Re: [PATCH v3 3/6] memcg: Simplify mem_cgroup_force_empty_list errorhandling

[Glauber Costa]

> 
> Changes since v1
> - use kerndoc
> - be more specific about mem_cgroup_move_parent possible failures
> 
> Signed-off-by: Michal Hocko <mhocko@xxxxxxx>
> Reviewed-by: Tejun Heo <tj@xxxxxxxxxx>
Reviewed-by: Glauber Costa <glommer@xxxxxxxxxxxxx>

> + * move charges to its parent or the root cgroup if the group has no
> + * parent (aka use_hierarchy==0).
> + * Although this might fail (get_page_unless_zero, isolate_lru_page or
> + * mem_cgroup_move_account fails) the failure is always temporary and
> + * it signals a race with a page removal/uncharge or migration. In the
> + * first case the page is on the way out and it will vanish from the LRU
> + * on the next attempt and the call should be retried later.
> + * Isolation from the LRU fails only if page has been isolated from
> + * the LRU since we looked at it and that usually means either global
> + * reclaim or migration going on. The page will either get back to the
> + * LRU or vanish.

I just wonder for how long can it go in the worst case?

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