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

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Date:   Fri, 11 Mar 2022 12:09:37 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     Miaohe Lin <linmiaohe@...wei.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 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.

> 
> [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.
> 
>> .
>>
>