Hi! On Thu 23-12-21 12:25:07, Christoph Hellwig wrote: > this is a 3rd approach to fix the loop autoclean delay. Instead of > working around the workqueue lockdep issues this switches the loop > driver to use a global workqueue and thus avoids the destroy_workqueue > call under disk->open_mutex entirely. Hum, I have nothing against this but I'm somewhat wondering: Lockdep was originally complaining because it somehow managed to find a write whose completion was indirectly dependent on disk->open_mutex and destroy_workqueue() could wait for such write to complete under disk->open_mutex. Now your patch will fix this lockdep complaint but we still would wait for the write to complete through blk_mq_freeze_queue() (just lockdep is not clever enough to detect this). So IHMO if there was a deadlock before, it will be still there with your changes. Now I'm not 100% sure the deadlock lockdep was complaining about is real in the first place because it involved some writes to proc files (taking some locks) and hibernation mutex and whatnot. But it is true that writing to a backing file will grab fs freeze protection and that can bring with it all sorts of interesting dependencies. Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
