The patch titled
Subject: mm, memcg: prevent memory.max load tearing
has been added to the -mm tree. Its filename is
mm-memcg-prevent-memorymax-load-tearing.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-memcg-prevent-memorymax-load-tearing.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-memcg-prevent-memorymax-load-tearing.patch
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------------------------------------------------------
From: Chris Down <chris@xxxxxxxxxxxxxx>
Subject: mm, memcg: prevent memory.max load tearing
This one is a bit more nuanced because we have memcg_max_mutex, which is
mostly just used for enforcing invariants, but we still need to READ_ONCE
since (despite its name) it doesn't really protect memory.max access.
On write (page_counter_set_max() and memory_max_write()) we use xchg(),
which uses smp_mb(), so that's already fine.
Link: http://lkml.kernel.org/r/50a31e5f39f8ae6c8fb73966ba1455f0924e8f44.1584034301.git.chris@xxxxxxxxxxxxxx
Signed-off-by: Chris Down <chris@xxxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Roman Gushchin <guro@xxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memcontrol.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
--- a/mm/memcontrol.c~mm-memcg-prevent-memorymax-load-tearing
+++ a/mm/memcontrol.c
@@ -1521,7 +1521,7 @@ void mem_cgroup_print_oom_meminfo(struct
pr_info("memory: usage %llukB, limit %llukB, failcnt %lu\n",
K((u64)page_counter_read(&memcg->memory)),
- K((u64)memcg->memory.max), memcg->memory.failcnt);
+ K((u64)READ_ONCE(memcg->memory.max)), memcg->memory.failcnt);
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)),
@@ -1552,7 +1552,7 @@ unsigned long mem_cgroup_get_max(struct
{
unsigned long max;
- max = memcg->memory.max;
+ max = READ_ONCE(memcg->memory.max);
if (mem_cgroup_swappiness(memcg)) {
unsigned long memsw_max;
unsigned long swap_max;
@@ -3068,7 +3068,7 @@ static int mem_cgroup_resize_max(struct
* Make sure that the new limit (memsw or memory limit) doesn't
* break our basic invariant rule memory.max <= memsw.max.
*/
- limits_invariant = memsw ? max >= memcg->memory.max :
+ limits_invariant = memsw ? max >= READ_ONCE(memcg->memory.max) :
max <= memcg->memsw.max;
if (!limits_invariant) {
mutex_unlock(&memcg_max_mutex);
@@ -3816,8 +3816,8 @@ static int memcg_stat_show(struct seq_fi
/* Hierarchical information */
memory = memsw = PAGE_COUNTER_MAX;
for (mi = memcg; mi; mi = parent_mem_cgroup(mi)) {
- memory = min(memory, mi->memory.max);
- memsw = min(memsw, mi->memsw.max);
+ memory = min(memory, READ_ONCE(mi->memory.max));
+ memsw = min(memsw, READ_ONCE(mi->memsw.max));
}
seq_printf(m, "hierarchical_memory_limit %llu\n",
(u64)memory * PAGE_SIZE);
@@ -4326,7 +4326,7 @@ void mem_cgroup_wb_stats(struct bdi_writ
*pheadroom = PAGE_COUNTER_MAX;
while ((parent = parent_mem_cgroup(memcg))) {
- unsigned long ceiling = min(memcg->memory.max,
+ unsigned long ceiling = min(READ_ONCE(memcg->memory.max),
READ_ONCE(memcg->high));
unsigned long used = page_counter_read(&memcg->memory);
_
Patches currently in -mm which might be from chris@xxxxxxxxxxxxxx are
mm-memcg-fix-corruption-on-64-bit-divisor-in-memoryhigh-throttling.patch
mm-memcg-throttle-allocators-based-on-ancestral-memoryhigh.patch
mm-memcg-prevent-memoryhigh-load-store-tearing.patch
mm-memcg-prevent-memorymax-load-tearing.patch
mm-memcg-prevent-memorylow-load-store-tearing.patch
mm-memcg-prevent-memorymin-load-store-tearing.patch
mm-memcg-prevent-memoryswapmax-load-tearing.patch
mm-memcg-prevent-mem_cgroup_protected-store-tearing.patch
