On Tue, Apr 22, 2014 at 5:47 PM, Michal Hocko <mhocko@xxxxxxx> wrote: > What about > 3. last_visited == last_node in the tree > > __mem_cgroup_iter_next returns NULL and the iterator would return > without visiting anything. Hi, Michal, yep, if 3 last_visited == last_node, then this means we have done a round-trip, thus __mem_cgroup_iter_next returns NULL, in turn mem_cgroup_iter() return NULL. This is what comments above mem_cgroup_iter() says: >Returns references to children of the hierarchy below @root, or >* @root itself, or %NULL after a full round-trip. Actually, this condition could be reduced to conditon 2.1 Thanks, Jianyu Zhan -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>