diff options
| author | Li Zefan <lizf@cn.fujitsu.com> | 2009-01-15 13:51:26 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-01-15 16:39:41 -0800 |
| commit | 068b38c1fa7a9210608f27ac521897ccc5f9b726 (patch) | |
| tree | 6ae0ca440bab074c03a4cd4528e8c1467458753f /mm/memcontrol.c | |
| parent | 0eb253e223c88b982461e59154fcad1b82597592 (diff) | |
| download | lwn-068b38c1fa7a9210608f27ac521897ccc5f9b726.tar.gz lwn-068b38c1fa7a9210608f27ac521897ccc5f9b726.zip | |
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 <lizf@cn.fujitsu.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Paul Menage <menage@google.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/memcontrol.c')
| -rw-r--r-- | mm/memcontrol.c | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index f0dc076adf05..4d0ea3ceba6d 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -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; } |