On Tue 04-12-12 16:36:17, Jeff Liu wrote:
> - Call swap_cgroup_init() when the first child memcg was created.
> - Free pages from swap cgroup once the latest child memcg was removed.
This should be a separate patch
> - Teach swap_cgroup_record()/swap_cgroup_cmpxchg()/swap_cgroup_lookup_id()
> to aware of the new static variable. i.e, swap_cgroup_initialized, so that
> they would not perform further jobs if swap cgroup is not active.
This should be a preparatory patch.
>
> Signed-off-by: Jie Liu <jeff.liu@xxxxxxxxxx>
> CC: Glauber Costa <glommer@xxxxxxxxxxxxx>
> CC: Michal Hocko <mhocko@xxxxxxx>
> CC: Kamezawa Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> CC: Johannes Weiner <hannes@xxxxxxxxxxx>
> CC: Mel Gorman <mgorman@xxxxxxx>
> CC: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> ---
> mm/memcontrol.c | 3 +++
> mm/page_cgroup.c | 9 +++++++++
> 2 files changed, 12 insertions(+)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index dd39ba0..1f14375 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -4982,6 +4982,8 @@ mem_cgroup_create(struct cgroup *cont)
> }
> hotcpu_notifier(memcg_cpu_hotplug_callback, 0);
> } else {
> + if (swap_cgroup_init())
> + goto free_out;
> parent = mem_cgroup_from_cont(cont->parent);
> memcg->use_hierarchy = parent->use_hierarchy;
> memcg->oom_kill_disable = parent->oom_kill_disable;
> @@ -5046,6 +5048,7 @@ static void mem_cgroup_destroy(struct cgroup *cont)
> struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
>
> kmem_cgroup_destroy(memcg);
> + swap_cgroup_destroy();
>
> mem_cgroup_put(memcg);
> }
> diff --git a/mm/page_cgroup.c b/mm/page_cgroup.c
> index f1b257b..63c6789 100644
> --- a/mm/page_cgroup.c
> +++ b/mm/page_cgroup.c
> @@ -429,6 +429,9 @@ unsigned short swap_cgroup_cmpxchg(swp_entry_t ent,
> unsigned long flags;
> unsigned short retval;
>
> + if (!atomic_read(&swap_cgroup_initialized))
> + return 0;
> +
> sc = lookup_swap_cgroup(ent, &ctrl);
>
> spin_lock_irqsave(&ctrl->lock, flags);
> @@ -456,6 +459,9 @@ unsigned short swap_cgroup_record(swp_entry_t ent, unsigned short id)
> unsigned short old;
> unsigned long flags;
>
> + if (!atomic_read(&swap_cgroup_initialized))
> + return 0;
> +
> sc = lookup_swap_cgroup(ent, &ctrl);
>
> spin_lock_irqsave(&ctrl->lock, flags);
> @@ -474,6 +480,9 @@ unsigned short swap_cgroup_record(swp_entry_t ent, unsigned short id)
> */
> unsigned short lookup_swap_cgroup_id(swp_entry_t ent)
> {
> + if (!atomic_read(&swap_cgroup_initialized))
> + return 0;
> +
> return lookup_swap_cgroup(ent, NULL)->id;
I think that the swap_cgroup_initialized test should be stuffed into
lookup_swap_cgroup because it would be less fragile.
--
Michal Hocko
SUSE Labs
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