linux-kernel - Re: [PATCH] mm/huge_memory: remove unneeded local variable follflags

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Date:   Fri, 11 Mar 2022 15:01:27 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     Anshuman Khandual <anshuman.khandual@....com>,
        <akpm@...ux-foundation.org>
CC:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm/huge_memory: remove unneeded local variable follflags

On 2022/3/11 14:39, Anshuman Khandual wrote:
> 
> 
> On 3/11/22 11:56, Miaohe Lin wrote:
>> On 2022/3/11 12:51, Anshuman Khandual wrote:
>>> Hi Miaohe,
>>>
>>> On 3/10/22 18:42, Miaohe Lin wrote:
>>>> We can pass FOLL_GET | FOLL_DUMP to follow_page directly to simplify
>>>> the code a bit.
>>>>
>>>> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
>>>> ---
>>>>  mm/huge_memory.c | 4 +---
>>>>  1 file changed, 1 insertion(+), 3 deletions(-)
>>>>
>>>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
>>>> index 3557aabe86fe..418d077da246 100644
>>>> --- a/mm/huge_memory.c
>>>> +++ b/mm/huge_memory.c
>>>> @@ -2838,7 +2838,6 @@ static int split_huge_pages_pid(int pid, unsigned long vaddr_start,
>>>>  	 */
>>>>  	for (addr = vaddr_start; addr < vaddr_end; addr += PAGE_SIZE) {
>>>>  		struct vm_area_struct *vma = find_vma(mm, addr);
>>>> -		unsigned int follflags;
>>>>  		struct page *page;
>>>>  
>>>>  		if (!vma || addr < vma->vm_start)
>>>> @@ -2851,8 +2850,7 @@ static int split_huge_pages_pid(int pid, unsigned long vaddr_start,
>>>>  		}
>>>>  
>>>>  		/* FOLL_DUMP to ignore special (like zero) pages */
>>>> -		follflags = FOLL_GET | FOLL_DUMP;
>>>> -		page = follow_page(vma, addr, follflags);
>>>> +		page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP);
>>>>  
>>>>  		if (IS_ERR(page))
>>>>  			continue;
>>>
>>> LGTM, but there is another similar instance in add_page_for_migration()
>>> inside mm/migrate.c, requiring this exact clean up.
>>>
>>
>> Thanks for comment. That similar case is done in my previous patch series[1]
>> aimed at migration cleanup and fixup. It might be more suitable to do that
>> clean up in that specialized series?
> 
> Both these similar scenarios i.e the one proposed here and other one in the
> migration series, should be folded into a separate single patch, either here
> or in the series itself.

Looks fine to me. Will do. Thanks.

> 
>>
>> [1]:https://lore.kernel.org/linux-mm/20220304093409.25829-4-linmiaohe@huawei.com/
>>
>>> Hence with that change in place.
>>>
>>> Reviewed-by: Anshuman Khandual <anshuman.khandual@....com>
>>
>> Thanks again.
>>
>>> .
>>>
>>
> .
>