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SubjectRe: [PATCH v2 3/8] mm/hugetlb: Add page_mask for hugetlb_follow_page_mask()
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On 20.06.23 18:28, Peter Xu wrote:
> On Tue, Jun 20, 2023 at 05:23:09PM +0200, David Hildenbrand wrote:
>> On 20.06.23 01:10, Peter Xu wrote:
>>> follow_page() doesn't need it, but we'll start to need it when unifying gup
>>> for hugetlb.
>>>
>>> Signed-off-by: Peter Xu <peterx@redhat.com>
>>> ---
>>> include/linux/hugetlb.h | 8 +++++---
>>> mm/gup.c | 3 ++-
>>> mm/hugetlb.c | 5 ++++-
>>> 3 files changed, 11 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
>>> index beb7c63d2871..2e2d89e79d6c 100644
>>> --- a/include/linux/hugetlb.h
>>> +++ b/include/linux/hugetlb.h
>>> @@ -131,7 +131,8 @@ int move_hugetlb_page_tables(struct vm_area_struct *vma,
>>> int copy_hugetlb_page_range(struct mm_struct *, struct mm_struct *,
>>> struct vm_area_struct *, struct vm_area_struct *);
>>> struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma,
>>> - unsigned long address, unsigned int flags);
>>> + unsigned long address, unsigned int flags,
>>> + unsigned int *page_mask);
>>> long follow_hugetlb_page(struct mm_struct *, struct vm_area_struct *,
>>> struct page **, unsigned long *, unsigned long *,
>>> long, unsigned int, int *);
>>> @@ -297,8 +298,9 @@ static inline void adjust_range_if_pmd_sharing_possible(
>>> {
>>> }
>>> -static inline struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma,
>>> - unsigned long address, unsigned int flags)
>>> +static inline struct page *hugetlb_follow_page_mask(
>>> + struct vm_area_struct *vma, unsigned long address, unsigned int flags,
>>> + unsigned int *page_mask)
>>> {
>>> BUILD_BUG(); /* should never be compiled in if !CONFIG_HUGETLB_PAGE*/
>>> }
>>> diff --git a/mm/gup.c b/mm/gup.c
>>> index abcd841d94b7..9fc9271cba8d 100644
>>> --- a/mm/gup.c
>>> +++ b/mm/gup.c
>>> @@ -780,7 +780,8 @@ static struct page *follow_page_mask(struct vm_area_struct *vma,
>>> * Ordinary GUP uses follow_hugetlb_page for hugetlb processing.
>>> */
>>> if (is_vm_hugetlb_page(vma))
>>> - return hugetlb_follow_page_mask(vma, address, flags);
>>> + return hugetlb_follow_page_mask(vma, address, flags,
>>> + &ctx->page_mask);
>>> pgd = pgd_offset(mm, address);
>>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
>>> index 9a6918c4250a..fbf6a09c0ec4 100644
>>> --- a/mm/hugetlb.c
>>> +++ b/mm/hugetlb.c
>>> @@ -6454,7 +6454,8 @@ static inline bool __follow_hugetlb_must_fault(struct vm_area_struct *vma,
>>> }
>>> struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma,
>>> - unsigned long address, unsigned int flags)
>>> + unsigned long address, unsigned int flags,
>>> + unsigned int *page_mask)
>>> {
>>> struct hstate *h = hstate_vma(vma);
>>> struct mm_struct *mm = vma->vm_mm;
>>> @@ -6499,6 +6500,8 @@ struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma,
>>> page = NULL;
>>> goto out;
>>> }
>>> +
>>> + *page_mask = ~huge_page_mask(h) >> PAGE_SHIFT;
>>
>> As discussed, can be simplified. But can be done on top (or not at all, but
>> it is confusing code).
>
> Since we decided to make this prettier.. At last I decided to go with this:
>
> *page_mask = (1U << huge_page_order(h)) - 1;
>
> The previous suggestion of PHYS_PFN() will do two shifts over PAGE_SIZE
> (the other one in huge_page_size()) which might be unnecessary, also, PHYS_
> can be slightly misleading too as prefix.
>
>>
>> Reviewed-by: David Hildenbrand <david@redhat.com>
>
> I'll take this with above change, please shoot if not applicable. Thanks,
>

Perfectly fine :)

--
Cheers,

David / dhildenb

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