syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.6.3764/19710 is trying to acquire lock:
ffffffff8e245220 (fs_reclaim){+.+.}-{0:0}, at: might_alloc include/linux/sched/mm.h:318 [inline]
ffffffff8e245220 (fs_reclaim){+.+.}-{0:0}, at: slab_pre_alloc_hook mm/slub.c:4898 [inline]
ffffffff8e245220 (fs_reclaim){+.+.}-{0:0}, at: slab_alloc_node mm/slub.c:5222 [inline]
ffffffff8e245220 (fs_reclaim){+.+.}-{0:0}, at: kmem_cache_alloc_lru_noprof+0x4a/0x6d0 mm/slub.c:5265

but task is already holding lock:
ffff888148eab8a0 (&sb->s_type->i_mutex_key#3){++++}-{4:4}, at: inode_lock include/linux/fs.h:980 [inline]
ffff888148eab8a0 (&sb->s_type->i_mutex_key#3){++++}-{4:4}, at: simple_start_creating+0x98/0x1e0 fs/libfs.c:2298

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #9 (&sb->s_type->i_mutex_key#3){++++}-{4:4}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
       down_write+0x96/0x1f0 kernel/locking/rwsem.c:1590
       inode_lock include/linux/fs.h:980 [inline]
       simple_start_creating+0x98/0x1e0 fs/libfs.c:2298
       debugfs_start_creating+0x10f/0x180 fs/debugfs/inode.c:397
       __debugfs_create_file+0x79/0x4f0 fs/debugfs/inode.c:432
       debugfs_create_file_full+0x3f/0x60 fs/debugfs/inode.c:469
       relay_create_buf_file kernel/relay.c:365 [inline]
       relay_open_buf+0x56e/0xe50 kernel/relay.c:394
       relay_open+0x427/0x920 kernel/relay.c:518
       do_blk_trace_setup+0x561/0x980 kernel/trace/blktrace.c:572
       blk_trace_setup+0x116/0x1f0 kernel/trace/blktrace.c:614
       blk_trace_ioctl+0x181/0x430 kernel/trace/blktrace.c:712
       blkdev_ioctl+0x41d/0x6d0 block/ioctl.c:694
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:597 [inline]
       __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #8 (relay_channels_mutex){+.+.}-{4:4}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
       __mutex_lock_common kernel/locking/mutex.c:598 [inline]
       __mutex_lock+0x187/0x1350 kernel/locking/mutex.c:760
       relay_prepare_cpu+0x29/0x200 kernel/relay.c:443
       cpuhp_invoke_callback+0x445/0x860 kernel/cpu.c:195
       __cpuhp_invoke_callback_range kernel/cpu.c:968 [inline]
       cpuhp_invoke_callback_range kernel/cpu.c:992 [inline]
       cpuhp_up_callbacks kernel/cpu.c:1023 [inline]
       _cpu_up+0x2c9/0x580 kernel/cpu.c:1685
       cpu_up+0x1d2/0x220 kernel/cpu.c:1717
       cpuhp_bringup_mask+0xb2/0x1a0 kernel/cpu.c:1783
       cpuhp_bringup_cpus_parallel+0x109/0x120 kernel/cpu.c:1873
       bringup_nonboot_cpus+0x17/0x30 kernel/cpu.c:1887
       smp_init+0x32/0x110 kernel/smp.c:1001
       kernel_init_freeable+0x316/0x4b0 init/main.c:1585
       kernel_init+0x1d/0x1d0 init/main.c:1483
       ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #7 (cpu_hotplug_lock){++++}-{0:0}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
       percpu_down_read_internal include/linux/percpu-rwsem.h:53 [inline]
       percpu_down_read include/linux/percpu-rwsem.h:77 [inline]
       cpus_read_lock+0x42/0x160 kernel/cpu.c:491
       static_key_slow_inc+0x12/0x30 kernel/jump_label.c:190
       tcp_md5_do_add+0x21f/0x3a0 net/ipv4/tcp_ipv4.c:1436
       tcp_v4_parse_md5_keys+0x412/0x600 net/ipv4/tcp_ipv4.c:1577
       do_tcp_setsockopt+0x11dc/0x1f20 net/ipv4/tcp.c:4059
       do_sock_setsockopt+0x17c/0x1b0 net/socket.c:2360
       __sys_setsockopt net/socket.c:2385 [inline]
       __do_sys_setsockopt net/socket.c:2391 [inline]
       __se_sys_setsockopt net/socket.c:2388 [inline]
       __x64_sys_setsockopt+0x13f/0x1b0 net/socket.c:2388
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #6 (sk_lock-AF_INET){+.+.}-{0:0}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
       lock_sock_nested+0x48/0x100 net/core/sock.c:3720
       lock_sock include/net/sock.h:1679 [inline]
       inet_shutdown+0x6a/0x390 net/ipv4/af_inet.c:907
       nbd_mark_nsock_dead+0x2e9/0x560 drivers/block/nbd.c:318
       recv_work+0x2138/0x24f0 drivers/block/nbd.c:1018
       process_one_work kernel/workqueue.c:3263 [inline]
       process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3346
       worker_thread+0x8a0/0xda0 kernel/workqueue.c:3427
       kthread+0x711/0x8a0 kernel/kthread.c:463
       ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #5 (&nsock->tx_lock){+.+.}-{4:4}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
       __mutex_lock_common kernel/locking/mutex.c:598 [inline]
       __mutex_lock+0x187/0x1350 kernel/locking/mutex.c:760
       nbd_handle_cmd drivers/block/nbd.c:1140 [inline]
       nbd_queue_rq+0x257/0xf10 drivers/block/nbd.c:1204
       blk_mq_dispatch_rq_list+0x4c0/0x1900 block/blk-mq.c:2129
       __blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline]
       blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline]
       __blk_mq_sched_dispatch_requests+0xda4/0x1570 block/blk-mq-sched.c:307
       blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329
       blk_mq_run_hw_queue+0x348/0x4f0 block/blk-mq.c:2367
       blk_mq_dispatch_list+0xd0c/0xe00 include/linux/spinlock.h:-1
       blk_mq_flush_plug_list+0x469/0x550 block/blk-mq.c:2976
       __blk_flush_plug+0x3d3/0x4b0 block/blk-core.c:1225
       blk_finish_plug block/blk-core.c:1252 [inline]
       __submit_bio+0x2d3/0x5a0 block/blk-core.c:651
       __submit_bio_noacct_mq block/blk-core.c:724 [inline]
       submit_bio_noacct_nocheck+0x2fb/0xa50 block/blk-core.c:755
       submit_bh fs/buffer.c:2829 [inline]
       block_read_full_folio+0x7b7/0x830 fs/buffer.c:2461
       filemap_read_folio+0x117/0x380 mm/filemap.c:2444
       do_read_cache_folio+0x350/0x590 mm/filemap.c:4024
       read_mapping_folio include/linux/pagemap.h:999 [inline]
       read_part_sector+0xb6/0x2b0 block/partitions/core.c:722
       adfspart_check_ICS+0xa4/0xa50 block/partitions/acorn.c:360
       check_partition block/partitions/core.c:141 [inline]
       blk_add_partitions block/partitions/core.c:589 [inline]
       bdev_disk_changed+0x75f/0x14b0 block/partitions/core.c:693
       blkdev_get_whole+0x380/0x510 block/bdev.c:748
       bdev_open+0x31e/0xd30 block/bdev.c:957
       blkdev_open+0x457/0x600 block/fops.c:694
       do_dentry_open+0x953/0x13f0 fs/open.c:965
       vfs_open+0x3b/0x340 fs/open.c:1097
       do_open fs/namei.c:3975 [inline]
       path_openat+0x2ee5/0x3830 fs/namei.c:4134
       do_filp_open+0x1fa/0x410 fs/namei.c:4161
       do_sys_openat2+0x121/0x1c0 fs/open.c:1437
       do_sys_open fs/open.c:1452 [inline]
       __do_sys_openat fs/open.c:1468 [inline]
       __se_sys_openat fs/open.c:1463 [inline]
       __x64_sys_openat+0x138/0x170 fs/open.c:1463
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #4 (&cmd->lock){+.+.}-{4:4}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
       __mutex_lock_common kernel/locking/mutex.c:598 [inline]
       __mutex_lock+0x187/0x1350 kernel/locking/mutex.c:760
       nbd_queue_rq+0xc8/0xf10 drivers/block/nbd.c:1196
       blk_mq_dispatch_rq_list+0x4c0/0x1900 block/blk-mq.c:2129
       __blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline]
       blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline]
       __blk_mq_sched_dispatch_requests+0xda4/0x1570 block/blk-mq-sched.c:307
       blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329
       blk_mq_run_hw_queue+0x348/0x4f0 block/blk-mq.c:2367
       blk_mq_dispatch_list+0xd0c/0xe00 include/linux/spinlock.h:-1
       blk_mq_flush_plug_list+0x469/0x550 block/blk-mq.c:2976
       __blk_flush_plug+0x3d3/0x4b0 block/blk-core.c:1225
       blk_finish_plug block/blk-core.c:1252 [inline]
       __submit_bio+0x2d3/0x5a0 block/blk-core.c:651
       __submit_bio_noacct_mq block/blk-core.c:724 [inline]
       submit_bio_noacct_nocheck+0x2fb/0xa50 block/blk-core.c:755
       submit_bh fs/buffer.c:2829 [inline]
       block_read_full_folio+0x7b7/0x830 fs/buffer.c:2461
       filemap_read_folio+0x117/0x380 mm/filemap.c:2444
       do_read_cache_folio+0x350/0x590 mm/filemap.c:4024
       read_mapping_folio include/linux/pagemap.h:999 [inline]
       read_part_sector+0xb6/0x2b0 block/partitions/core.c:722
       adfspart_check_ICS+0xa4/0xa50 block/partitions/acorn.c:360
       check_partition block/partitions/core.c:141 [inline]
       blk_add_partitions block/partitions/core.c:589 [inline]
       bdev_disk_changed+0x75f/0x14b0 block/partitions/core.c:693
       blkdev_get_whole+0x380/0x510 block/bdev.c:748
       bdev_open+0x31e/0xd30 block/bdev.c:957
       blkdev_open+0x457/0x600 block/fops.c:694
       do_dentry_open+0x953/0x13f0 fs/open.c:965
       vfs_open+0x3b/0x340 fs/open.c:1097
       do_open fs/namei.c:3975 [inline]
       path_openat+0x2ee5/0x3830 fs/namei.c:4134
       do_filp_open+0x1fa/0x410 fs/namei.c:4161
       do_sys_openat2+0x121/0x1c0 fs/open.c:1437
       do_sys_open fs/open.c:1452 [inline]
       __do_sys_openat fs/open.c:1468 [inline]
       __se_sys_openat fs/open.c:1463 [inline]
       __x64_sys_openat+0x138/0x170 fs/open.c:1463
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #3 (set->srcu){.+.+}-{0:0}:
       lock_sync+0xba/0x160 kernel/locking/lockdep.c:5916
       srcu_lock_sync include/linux/srcu.h:173 [inline]
       __synchronize_srcu+0x96/0x3a0 kernel/rcu/srcutree.c:1439
       elevator_switch+0x12b/0x640 block/elevator.c:588
       elevator_change+0x315/0x4c0 block/elevator.c:691
       elevator_set_default+0x186/0x260 block/elevator.c:767
       blk_register_queue+0x34e/0x3f0 block/blk-sysfs.c:942
       __add_disk+0x677/0xd50 block/genhd.c:528
       add_disk_fwnode+0xfc/0x480 block/genhd.c:597
       add_disk include/linux/blkdev.h:775 [inline]
       nbd_dev_add+0x717/0xae0 drivers/block/nbd.c:1981
       nbd_init+0x168/0x1f0 drivers/block/nbd.c:2688
       do_one_initcall+0x236/0x820 init/main.c:1283
       do_initcall_level+0x104/0x190 init/main.c:1345
       do_initcalls+0x59/0xa0 init/main.c:1361
       kernel_init_freeable+0x334/0x4b0 init/main.c:1593
       kernel_init+0x1d/0x1d0 init/main.c:1483
       ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #2 (&q->elevator_lock){+.+.}-{4:4}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
       __mutex_lock_common kernel/locking/mutex.c:598 [inline]
       __mutex_lock+0x187/0x1350 kernel/locking/mutex.c:760
       elevator_change+0x1e5/0x4c0 block/elevator.c:689
       elevator_set_none+0x42/0xb0 block/elevator.c:782
       blk_mq_elv_switch_none block/blk-mq.c:5032 [inline]
       __blk_mq_update_nr_hw_queues block/blk-mq.c:5075 [inline]
       blk_mq_update_nr_hw_queues+0x598/0x1ab0 block/blk-mq.c:5133
       nbd_start_device+0x17f/0xb10 drivers/block/nbd.c:1486
       nbd_genl_connect+0x135b/0x18f0 drivers/block/nbd.c:2236
       genl_family_rcv_msg_doit+0x215/0x300 net/netlink/genetlink.c:1115
       genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
       genl_rcv_msg+0x60e/0x790 net/netlink/genetlink.c:1210
       netlink_rcv_skb+0x208/0x470 net/netlink/af_netlink.c:2552
       genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
       netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
       netlink_unicast+0x82f/0x9e0 net/netlink/af_netlink.c:1346
       netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1896
       sock_sendmsg_nosec net/socket.c:727 [inline]
       __sock_sendmsg+0x21c/0x270 net/socket.c:742
       ____sys_sendmsg+0x505/0x830 net/socket.c:2630
       ___sys_sendmsg+0x21f/0x2a0 net/socket.c:2684
       __sys_sendmsg net/socket.c:2716 [inline]
       __do_sys_sendmsg net/socket.c:2721 [inline]
       __se_sys_sendmsg net/socket.c:2719 [inline]
       __x64_sys_sendmsg+0x19b/0x260 net/socket.c:2719
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&q->q_usage_counter(io)#49){++++}-{0:0}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
       blk_alloc_queue+0x538/0x620 block/blk-core.c:461
       blk_mq_alloc_queue block/blk-mq.c:4399 [inline]
       __blk_mq_alloc_disk+0x15c/0x340 block/blk-mq.c:4446
       nbd_dev_add+0x46c/0xae0 drivers/block/nbd.c:1951
       nbd_init+0x168/0x1f0 drivers/block/nbd.c:2688
       do_one_initcall+0x236/0x820 init/main.c:1283
       do_initcall_level+0x104/0x190 init/main.c:1345
       do_initcalls+0x59/0xa0 init/main.c:1361
       kernel_init_freeable+0x334/0x4b0 init/main.c:1593
       kernel_init+0x1d/0x1d0 init/main.c:1483
       ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #0 (fs_reclaim){+.+.}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3165 [inline]
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3908
       __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
       __fs_reclaim_acquire mm/page_alloc.c:4269 [inline]
       fs_reclaim_acquire+0x72/0x100 mm/page_alloc.c:4283
       might_alloc include/linux/sched/mm.h:318 [inline]
       slab_pre_alloc_hook mm/slub.c:4898 [inline]
       slab_alloc_node mm/slub.c:5222 [inline]
       kmem_cache_alloc_lru_noprof+0x4a/0x6d0 mm/slub.c:5265
       __d_alloc+0x36/0x7a0 fs/dcache.c:1690
       d_alloc_parallel+0xe5/0x15e0 fs/dcache.c:2549
       __lookup_slow+0x116/0x3d0 fs/namei.c:1801
       simple_start_creating+0xfd/0x1e0 fs/libfs.c:2303
       debugfs_start_creating+0x10f/0x180 fs/debugfs/inode.c:397
       debugfs_create_dir+0x28/0x420 fs/debugfs/inode.c:581
       nbd_dev_dbg_init drivers/block/nbd.c:1825 [inline]
       nbd_start_device+0x32a/0xb10 drivers/block/nbd.c:1506
       nbd_genl_connect+0x135b/0x18f0 drivers/block/nbd.c:2236
       genl_family_rcv_msg_doit+0x215/0x300 net/netlink/genetlink.c:1115
       genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
       genl_rcv_msg+0x60e/0x790 net/netlink/genetlink.c:1210
       netlink_rcv_skb+0x208/0x470 net/netlink/af_netlink.c:2552
       genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
       netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
       netlink_unicast+0x82f/0x9e0 net/netlink/af_netlink.c:1346
       netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1896
       sock_sendmsg_nosec net/socket.c:727 [inline]
       __sock_sendmsg+0x21c/0x270 net/socket.c:742
       ____sys_sendmsg+0x505/0x830 net/socket.c:2630
       ___sys_sendmsg+0x21f/0x2a0 net/socket.c:2684
       __sys_sendmsg net/socket.c:2716 [inline]
       __do_sys_sendmsg net/socket.c:2721 [inline]
       __se_sys_sendmsg net/socket.c:2719 [inline]
       __x64_sys_sendmsg+0x19b/0x260 net/socket.c:2719
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  fs_reclaim --> relay_channels_mutex --> &sb->s_type->i_mutex_key#3

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&sb->s_type->i_mutex_key#3);
                               lock(relay_channels_mutex);
                               lock(&sb->s_type->i_mutex_key#3);
  lock(fs_reclaim);

 *** DEADLOCK ***

4 locks held by syz.6.3764/19710:
 #0: ffffffff8f558090 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1218
 #1: ffffffff8f557ea8 (genl_mutex){+.+.}-{4:4}, at: genl_lock net/netlink/genetlink.c:35 [inline]
 #1: ffffffff8f557ea8 (genl_mutex){+.+.}-{4:4}, at: genl_op_lock net/netlink/genetlink.c:60 [inline]
 #1: ffffffff8f557ea8 (genl_mutex){+.+.}-{4:4}, at: genl_rcv_msg+0x10d/0x790 net/netlink/genetlink.c:1209
 #2: ffff888025570270 (&nbd->config_lock){+.+.}-{4:4}, at: nbd_start_device+0x189/0xb10 drivers/block/nbd.c:1487
 #3: ffff888148eab8a0 (&sb->s_type->i_mutex_key#3){++++}-{4:4}, at: inode_lock include/linux/fs.h:980 [inline]
 #3: ffff888148eab8a0 (&sb->s_type->i_mutex_key#3){++++}-{4:4}, at: simple_start_creating+0x98/0x1e0 fs/libfs.c:2298

stack backtrace:
CPU: 1 UID: 0 PID: 19710 Comm: syz.6.3764 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2043
 check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2175
 check_prev_add kernel/locking/lockdep.c:3165 [inline]
 check_prevs_add kernel/locking/lockdep.c:3284 [inline]
 validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3908
 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237
 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
 __fs_reclaim_acquire mm/page_alloc.c:4269 [inline]
 fs_reclaim_acquire+0x72/0x100 mm/page_alloc.c:4283
 might_alloc include/linux/sched/mm.h:318 [inline]
 slab_pre_alloc_hook mm/slub.c:4898 [inline]
 slab_alloc_node mm/slub.c:5222 [inline]
 kmem_cache_alloc_lru_noprof+0x4a/0x6d0 mm/slub.c:5265
 __d_alloc+0x36/0x7a0 fs/dcache.c:1690
 d_alloc_parallel+0xe5/0x15e0 fs/dcache.c:2549
 __lookup_slow+0x116/0x3d0 fs/namei.c:1801
 simple_start_creating+0xfd/0x1e0 fs/libfs.c:2303
 debugfs_start_creating+0x10f/0x180 fs/debugfs/inode.c:397
 debugfs_create_dir+0x28/0x420 fs/debugfs/inode.c:581
 nbd_dev_dbg_init drivers/block/nbd.c:1825 [inline]
 nbd_start_device+0x32a/0xb10 drivers/block/nbd.c:1506
 nbd_genl_connect+0x135b/0x18f0 drivers/block/nbd.c:2236
 genl_family_rcv_msg_doit+0x215/0x300 net/netlink/genetlink.c:1115
 genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
 genl_rcv_msg+0x60e/0x790 net/netlink/genetlink.c:1210
 netlink_rcv_skb+0x208/0x470 net/netlink/af_netlink.c:2552
 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
 netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
 netlink_unicast+0x82f/0x9e0 net/netlink/af_netlink.c:1346
 netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1896
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg+0x21c/0x270 net/socket.c:742
 ____sys_sendmsg+0x505/0x830 net/socket.c:2630
 ___sys_sendmsg+0x21f/0x2a0 net/socket.c:2684
 __sys_sendmsg net/socket.c:2716 [inline]
 __do_sys_sendmsg net/socket.c:2721 [inline]
 __se_sys_sendmsg net/socket.c:2719 [inline]
 __x64_sys_sendmsg+0x19b/0x260 net/socket.c:2719
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f65edb8eec9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f65ee9a4038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f65edde5fa0 RCX: 00007f65edb8eec9
RDX: 0000000020000000 RSI: 0000200000001ac0 RDI: 0000000000000006
RBP: 00007f65edc11f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f65edde6038 R14: 00007f65edde5fa0 R15: 00007ffc6fca7418
 </TASK>
nbd0: detected capacity change from 0 to 127