From 9c670ea37947a82cb6d4df69139f7e46ed71a0ac Mon Sep 17 00:00:00 2001
From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Date: Fri, 8 Sep 2017 16:10:53 -0700
Subject: [PATCH] mm: thp: introduce CONFIG_ARCH_ENABLE_THP_MIGRATION

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

Link: http://lkml.kernel.org/r/20170717193955.20207-5-zi.yan@sent.com
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Zi Yan <zi.yan@cs.rutgers.edu>
Reviewed-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: David Nellans <dnellans@nvidia.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 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 4b278a33ccbb..07d9b6c75328 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2343,6 +2343,10 @@ 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
+
 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 ee696347f928..d8f35a0865dc 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -233,6 +233,11 @@ 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)
+{
+	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; })
@@ -336,6 +341,11 @@ static inline struct page *follow_devmap_pud(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 0ded10a22639..9ef8c2ea92ad 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -262,6 +262,9 @@ 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
 
-- 
2.20.1