The mix of blk-sysfs and block in the subject lines is a bit odd. Maybe just use the block prefix everywhere? Also q->sysfs_lock is almost unused now and we should probably look into killing it entirely. blk_mq_hw_sysfs_show takes it around the ->show methods which looks pretty useless. The debugfs code takes it for a few undocumented things, which are worth digging into and if needed split into a separate lock. The concurrent ranges code takes it - I think that is because it does register a complex sysfs hierarchy from something that could race with add_disk / del_gendisk. Damien, can you help with your thoughts? (sd.c also has a comment reference it and the removed sysfs_dir_lock which needs fixing anyway). blk_register_queue still takes it around a pretty random range of code including nesting with other locks. I can't see what it protects against, but it could use a careful look. blk_unregister_queue takes it just to clear QUEUE_FLAG_REGISTERED, which by definition can't really protect against anything. Also the sysfs_lock in the elevator_queue should probably go away or be replaced with the new elevator_lock for the non-show/store path for the same reasons as outlined in this series.
