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    SubjectRe: [RFC PATCH 08/26] hugetlb: add hugetlb_free_range to free PT structures
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    On 24/06/22 11:06 pm, James Houghton wrote:
    > This is a helper function for freeing the bits of the page table that
    > map a particular HugeTLB PTE.
    >
    > Signed-off-by: James Houghton <jthoughton@google.com>
    > ---
    > include/linux/hugetlb.h | 2 ++
    > mm/hugetlb.c | 17 +++++++++++++++++
    > 2 files changed, 19 insertions(+)
    >
    > diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
    > index 1d4ec9dfdebf..33ba48fac551 100644
    > --- a/include/linux/hugetlb.h
    > +++ b/include/linux/hugetlb.h
    > @@ -107,6 +107,8 @@ bool hugetlb_pte_none_mostly(const struct hugetlb_pte *hpte);
    > pte_t hugetlb_ptep_get(const struct hugetlb_pte *hpte);
    > void hugetlb_pte_clear(struct mm_struct *mm, const struct hugetlb_pte *hpte,
    > unsigned long address);
    > +void hugetlb_free_range(struct mmu_gather *tlb, const struct hugetlb_pte *hpte,
    > + unsigned long start, unsigned long end);
    >
    > struct hugepage_subpool {
    > spinlock_t lock;
    > diff --git a/mm/hugetlb.c b/mm/hugetlb.c
    > index 1a1434e29740..a2d2ffa76173 100644
    > --- a/mm/hugetlb.c
    > +++ b/mm/hugetlb.c
    > @@ -1120,6 +1120,23 @@ static bool vma_has_reserves(struct vm_area_struct *vma, long chg)
    > return false;
    > }
    >
    > +void hugetlb_free_range(struct mmu_gather *tlb, const struct hugetlb_pte *hpte,
    > + unsigned long start, unsigned long end)
    > +{
    > + unsigned long floor = start & hugetlb_pte_mask(hpte);
    > + unsigned long ceiling = floor + hugetlb_pte_size(hpte);
    > +
    > + if (hugetlb_pte_size(hpte) >= PGDIR_SIZE) {

    sorry again did not understand why it is >= check and not just ==, does it help

    in non-x86 arches.

    > + free_p4d_range(tlb, (pgd_t *)hpte->ptep, start, end, floor, ceiling);
    > + } else if (hugetlb_pte_size(hpte) >= P4D_SIZE) {
    > + free_pud_range(tlb, (p4d_t *)hpte->ptep, start, end, floor, ceiling);
    > + } else if (hugetlb_pte_size(hpte) >= PUD_SIZE) {
    > + free_pmd_range(tlb, (pud_t *)hpte->ptep, start, end, floor, ceiling);
    > + } else if (hugetlb_pte_size(hpte) >= PMD_SIZE) {
    > + free_pte_range(tlb, (pmd_t *)hpte->ptep, start);
    > + }
    > +}
    > +
    > bool hugetlb_pte_present_leaf(const struct hugetlb_pte *hpte)
    > {
    > pgd_t pgd;

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