linux-kernel - Re: [PATCH v2 18/20] mm, hugetlb: clean-up error handling in hugetlb

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Date:	Mon, 26 Aug 2013 19:42:35 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Rik van Riel <riel@...hat.com>, Mel Gorman <mgorman@...e.de>,
	Michal Hocko <mhocko@...e.cz>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Hugh Dickins <hughd@...gle.com>,
	Davidlohr Bueso <davidlohr.bueso@...com>,
	David Gibson <david@...son.dropbear.id.au>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Joonsoo Kim <js1304@...il.com>,
	Wanpeng Li <liwanp@...ux.vnet.ibm.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Hillf Danton <dhillf@...il.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: Re: [PATCH v2 18/20] mm, hugetlb: clean-up error handling in hugetlb_cow()

Joonsoo Kim <iamjoonsoo.kim@....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@....com>

Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@...ux.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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