linux-kernel - Re: [PATCH v2] mm: simplify find_vma

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Date:	Fri, 9 Dec 2011 17:49:27 -0500
From:	KOSAKI Motohiro <kosaki.motohiro@...il.com>
To:	Joe Perches <joe@...ches.com>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Shaohua Li <shaohua.li@...el.com>
Subject: Re: [PATCH v2] mm: simplify find_vma_prev

>> diff --git a/mm/mmap.c b/mm/mmap.c
> []
>> @@ -1603,39 +1603,21 @@ struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
>>
>>  EXPORT_SYMBOL(find_vma);
>>
>> -/* Same as find_vma, but also return a pointer to the previous VMA in *pprev. */
>> +/*
>> + * Same as find_vma, but also return a pointer to the previous VMA in *pprev.
>> + * Note: pprev is set to NULL when return value is NULL.
>> + */
>>  struct vm_area_struct *
>> -find_vma_prev(struct mm_struct *mm, unsigned long addr,
>> -                     struct vm_area_struct **pprev)
>
>> +find_vma_prev(struct mm_struct *mm, unsigned long addr, struct vm_area_struct **pprev)
>
> eh.  This declaration change seems gratuitous and it exceeds 80 columns.
>
>> +     *pprev = NULL;
>> +     vma = find_vma(mm, addr);
>> +     if (vma)
>> +             *pprev = vma->vm_prev;
>
> There's no need to possibly set *pprev twice.
>
> Maybe
> {
>        struct vm_area_struct *vma = find_vma(mm, addr);
>
>        *pprev = vma ? vma->vm_prev : NULL;
> or
>        if (vma)
>                *pprev = vma->vm_prev;
>        else
>                *pprev = NULL;
>
>        return vma;

Thank you for reviewing. Updated.
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