The patch titled
Subject: memcg: cleanup racy sum avoidance code
has been added to the -mm tree. Its filename is
memcg-cleanup-racy-sum-avoidance-code.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/memcg-cleanup-racy-sum-avoidance-code.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/memcg-cleanup-racy-sum-avoidance-code.patch
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------------------------------------------------------
From: Shakeel Butt <shakeelb@xxxxxxxxxx>
Subject: memcg: cleanup racy sum avoidance code
We used to have per-cpu memcg and lruvec stats and the readers have to
traverse and sum the stats from each cpu. This summing was racy and may
expose transient negative values. So, an explicit check was added to
avoid such scenarios. Now these stats are moved to rstat infrastructure
and are no more per-cpu, so we can remove the fixup for transient negative
values.
Link: https://lkml.kernel.org/r/20210728012243.3369123-1-shakeelb@xxxxxxxxxx
Signed-off-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
Acked-by: Roman Gushchin <guro@xxxxxx>
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/memcontrol.h | 15 ++-------------
1 file changed, 2 insertions(+), 13 deletions(-)
--- a/include/linux/memcontrol.h~memcg-cleanup-racy-sum-avoidance-code
+++ a/include/linux/memcontrol.h
@@ -977,30 +977,19 @@ static inline void mod_memcg_state(struc
static inline unsigned long memcg_page_state(struct mem_cgroup *memcg, int idx)
{
- long x = READ_ONCE(memcg->vmstats.state[idx]);
-#ifdef CONFIG_SMP
- if (x < 0)
- x = 0;
-#endif
- return x;
+ return READ_ONCE(memcg->vmstats.state[idx]);
}
static inline unsigned long lruvec_page_state(struct lruvec *lruvec,
enum node_stat_item idx)
{
struct mem_cgroup_per_node *pn;
- long x;
if (mem_cgroup_disabled())
return node_page_state(lruvec_pgdat(lruvec), idx);
pn = container_of(lruvec, struct mem_cgroup_per_node, lruvec);
- x = READ_ONCE(pn->lruvec_stats.state[idx]);
-#ifdef CONFIG_SMP
- if (x < 0)
- x = 0;
-#endif
- return x;
+ return READ_ONCE(pn->lruvec_stats.state[idx]);
}
static inline unsigned long lruvec_page_state_local(struct lruvec *lruvec,
_
Patches currently in -mm which might be from shakeelb@xxxxxxxxxx are
slub-fix-unreclaimable-slab-stat-for-bulk-free.patch
writeback-memcg-simplify-cgroup_writeback_by_id.patch
memcg-switch-lruvec-stats-to-rstat.patch
memcg-infrastructure-to-flush-memcg-stats.patch
memcg-infrastructure-to-flush-memcg-stats-v5.patch
memcg-cleanup-racy-sum-avoidance-code.patch
