On 2021/3/27 3:57, Mike Kravetz wrote:
> On 3/25/21 7:10 PM, Miaohe Lin wrote:
>> On 2021/3/25 8:28, Mike Kravetz wrote:
>>> The new remove_hugetlb_page() routine is designed to remove a hugetlb
>>> page from hugetlbfs processing. It will remove the page from the active
>>> or free list, update global counters and set the compound page
>>> destructor to NULL so that PageHuge() will return false for the 'page'.
>>> After this call, the 'page' can be treated as a normal compound page or
>>> a collection of base size pages.
>>>
>>> remove_hugetlb_page is to be called with the hugetlb_lock held.
>>>
>>> Creating this routine and separating functionality is in preparation for
>>> restructuring code to reduce lock hold times.
>>>
>>> Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
>>> ---
>>> mm/hugetlb.c | 70 +++++++++++++++++++++++++++++++++-------------------
>>> 1 file changed, 45 insertions(+), 25 deletions(-)
>>>
>>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
>>> index 404b0b1c5258..3938ec086b5c 100644
>>> --- a/mm/hugetlb.c
>>> +++ b/mm/hugetlb.c
>>> @@ -1327,6 +1327,46 @@ static inline void destroy_compound_gigantic_page(struct page *page,
>>> unsigned int order) { }
>>> #endif
>>>
>>> +/*
>>> + * Remove hugetlb page from lists, and update dtor so that page appears
>>> + * as just a compound page. A reference is held on the page.
>>> + * NOTE: hugetlb specific page flags stored in page->private are not
>>> + * automatically cleared. These flags may be used in routines
>>> + * which operate on the resulting compound page.
>>
>> It seems HPageFreed and HPageTemporary is cleared. Which hugetlb specific page flags
>> is reserverd here and why? Could you please give a simple example to clarify
>> this in the comment to help understand this NOTE?
>>
>
> I will remove that NOTE: in the comment to avoid any confusion.
>
> The NOTE was add in the RFC that contained a separate patch to add a flag
> that tracked huge pages allocated from CMA. That flag needed to remain
> for subsequent freeing of such pages. This is no longer needed.
>
Many thanks for explaination. I was confused about that NOTE. :)
>> The code looks good to me. Many thanks!
>> Reviewed-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
>
> Thanks,
>
