[PATCH v2 04/12] mm: thp: introduce CONFIG_ARCH_ENABLE_THP_MIGRATION

[Naoya Horiguchi]

Introduces CONFIG_ARCH_ENABLE_THP_MIGRATION to limit thp migration
functionality to x86_64, which should be safer at the first step.

Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
---
v1 -> v2:
- fixed config name in subject and patch description
---
 arch/x86/Kconfig        |  4 ++++
 include/linux/huge_mm.h | 14 ++++++++++++++
 mm/Kconfig              |  3 +++
 3 files changed, 21 insertions(+)

diff --git v4.9-rc2-mmotm-2016-10-27-18-27/arch/x86/Kconfig v4.9-rc2-mmotm-2016-10-27-18-27_patched/arch/x86/Kconfig
index 19d237b..63b2f24 100644
--- v4.9-rc2-mmotm-2016-10-27-18-27/arch/x86/Kconfig
+++ v4.9-rc2-mmotm-2016-10-27-18-27_patched/arch/x86/Kconfig
@@ -2246,6 +2246,10 @@ config ARCH_ENABLE_HUGEPAGE_MIGRATION
 	def_bool y
 	depends on X86_64 && HUGETLB_PAGE && MIGRATION
 
+config ARCH_ENABLE_THP_MIGRATION
+	def_bool y
+	depends on X86_64 && TRANSPARENT_HUGEPAGE && MIGRATION
+
 menu "Power management and ACPI options"
 
 config ARCH_HIBERNATION_HEADER
diff --git v4.9-rc2-mmotm-2016-10-27-18-27/include/linux/huge_mm.h v4.9-rc2-mmotm-2016-10-27-18-27_patched/include/linux/huge_mm.h
index 31f2c32..fcbca51 100644
--- v4.9-rc2-mmotm-2016-10-27-18-27/include/linux/huge_mm.h
+++ v4.9-rc2-mmotm-2016-10-27-18-27_patched/include/linux/huge_mm.h
@@ -161,6 +161,15 @@ void mm_put_huge_zero_page(struct mm_struct *mm);
 
 #define mk_huge_pmd(page, prot) pmd_mkhuge(mk_pmd(page, prot))
 
+static inline bool thp_migration_supported(void)
+{
+#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
+	return true;
+#else
+	return false;
+#endif
+}
+
 #else /* CONFIG_TRANSPARENT_HUGEPAGE */
 #define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; })
 #define HPAGE_PMD_MASK ({ BUILD_BUG(); 0; })
@@ -232,6 +241,11 @@ static inline struct page *follow_devmap_pmd(struct vm_area_struct *vma,
 {
 	return NULL;
 }
+
+static inline bool thp_migration_supported(void)
+{
+	return false;
+}
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 
 #endif /* _LINUX_HUGE_MM_H */
diff --git v4.9-rc2-mmotm-2016-10-27-18-27/mm/Kconfig v4.9-rc2-mmotm-2016-10-27-18-27_patched/mm/Kconfig
index be0ee11..1965310 100644
--- v4.9-rc2-mmotm-2016-10-27-18-27/mm/Kconfig
+++ v4.9-rc2-mmotm-2016-10-27-18-27_patched/mm/Kconfig
@@ -289,6 +289,9 @@ config MIGRATION
 config ARCH_ENABLE_HUGEPAGE_MIGRATION
 	bool
 
+config ARCH_ENABLE_THP_MIGRATION
+	bool
+
 config PHYS_ADDR_T_64BIT
 	def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
 
-- 
2.7.0