mm: make folio_pte_batch available outside of mm/memory.c

madvise, mprotect and some others might need folio_pte_batch to check if a
range of PTEs are completely mapped to a large folio with contiguous
physical addresses.  Let's make it available in mm/internal.h.

While at it, add proper kernel doc and sanity-check more input parameters
using two additional VM_WARN_ON_FOLIO().

[21cnbao@gmail.com: build fix]
Link: https://lkml.kernel.org/r/CAGsJ_4wWzG-37D82vqP_zt+Fcbz+URVe5oXLBc4M5wbN8A_gpQ@mail.gmail.com
[david@redhat.com: improve the doc for the exported func]
Link: https://lkml.kernel.org/r/20240227104201.337988-1-21cnbao@gmail.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
Suggested-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: Yin Fengwei <fengwei.yin@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/internal.h b/mm/internal.h
index 5be91e2f99434afcd9a85d0ef87b13b62ab20bed..d1c69119b24fb34e8271fc858965972a2fbdf354 100644 (file)
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -83,6 +83,99 @@ static inline void *folio_raw_mapping(struct folio *folio)
        return (void *)(mapping & ~PAGE_MAPPING_FLAGS);
 }
 
+#ifdef CONFIG_MMU
+
+/* Flags for folio_pte_batch(). */
+typedef int __bitwise fpb_t;
+
+/* Compare PTEs after pte_mkclean(), ignoring the dirty bit. */
+#define FPB_IGNORE_DIRTY               ((__force fpb_t)BIT(0))
+
+/* Compare PTEs after pte_clear_soft_dirty(), ignoring the soft-dirty bit. */
+#define FPB_IGNORE_SOFT_DIRTY          ((__force fpb_t)BIT(1))
+
+static inline pte_t __pte_batch_clear_ignored(pte_t pte, fpb_t flags)
+{
+       if (flags & FPB_IGNORE_DIRTY)
+               pte = pte_mkclean(pte);
+       if (likely(flags & FPB_IGNORE_SOFT_DIRTY))
+               pte = pte_clear_soft_dirty(pte);
+       return pte_wrprotect(pte_mkold(pte));
+}
+
+/**
+ * folio_pte_batch - detect a PTE batch for a large folio
+ * @folio: The large folio to detect a PTE batch for.
+ * @addr: The user virtual address the first page is mapped at.
+ * @start_ptep: Page table pointer for the first entry.
+ * @pte: Page table entry for the first page.
+ * @max_nr: The maximum number of table entries to consider.
+ * @flags: Flags to modify the PTE batch semantics.
+ * @any_writable: Optional pointer to indicate whether any entry except the
+ *               first one is writable.
+ *
+ * Detect a PTE batch: consecutive (present) PTEs that map consecutive
+ * pages of the same large folio.
+ *
+ * All PTEs inside a PTE batch have the same PTE bits set, excluding the PFN,
+ * the accessed bit, writable bit, dirty bit (with FPB_IGNORE_DIRTY) and
+ * soft-dirty bit (with FPB_IGNORE_SOFT_DIRTY).
+ *
+ * start_ptep must map any page of the folio. max_nr must be at least one and
+ * must be limited by the caller so scanning cannot exceed a single page table.
+ *
+ * Return: the number of table entries in the batch.
+ */
+static inline int folio_pte_batch(struct folio *folio, unsigned long addr,
+               pte_t *start_ptep, pte_t pte, int max_nr, fpb_t flags,
+               bool *any_writable)
+{
+       unsigned long folio_end_pfn = folio_pfn(folio) + folio_nr_pages(folio);
+       const pte_t *end_ptep = start_ptep + max_nr;
+       pte_t expected_pte, *ptep;
+       bool writable;
+       int nr;
+
+       if (any_writable)
+               *any_writable = false;
+
+       VM_WARN_ON_FOLIO(!pte_present(pte), folio);
+       VM_WARN_ON_FOLIO(!folio_test_large(folio) || max_nr < 1, folio);
+       VM_WARN_ON_FOLIO(page_folio(pfn_to_page(pte_pfn(pte))) != folio, folio);
+
+       nr = pte_batch_hint(start_ptep, pte);
+       expected_pte = __pte_batch_clear_ignored(pte_advance_pfn(pte, nr), flags);
+       ptep = start_ptep + nr;
+
+       while (ptep < end_ptep) {
+               pte = ptep_get(ptep);
+               if (any_writable)
+                       writable = !!pte_write(pte);
+               pte = __pte_batch_clear_ignored(pte, flags);
+
+               if (!pte_same(pte, expected_pte))
+                       break;
+
+               /*
+                * Stop immediately once we reached the end of the folio. In
+                * corner cases the next PFN might fall into a different
+                * folio.
+                */
+               if (pte_pfn(pte) >= folio_end_pfn)
+                       break;
+
+               if (any_writable)
+                       *any_writable |= writable;
+
+               nr = pte_batch_hint(ptep, pte);
+               expected_pte = pte_advance_pfn(expected_pte, nr);
+               ptep += nr;
+       }
+
+       return min(ptep - start_ptep, max_nr);
+}
+#endif /* CONFIG_MMU */
+
 void __acct_reclaim_writeback(pg_data_t *pgdat, struct folio *folio,
                                                int nr_throttled);
 static inline void acct_reclaim_writeback(struct folio *folio)

diff --git a/mm/memory.c b/mm/memory.c
index 230bcd12a3362dc06d7ca1d2dbf060e10ca10c56..abd4f33d62c94e7d3c71da6740d0d7e52a2eae60 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -953,82 +953,6 @@ static __always_inline void __copy_present_ptes(struct vm_area_struct *dst_vma,
        set_ptes(dst_vma->vm_mm, addr, dst_pte, pte, nr);
 }
 
-/* Flags for folio_pte_batch(). */
-typedef int __bitwise fpb_t;
-
-/* Compare PTEs after pte_mkclean(), ignoring the dirty bit. */
-#define FPB_IGNORE_DIRTY               ((__force fpb_t)BIT(0))
-
-/* Compare PTEs after pte_clear_soft_dirty(), ignoring the soft-dirty bit. */
-#define FPB_IGNORE_SOFT_DIRTY          ((__force fpb_t)BIT(1))
-
-static inline pte_t __pte_batch_clear_ignored(pte_t pte, fpb_t flags)
-{
-       if (flags & FPB_IGNORE_DIRTY)
-               pte = pte_mkclean(pte);
-       if (likely(flags & FPB_IGNORE_SOFT_DIRTY))
-               pte = pte_clear_soft_dirty(pte);
-       return pte_wrprotect(pte_mkold(pte));
-}
-
-/*
- * Detect a PTE batch: consecutive (present) PTEs that map consecutive
- * pages of the same folio.
- *
- * All PTEs inside a PTE batch have the same PTE bits set, excluding the PFN,
- * the accessed bit, writable bit, dirty bit (with FPB_IGNORE_DIRTY) and
- * soft-dirty bit (with FPB_IGNORE_SOFT_DIRTY).
- *
- * If "any_writable" is set, it will indicate if any other PTE besides the
- * first (given) PTE is writable.
- */
-static inline int folio_pte_batch(struct folio *folio, unsigned long addr,
-               pte_t *start_ptep, pte_t pte, int max_nr, fpb_t flags,
-               bool *any_writable)
-{
-       unsigned long folio_end_pfn = folio_pfn(folio) + folio_nr_pages(folio);
-       const pte_t *end_ptep = start_ptep + max_nr;
-       pte_t expected_pte, *ptep;
-       bool writable;
-       int nr;
-
-       if (any_writable)
-               *any_writable = false;
-
-       VM_WARN_ON_FOLIO(!pte_present(pte), folio);
-
-       nr = pte_batch_hint(start_ptep, pte);
-       expected_pte = __pte_batch_clear_ignored(pte_advance_pfn(pte, nr), flags);
-       ptep = start_ptep + nr;
-
-       while (ptep < end_ptep) {
-               pte = ptep_get(ptep);
-               if (any_writable)
-                       writable = !!pte_write(pte);
-               pte = __pte_batch_clear_ignored(pte, flags);
-
-               if (!pte_same(pte, expected_pte))
-                       break;
-
-               /*
-                * Stop immediately once we reached the end of the folio. In
-                * corner cases the next PFN might fall into a different
-                * folio.
-                */
-               if (pte_pfn(pte) >= folio_end_pfn)
-                       break;
-
-               if (any_writable)
-                       *any_writable |= writable;
-
-               nr = pte_batch_hint(ptep, pte);
-               expected_pte = pte_advance_pfn(expected_pte, nr);
-               ptep += nr;
-       }
-
-       return min(ptep - start_ptep, max_nr);
-}
-
 /*
  * Copy one present PTE, trying to batch-process subsequent PTEs that map
  * consecutive pages of the same folio by copying them as well.