diff --git a/sys/vm/vm_page.c b/sys/vm/vm_page.c
--- a/sys/vm/vm_page.c
+++ b/sys/vm/vm_page.c
@@ -775,12 +775,12 @@
 		 * phys_avail's ranges to the free lists.
 		 */
 		for (i = 0; phys_avail[i + 1] != 0; i += 2) {
-			if (seg->end < phys_avail[i] ||
+			if (seg->end <= phys_avail[i] ||
 			    seg->start >= phys_avail[i + 1])
 				continue;
 
 			startp = MAX(seg->start, phys_avail[i]);
-			m = seg->first_page + atop(seg->start - startp);
+			m = seg->first_page + atop(startp - seg->start);
 			endp = MIN(seg->end, phys_avail[i + 1]);
 			pagecount = (u_long)atop(endp - startp);
 			if (pagecount == 0)