Messages in this thread Patch in this message | | | Date | Fri, 16 Jan 2009 10:50:09 +0900 | From | Daisuke Nishimura <> | Subject | [BUGFIX][PATCH] memcg: get/put parents at create/free |
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This version works well in my test.
Andrew, please pick up this one.
=== From: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
The lifetime of struct cgroup and struct mem_cgroup is different and mem_cgroup has its own reference count for handling references from swap_cgroup.
This causes strange problem that the parent mem_cgroup dies while child mem_cgroup alive, and this problem causes a bug in case of use_hierarchy==1 because res_counter_uncharge climbs up the tree.
This patch is for avoiding it by getting the parent at create, and putting it at freeing.
Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Reviewed-by; KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> --- mm/memcontrol.c | 23 ++++++++++++++++++++++- 1 files changed, 22 insertions(+), 1 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index fb62b43..45e1b51 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -202,6 +202,8 @@ pcg_default_flags[NR_CHARGE_TYPE] = { static void mem_cgroup_get(struct mem_cgroup *mem); static void mem_cgroup_put(struct mem_cgroup *mem); +static struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *mem); +static void mem_cgroup_get_parent(struct mem_cgroup *mem); static void mem_cgroup_charge_statistics(struct mem_cgroup *mem, struct page_cgroup *pc, @@ -2185,10 +2187,28 @@ static void mem_cgroup_get(struct mem_cgroup *mem) static void mem_cgroup_put(struct mem_cgroup *mem) { - if (atomic_dec_and_test(&mem->refcnt)) + if (atomic_dec_and_test(&mem->refcnt)) { + struct mem_cgroup *parent = parent_mem_cgroup(mem); __mem_cgroup_free(mem); + if (parent) + mem_cgroup_put(parent); + } +} + +static struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *mem) +{ + if (!mem->res.parent) + return NULL; + return mem_cgroup_from_res_counter(mem->res.parent, res); } +static void mem_cgroup_get_parent(struct mem_cgroup *mem) +{ + struct mem_cgroup *parent = parent_mem_cgroup(mem); + + if (parent) + mem_cgroup_get(parent); +} #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP static void __init enable_swap_cgroup(void) @@ -2237,6 +2257,7 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont) if (parent) mem->swappiness = get_swappiness(parent); atomic_set(&mem->refcnt, 1); + mem_cgroup_get_parent(mem); return &mem->css; free_out: __mem_cgroup_free(mem);
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