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SubjectRe: [PATCH v2 18/20] mm, hugetlb: clean-up error handling in hugetlb_cow()
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Joonsoo Kim <iamjoonsoo.kim@lge.com> writes:

> Current code include 'Caller expects lock to be held' in every error path.
> We can clean-up it as we do error handling in one place.
>
> 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 7e9a651..8743e5c 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -2500,6 +2500,7 @@ static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
> int outside_reserve = 0;
> long chg;
> bool use_reserve = false;
> + int ret = 0;
> unsigned long mmun_start; /* For mmu_notifiers */
> unsigned long mmun_end; /* For mmu_notifiers */
>
> @@ -2524,10 +2525,8 @@ retry_avoidcopy:
> * anon_vma prepared.
> */
> if (unlikely(anon_vma_prepare(vma))) {
> - page_cache_release(old_page);
> - /* Caller expects lock to be held */
> - spin_lock(&mm->page_table_lock);
> - return VM_FAULT_OOM;
> + ret = VM_FAULT_OOM;
> + goto out_old_page;
> }
>
> /*
> @@ -2546,11 +2545,8 @@ retry_avoidcopy:
> 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;
> + ret = VM_FAULT_OOM;
> + goto out_old_page;
> }
> use_reserve = !chg;
> }
> @@ -2584,9 +2580,8 @@ retry_avoidcopy:
> WARN_ON_ONCE(1);
> }
>
> - /* Caller expects lock to be held */
> - spin_lock(&mm->page_table_lock);
> - return VM_FAULT_SIGBUS;
> + ret = VM_FAULT_SIGBUS;
> + goto out_lock;
> }
>
> copy_user_huge_page(new_page, old_page, address, vma,
> @@ -2617,11 +2612,12 @@ retry_avoidcopy:
> spin_unlock(&mm->page_table_lock);
> mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
> page_cache_release(new_page);
> +out_old_page:
> page_cache_release(old_page);
> -
> +out_lock:
> /* Caller expects lock to be held */
> spin_lock(&mm->page_table_lock);
> - return 0;
> + return ret;
> }
>
> /* Return the pagecache page at a given address within a VMA */
> --
> 1.7.9.5



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