memcg: fix a race when setting memory.swappiness
Subsystems (2)
PATCH 1/1 memcg: fix a race when setting memory.swappiness
(suppose: memcg->use_hierarchy == 0 and memcg->swappiness == 60)
echo 10 > /memcg/0/swappiness |
mem_cgroup_swappiness_write() |
... | echo 1 > /memcg/0/use_hierarchy
| mkdir /mnt/0/1
| sub_memcg->swappiness = 60;
memcg->swappiness = 10; |In the above scenario, we end up having 2 different swappiness values in a single hierarchy.
We should hold cgroup_lock() when cheking cgrp->children list.
Signed-off-by Li Zefan <[email protected]>
--- mm/memcontrol.c | 10 +++++++++- 1 files changed, 9 insertions(+), 1 deletions(-)
mm/memcontrol.c +9 -1
@@ -1992,6 +1992,7 @@ static int mem_cgroup_swappiness_write(struct cgroup *cgrp, struct cftype *cft, {struct mem_cgroup *memcg =mem_cgroup_from_cont (cgrp);struct mem_cgroup *parent; +if (val >100 )return -EINVAL ;
@@ -1999,15 +2000,22 @@ static int mem_cgroup_swappiness_write(struct cgroup *cgrp, struct cftype *cft,return -EINVAL ; parent =mem_cgroup_from_cont (cgrp->parent); + +cgroup_lock (); +/* If under hierarchy, only empty-root can set this value */ if ((parent->use_hierarchy) || - (memcg->use_hierarchy && !list_empty (&cgrp->children))) + (memcg->use_hierarchy && !list_empty (&cgrp->children))) { +cgroup_unlock ();return -EINVAL ; + }spin_lock (&memcg->reclaim_param_lock); memcg->swappiness = val;spin_unlock (&memcg->reclaim_param_lock); +cgroup_unlock (); +return 0 ; }
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