From: Sage Weil <sage@inktank.com>
Date: Wed, 20 Mar 2013 14:59:26 +0000 (-0700)
Subject: crush: prevent formation of a loop
X-Git-Tag: v0.62~177^2~10
X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=fe4e86c6acd8424da625a0eb1b9171db44234201;p=ceph.git

crush: prevent formation of a loop

If we are adding an item, ensure it cannot form a loop in the tree/map/
DAG.

Signed-off-by: Sage Weil <sage@inktank.com>
---

diff --git a/src/crush/CrushWrapper.cc b/src/crush/CrushWrapper.cc
index 766fad6e0afe..bb2390122361 100644
--- a/src/crush/CrushWrapper.cc
+++ b/src/crush/CrushWrapper.cc
@@ -305,6 +305,13 @@ int CrushWrapper::insert_item(CephContext *cct, int item, float weight, string n
 	return -EEXIST;
       }
     
+    // are we forming a loop?
+    if (subtree_contains(cur, b->id)) {
+      ldout(cct, 1) << "insert_item " << cur << " already contains " << b->id
+		    << "; cannot form loop" << dendl;
+      return -ELOOP;
+    }
+
     ldout(cct, 5) << "insert_item adding " << cur << " weight " << weight
 		  << " to bucket " << id << dendl;
     int r = crush_bucket_add_item(b, cur, 0);