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

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Date:	Fri, 21 Nov 2014 13:57:40 +0000
From:	Mel Gorman <mgorman@...e.de>
To:	Linux Kernel <linux-kernel@...r.kernel.org>,
	Linux-MM <linux-mm@...ck.org>,
	LinuxPPC-dev <linuxppc-dev@...ts.ozlabs.org>
Cc:	Aneesh Kumar <aneesh.kumar@...ux.vnet.ibm.com>,
	Hugh Dickins <hughd@...gle.com>, Dave Jones <davej@...hat.com>,
	Rik van Riel <riel@...hat.com>,
	Ingo Molnar <mingo@...hat.com>,
	Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>
Subject: [PATCH 02/10] mm: Add p[te|md] protnone helpers for use by NUMA balancing

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

Signed-off-by: Mel Gorman <mgorman@...e.de>
Acked-by: Linus Torvalds <torvalds@...ux-foundation.org>
Acked-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
---
 arch/powerpc/include/asm/pgtable.h | 15 +++++++++++++++
 arch/x86/include/asm/pgtable.h     | 16 ++++++++++++++++
 include/asm-generic/pgtable.h      | 20 ++++++++++++++++++++
 3 files changed, 51 insertions(+)

diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
index a8805fe..490bd6d 100644
--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h
@@ -39,6 +39,21 @@ 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
+/*
+ * 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(pte_t pte)
+{
+	return (pte_val(pte) &
+		(_PAGE_PRESENT | _PAGE_USER)) == _PAGE_PRESENT;
+}
+
+static inline int pmd_protnone(pmd_t pmd)
+{
+	return pte_protnone(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 081d6f4..2e25780 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -502,6 +502,22 @@ 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(pte_t pte)
+{
+	return pte_flags(pte) & _PAGE_PROTNONE;
+}
+
+static inline int pmd_protnone(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 177d597..d497d08 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -688,6 +688,26 @@ 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 and is only ever set
+ * when the VMA is accessible. For PROT_NONE VMAs, the PTEs are not marked
+ * _PAGE_PROTNONE so by by default, implement the helper as "always no". It
+ * is the responsibility of the caller to distinguish between PROT_NONE
+ * protections and NUMA hinting fault protections.
+ */
+static inline int pte_protnone(pte_t pte)
+{
+	return 0;
+}
+
+static inline int pmd_protnone(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

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