PERFORCE change 116027 for review

[Oleksandr Tymoshenko]

http://perforce.freebsd.org/chv.cgi?CH=116027

Change 116027 by gonzo at gonzo_jeeves on 2007/03/17 14:09:44

	o Back to the wonderful world of prefaulting: by clearing write 
	    permissions in pmap_enter_quick we ensure that COW will be
	    performed.
	
	    Suggested by: alc

Affected files ...

.. //depot/projects/mips2/src/sys/mips/mips/pmap.c#22 edit

Differences ...

==== //depot/projects/mips2/src/sys/mips/mips/pmap.c#22 (text+ko) ====

@@ -1334,7 +1334,8 @@
 pmap_enter_quick(pmap_t pmap, vm_offset_t va, vm_page_t m, vm_prot_t prot)
 {
 
-	pmap_enter(pmap, va, m, prot, FALSE);
+	pmap_enter(pmap, va, m, prot & (VM_PROT_READ | VM_PROT_EXECUTE),
+	    FALSE);
 }
 
 /*
@@ -1663,11 +1664,14 @@
 boolean_t
 pmap_is_prefaultable(pmap_t pmap, vm_offset_t va)
 {
-	/* 
-	 * XXX: prefault causes bugs with COW, so let's stick
-	 * with all pages not eligible to prefault.
-	 */
-	return (FALSE);
+	pt_entry_t *pte;
+
+	pte = pmap_pte(pmap, va);
+
+	if ((pte != NULL) && pte_valid(pte))
+		return (FALSE);
+
+	return (TRUE);
 }
 
 /*