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Date:   Fri, 24 Jun 2022 17:36:38 +0000
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Subject: [RFC PATCH 08/26] hugetlb: add hugetlb_free_range to free PT structures
From:   James Houghton <jthoughton@google.com>
To:     Mike Kravetz <mike.kravetz@oracle.com>,
        Muchun Song <songmuchun@bytedance.com>,
        Peter Xu <peterx@redhat.com>
Cc:     David Hildenbrand <david@redhat.com>,
        David Rientjes <rientjes@google.com>,
        Axel Rasmussen <axelrasmussen@google.com>,
        Mina Almasry <almasrymina@google.com>,
        Jue Wang <juew@google.com>,
        Manish Mishra <manish.mishra@nutanix.com>,
        "Dr . David Alan Gilbert" <dgilbert@redhat.com>,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        James Houghton <jthoughton@google.com>
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Precedence: bulk

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) {
+		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;
-- 
2.37.0.rc0.161.g10f37bed90-goog