crush: use breadth-first search for indep mode

Reflects ceph.git commit 86e978036a4ecbac4c875e7c00f6c5bbe37282d3.

Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>
diff --git a/include/linux/crush/crush.h b/include/linux/crush/crush.h
index 3d6a129..4023b1b 100644
--- a/include/linux/crush/crush.h
+++ b/include/linux/crush/crush.h
@@ -22,7 +22,8 @@
 #define CRUSH_MAX_DEPTH 10  /* max crush hierarchy depth */
 
 
-#define CRUSH_ITEM_UNDEF  0x7fffffff  /* undefined result */
+#define CRUSH_ITEM_UNDEF  0x7ffffffe  /* undefined result (internal use only) */
+#define CRUSH_ITEM_NONE   0x7fffffff  /* no result */
 
 /*
  * CRUSH uses user-defined "rules" to describe how inputs should be