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From:   Martin Schwidefsky <schwidefsky@de.ibm.com>
To:     Li Wang <liwang@redhat.com>, Guenter Roeck <linux@roeck-us.net>,
        Janosch Frank <frankja@linux.vnet.ibm.com>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Heiko Carstens <heiko.carstens@de.ibm.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Linux-MM <linux-mm@kvack.org>,
        Martin Schwidefsky <schwidefsky@de.ibm.com>
Subject: [PATCH 1/3] mm: introduce mm_[p4d|pud|pmd]_folded
Date:   Mon, 15 Oct 2018 18:42:37 +0200
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Add three architecture overrideable function to test if the
p4d, pud, or pmd layer of a page table is folded or not.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
---
 include/linux/mm.h | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 0416a7204be3..d1029972541c 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -105,6 +105,46 @@ extern int mmap_rnd_compat_bits __read_mostly;
 #define mm_zero_struct_page(pp)  ((void)memset((pp), 0, sizeof(struct page)))
 #endif
 
+/*
+ * On some architectures it depends on the mm if the p4d/pud or pmd
+ * layer of the page table hierarchy is folded or not.
+ */
+#ifndef mm_p4d_folded
+#define mm_p4d_folded(mm) mm_p4d_folded(mm)
+static inline bool mm_p4d_folded(struct mm_struct *mm)
+{
+#ifdef __PAGETABLE_P4D_FOLDED
+	return 1;
+#else
+	return 0;
+#endif
+}
+#endif
+
+#ifndef mm_pud_folded
+#define mm_pud_folded(mm) mm_pud_folded(mm)
+static inline bool mm_pud_folded(struct mm_struct *mm)
+{
+#ifdef __PAGETABLE_PUD_FOLDED
+	return 1;
+#else
+	return 0;
+#endif
+}
+#endif
+
+#ifndef mm_pmd_folded
+#define mm_pmd_folded(mm) mm_pmd_folded(mm)
+static inline bool mm_pmd_folded(struct mm_struct *mm)
+{
+#ifdef __PAGETABLE_PMD_FOLDED
+	return 1;
+#else
+	return 0;
+#endif
+}
+#endif
+
 /*
  * Default maximum number of active map areas, this limits the number of vmas
  * per mm struct. Users can overwrite this number by sysctl but there is a
-- 
2.16.4