Re: [PATCH 15/18] mm, hugetlb: move up anon_vma_prepare()

[Naoya Horiguchi]

On Mon, Jul 29, 2013 at 02:32:06PM +0900, Joonsoo Kim wrote:
> If we fail with a allocated hugepage, it is hard to recover properly.
> One such example is reserve count. We don't have any method to recover
> reserve count. Although, I will introduce a function to recover reserve
> count in following patch, it is better not to allocate a hugepage
> as much as possible. So move up anon_vma_prepare() which can be failed
> in OOM situation.
> 
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>

Reviewed-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>

> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 683fd38..bb8a45f 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -2536,6 +2536,15 @@ retry_avoidcopy:
>  	/* Drop page_table_lock as buddy allocator may be called */
>  	spin_unlock(&mm->page_table_lock);
>  
> +	/*
> +	 * When the original hugepage is shared one, it does not have
> +	 * anon_vma prepared.
> +	 */
> +	if (unlikely(anon_vma_prepare(vma))) {
> +		ret = VM_FAULT_OOM;
> +		goto out_old_page;
> +	}
> +
>  	use_reserve = vma_has_reserves(h, vma, address);
>  	if (use_reserve == -ENOMEM) {
>  		ret = VM_FAULT_OOM;
> @@ -2590,15 +2599,6 @@ retry_avoidcopy:
>  		goto out_lock;
>  	}
>  
> -	/*
> -	 * When the original hugepage is shared one, it does not have
> -	 * anon_vma prepared.
> -	 */
> -	if (unlikely(anon_vma_prepare(vma))) {
> -		ret = VM_FAULT_OOM;
> -		goto out_new_page;
> -	}
> -
>  	copy_user_huge_page(new_page, old_page, address, vma,
>  			    pages_per_huge_page(h));
>  	__SetPageUptodate(new_page);
> @@ -2625,7 +2625,6 @@ retry_avoidcopy:
>  	spin_unlock(&mm->page_table_lock);
>  	mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
>  
> -out_new_page:
>  	page_cache_release(new_page);
>  out_old_page:
>  	page_cache_release(old_page);
> -- 
> 1.7.9.5
> 
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