[PATCH v1 02/11] mm: thp: introduce CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION

[Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>]

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@ah.jp.nec.com>
---
 arch/x86/Kconfig        |  4 ++++
 include/linux/huge_mm.h | 14 ++++++++++++++
 mm/Kconfig              |  3 +++
 3 files changed, 21 insertions(+)

diff --git v4.5-rc5-mmotm-2016-02-24-16-18/arch/x86/Kconfig v4.5-rc5-mmotm-2016-02-24-16-18_patched/arch/x86/Kconfig
index 993aca4..7a563cf 100644
--- v4.5-rc5-mmotm-2016-02-24-16-18/arch/x86/Kconfig
+++ v4.5-rc5-mmotm-2016-02-24-16-18_patched/arch/x86/Kconfig
@@ -2198,6 +2198,10 @@ 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 v4.5-rc5-mmotm-2016-02-24-16-18/include/linux/huge_mm.h v4.5-rc5-mmotm-2016-02-24-16-18_patched/include/linux/huge_mm.h
index 459fd25..09b215d 100644
--- v4.5-rc5-mmotm-2016-02-24-16-18/include/linux/huge_mm.h
+++ v4.5-rc5-mmotm-2016-02-24-16-18_patched/include/linux/huge_mm.h
@@ -156,6 +156,15 @@ static inline bool is_huge_zero_pmd(pmd_t pmd)
 
 struct page *get_huge_zero_page(void);
 
+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; })
@@ -213,6 +222,11 @@ 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 v4.5-rc5-mmotm-2016-02-24-16-18/mm/Kconfig v4.5-rc5-mmotm-2016-02-24-16-18_patched/mm/Kconfig
index f2c1a07..64e7ab6 100644
--- v4.5-rc5-mmotm-2016-02-24-16-18/mm/Kconfig
+++ v4.5-rc5-mmotm-2016-02-24-16-18_patched/mm/Kconfig
@@ -265,6 +265,9 @@ 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

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