[PATCH 02/10] mm: Add p[te|md] protnone helpers for use by NUMA balancing

[Mel Gorman]

This is a preparatory patch that introduces protnone helpers for automatic
NUMA balancing.

Signed-off-by: Mel Gorman <mgorman at suse.de>
Acked-by: Linus Torvalds <torvalds at linux-foundation.org>
Acked-by: Aneesh Kumar K.V <aneesh.kumar at linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/pgtable.h | 11 +++++++++++
 arch/x86/include/asm/pgtable.h     | 16 ++++++++++++++++
 include/asm-generic/pgtable.h      | 19 +++++++++++++++++++
 3 files changed, 46 insertions(+)

diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
index 316f9a5..452c3b4 100644
--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h
@@ -39,6 +39,17 @@ static inline int pte_none(pte_t pte)		{ return (pte_val(pte) & ~_PTE_NONE_MASK)
 static inline pgprot_t pte_pgprot(pte_t pte)	{ return __pgprot(pte_val(pte) & PAGE_PROT_BITS); }
 
 #ifdef CONFIG_NUMA_BALANCING
+static inline int pte_protnone_numa(pte_t pte)
+{
+	return (pte_val(pte) &
+		(_PAGE_PRESENT | _PAGE_USER)) == _PAGE_PRESENT;
+}
+
+static inline int pmd_protnone_numa(pmd_t pmd)
+{
+	return pte_protnone_numa(pmd_pte(pmd));
+}
+
 static inline int pte_present(pte_t pte)
 {
 	return pte_val(pte) & _PAGE_NUMA_MASK;
diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index aa97a07..613cd00 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -497,6 +497,22 @@ static inline int pmd_present(pmd_t pmd)
 				 _PAGE_NUMA);
 }
 
+#ifdef CONFIG_NUMA_BALANCING
+/*
+ * These work without NUMA balancing but the kernel does not care. See the
+ * comment in include/asm-generic/pgtable.h
+ */
+static inline int pte_protnone_numa(pte_t pte)
+{
+	return pte_flags(pte) & _PAGE_PROTNONE;
+}
+
+static inline int pmd_protnone_numa(pmd_t pmd)
+{
+	return pmd_flags(pmd) & _PAGE_PROTNONE;
+}
+#endif /* CONFIG_NUMA_BALANCING */
+
 static inline int pmd_none(pmd_t pmd)
 {
 	/* Only check low word on 32-bit platforms, since it might be
diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 752e30d..7e74122 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -677,6 +677,25 @@ static inline int pmd_trans_unstable(pmd_t *pmd)
 #endif
 }
 
+#ifndef CONFIG_NUMA_BALANCING
+/*
+ * Technically a PTE can be PROTNONE even when not doing NUMA balancing but
+ * the only case the kernel cares is for NUMA balancing. By default,
+ * implement the helper as "always no". Note that this does not check VMA
+ * protection bits meaning that it is up to the caller to distinguish between
+ * PROT_NONE protections and NUMA hinting fault protections.
+ */
+static inline int pte_protnone_numa(pte_t pte)
+{
+	return 0;
+}
+
+static inline int pmd_protnone_numa(pmd_t pmd)
+{
+	return 0;
+}
+#endif /* CONFIG_NUMA_BALANCING */
+
 #ifdef CONFIG_NUMA_BALANCING
 /*
  * _PAGE_NUMA distinguishes between an unmapped page table entry, an entry that
-- 
2.1.2