Re: [PATCH] mm/hugetlb: Remove redundant VM_BUG_ON_PAGE on putback_active_hugepage()

[Miaohe Lin]

Hi:
On 2021/2/9 11:39, Mike Kravetz wrote:
> On 2/8/21 6:10 PM, Miaohe Lin wrote:
>> Hi:
>> On 2021/2/9 9:26, Mike Kravetz wrote:
>>> On 2/8/21 12:37 AM, Miaohe Lin wrote:
>>>> PageHead(page) is implicitly checked in set_page_huge_active() via the
>>>> PageHeadHuge(page) check. So remove this explicit one.
>>>
>>> I do not disagree with the code change.  However, this commit message
>>> is not accurate.  set_page_huge_active() no longer exists in the tree
>>> you are changing.  It was replaced with SetHPageMigratable.  Also, the
>>> VM_BUG_ON_PAGE(!PageHeadHuge(page), page) was removed in the process.
>>> So, there is no redundant check.
>>>
>>> However, a quick audit of calling code reveals that all callers know they
>>> are operating on a hugetlb head page.
>>>
>>
>> So I should change the commit log like:
>>
>> 	All callers know they are operating on a hugetlb head page. So this VM_BUG_ON_PAGE
>> 	can't catch anything useful.
>>
>> and send a v2. Right?
> 
> Correct,
> 
Will do. Thanks a lot.