Don't change PG until it runs out of paths.
--- diff/drivers/md/dm-mpath.c	2005-01-12 19:14:21.000000000 +0000
+++ source/drivers/md/dm-mpath.c	2005-01-12 19:14:33.000000000 +0000
@@ -211,16 +211,41 @@
 	}
 }
 
+static struct pgpath *__choose_path_in_pg(struct multipath *m,
+					  struct priority_group *pg)
+{
+	struct path *path;
+	struct pgpath *pgpath;
+
+	path = pg->ps.type->select_path(&pg->ps, &m->current_count);
+	if (!path) {
+		return NULL;
+	}
+
+	pgpath = path_to_pgpath(path);
+
+	if (m->current_pg != pg)
+		__switch_pg(m, pgpath);
+
+	return pgpath;
+}
+
 static void __choose_pgpath(struct multipath *m)
 {
 	struct priority_group *pg;
 	struct pgpath *pgpath = NULL;
-	struct path *path;
 	unsigned bypassed = 1;
 
 	if (!m->nr_valid_paths)
 		goto out;
 
+	/* Don't change PG until it has no remaining paths */
+	if (m->current_pg) {
+		pgpath = __choose_path_in_pg(m, m->current_pg);
+		if (pgpath)
+			goto out;
+	}
+
 	/*
 	 * Loop through priority groups until we find a valid path.
 	 * First time we skip PGs marked 'bypassed'.
@@ -230,17 +255,9 @@
 		list_for_each_entry (pg, &m->priority_groups, list) {
 			if (pg->bypassed == bypassed)
 				continue;
-			path = pg->ps.type->select_path(&pg->ps,
-							&m->current_count);
-			if (!path)
-				continue;
-
-			pgpath = path_to_pgpath(path);
-
-			if (m->current_pg != pg)
-				__switch_pg(m, pgpath);
-
-			goto out;
+			pgpath = __choose_path_in_pg(m, pg);
+			if (pgpath)
+				goto out;
 		}
 	} while (bypassed--);