {
- if (page_counter_read(&memcg->memory) > memcg->high) {
+ if (page_counter_read(&memcg->memory) > READ_ONCE(memcg->high)) {
/* Don't bother a random interrupted task */
if (in_interrupt()) {
schedule_work(&memcg->high_work);
@@ -4325,7 +4325,8 @@ void mem_cgroup_wb_stats(struct bdi_writeback *wb, unsigned long *pfilepages,
*pheadroom = PAGE_COUNTER_MAX;
while ((parent = parent_mem_cgroup(memcg))) {
- unsigned long ceiling = min(memcg->memory.max, memcg->high);
+ unsigned long ceiling = min(memcg->memory.max,
+ READ_ONCE(memcg->high));
unsigned long used = page_counter_read(&memcg->memory);
*pheadroom = min(*pheadroom, ceiling - min(ceiling, used));
@@ -5047,7 +5048,7 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
if (!memcg)
return ERR_PTR(error);
- memcg->high = PAGE_COUNTER_MAX;
+ WRITE_ONCE(memcg->high, PAGE_COUNTER_MAX);
memcg->soft_limit = PAGE_COUNTER_MAX;
if (parent) {
memcg->swappiness = mem_cgroup_swappiness(parent);
@@ -5200,7 +5201,7 @@ static void mem_cgroup_css_reset(struct cgroup_subsys_state *css)
page_counter_set_max(&memcg->tcpmem, PAGE_COUNTER_MAX);
page_counter_set_min(&memcg->memory, 0);
page_counter_set_low(&memcg->memory, 0);
- memcg->high = PAGE_COUNTER_MAX;
+ WRITE_ONCE(memcg->high, PAGE_COUNTER_MAX);
memcg->soft_limit = PAGE_COUNTER_MAX;
memcg_wb_domain_size_changed(memcg);
}
@@ -6016,7 +6017,7 @@ static ssize_t memory_high_write(struct kernfs_open_file *of,
if (err)
return err;
- memcg->high = high;
+ WRITE_ONCE(memcg->high, high);
for (;;) {
unsigned long nr_pages = page_counter_read(&memcg->memory);
--
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