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SubjectRe: [PATCH v2 16/20] mm, hugetlb: move down outside_reserve check
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Joonsoo Kim <iamjoonsoo.kim@lge.com> writes:

> Just move down outside_reserve check and don't check
> vma_need_reservation() when outside_resever is true. It is slightly
> optimized implementation.
>
> This makes code more readable.
>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>

I guess this address the comment I had with the previous patch

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

>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 24de2ca..2372f75 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -2499,7 +2499,7 @@ static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
> struct page *old_page, *new_page;
> int outside_reserve = 0;
> long chg;
> - bool use_reserve;
> + bool use_reserve = false;
> unsigned long mmun_start; /* For mmu_notifiers */
> unsigned long mmun_end; /* For mmu_notifiers */
>
> @@ -2514,6 +2514,11 @@ retry_avoidcopy:
> return 0;
> }
>
> + page_cache_get(old_page);
> +
> + /* Drop page_table_lock as buddy allocator may be called */
> + spin_unlock(&mm->page_table_lock);
> +
> /*
> * If the process that created a MAP_PRIVATE mapping is about to
> * perform a COW due to a shared page count, attempt to satisfy
> @@ -2527,19 +2532,17 @@ retry_avoidcopy:
> old_page != pagecache_page)
> outside_reserve = 1;
>
> - page_cache_get(old_page);
> -
> - /* Drop page_table_lock as buddy allocator may be called */
> - spin_unlock(&mm->page_table_lock);
> - chg = vma_needs_reservation(h, vma, address);
> - if (chg == -ENOMEM) {
> - page_cache_release(old_page);
> + if (!outside_reserve) {
> + chg = vma_needs_reservation(h, vma, address);
> + if (chg == -ENOMEM) {
> + page_cache_release(old_page);
>
> - /* Caller expects lock to be held */
> - spin_lock(&mm->page_table_lock);
> - return VM_FAULT_OOM;
> + /* Caller expects lock to be held */
> + spin_lock(&mm->page_table_lock);
> + return VM_FAULT_OOM;
> + }
> + use_reserve = !chg;
> }
> - use_reserve = !chg && !outside_reserve;
>
> new_page = alloc_huge_page(vma, address, use_reserve);
>
> --
> 1.7.9.5



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