On Thu, Dec 01, 2022 at 10:12:13AM +0800, Yu Kuai wrote: > 1) By mentioning that "del_gendisk() is quiescing the queue", do you > suggest to add rcu_read_lock()? This seems wrong because blk_iocost_init > requires memory allocation. Quiescing uses SRCU so that should be fine but I'm not sure whether this is the right one to piggyback on. Jens should have a better idea. Thanks. -- tejun