On Wed, 7 Mar 2012 19:14:49 -0800 (PST)
David Rientjes <rientjes@xxxxxxxxxx> wrote:
> This patch prevents tasks from being attached to a memcg if there is a
> hard limit of zero. Additionally, the hard limit may not be changed to
> zero if there are tasks attached.
>
> This is consistent with cpusets which do not allow tasks to be attached
> if there are no mems and prevents all mems from being removed if there
> are tasks attached.
>
> Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
I hope Documenation/cgroup/memory.txt should be updated and make this behavior as 'spec'.
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> ---
> mm/memcontrol.c | 13 +++++++++++--
> 1 file changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -3868,9 +3868,14 @@ static int mem_cgroup_write(struct cgroup *cont, struct cftype *cft,
> ret = res_counter_memparse_write_strategy(buffer, &val);
> if (ret)
> break;
> - if (type == _MEM)
> + if (type == _MEM) {
> + /* Don't allow zero limit with tasks attached */
> + if (!val && cgroup_task_count(cont)) {
> + ret = -ENOSPC;
> + break;
> + }
> ret = mem_cgroup_resize_limit(memcg, val);
> - else
> + } else
> ret = mem_cgroup_resize_memsw_limit(memcg, val);
> break;
> case RES_SOFT_LIMIT:
> @@ -5306,6 +5311,10 @@ static int mem_cgroup_can_attach(struct cgroup_subsys *ss,
> int ret = 0;
> struct mem_cgroup *memcg = mem_cgroup_from_cont(cgroup);
>
> + /* Don't allow tasks attached with a zero limit */
> + if (!res_counter_read_u64(&memcg->res, RES_LIMIT))
> + return -ENOSPC;
> +
> if (memcg->move_charge_at_immigrate) {
> struct mm_struct *mm;
> struct mem_cgroup *from = mem_cgroup_from_task(p);
>
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