[PATCH v1 02/12] mm: thp: introduce CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION

[zi . yan]

From: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>

Introduces CONFIG_ARCH_ENABLE_HUGEPAGE_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>
---
 arch/x86/Kconfig        |  4 ++++
 include/linux/huge_mm.h | 10 ++++++++++
 mm/Kconfig              |  3 +++
 3 files changed, 17 insertions(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 2a1f0ce..ad99c05 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2234,6 +2234,10 @@ 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 a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 6f14de4..4ae156e 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -157,6 +157,11 @@ void put_huge_zero_page(void);
 
 #define mk_huge_pmd(page, prot) pmd_mkhuge(mk_pmd(page, prot))
 
+static inline bool thp_migration_supported(void)
+{
+	return IS_ENABLED(CONFIG_ARCH_ENABLE_THP_MIGRATION);
+}
+
 #else /* CONFIG_TRANSPARENT_HUGEPAGE */
 #define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; })
 #define HPAGE_PMD_MASK ({ BUILD_BUG(); 0; })
@@ -223,6 +228,11 @@ 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 a/mm/Kconfig b/mm/Kconfig
index be0ee11..1965310 100644
--- a/mm/Kconfig
+++ b/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
 
-- 
2.9.3