Re: [PATCH v5 5/6] mm: convert copy_user_huge_page() to copy_user_folio()

zhangpeng (AS)
2023-04-08T04:43:26Z

On 2023/4/7 7:55, Mike Kravetz wrote:

> On 03/31/23 17:39, Peng Zhang wrote:
>> From: ZhangPeng <zhangpeng362@huawei.com>
>>
>> Replace copy_user_huge_page() with copy_user_folio(). copy_user_folio()
>> does the same as copy_user_huge_page(), but takes in folios instead of
>> pages. Convert copy_user_gigantic_page() to take in folios.
>> Remove pages_per_huge_page from copy_user_folio(), because we can get
>> that from folio_nr_pages(dst).
>>
>> Signed-off-by: ZhangPeng <zhangpeng362@huawei.com>
>> ---
>> include/linux/mm.h | 7 +++----
>> mm/hugetlb.c | 10 ++++------
>> mm/memory.c | 28 ++++++++++++++--------------
>> 3 files changed, 21 insertions(+), 24 deletions(-)
> No technical problems with the patch, but ...
>>
>> @@ -5847,15 +5847,15 @@ static void copy_subpage(unsigned long addr, int idx, void *arg)
>> addr, copy_arg->vma);
>> }
>>
>> -void copy_user_huge_page(struct page *dst, struct page *src,
>> - unsigned long addr_hint, struct vm_area_struct *vma,
>> - unsigned int pages_per_huge_page)
>> +void copy_user_folio(struct folio *dst, struct folio *src,
>> + unsigned long addr_hint, struct vm_area_struct *vma)
>> {
>> + unsigned int pages_per_huge_page = folio_nr_pages(dst);
>> unsigned long addr = addr_hint &
>> ~(((unsigned long)pages_per_huge_page << PAGE_SHIFT) - 1);
>> struct copy_subpage_arg arg = {
>> - .dst = dst,
>> - .src = src,
>> + .dst = &dst->page,
>> + .src = &src->page,
>> .vma = vma,
>> };
>>
> I seem to recall that Matthew suggested changing the function name to
> copy_user_folio. My only concern is that the name now sounds like a
> general purpose routine for copying folios. It certainly would work
> for a single page folio, but there is a bunch of unnecessary overhead
> in that case.
>
> That makes me think there should perhaps be an optimized path for single
> page folios that just does copy_user_highpage(). But, the argument addr_hint
> does not make much sense in the single page folio case. So, I am not
> sure if I agree with leaving large/huge out of the function name.
>
> Just wondering if Matthew has any additional thoughts?

Agreed. In my opinion, it's better to leave large/huge out of the
function name.
Also wondering if Matthew has any additional considerations?

Best Regards,
Peng