Messages in this thread | | | Date | Thu, 15 Jan 2009 18:12:43 -0800 | From | Andrew Morton <> | Subject | Re: [BUGFIX][PATCH] memcg: get/put parents at create/free |
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On Fri, 16 Jan 2009 10:50:09 +0900 Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:
> 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);
It seems strange that we add a little helper function for the get(), but open-code the put()?
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