Re: [PATCH] mm/memcg: return -EBUSY when oom-kill-disable modified and memcg use_hierarchy, has children

[Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

(2012/07/05 19:55), Wanpeng Li wrote:
> From: Wanpeng Li <liwp@linux.vnet.ibm.com>
> 
> When oom-kill-disable modified by the user and current memcg use_hierarchy,
> the change can occur, provided the current memcg has no children. If it
> has children, return -EBUSY is enough.
> 
> Signed-off-by: Wanpeng Li <liwp.linux@gmail.com>

I'm sorry what is the point ? You think -EBUSY should be returned in this case 
rather than -EINVAl ? Then, why ?


> ---
>   mm/memcontrol.c |    7 +++++--
>   1 files changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 63e36e7..4b64fe0 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -4521,11 +4521,14 @@ static int mem_cgroup_oom_control_write(struct cgroup *cgrp,
>   
>   	cgroup_lock();
>   	/* oom-kill-disable is a flag for subhierarchy. */
> -	if ((parent->use_hierarchy) ||
> -	    (memcg->use_hierarchy && !list_empty(&cgrp->children))) {
> +	if (parent->use_hierarchy) {
>   		cgroup_unlock();
>   		return -EINVAL;
> +	} else if (memcg->use_hierarchy && !list_empty(&cgrp->children)) {
> +		cgroup_unlock();
> +		return -EBUSY;
>   	}
> +
>   	memcg->oom_kill_disable = val;
>   	if (!val)
>   		memcg_oom_recover(memcg);
>