BP_fnode_parent
anode->btree.flags |= BP_fnode_parent;
anode->btree.flags |= BP_fnode_parent;
anode->btree.flags &= ~BP_fnode_parent;
anode->btree.flags |= BP_fnode_parent;
ranode->btree.flags |= BP_fnode_parent;
unode->btree.flags &= ~BP_fnode_parent;
return bp->flags & BP_fnode_parent;