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>

1 files changed, 0 insertions, 76 deletions

diff --git a/mm/memory.c b/mm/memory.c
index 230bcd12a336..abd4f33d62c9 100644
--- 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.