[PATCH v8 1/3] mm/mremap: Allow arch runtime override

["Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>]

Architectures like ppc64 support faster mremap only with radix
translation. Hence allow a runtime check w.r.t support for fast mremap.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
---
 arch/powerpc/include/asm/tlb.h |  6 ++++++
 mm/mremap.c                    | 15 ++++++++++++++-
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/tlb.h b/arch/powerpc/include/asm/tlb.h
index 160422a439aa..09a9ae5f3656 100644
--- a/arch/powerpc/include/asm/tlb.h
+++ b/arch/powerpc/include/asm/tlb.h
@@ -83,5 +83,11 @@ static inline int mm_is_thread_local(struct mm_struct *mm)
 }
 #endif
 
+#define arch_supports_page_table_move arch_supports_page_table_move
+static inline bool arch_supports_page_table_move(void)
+{
+	return radix_enabled();
+}
+
 #endif /* __KERNEL__ */
 #endif /* __ASM_POWERPC_TLB_H */
diff --git a/mm/mremap.c b/mm/mremap.c
index c3cad539a7aa..ca9d345f22e8 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -25,7 +25,7 @@
 #include <linux/userfaultfd_k.h>
 
 #include <asm/cacheflush.h>
-#include <asm/tlbflush.h>
+#include <asm/tlb.h>
 #include <asm/pgalloc.h>
 
 #include "internal.h"
@@ -210,6 +210,15 @@ static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
 		drop_rmap_locks(vma);
 }
 
+#ifndef arch_supports_page_table_move
+#define arch_supports_page_table_move arch_supports_page_table_move
+static inline bool arch_supports_page_table_move(void)
+{
+	return IS_ENABLED(CONFIG_HAVE_MOVE_PMD) ||
+		IS_ENABLED(CONFIG_HAVE_MOVE_PUD);
+}
+#endif
+
 #ifdef CONFIG_HAVE_MOVE_PMD
 static bool move_normal_pmd(struct vm_area_struct *vma, unsigned long old_addr,
 		  unsigned long new_addr, pmd_t *old_pmd, pmd_t *new_pmd)
@@ -218,6 +227,8 @@ static bool move_normal_pmd(struct vm_area_struct *vma, unsigned long old_addr,
 	struct mm_struct *mm = vma->vm_mm;
 	pmd_t pmd;
 
+	if (!arch_supports_page_table_move())
+		return false;
 	/*
 	 * The destination pmd shouldn't be established, free_pgtables()
 	 * should have released it.
@@ -284,6 +295,8 @@ static bool move_normal_pud(struct vm_area_struct *vma, unsigned long old_addr,
 	struct mm_struct *mm = vma->vm_mm;
 	pud_t pud;
 
+	if (!arch_supports_page_table_move())
+		return false;
 	/*
 	 * The destination pud shouldn't be established, free_pgtables()
 	 * should have released it.
-- 
2.31.1