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 766fad6e0afe32e9dc8a8da6992bc88ee673cd36..bb23901223612cb4b2a53c3dbe39ec31c5b0bd59 100644 (file)
--- 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);