Hello Jens, The three patches in this series are what I came up with after having analyzed a lockdep complaint triggered by blk_unregister_queue. Please consider these patches for kernel v4.16. Thanks, Bart. Bart Van Assche (3): block: Unexport elv_register_queue() and elv_unregister_queue() block: Document scheduler change code locking requirements block: Protect less code with sysfs_lock in blk_{un,}register_queue() block/blk-sysfs.c | 13 ++++--------- block/blk.h | 3 +++ block/elevator.c | 10 ++++++++-- include/linux/elevator.h | 2 -- 4 files changed, 15 insertions(+), 13 deletions(-) -- 2.15.1