On 06/28/2012 08:55 AM, Andrea Arcangeli wrote:

  static inline int pte_file(pte_t pte)
  {
-	return pte_flags(pte)&  _PAGE_FILE;
+	return (pte_flags(pte)&  _PAGE_FILE) == _PAGE_FILE;
  }

Wait, why is this change made?  Surely _PAGE_FILE is just
one single bit and this change is not useful?

If there is a reason for this change, please document it.

Somewhat subtle. Better documentation in patch 5 will
help explain this.

+#ifdef CONFIG_AUTONUMA
+static inline int pte_numa(pte_t pte)
+{
+	return (pte_flags(pte)&
+		(_PAGE_NUMA_PTE|_PAGE_PRESENT)) == _PAGE_NUMA_PTE;
+}
+
+static inline int pmd_numa(pmd_t pmd)
+{
+	return (pmd_flags(pmd)&
+		(_PAGE_NUMA_PMD|_PAGE_PRESENT)) == _PAGE_NUMA_PMD;
+}
+#endif

These could use a little explanation of how _PAGE_NUMA_* is
used and what the flags mean.

+static inline pte_t pte_mknotnuma(pte_t pte)
+{
+	pte = pte_clear_flags(pte, _PAGE_NUMA_PTE);
+	return pte_set_flags(pte, _PAGE_PRESENT|_PAGE_ACCESSED);
+}
+
+static inline pmd_t pmd_mknotnuma(pmd_t pmd)
+{
+	pmd = pmd_clear_flags(pmd, _PAGE_NUMA_PMD);
+	return pmd_set_flags(pmd, _PAGE_PRESENT|_PAGE_ACCESSED);
+}
+
+static inline pte_t pte_mknuma(pte_t pte)
+{
+	pte = pte_set_flags(pte, _PAGE_NUMA_PTE);
+	return pte_clear_flags(pte, _PAGE_PRESENT);
+}
+
+static inline pmd_t pmd_mknuma(pmd_t pmd)
+{
+	pmd = pmd_set_flags(pmd, _PAGE_NUMA_PMD);
+	return pmd_clear_flags(pmd, _PAGE_PRESENT);
  }

These functions could use some explanation, too.

Why do the top ones set _PAGE_ACCESSED, while the bottom ones
leave _PAGE_ACCESSED alone?

I can guess the answer, but it should be documented so it is
also clear to people with less experience in the VM.

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