On Mon 08-04-13 14:36:32, Li Zefan wrote:
> Now memcg has the same life cycle with its corresponding cgroup, and
> a cgroup is freed via RCU and then mem_cgroup_css_free() is called
> in a work function, so we can simply call __mem_cgroup_free() in
> mem_cgroup_css_free().
>
> This actually reverts 59927fb984de1703c67bc640c3e522d8b5276c73
> ("memcg: free mem_cgroup by RCU to fix oops").
>
> Cc: Hugh Dickins <hughd@xxxxxxxxxx>
> Signed-off-by: Li Zefan <lizefan@xxxxxxxxxx>
OK, makes sense after the previous changes.
Acked-by: Michal Hocko <mhocko@xxxxxxx>
> ---
> mm/memcontrol.c | 51 +++++----------------------------------------------
> 1 file changed, 5 insertions(+), 46 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index a6d44bc..5aa6e91 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -261,28 +261,10 @@ struct mem_cgroup {
> */
> struct res_counter res;
>
> - union {
> - /*
> - * the counter to account for mem+swap usage.
> - */
> - struct res_counter memsw;
> -
> - /*
> - * rcu_freeing is used only when freeing struct mem_cgroup,
> - * so put it into a union to avoid wasting more memory.
> - * It must be disjoint from the css field. It could be
> - * in a union with the res field, but res plays a much
> - * larger part in mem_cgroup life than memsw, and might
> - * be of interest, even at time of free, when debugging.
> - * So share rcu_head with the less interesting memsw.
> - */
> - struct rcu_head rcu_freeing;
> - /*
> - * We also need some space for a worker in deferred freeing.
> - * By the time we call it, rcu_freeing is no longer in use.
> - */
> - struct work_struct work_freeing;
> - };
> + /*
> + * the counter to account for mem+swap usage.
> + */
> + struct res_counter memsw;
>
> /*
> * the counter to account for kernel memory usage.
> @@ -6097,29 +6079,6 @@ static void __mem_cgroup_free(struct mem_cgroup *memcg)
> vfree(memcg);
> }
>
> -
> -/*
> - * Helpers for freeing a kmalloc()ed/vzalloc()ed mem_cgroup by RCU,
> - * but in process context. The work_freeing structure is overlaid
> - * on the rcu_freeing structure, which itself is overlaid on memsw.
> - */
> -static void free_work(struct work_struct *work)
> -{
> - struct mem_cgroup *memcg;
> -
> - memcg = container_of(work, struct mem_cgroup, work_freeing);
> - __mem_cgroup_free(memcg);
> -}
> -
> -static void free_rcu(struct rcu_head *rcu_head)
> -{
> - struct mem_cgroup *memcg;
> -
> - memcg = container_of(rcu_head, struct mem_cgroup, rcu_freeing);
> - INIT_WORK(&memcg->work_freeing, free_work);
> - schedule_work(&memcg->work_freeing);
> -}
> -
> /*
> * Returns the parent mem_cgroup in memcgroup hierarchy with hierarchy enabled.
> */
> @@ -6269,7 +6228,7 @@ static void mem_cgroup_css_free(struct cgroup *cont)
>
> mem_cgroup_sockets_destroy(memcg);
>
> - call_rcu(&memcg->rcu_freeing, free_rcu);
> + __mem_cgroup_free(memcg);
> }
>
> #ifdef CONFIG_MMU
> --
> 1.8.0.2
> --
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--
Michal Hocko
SUSE Labs
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