Hello, On Wed, Nov 25, 2020 at 08:49:19PM +0800, yukuai (C) wrote: > > You can't continue iteration after dropping both locks. You'd have to jump > > out of loop and start list_for_each_entry_safe() again. > > Thanks for your review, it's right. On the other hand > blkcg_activate_policy() and blkcg_deactivate_policy() might have the > same issue. My idea is that inserting a bookmark to the list, and > restard from here.
For destruction, as we're destroying the list anyway, we don't need to insert bookmark and start over from the beginning. For [de]activate policy, we might need something fancier or change locking so that we can sleep while iterating. However, policy [de]activations are a lot less of a problem as they aren't operations which can happen commonly. > By the way, I found that blk_throtl_update_limit_valid() is called from > throtl_pd_offline(). If CONFIG_BLK_DEV_THROTTLING_LOW is off, lower > limit will always be zero, therefor a lot of time will be wasted to > iterate descendants to find a nonzero lower limit. > > Do you think it's ok to do such modification: Yeah, sure. Looks fine to me. Thanks. -- tejun
