[cgutman] 54993: [NTOSKRNL] - Only return the dirty bit if the PTE is actually valid - Avoid an unneeded TLB flush when setting the dirty bit

Author: cgutman
Date: Tue Jan 17 18:06:53 2012
New Revision: 54993

URL: http://svn.reactos.org/svn/reactos?rev=54993&view=rev
Log:
[NTOSKRNL]
- Only return the dirty bit if the PTE is actually valid
- Avoid an unneeded TLB flush when setting the dirty bit

Modified:
    trunk/reactos/ntoskrnl/mm/i386/page.c

Modified: trunk/reactos/ntoskrnl/mm/i386/page.c
URL:
http://svn.reactos.org/svn/reactos/trunk/reactos/ntoskrnl/mm/i386/page.c?re…
==============================================================================
--- trunk/reactos/ntoskrnl/mm/i386/page.c [iso-8859-1] (original)
+++ trunk/reactos/ntoskrnl/mm/i386/page.c [iso-8859-1] Tue Jan 17 18:06:53 2012
@@ -539,7 +539,7 @@
      */
     if (WasDirty != NULL)
     {
-        *WasDirty = Pte & PA_DIRTY ? TRUE : FALSE;
+        *WasDirty = ((Pte & PA_DIRTY) && (Pte & PA_PRESENT)) ? TRUE :
FALSE;
     }
     if (Page != NULL)
     {
@@ -687,12 +687,10 @@
     {
         KeBugCheck(MEMORY_MANAGEMENT);
     }
-    else if (!(Pte & PA_DIRTY))
-    {
-        MiFlushTlb(Pt, Address);
-    }
-    else
-    {
+    else
+    {
+        /* The processor will never clear this bit itself, therefore
+         * we do not need to flush the TLB here when setting it */
         MmUnmapPageTable(Pt);
     }
 }