Messages in this thread | | | Date | Fri, 16 Jan 2009 11:17:02 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [BUGFIX][PATCH] memcg: get/put parents at create/free |
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On Thu, 15 Jan 2009 18:12:43 -0800 Andrew Morton <akpm@linux-foundation.org> wrote:
> 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()? > Maybe I don't feel this as strange because I saw update history of this patch ;( As you pointed out, I like open-code rather than helper here. Nishimura-san, could you update ?
Thanks, -Kame
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