On Tue, Dec 27, 2022 at 08:55:01PM +0800, Yu Kuai wrote: > From: Yu Kuai <yukuai3@xxxxxxxxxx> > > iocost requires that child iocg must exit before parent iocg, otherwise > kernel might crash in ioc_timer_fn(). However, currently iocg is exited > in pd_free_fn(), which can't guarantee such order: > > 1) remove cgroup can concurrent with deactivate policy; > 2) blkg_free() triggered by remove cgroup is asynchronously, remove > child cgroup can concurrent with remove parent cgroup; > > Fix the problem by add refcounting for iocg, and child iocg will grab > reference of parent iocg, so that parent iocg will wait for all child > iocg to be exited. Wouldn't it be better to do this refcnting in the blk-cgroup core code rather than in blk-iocost? Thanks. -- tejun
