Hello Jens, Several block drivers call alloc_disk() followed by put_disk() if something fails before device_add_disk() is called without calling blk_cleanup_queue(). Make sure that also for this scenario a request queue is dissociated from the cgroup controller. This patch avoids that loading the parport_pc, paride and pf drivers trigger a kernel crash. Since this patch series fixes a regression, please consider these patches for kernel v4.19. Thanks, Bart. Changes between v4 and v5: - Instead of using #ifdef CONFIG_CGROUP / #endif, introduced a new function in the cgroups code. Changes between v3 and v4: - Added "Cc: stable" tags. Changes between v2 and v3: - Avoid code duplication by introducing a new helper function. Changes between v1 and v2: - Fixed the build for CONFIG_BLK_CGROUP=n. Bart Van Assche (3): blkcg: Introduce blkg_root_lookup() block: Introduce blk_exit_queue() block: Ensure that a request queue is dissociated from the cgroup controller block/blk-core.c | 54 +++++++++++++++++++++----------------- block/blk-sysfs.c | 15 +++++++++++ block/blk.h | 1 + include/linux/blk-cgroup.h | 18 +++++++++++++ 4 files changed, 64 insertions(+), 24 deletions(-) -- 2.18.0