Re: [PATCH v2 17/20] mm, hugetlb: move up anon_vma_prepare()

[Aneesh Kumar K.V]

Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> writes:

> If we fail with a allocated hugepage, we need some effort to recover
> properly. So, 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: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>

>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 2372f75..7e9a651 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -2520,6 +2520,17 @@ retry_avoidcopy:
>  	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))) {
> +		page_cache_release(old_page);
> +		/* Caller expects lock to be held */
> +		spin_lock(&mm->page_table_lock);
> +		return VM_FAULT_OOM;
> +	}
> +
> +	/*
>  	 * If the process that created a MAP_PRIVATE mapping is about to
>  	 * perform a COW due to a shared page count, attempt to satisfy
>  	 * the allocation without using the existing reserves. The pagecache
> @@ -2578,18 +2589,6 @@ retry_avoidcopy:
>  		return VM_FAULT_SIGBUS;
>  	}
>
> -	/*
> -	 * When the original hugepage is shared one, it does not have
> -	 * anon_vma prepared.
> -	 */
> -	if (unlikely(anon_vma_prepare(vma))) {
> -		page_cache_release(new_page);
> -		page_cache_release(old_page);
> -		/* Caller expects lock to be held */
> -		spin_lock(&mm->page_table_lock);
> -		return VM_FAULT_OOM;
> -	}
> -
>  	copy_user_huge_page(new_page, old_page, address, vma,
>  			    pages_per_huge_page(h));
>  	__SetPageUptodate(new_page);
> -- 
> 1.7.9.5

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