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2024-02-20 102a0743326a03cd1a1202ceda21e175b7d3575c

 kernel/mm/hugetlb.c
..
..
@@ -78,6 +78,9 @@
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 static int num_fault_mutexes;
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 struct mutex *hugetlb_fault_mutex_table ____cacheline_aligned_in_smp;
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+static void hugetlb_unshare_pmds(struct vm_area_struct *vma,
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+		unsigned long start, unsigned long end);
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+
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 static inline bool PageHugeFreed(struct page *head)
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 {
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 	return page_private(head + 4) == -1UL;
..
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@@ -3698,6 +3701,25 @@
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 {
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 	if (addr & ~(huge_page_mask(hstate_vma(vma))))
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 		return -EINVAL;
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+
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+	/*
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+	 * PMD sharing is only possible for PUD_SIZE-aligned address ranges
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+	 * in HugeTLB VMAs. If we will lose PUD_SIZE alignment due to this
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+	 * split, unshare PMDs in the PUD_SIZE interval surrounding addr now.
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+	 */
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+	if (addr & ~PUD_MASK) {
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+		/*
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+		 * hugetlb_vm_op_split is called right before we attempt to
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+		 * split the VMA. We will need to unshare PMDs in the old and
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+		 * new VMAs, so let's unshare before we split.
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+		 */
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+		unsigned long floor = addr & PUD_MASK;
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+		unsigned long ceil = floor + PUD_SIZE;
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+
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+		if (floor >= vma->vm_start && ceil <= vma->vm_end)
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+			hugetlb_unshare_pmds(vma, floor, ceil);
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+	}
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+
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 	return 0;
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 }
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..
..
@@ -5696,14 +5718,14 @@
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 	return pte_page(*(pte_t *)pgd) + ((address & ~PGDIR_MASK) >> PAGE_SHIFT);
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 }
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-bool isolate_huge_page(struct page *page, struct list_head *list)
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+int isolate_hugetlb(struct page *page, struct list_head *list)
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 {
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-	bool ret = true;
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+	int ret = 0;
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 	spin_lock(&hugetlb_lock);
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 	if (!PageHeadHuge(page) || !page_huge_active(page) ||
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 	    !get_page_unless_zero(page)) {
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-		ret = false;
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+		ret = -EBUSY;
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 		goto unlock;
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 	}
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 	clear_page_huge_active(page);
..
..
@@ -5756,25 +5778,20 @@
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 	}
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 }
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-/*
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- * This function will unconditionally remove all the shared pmd pgtable entries
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- * within the specific vma for a hugetlbfs memory range.
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- */
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-void hugetlb_unshare_all_pmds(struct vm_area_struct *vma)
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+static void hugetlb_unshare_pmds(struct vm_area_struct *vma,
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+				   unsigned long start,
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+				   unsigned long end)
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 {
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 	struct hstate *h = hstate_vma(vma);
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 	unsigned long sz = huge_page_size(h);
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 	struct mm_struct *mm = vma->vm_mm;
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 	struct mmu_notifier_range range;
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-	unsigned long address, start, end;
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+	unsigned long address;
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 	spinlock_t *ptl;
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 	pte_t *ptep;
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 	if (!(vma->vm_flags & VM_MAYSHARE))
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 		return;
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-
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-	start = ALIGN(vma->vm_start, PUD_SIZE);
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-	end = ALIGN_DOWN(vma->vm_end, PUD_SIZE);
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5795
 
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 	if (start >= end)
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 		return;
..
..
@@ -5808,6 +5825,16 @@
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 	mmu_notifier_invalidate_range_end(&range);
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 }
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5828
+/*
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+ * This function will unconditionally remove all the shared pmd pgtable entries
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+ * within the specific vma for a hugetlbfs memory range.
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+ */
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+void hugetlb_unshare_all_pmds(struct vm_area_struct *vma)
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+{
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+	hugetlb_unshare_pmds(vma, ALIGN(vma->vm_start, PUD_SIZE),
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+			ALIGN_DOWN(vma->vm_end, PUD_SIZE));
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+}
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+
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 #ifdef CONFIG_CMA
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 static bool cma_reserve_called __initdata;
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