Re: [Patch v2 2/3] mm/memcg: __mem_cgroup_remove_exceeded could handle a !on-tree mz properly

[Michal Hocko <mhocko@suse.com>]

On Sat 12-03-22 07:16:22, Wei Yang wrote:
> There is no tree operation if mz is not on-tree.

This doesn't explain problem you are trying to solve nor does it make
much sense to me TBH.

> Let's remove the extra check.

What would happen if the mz was already in the excess tree and the
excess has grown?

> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
> ---
>  mm/memcontrol.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index d70bf5cf04eb..344a7e891bc5 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -545,9 +545,11 @@ static void mem_cgroup_update_tree(struct mem_cgroup *memcg, int nid)
>  			unsigned long flags;
>  
>  			spin_lock_irqsave(&mctz->lock, flags);
> -			/* if on-tree, remove it */
> -			if (mz->on_tree)
> -				__mem_cgroup_remove_exceeded(mz, mctz);
> +			/*
> +			 * remove it first
> +			 * If not on-tree, no tree ops.
> +			 */
> +			__mem_cgroup_remove_exceeded(mz, mctz);
>  			/*
>  			 * Insert again. mz->usage_in_excess will be updated.
>  			 * If excess is 0, no tree ops.
> -- 
> 2.33.1

-- 
Michal Hocko
SUSE Labs