On Tue 21-08-18 18:10:42, Mike Kravetz wrote:
[...]
> diff --git a/mm/rmap.c b/mm/rmap.c
> index eb477809a5c0..8cf853a4b093 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -1362,11 +1362,21 @@ static bool try_to_unmap_one(struct page *page,
> struct vm_area_struct *vma,
> }
>
> /*
> - * We have to assume the worse case ie pmd for invalidation. Note that
> - * the page can not be free in this function as call of try_to_unmap()
> - * must hold a reference on the page.
> + * For THP, we have to assume the worse case ie pmd for invalidation.
> + * For hugetlb, it could be much worse if we need to do pud
> + * invalidation in the case of pmd sharing.
> + *
> + * Note that the page can not be free in this function as call of
> + * try_to_unmap() must hold a reference on the page.
> */
> end = min(vma->vm_end, start + (PAGE_SIZE << compound_order(page)));
> + if (PageHuge(page)) {
> + /*
> + * If sharing is possible, start and end will be adjusted
> + * accordingly.
> + */
> + (void)huge_pmd_sharing_possible(vma, &start, &end);
> + }
> mmu_notifier_invalidate_range_start(vma->vm_mm, start, end);
I do not get this part. Why don't we simply unconditionally invalidate
the whole huge page range?
>
> while (page_vma_mapped_walk(&pvmw)) {
> @@ -1409,6 +1419,32 @@ static bool try_to_unmap_one(struct page *page, struct
> vm_area_struct *vma,
> subpage = page - page_to_pfn(page) + pte_pfn(*pvmw.pte);
> address = pvmw.address;
>
> + if (PageHuge(page)) {
> + if (huge_pmd_unshare(mm, &address, pvmw.pte)) {
huge_pmd_unshare is documented to require a pte lock. Where do we take
it?
--
Michal Hocko
SUSE Labs
