[PATCH] thp: make pmd_present more accurate

[Andrea Arcangeli]

In many places !pmd_present has been converted to pmd_none. For pmds
that's equivalent and pmd_none is quicker so using pmd_none is
better.

However we should provide a more accurate pmd_present too. This will
avoid the risk of code thinking the pmd is non present because it's
under __split_huge_page_map, see the pmd_mknotpresent there and the
comment above it.

Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
---
 arch/x86/include/asm/pgtable.h |    8 +++++++-
 1 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 49afb3f..b49e70d 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -415,7 +415,13 @@ static inline int pte_hidden(pte_t pte)
 
 static inline int pmd_present(pmd_t pmd)
 {
-	return pmd_flags(pmd) & _PAGE_PRESENT;
+	/*
+	 * Checking for _PAGE_PSE is needed too because
+	 * split_huge_page will temporarily clear the present bit (but
+	 * the _PAGE_PSE flag will remain set at all times while the
+	 * _PAGE_PRESENT bit is clear).
+	 */
+	return pmd_flags(pmd) & (_PAGE_PRESENT | _PAGE_PROTNONE | _PAGE_PSE);
 }
 
 static inline int pmd_none(pmd_t pmd)


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