[078/155] mm, memcg: prevent memory.swap.max load tearing

Commit Message

Andrew Morton April 2, 2020, 4:07 a.m. UTC

From: Chris Down <[e-mail]>
Subject: mm, memcg: prevent memory.swap.max load tearing

The write side of this is xchg()/smp_mb(), so that's all good.  Just a few
sites missing a READ_ONCE.

Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Chris Down <[e-mail]>
Acked-by: Michal Hocko <[e-mail]>
Cc: Johannes Weiner <[e-mail]>
Cc: Roman Gushchin <[e-mail]>
Cc: Tejun Heo <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/memcontrol.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

Patch

--- a/mm/memcontrol.c~mm-memcg-prevent-memoryswapmax-load-tearing
+++ a/mm/memcontrol.c
@@ -1525,7 +1525,7 @@  void mem_cgroup_print_oom_meminfo(struct
 	if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
 		pr_info("swap: usage %llukB, limit %llukB, failcnt %lu\n",
 			K((u64)page_counter_read(&memcg->swap)),
-			K((u64)memcg->swap.max), memcg->swap.failcnt);
+			K((u64)READ_ONCE(memcg->swap.max)), memcg->swap.failcnt);
 	else {
 		pr_info("memory+swap: usage %llukB, limit %llukB, failcnt %lu\n",
 			K((u64)page_counter_read(&memcg->memsw)),
@@ -1558,7 +1558,7 @@  unsigned long mem_cgroup_get_max(struct
 		unsigned long swap_max;
 
 		memsw_max = memcg->memsw.max;
-		swap_max = memcg->swap.max;
+		swap_max = READ_ONCE(memcg->swap.max);
 		swap_max = min(swap_max, (unsigned long)total_swap_pages);
 		max = min(max + swap_max, memsw_max);
 	}
@@ -7117,7 +7117,8 @@  bool mem_cgroup_swap_full(struct page *p
 		return false;
 
 	for (; memcg != root_mem_cgroup; memcg = parent_mem_cgroup(memcg))
-		if (page_counter_read(&memcg->swap) * 2 >= memcg->swap.max)
+		if (page_counter_read(&memcg->swap) * 2 >=
+		    READ_ONCE(memcg->swap.max))
 			return true;
 
 	return false;