[PATCH 3.18 28/47] MIPS: Ensure pmd_present() returns false after pmd_mknotpresent()

3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Huacai Chen <[email protected]>

commit 92aa0718c9fa5160ad2f0e7b5bffb52f1ea1e51a upstream.

This patch is borrowed from ARM64 to ensure pmd_present() returns false
after pmd_mknotpresent(). This is needed for THP.

References: 5bb1cc0ff9a6 ("arm64: Ensure pmd_present() returns false after pmd_mknotpresent()")
Reviewed-by: James Hogan <[email protected]>
Signed-off-by: Huacai Chen <[email protected]>
Signed-off-by: Paul Burton <[email protected]>
Patchwork: https://patchwork.linux-mips.org/patch/21135/
Cc: Ralf Baechle <[email protected]>
Cc: James Hogan <[email protected]>
Cc: Steven J . Hill <[email protected]>
Cc: [email protected]
Cc: Fuxin Zhang <[email protected]>
Cc: Zhangjin Wu <[email protected]>
Cc: <[email protected]> # 3.8+
Signed-off-by: Greg Kroah-Hartman <[email protected]>

---
 arch/mips/include/asm/pgtable-64.h |    5 +++++
 1 file changed, 5 insertions(+)

--- a/arch/mips/include/asm/pgtable-64.h
+++ b/arch/mips/include/asm/pgtable-64.h
@@ -189,6 +189,11 @@ static inline int pmd_bad(pmd_t pmd)
 
 static inline int pmd_present(pmd_t pmd)
 {
+#ifdef CONFIG_MIPS_HUGE_TLB_SUPPORT
+	if (unlikely(pmd_val(pmd) & _PAGE_HUGE))
+		return pmd_val(pmd) & _PAGE_PRESENT;
+#endif
+
 	return pmd_val(pmd) != (unsigned long) invalid_pte_table;
 }