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authorYue Zhao <findns94@gmail.com>2023-03-06 23:41:38 +0800
committerAndrew Morton <akpm@linux-foundation.org>2023-03-28 16:20:13 -0700
commit2178e20c24406548c97b18a2d9781d16c35b8881 (patch)
tree06ab854b92d1327b115ceca93d24d6e6aa4d5916 /mm/memcontrol.c
parent17c56de6a8c9970f56375c13f8654bbcbc94c090 (diff)
mm, memcg: Prevent memory.soft_limit_in_bytes load/store tearing
The knob for cgroup v1 memory controller: memory.soft_limit_in_bytes is not protected by any locking so it can be modified while it is used. This is not an actual problem because races are unlikely. But it is better to use [READ|WRITE]_ONCE to prevent compiler from doing anything funky. The access of memcg->soft_limit is lockless, so it can be concurrently set at the same time as we are trying to read it. All occurrences of memcg->soft_limit are updated with [READ|WRITE]_ONCE. [findns94@gmail.com: v3] Link: https://lkml.kernel.org/r/20230308162555.14195-5-findns94@gmail.com Link: https://lkml.kernel.org/r/20230306154138.3775-5-findns94@gmail.com Signed-off-by: Yue Zhao <findns94@gmail.com> Acked-by: Shakeel Butt <shakeelb@google.com> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Muchun Song <muchun.song@linux.dev> Cc: Tang Yizhou <tangyeechou@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/memcontrol.c')
-rw-r--r--mm/memcontrol.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 5b7062d0f5e0..13ec89c45389 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3728,7 +3728,7 @@ static u64 mem_cgroup_read_u64(struct cgroup_subsys_state *css,
case RES_FAILCNT:
return counter->failcnt;
case RES_SOFT_LIMIT:
- return (u64)memcg->soft_limit * PAGE_SIZE;
+ return (u64)READ_ONCE(memcg->soft_limit) * PAGE_SIZE;
default:
BUG();
}
@@ -3870,7 +3870,7 @@ static ssize_t mem_cgroup_write(struct kernfs_open_file *of,
if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
ret = -EOPNOTSUPP;
} else {
- memcg->soft_limit = nr_pages;
+ WRITE_ONCE(memcg->soft_limit, nr_pages);
ret = 0;
}
break;
@@ -5347,7 +5347,7 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
return ERR_CAST(memcg);
page_counter_set_high(&memcg->memory, PAGE_COUNTER_MAX);
- memcg->soft_limit = PAGE_COUNTER_MAX;
+ WRITE_ONCE(memcg->soft_limit, PAGE_COUNTER_MAX);
#if defined(CONFIG_MEMCG_KMEM) && defined(CONFIG_ZSWAP)
memcg->zswap_max = PAGE_COUNTER_MAX;
#endif
@@ -5502,7 +5502,7 @@ static void mem_cgroup_css_reset(struct cgroup_subsys_state *css)
page_counter_set_min(&memcg->memory, 0);
page_counter_set_low(&memcg->memory, 0);
page_counter_set_high(&memcg->memory, PAGE_COUNTER_MAX);
- memcg->soft_limit = PAGE_COUNTER_MAX;
+ WRITE_ONCE(memcg->soft_limit, PAGE_COUNTER_MAX);
page_counter_set_high(&memcg->swap, PAGE_COUNTER_MAX);
memcg_wb_domain_size_changed(memcg);
}