Michal Hocko <mhocko@xxxxxxx> writes:
> On Fri 16-03-12 23:09:28, Aneesh Kumar K.V wrote:
>> From: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
>>
>> hugepage_activelist will be used to track currently used HugeTLB pages.
>> We need to find the in-use HugeTLB pages to support memcg removal.
>> On memcg removal we update the page's memory cgroup to point to
>> parent cgroup.
>>
>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
>> ---
>> include/linux/hugetlb.h | 1 +
>> mm/hugetlb.c | 23 ++++++++++++++++++-----
>> 2 files changed, 19 insertions(+), 5 deletions(-)
>>
>> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
>> index cbd8dc5..6919100 100644
>> --- a/include/linux/hugetlb.h
>> +++ b/include/linux/hugetlb.h
> [...]
>> @@ -2319,14 +2322,24 @@ void __unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
>> page = pte_page(pte);
>> if (pte_dirty(pte))
>> set_page_dirty(page);
>> - list_add(&page->lru, &page_list);
>> +
>> + spin_lock(&hugetlb_lock);
>> + list_move(&page->lru, &page_list);
>> + spin_unlock(&hugetlb_lock);
>
> Why do we really need the spinlock here?
It does a list_del from hugepage_activelist.
>
>> }
>> spin_unlock(&mm->page_table_lock);
>> flush_tlb_range(vma, start, end);
>> mmu_notifier_invalidate_range_end(mm, start, end);
>> list_for_each_entry_safe(page, tmp, &page_list, lru) {
>> page_remove_rmap(page);
>> - list_del(&page->lru);
>> + /*
>> + * We need to move it back huge page active list. If we are
>> + * holding the last reference, below put_page will move it
>> + * back to free list.
>> + */
>> + spin_lock(&hugetlb_lock);
>> + list_move(&page->lru, &h->hugepage_activelist);
>> + spin_unlock(&hugetlb_lock);
>
> This spinlock usage doesn't look nice but I guess we do not have many
> other options.
>
-aneesh
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