On Fri, 2017-02-17 at 16:30 -0800, Omar Sandoval wrote: > Hi, everyone, > > As per $SUBJECT, I can cause a crash on v4.10-rc8, Jens' block/for > -next, > and Jan's bdi branch [1] by doing this: > > # lsscsi > [0:0:0:0] disk QEMU QEMU HARDDISK 2.5+ /dev/sda > # echo 0:0:0:0 > /sys/bus/scsi/drivers/sd/unbind > # echo 0:0:0:0 > /sys/bus/scsi/drivers/sd/bind > > The resulting trace looks like this: > > [ 19.347924] kobject (ffff8800791ea0b8): tried to init an > initialized object, something is seriously wrong. > [ 19.349781] CPU: 1 PID: 84 Comm: kworker/u8:1 Not tainted 4.10.0 > -rc7-00210-g53f39eeaa263 #34 > [ 19.350686] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), > BIOS 1.10.1-20161122_114906-anatol 04/01/2014 > [ 19.350920] Workqueue: events_unbound async_run_entry_fn > [ 19.350920] Call Trace: > [ 19.350920] dump_stack+0x63/0x83 > [ 19.350920] kobject_init+0x77/0x90 > [ 19.350920] blk_mq_register_dev+0x40/0x130 > [ 19.350920] blk_register_queue+0xb6/0x190 > [ 19.350920] device_add_disk+0x1ec/0x4b0 > [ 19.350920] sd_probe_async+0x10d/0x1c0 [sd_mod] > [ 19.350920] async_run_entry_fn+0x48/0x150 > [ 19.350920] process_one_work+0x1d0/0x480 > [ 19.350920] worker_thread+0x48/0x4e0 > [ 19.350920] kthread+0x101/0x140 > [ 19.350920] ? process_one_work+0x480/0x480 > [ 19.350920] ? kthread_create_on_node+0x60/0x60 > [ 19.350920] ret_from_fork+0x2c/0x40 > > Additionally, on v4.10-rc8, but not on block/for-next or Jan's > branch, > doing this: > > # echo 0:0:0:0 > /sys/bus/scsi/drivers/sd/unbind > # modprobe scsi_debug > > Causes this trace: > > [ 18.876096] ------------[ cut here ]------------ > [ 18.877057] WARNING: CPU: 1 PID: 90 at fs/sysfs/dir.c:31 > sysfs_warn_dup+0x62/0x80 > [ 18.878270] sysfs: cannot create duplicate filename > '/devices/virtual/bdi/8:0' > [ 18.879435] Modules linked in: scsi_debug btrfs xor raid6_pq > sd_mod virtio_scsi scsi_mod nvme nvme_core virtio_net > [ 18.881118] CPU: 1 PID: 90 Comm: kworker/u8:2 Not tainted 4.10.0 > -rc8 #34 > [ 18.882114] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), > BIOS 1.10.1-20161122_114906-anatol 04/01/2014 > [ 18.883872] Workqueue: events_unbound async_run_entry_fn > [ 18.884408] Call Trace: > [ 18.884408] dump_stack+0x63/0x83 > [ 18.884408] __warn+0xcb/0xf0 > [ 18.884408] warn_slowpath_fmt+0x5f/0x80 > [ 18.884408] ? kernfs_path_from_node+0x4f/0x60 > [ 18.884408] sysfs_warn_dup+0x62/0x80 > [ 18.884408] sysfs_create_dir_ns+0x77/0x90 > [ 18.884408] kobject_add_internal+0xbe/0x350 > [ 18.884408] kobject_add+0x75/0xd0 > [ 18.884408] device_add+0x121/0x680 > [ 18.884408] device_create_groups_vargs+0xe0/0xf0 > [ 18.884408] device_create_vargs+0x1c/0x20 > [ 18.884408] bdi_register+0x90/0x1b0 > [ 18.884408] ? sd_revalidate_disk+0x34a/0x1d00 [sd_mod] > [ 18.884408] bdi_register_owner+0x36/0x60 > [ 18.884408] device_add_disk+0x165/0x4a0 > [ 18.884408] ? update_autosuspend+0x51/0x60 > [ 18.884408] ? __pm_runtime_use_autosuspend+0x5c/0x70 > [ 18.884408] sd_probe_async+0x10d/0x1c0 [sd_mod] > [ 18.884408] async_run_entry_fn+0x4a/0x170 > [ 18.884408] process_one_work+0x165/0x430 > [ 18.884408] worker_thread+0x4e/0x490 > [ 18.884408] kthread+0x101/0x140 > [ 18.884408] ? process_one_work+0x430/0x430 > [ 18.884408] ? kthread_create_on_node+0x60/0x60 > [ 18.884408] ret_from_fork+0x2c/0x40 > [ 18.913090] ---[ end trace f43b051485c2a749 ]--- > > On all three kernels, it looks like the bdi sysfs entry hangs around > after the block device has already been removed: This seems to be related to a 0day test we got on the block tree, details here: http://marc.info/?t=148624068800001 I root caused the above to something not being released when it should be, so it looks like you have the same problem. It seems to be a recent commit in the block tree, so could you bisect it since you have a nice reproducer? Thanks, James
