On Mon, Dec 16, 2013 at 11:40:42AM +0100, Michal Hocko wrote: > > How would this work? The task which pushed the memory to the swap is > > still alive (living in a different group) and the swap will be there > > after the last reference to css as well. > > Or did you mean to get css reference in swap_cgroup_record and release > it in __mem_cgroup_try_charge_swapin? > > That would prevent the warning (assuming idr_remove would move to > css_free[1]) but I am not sure this is the right thing to do. memsw charges > will be accounted to the parent already (assuming there is one) without > anybody to uncharge them because all uncharges would fallback to the > root memcg after css_offline. > > Hugh's approach seems much better. Hmmm... I think it's reasonable for css's to expect cgrp->id to not be recycled before all css refs are gone. If Hugh's patches are something desriable independent of cgrp->id issues, great, but, if not, let's first try to get it right from cgroup core. Is it enough for css_from_id() to return NULL after offline until all refs are gone? That should be an easy fix. Thanks. -- tejun -- 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>