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Date: Tue, 3 Jun 2014 15:22:55 +0200 From: Michal Hocko <mhocko@...e.cz> To: Johannes Weiner <hannes@...xchg.org> Cc: Andrew Morton <akpm@...ux-foundation.org>, Hugh Dickins <hughd@...gle.com>, Tejun Heo <tj@...nel.org>, Vladimir Davydov <vdavydov@...allels.com>, cgroups@...r.kernel.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org Subject: Re: [patch 05/10] mm: memcontrol: catch root bypass in move precharge On Thu 29-05-14 12:15:57, Johannes Weiner wrote: > When mem_cgroup_try_charge() returns -EINTR, it bypassed the charge to > the root memcg. But move precharging does not catch this and treats > this case as if no charge had happened, thus leaking a charge against > root. Because of an old optimization, the root memcg's res_counter is > not actually charged right now, but it's still an imbalance and > subsequent patches will charge the root memcg again. > > Catch those bypasses to the root memcg and properly cancel them before > giving up the move. > > Signed-off-by: Johannes Weiner <hannes@...xchg.org> Acked-by: Michal Hocko <mhocko@...e.cz> > --- > mm/memcontrol.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 8957d6c945b8..184e67cce4e4 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -6485,8 +6485,15 @@ one_by_one: > cond_resched(); > } > ret = mem_cgroup_try_charge(memcg, GFP_KERNEL, 1, false); > + /* > + * In case of failure, any residual charges against > + * mc.to will be dropped by mem_cgroup_clear_mc() > + * later on. However, cancel any charges that are > + * bypassed to root right away or they'll be lost. > + */ > + if (ret == -EINTR) > + __mem_cgroup_cancel_charge(root_mem_cgroup, 1); > if (ret) > - /* mem_cgroup_clear_mc() will do uncharge later */ > return ret; > mc.precharge++; > } > -- > 1.9.3 > -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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