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SubjectRe: [PATCH v2 12/20] mm, hugetlb: remove vma_has_reserves()
Date
Joonsoo Kim <iamjoonsoo.kim@lge.com> writes:

> vma_has_reserves() can be substituted by using return value of
> vma_needs_reservation(). If chg returned by vma_needs_reservation()
> is 0, it means that vma has reserves. Otherwise, it means that vma don't
> have reserves and need a hugepage outside of reserve pool. This definition
> is perfectly same as vma_has_reserves(), so remove vma_has_reserves().
>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>

Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index e6c0c77..22ceb04 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -473,39 +473,6 @@ void reset_vma_resv_huge_pages(struct vm_area_struct *vma)
> vma->vm_private_data = (void *)0;
> }
>
> -/* Returns true if the VMA has associated reserve pages */
> -static int vma_has_reserves(struct vm_area_struct *vma, long chg)
> -{
> - if (vma->vm_flags & VM_NORESERVE) {
> - /*
> - * This address is already reserved by other process(chg == 0),
> - * so, we should decreament reserved count. Without
> - * decreamenting, reserve count is remained after releasing
> - * inode, because this allocated page will go into page cache
> - * and is regarded as coming from reserved pool in releasing
> - * step. Currently, we don't have any other solution to deal
> - * with this situation properly, so add work-around here.
> - */
> - if (vma->vm_flags & VM_MAYSHARE && chg == 0)
> - return 1;
> - else
> - return 0;
> - }
> -
> - /* Shared mappings always use reserves */
> - if (vma->vm_flags & VM_MAYSHARE)
> - return 1;
> -
> - /*
> - * Only the process that called mmap() has reserves for
> - * private mappings.
> - */
> - if (is_vma_resv_set(vma, HPAGE_RESV_OWNER))
> - return 1;
> -
> - return 0;
> -}
> -
> static void copy_gigantic_page(struct page *dst, struct page *src)
> {
> int i;
> @@ -580,8 +547,7 @@ static struct page *dequeue_huge_page_vma(struct hstate *h,
> * have no page reserves. This check ensures that reservations are
> * not "stolen". The child may still get SIGKILLed
> */
> - if (!vma_has_reserves(vma, chg) &&
> - h->free_huge_pages - h->resv_huge_pages == 0)
> + if (chg && h->free_huge_pages - h->resv_huge_pages == 0)
> return NULL;
>
> /* If reserves cannot be used, ensure enough pages are in the pool */
> @@ -600,7 +566,7 @@ retry_cpuset:
> if (page) {
> if (avoid_reserve)
> break;
> - if (!vma_has_reserves(vma, chg))
> + if (chg)
> break;
>
> SetPagePrivate(page);

Can you add a comment above both the place to explain why checking chg
is good enough ?

-aneesh



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