if( bt_lockpage (bt, page_no, BtLockParent) )
return bt->err;
+ if( bt_unlockpage (bt, page_no, BtLockWrite) )
+ return bt->err;
+
// insert new fence for reformulated left block
if( bt_insertkey (bt, fencekey+1, *fencekey, lvl+1, page_no, time(NULL)) )