Merge branch 'fixes' into next

[linux-2.6-block.git] / arch / powerpc / include / asm / book3s / 64 / pgtable.h

diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
index ac6eb9816b649264c95934caf9f8710343bca915..5faceeefd9f999fe6ef4c70df5d9bdedbac68ee2 100644 (file)
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -884,6 +884,23 @@ static inline int pmd_present(pmd_t pmd)
        return false;
 }
 
+static inline int pmd_is_serializing(pmd_t pmd)
+{
+       /*
+        * If the pmd is undergoing a split, the _PAGE_PRESENT bit is clear
+        * and _PAGE_INVALID is set (see pmd_present, pmdp_invalidate).
+        *
+        * This condition may also occur when flushing a pmd while flushing
+        * it (see ptep_modify_prot_start), so callers must ensure this
+        * case is fine as well.
+        */
+       if ((pmd_raw(pmd) & cpu_to_be64(_PAGE_PRESENT | _PAGE_INVALID)) ==
+                                               cpu_to_be64(_PAGE_INVALID))
+               return true;
+
+       return false;
+}
+
 static inline int pmd_bad(pmd_t pmd)
 {
        if (radix_enabled())
@@ -1100,6 +1117,19 @@ static inline int pmd_protnone(pmd_t pmd)
 #define pmd_access_permitted pmd_access_permitted
 static inline bool pmd_access_permitted(pmd_t pmd, bool write)
 {
+       /*
+        * pmdp_invalidate sets this combination (which is not caught by
+        * !pte_present() check in pte_access_permitted), to prevent
+        * lock-free lookups, as part of the serialize_against_pte_lookup()
+        * synchronisation.
+        *
+        * This also catches the case where the PTE's hardware PRESENT bit is
+        * cleared while TLB is flushed, which is suboptimal but should not
+        * be frequent.
+        */
+       if (pmd_is_serializing(pmd))
+               return false;
+
        return pte_access_permitted(pmd_pte(pmd), write);
 }