Changed COW to reuse current page if it is the last reference.

[tpg/acess2.git] / Kernel / arch / x86 / mm_virt.c

diff --git a/Kernel/arch/x86/mm_virt.c b/Kernel/arch/x86/mm_virt.c
index 25da743..8fe1b4a 100644 (file)
--- a/Kernel/arch/x86/mm_virt.c
+++ b/Kernel/arch/x86/mm_virt.c
@@ -105,10 +105,18 @@ void MM_PageFault(Uint Addr, Uint ErrorCode, tRegs *Regs)
         && gaPageTable[Addr>>12] & PF_COW )
        {
                tPAddr  paddr;
-               paddr = MM_DuplicatePage( Addr );
-               MM_DerefPhys( gaPageTable[Addr>>12] & ~0xFFF );
-               gaPageTable[Addr>>12] &= PF_USER;
-               gaPageTable[Addr>>12] |= paddr|PF_PRESENT|PF_WRITE;
+               if(MM_GetRefCount( gaPageTable[Addr>>12] & ~0xFFF ) == 0)
+               {
+                       gaPageTable[Addr>>12] &= ~PF_COW;
+                       gaPageTable[Addr>>12] |= PF_PRESENT|PF_WRITE;
+               }
+               else
+               {
+                       paddr = MM_DuplicatePage( Addr );
+                       MM_DerefPhys( gaPageTable[Addr>>12] & ~0xFFF );
+                       gaPageTable[Addr>>12] &= PF_USER;
+                       gaPageTable[Addr>>12] |= paddr|PF_PRESENT|PF_WRITE;
+               }
                INVLPG( Addr & ~0xFFF );
                //LEAVE('-')
                return;