On Fri, Jun 29, 2012 at 11:02:41AM -0400, Rik van Riel wrote:

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

quoted

  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.

I splitted it off to a separated patch with proper commit log here.

http://git.kernel.org/?p=linux/kernel/git/andrea/aa.git;a=commitdiff;h=7b2292c7ab86205f3d630533dc9987449fea6347

I haven't checked if it spawns the same warning without the patchset
applied, but I need the build not to show warnings, so while it may be
irrelevant warning for upstream, I don't like to have warnings.

quoted

  static inline int pte_hidden(pte_t pte)

@@ -415,7 +417,46 @@ static inline int pte_hidden(pte_t pte)

  static inline int pmd_present(pmd_t pmd)
  {
-	return pmd_flags(pmd)&  _PAGE_PRESENT;
+	return pmd_flags(pmd)&  (_PAGE_PRESENT | _PAGE_PROTNONE |
+				 _PAGE_NUMA_PMD);
+}

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

It's as subtle as PROTNONE but I added more explanation below as well
as in patch 5.

quoted

+#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.

Added:

http://git.kernel.org/?p=linux/kernel/git/andrea/aa.git;a=commitdiff;h=0e6537227de32c40bbf0a5bc6b11d27ba5779e68

quoted

+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.

Added too in prev link.

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