Merge branch 'for-next/faultaround' into for-next/core

Initialise prefaulted PTEs as 'old' for arm64 when hardware access-flag
updates are supported, which drastically improves vmscan performance.

* for-next/faultaround:
  mm: filemap: Fix microblaze build failure with 'mmu_defconfig'
  mm/nommu: Fix return type of filemap_map_pages()
  mm: Mark anonymous struct field of 'struct vm_fault' as 'const'
  mm: Use static initialisers for immutable fields of 'struct vm_fault'
  mm: Avoid modifying vmf.address in __collapse_huge_page_swapin()
  mm: Pass 'address' to map to do_set_pte() and drop FAULT_FLAG_PREFAULT
  mm: Move immutable fields of 'struct vm_fault' into anonymous struct
  arm64: mm: Implement arch_wants_old_prefaulted_pte()
  mm: Allow architectures to request 'old' entries when prefaulting
  mm: Cleanup faultaround and finish_fault() codepaths

1 files changed, 11 insertions, 1 deletions

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 501562793ce2..e17b96d0e4b5 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -980,7 +980,17 @@ static inline bool arch_faults_on_old_pte(void)
 
 	return !cpu_has_hw_af();
 }
-#define arch_faults_on_old_pte arch_faults_on_old_pte
+#define arch_faults_on_old_pte		arch_faults_on_old_pte
+
+/*
+ * Experimentally, it's cheap to set the access flag in hardware and we
+ * benefit from prefaulting mappings as 'old' to start with.
+ */
+static inline bool arch_wants_old_prefaulted_pte(void)
+{
+	return !arch_faults_on_old_pte();
+}
+#define arch_wants_old_prefaulted_pte	arch_wants_old_prefaulted_pte
 
 #endif /* !__ASSEMBLY__ */