Messages in this thread | | | Date | Fri, 4 Dec 2015 11:01:28 -0500 | From | Johannes Weiner <> | Subject | Re: memcg uncharge page counter mismatch |
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On Thu, Dec 03, 2015 at 04:47:29PM +0100, Michal Hocko wrote: > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 79a29d564bff..143c933f0b81 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -4895,6 +4895,14 @@ static int mem_cgroup_move_charge_pte_range(pmd_t *pmd, > switch (get_mctgt_type(vma, addr, ptent, &target)) { > case MC_TARGET_PAGE: > page = target.page; > + /* > + * We can have a part of the split pmd here. Moving it > + * can be done but it would be too convoluted so simply > + * ignore such a partial THP and keep it in original > + * memcg. There should be somebody mapping the head. > + */ > + if (PageCompound(page)) > + goto put; > if (isolate_lru_page(page)) > goto put; > if (!mem_cgroup_move_account(page, false,
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
The charge moving concept is fundamentally flawed and its implementation here is incomplete and races with reclaim.
Really, nobody should be using this. Absent any actual regression reports, a minimal fix to stop this code from generating warnings should be enough.
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