Index: vm_reserv.c
===================================================================
--- vm_reserv.c
+++ vm_reserv.c
@@ -168,6 +168,27 @@
 }
 
 /*
+ * Are all bits in the population map range clear?
+ */
+static __inline boolean_t
+popmap_range_is_clear(popmap_t popmap[], int start, int count)
+{
+	popmap_t mask;
+	int end, i;
+
+	end = start + count;
+	for (i = start / NBPOPMAP, mask = -1UL << (start % NBPOPMAP);
+	     i < end / NBPOPMAP && (mask & popmap[i]) == 0;
+	     i++, mask = -1UL);
+	if (i < end / NBPOPMAP)
+		return (false);
+	if (end % NBPOPMAP == 0)
+		return (true);
+	mask &= ~(-1UL << (end % NBPOPMAP));
+	return ((mask & popmap[i]) == 0);
+}
+
+/*
  * The reservation structure
  *
  * A reservation structure is constructed whenever a large physical page is
@@ -646,11 +667,8 @@
 	    ((pa ^ (pa + size - 1)) & ~(boundary - 1)) != 0)
 		goto out;
 	/* Handle vm_page_rename(m, new_object, ...). */
-	for (i = 0; i < npages; i++) {
-		if (popmap_is_set(rv->popmap, index + i))
-			goto out;
-	}
-	if (!vm_domain_allocate(vmd, req, npages))
+	if (!popmap_range_is_clear(rv->popmap, index, npages) ||
+	    !vm_domain_allocate(vmd, req, npages))
 		goto out;
 	for (i = 0; i < npages; i++)
 		vm_reserv_populate(rv, index + i);