[PATCH 1/3] mm: add functions folio_in_range() and folio_within_vma()

[Yin Fengwei]

It will be used to check whether the folio is mapped to specific
VMA and whether the mapping address of folio is in the range.

Also a helper function folio_within_vma() to check whether folio
is in the range of vma based on folio_in_range().

Signed-off-by: Yin Fengwei <fengwei.yin@xxxxxxxxx>
---
 mm/internal.h | 69 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 69 insertions(+)

diff --git a/mm/internal.h b/mm/internal.h
index 5a03bc4782a2..63de32154a48 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -585,6 +585,75 @@ extern long faultin_vma_page_range(struct vm_area_struct *vma,
 				   bool write, int *locked);
 extern bool mlock_future_ok(struct mm_struct *mm, unsigned long flags,
 			       unsigned long bytes);
+
+/*
+ * Check whether the folio is in specific range
+ *
+ * First, check whether the folio is in the range of vma.
+ * Then, check whether the folio is mapped to the range of [start, end].
+ * In the end, check whether the folio is fully mapped to the range.
+ *
+ * @pte page table pointer will be checked whether the large folio
+ *      is fully mapped to. Currently, if mremap in the middle of
+ *      large folio, the large folio could be mapped to to different
+ *      VMA and address check can't identify this situation.
+ */
+static inline bool
+folio_in_range(struct folio *folio, struct vm_area_struct *vma,
+		unsigned long start, unsigned long end, pte_t *pte)
+{
+	pte_t ptent;
+	unsigned long i, nr = folio_nr_pages(folio);
+	pgoff_t pgoff, addr;
+	unsigned long vma_pglen = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
+
+	VM_WARN_ON_FOLIO(folio_test_ksm(folio), folio);
+
+	if (start < vma->vm_start)
+		start = vma->vm_start;
+	if (end > vma->vm_end)
+		end = vma->vm_end;
+
+	pgoff = folio_pgoff(folio);
+	/* if folio start address is not in vma range */
+	if (pgoff < vma->vm_pgoff || pgoff > vma->vm_pgoff + vma_pglen)
+		return false;
+
+	addr = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
+	if (addr < start || end - addr < folio_size(folio))
+		return false;
+
+	/* not necessary to check pte for none large folio */
+	if (!folio_test_large(folio))
+		return true;
+
+	if (!pte)
+		return false;
+
+	/* check whether parameter pte is associated with folio */
+	ptent = ptep_get(pte);
+	if (pte_none(ptent) || !pte_present(ptent) ||
+			pte_pfn(ptent) - folio_pfn(folio) >= nr)
+		return false;
+
+	pte -= pte_pfn(ptent) - folio_pfn(folio);
+	for (i = 0; i < nr; i++, pte++) {
+		ptent = ptep_get(pte);
+
+		if (pte_none(ptent) || !pte_present(ptent) ||
+				pte_pfn(ptent) - folio_pfn(folio) >= nr)
+			return false;
+	}
+
+	return true;
+}
+
+static inline bool
+folio_within_vma(struct folio *folio, struct vm_area_struct *vma, pte_t *pte)
+{
+	return folio_in_range(folio, vma, vma->vm_start, vma->vm_end, pte);
+}
+
 /*
  * mlock_vma_folio() and munlock_vma_folio():
  * should be called with vma's mmap_lock held for read or write,
-- 
2.39.2