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    SubjectRe: [patch 5/8] memcg: remove unnecessary !mm check from try_get_mem_cgroup_from_mm()
    On Fri 07-02-14 12:04:22, Johannes Weiner wrote:
    > Users pass either a mm that has been established under task lock, or
    > use a verified current->mm, which means the task can't be exiting.
    >
    > Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>

    Acked-by: Michal Hocko <mhocko@suse.cz>

    > ---
    > mm/memcontrol.c | 7 -------
    > 1 file changed, 7 deletions(-)
    >
    > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
    > index e1d7f33227e4..689fffdee471 100644
    > --- a/mm/memcontrol.c
    > +++ b/mm/memcontrol.c
    > @@ -1075,13 +1075,6 @@ struct mem_cgroup *try_get_mem_cgroup_from_mm(struct mm_struct *mm)
    > {
    > struct mem_cgroup *memcg = NULL;
    >
    > - if (!mm)
    > - return NULL;
    > - /*
    > - * Because we have no locks, mm->owner's may be being moved to other
    > - * cgroup. We use css_tryget() here even if this looks
    > - * pessimistic (rather than adding locks here).
    > - */
    > rcu_read_lock();
    > do {
    > memcg = mem_cgroup_from_task(rcu_dereference(mm->owner));
    > --
    > 1.8.5.3
    >

    --
    Michal Hocko
    SUSE Labs


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