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SubjectRe: [PATCH] mm: get rid of odd jump label in find_mergeable_anon_vma
On Fri, Nov 15, 2019 at 01:58:02PM +0100, David Hildenbrand wrote:
>On 15.11.19 07:36, linmiaohe wrote:
>> From: Miaohe Lin <linmiaohe@huawei.com>
>
>I'm pro removing unnecessary jump labels.
>
>Subject: "mm: get rid of jump labels in find_mergeable_anon_vma()"
>
>>
>> The odd jump label try_prev and none is not really need
>
>s/odd jump label/jump labels/
>
>s/is/are/
>
>> in func find_mergeable_anon_vma, eliminate them to
>> improve readability.
>>
>> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
>> ---
>> mm/mmap.c | 18 +++++++-----------
>> 1 file changed, 7 insertions(+), 11 deletions(-)
>>
>> diff --git a/mm/mmap.c b/mm/mmap.c
>> index 4d4db76a07da..ab980d468a10 100644
>> --- a/mm/mmap.c
>> +++ b/mm/mmap.c
>> @@ -1276,25 +1276,21 @@ static struct anon_vma *reusable_anon_vma(struct vm_area_struct *old, struct vm_
>> */
>> struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *vma)
>> {
>> - struct anon_vma *anon_vma;
>> + struct anon_vma *anon_vma = NULL;
>> struct vm_area_struct *near;
>>
>> near = vma->vm_next;
>> - if (!near)
>> - goto try_prev;
>> -
>> - anon_vma = reusable_anon_vma(near, vma, near);
>> + if (near)
>> + anon_vma = reusable_anon_vma(near, vma, near);> if (anon_vma)
>> return anon_vma;
>
>Let me suggest the following instead:
>
>/* Try next first */
>near = vma->vm_next;
>if (near) {
> anon_vma = reusable_anon_vma(near, vma, near);
> if (anon_vma)
> return anon_vma;
>}
>/* Try prev next */
>near = vma->vm_prev;
>if (near) {
> anon_vma = reusable_anon_vma(near, vma, near);
> if (anon_vma)
> return anon_vma;
>}
>

Can we have an array with vma->vm_next and vma->vm_prev, then iterate on the
array?

>> -try_prev:
>> - near = vma->vm_prev;
>> - if (!near)
>> - goto none;
>>
>> - anon_vma = reusable_anon_vma(near, near, vma);
>> + near = vma->vm_prev;
>> + if (near)
>> + anon_vma = reusable_anon_vma(near, near, vma);
>> if (anon_vma)
>> return anon_vma;
>> -none:
>> +
>> /*
>> * There's no absolute need to look only at touching neighbours:
>> * we could search further afield for "compatible" anon_vmas.
>>
>
>
>--
>
>Thanks,
>
>David / dhildenb

--
Wei Yang
Help you, Help me

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