(2012/10/31 13:22), Tejun Heo wrote:
> From: Michal Hocko <mhocko@xxxxxxx>
>
> Now that pre_destroy callbacks are called from the context where neither
> any task can attach the group nor any children group can be added there
> is no other way to fail from mem_cgroup_pre_destroy.
> mem_cgroup_pre_destroy doesn't have to take a reference to memcg's css
> because all css' are marked dead already.
>
> tj: Remove now unused local variable @cgrp from
> mem_cgroup_reparent_charges().
>
> Signed-off-by: Michal Hocko <mhocko@xxxxxxx>
> Reviewed-by: Glauber Costa <glommer@xxxxxxxxxxxxx>
> Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
+1
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> ---
> mm/memcontrol.c | 19 ++++++-------------
> 1 file changed, 6 insertions(+), 13 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 1033b2b..47c4680 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -3740,14 +3740,11 @@ static void mem_cgroup_force_empty_list(struct mem_cgroup *memcg,
> *
> * Caller is responsible for holding css reference on the memcg.
> */
> -static int mem_cgroup_reparent_charges(struct mem_cgroup *memcg)
> +static void mem_cgroup_reparent_charges(struct mem_cgroup *memcg)
> {
> - struct cgroup *cgrp = memcg->css.cgroup;
> int node, zid;
>
> do {
> - if (cgroup_task_count(cgrp) || !list_empty(&cgrp->children))
> - return -EBUSY;
> /* This is for making all *used* pages to be on LRU. */
> lru_add_drain_all();
> drain_all_stock_sync(memcg);
> @@ -3773,8 +3770,6 @@ static int mem_cgroup_reparent_charges(struct mem_cgroup *memcg)
> * charge before adding to the LRU.
> */
> } while (res_counter_read_u64(&memcg->res, RES_USAGE) > 0);
> -
> - return 0;
> }
>
> /*
> @@ -3811,7 +3806,9 @@ static int mem_cgroup_force_empty(struct mem_cgroup *memcg)
>
> }
> lru_add_drain();
> - return mem_cgroup_reparent_charges(memcg);
> + mem_cgroup_reparent_charges(memcg);
> +
> + return 0;
> }
>
> static int mem_cgroup_force_empty_write(struct cgroup *cont, unsigned int event)
> @@ -5008,13 +5005,9 @@ free_out:
> static int mem_cgroup_pre_destroy(struct cgroup *cont)
> {
> struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
> - int ret;
>
> - css_get(&memcg->css);
> - ret = mem_cgroup_reparent_charges(memcg);
> - css_put(&memcg->css);
> -
> - return ret;
> + mem_cgroup_reparent_charges(memcg);
> + return 0;
> }
>
> static void mem_cgroup_destroy(struct cgroup *cont)
>
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