Index: sys/vm/vm_pageout.c
===================================================================
--- sys/vm/vm_pageout.c
+++ sys/vm/vm_pageout.c
@@ -339,6 +339,25 @@
 	return (false);
 }
 
+/*
+ * We can cluster only if the page is not clean, busy, or held, and the page is
+ * in the laundry queue.
+ */
+static bool
+vm_pageout_flushable(vm_page_t m)
+{
+	if (vm_page_tryxbusy(m) == 0)
+		return (false);
+	if (!vm_page_wired(m)) {
+		vm_page_test_dirty(m);
+		if (m->dirty != 0 && vm_page_in_laundry(m) &&
+		    vm_page_try_remove_write(m))
+			return (true);
+	}
+	vm_page_xunbusy(m);
+	return (false);
+}
+
 /*
  * Scan for pages at adjacent offsets within the given page's object that are
  * eligible for laundering, form a cluster of these pages and the given page,
@@ -348,7 +367,7 @@
 vm_pageout_cluster(vm_page_t m)
 {
 	vm_object_t object;
-	vm_page_t mc[2 * vm_pageout_page_count - 1], p, pb, ps;
+	vm_page_t mc[2 * vm_pageout_page_count - 1];
 	vm_pindex_t pindex;
 	int ib, is, page_base, pageout_count;
 
@@ -360,14 +379,11 @@
 
 	pageout_count = 1;
 	page_base = nitems(mc) / 2;
-	mc[page_base] = pb = ps = m;
+	mc[page_base] = m;
 	ib = 1;
 	is = 1;
 
 	/*
-	 * We can cluster only if the page is not clean, busy, or held, and
-	 * the page is in the laundry queue.
-	 *
 	 * During heavy mmap/modification loads the pageout
 	 * daemon can really fragment the underlying file
 	 * due to flushing pages out of order and not trying to
@@ -377,33 +393,19 @@
 	 * forward scan if room remains.
 	 */
 more:
+	m = mc[page_base];
 	while (ib != 0 && pageout_count < vm_pageout_page_count) {
 		if (ib > pindex) {
+			/* Don't walk backward from pindex 0. */
 			ib = 0;
 			break;
 		}
-		if ((p = vm_page_prev(pb)) == NULL ||
-		    vm_page_tryxbusy(p) == 0) {
-			ib = 0;
-			break;
-		}
-		if (vm_page_wired(p)) {
+		m = vm_page_prev(m);
+		if (m == NULL || !vm_pageout_flushable(m)) {
 			ib = 0;
-			vm_page_xunbusy(p);
 			break;
 		}
-		vm_page_test_dirty(p);
-		if (p->dirty == 0) {
-			ib = 0;
-			vm_page_xunbusy(p);
-			break;
-		}
-		if (!vm_page_in_laundry(p) || !vm_page_try_remove_write(p)) {
-			vm_page_xunbusy(p);
-			ib = 0;
-			break;
-		}
-		mc[--page_base] = pb = p;
+		mc[--page_base] = m;
 		++pageout_count;
 		++ib;
 
@@ -414,25 +416,13 @@
 		if ((pindex - (ib - 1)) % vm_pageout_page_count == 0)
 			break;
 	}
+	m = mc[page_base + pageout_count - 1];
 	while (pageout_count < vm_pageout_page_count && 
 	    pindex + is < object->size) {
-		if ((p = vm_page_next(ps)) == NULL ||
-		    vm_page_tryxbusy(p) == 0)
+		m = vm_page_next(m);
+		if (m == NULL || !vm_pageout_flushable(m))
 			break;
-		if (vm_page_wired(p)) {
-			vm_page_xunbusy(p);
-			break;
-		}
-		vm_page_test_dirty(p);
-		if (p->dirty == 0) {
-			vm_page_xunbusy(p);
-			break;
-		}
-		if (!vm_page_in_laundry(p) || !vm_page_try_remove_write(p)) {
-			vm_page_xunbusy(p);
-			break;
-		}
-		mc[page_base + pageout_count] = ps = p;
+		mc[page_base + pageout_count] = m;
 		++pageout_count;
 		++is;
 	}