On Fri, Dec 10, 2021 at 04:31:43PM +0800, Yu Kuai <yukuai3@xxxxxxxxxx> wrote: > + * queue_lock is held, rcu lock is not needed here. > + */ > + blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg) > + tg_drain_bios(&blkg_to_tg(blkg)->service_queue); FTR, I acknowledge this can work due to RCU peculiarities, however, I don't understand why is it preferred against more robust explict rcu_read_lock(). (All in all, this isn't a deal breaker and I'm not confident evaluating the rest of the patch.) Michal
