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

Yin Fengwei
2023-07-28T07:12:00Z

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@intel.com>
---
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