Messages in this thread Patch in this message | | | Date | Fri, 16 Jan 2009 13:22:53 +0900 | From | Daisuke Nishimura <> | Subject | Re: [BUGFIX][PATCH] memcg: get/put parents at create/free |
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This is a fix for memcg-get-put-parents-at-create-free.patch.
=== From: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Andrew suggested that it's strange to add a little helper function for get(), while put() is open-code.
This patch also adds a few comments.
Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> --- mm/memcontrol.c | 20 ++++++++++---------- 1 files changed, 10 insertions(+), 10 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 45e1b51..92790e4 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -203,7 +203,6 @@ 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, @@ -2195,6 +2194,9 @@ static void mem_cgroup_put(struct mem_cgroup *mem) } } +/* + * Returns the parent mem_cgroup in memcgroup hierarchy with hierarchy enabled. + */ static struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *mem) { if (!mem->res.parent) @@ -2202,14 +2204,6 @@ static struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *mem) 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) { @@ -2247,6 +2241,13 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont) if (parent && parent->use_hierarchy) { res_counter_init(&mem->res, &parent->res); res_counter_init(&mem->memsw, &parent->memsw); + /* + * We increment refcnt of the parent to ensure that we can + * safely access it on res_counter_charge/uncharge. + * This refcnt will be decremented when freeing this + * mem_cgroup(see mem_cgroup_put). + */ + mem_cgroup_get(parent); } else { res_counter_init(&mem->res, NULL); res_counter_init(&mem->memsw, NULL); @@ -2257,7 +2258,6 @@ 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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