======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.1.9668/17155 is trying to acquire lock:
ffffffff90094cc0 (fs_reclaim){+.+.}-{0:0}, at: kmem_cache_alloc_lru_noprof+0x65/0x5f0

but task is already holding lock:
ffff88811461ac90 (&sb->s_type->i_mutex_key#3/1){+.+.}-{4:4}, at: start_dirop+0x4f/0x90

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #8 (&sb->s_type->i_mutex_key#3/1){+.+.}-{4:4}:
       down_write_nested+0x98/0x200
       start_dirop+0x4f/0x90
       simple_start_creating+0xcc/0x110
       debugfs_start_creating+0xca/0x1b0
       debugfs_create_dir+0x24/0x350
       slab_late_init+0x4d/0x120
       do_one_initcall+0x250/0x870
       do_initcall_level+0x10a/0x1a0
       do_initcalls+0x59/0xa0
       kernel_init_freeable+0x29d/0x3e0
       kernel_init+0x22/0x1d0
       ret_from_fork+0x514/0xb70
       ret_from_fork_asm+0x1a/0x30

-> #7 (slab_mutex){+.+.}-{4:4}:
       __mutex_lock+0x197/0x15a0
       kmem_cache_destroy+0x73/0x180
       nfsd_file_cache_shutdown+0x126/0x370
       nfsd_svc+0x539/0x710
       nfsd_nl_threads_set_doit+0xa6c/0xc30
       genl_family_rcv_msg_doit+0x233/0x340
       genl_rcv_msg+0x614/0x7a0
       netlink_rcv_skb+0x226/0x4a0
       genl_rcv+0x28/0x40
       netlink_unicast+0x8ef/0xa80
       netlink_sendmsg+0x7f0/0xb20
       sock_sendmsg_nosec+0x14e/0x190
       ____sys_sendmsg+0x54e/0x850
       ___sys_sendmsg+0x2a5/0x360
       __x64_sys_sendmsg+0x1b1/0x290
       do_syscall_64+0x166/0x520
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #6 (cpu_hotplug_lock){++++}-{0:0}:
       cpus_read_lock+0x3d/0x160
       static_key_slow_inc+0x12/0x30
       nbd_genl_reconnect_sock_cb+0x69a/0xbb0
       nbd_genl_foreach_sock+0x265/0x450
       nbd_genl_reconfigure+0xbbb/0x1040
       genl_family_rcv_msg_doit+0x233/0x340
       genl_rcv_msg+0x614/0x7a0
       netlink_rcv_skb+0x226/0x4a0
       genl_rcv+0x28/0x40
       netlink_unicast+0x8ef/0xa80
       netlink_sendmsg+0x7f0/0xb20
       sock_sendmsg_nosec+0x14e/0x190
       ____sys_sendmsg+0x54e/0x850
       ___sys_sendmsg+0x2a5/0x360
       __x64_sys_sendmsg+0x1b1/0x290
       do_syscall_64+0x166/0x520
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #5 (&nsock->tx_lock){+.+.}-{4:4}:
       __mutex_lock+0x197/0x15a0
       nbd_queue_rq+0x373/0xff0
       blk_mq_dispatch_rq_list+0x499/0x1990
       __blk_mq_sched_dispatch_requests+0xd36/0x1580
       blk_mq_sched_dispatch_requests+0xd7/0x190
       blk_mq_run_work_fn+0x167/0x2f0
       process_scheduled_works+0xc3d/0x1630
       worker_thread+0xa47/0xfb0
       kthread+0x38b/0x480
       ret_from_fork+0x514/0xb70
       ret_from_fork_asm+0x1a/0x30

-> #4 (&cmd->lock){+.+.}-{4:4}:
       __mutex_lock+0x197/0x15a0
       nbd_queue_rq+0xc1/0xff0
       blk_mq_dispatch_rq_list+0x499/0x1990
       __blk_mq_sched_dispatch_requests+0xd36/0x1580
       blk_mq_sched_dispatch_requests+0xd7/0x190
       blk_mq_run_work_fn+0x167/0x2f0
       process_scheduled_works+0xc3d/0x1630
       worker_thread+0xa47/0xfb0
       kthread+0x38b/0x480
       ret_from_fork+0x514/0xb70
       ret_from_fork_asm+0x1a/0x30

-> #3 (set->srcu){.+.+}-{0:0}:
       __synchronize_srcu+0xca/0x2f0
       elevator_switch+0x1e8/0x7b0
       elevator_change+0x2fa/0x480
       elevator_set_default+0x375/0x440
       blk_register_queue+0x404/0x4f0
       __add_disk+0x6b8/0xdb0
       add_disk_fwnode+0x100/0x3a0
       nbd_dev_add+0x733/0xb60
       nbd_init+0x168/0x1f0
       do_one_initcall+0x250/0x870
       do_initcall_level+0x10a/0x1a0
       do_initcalls+0x59/0xa0
       kernel_init_freeable+0x29d/0x3e0
       kernel_init+0x22/0x1d0
       ret_from_fork+0x514/0xb70
       ret_from_fork_asm+0x1a/0x30

-> #2 (&q->elevator_lock){+.+.}-{4:4}:
       __mutex_lock+0x197/0x15a0
       elevator_change+0x1af/0x480
       elevator_set_none+0xb5/0x140
       blk_mq_update_nr_hw_queues+0x5ef/0x19e0
       nbd_start_device+0x189/0xb30
       nbd_genl_connect+0x167d/0x1cd0
       genl_family_rcv_msg_doit+0x233/0x340
       genl_rcv_msg+0x614/0x7a0
       netlink_rcv_skb+0x226/0x4a0
       genl_rcv+0x28/0x40
       netlink_unicast+0x8ef/0xa80
       netlink_sendmsg+0x7f0/0xb20
       sock_sendmsg_nosec+0x14e/0x190
       ____sys_sendmsg+0x54e/0x850
       ___sys_sendmsg+0x2a5/0x360
       __x64_sys_sendmsg+0x1b1/0x290
       do_syscall_64+0x166/0x520
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&q->q_usage_counter(io)#54){++++}-{0:0}:
       blk_alloc_queue+0x544/0x690
       __blk_mq_alloc_disk+0x194/0x390
       nbd_dev_add+0x494/0xb60
       nbd_init+0x168/0x1f0
       do_one_initcall+0x250/0x870
       do_initcall_level+0x10a/0x1a0
       do_initcalls+0x59/0xa0
       kernel_init_freeable+0x29d/0x3e0
       kernel_init+0x22/0x1d0
       ret_from_fork+0x514/0xb70
       ret_from_fork_asm+0x1a/0x30

-> #0 (fs_reclaim){+.+.}-{0:0}:
       __lock_acquire+0x164c/0x2de0
       lock_acquire+0x115/0x350
       fs_reclaim_acquire+0x71/0x100
       kmem_cache_alloc_lru_noprof+0x65/0x5f0
       __d_alloc+0x37/0x820
       d_alloc+0x4b/0x190
       lookup_one_qstr_excl+0xd8/0x360
       start_dirop+0x5c/0x90
       simple_start_creating+0xcc/0x110
       debugfs_start_creating+0xca/0x1b0
       debugfs_create_dir+0x24/0x350
       nsim_fib_create+0x752/0xae0
       nsim_dev_reload_up+0x3ea/0x880
       devlink_reload+0x40b/0x7f0
       devlink_nl_reload_doit+0xa96/0xc80
       genl_family_rcv_msg_doit+0x233/0x340
       genl_rcv_msg+0x614/0x7a0
       netlink_rcv_skb+0x226/0x4a0
       genl_rcv+0x28/0x40
       netlink_unicast+0x8ef/0xa80
       netlink_sendmsg+0x7f0/0xb20
       sock_sendmsg_nosec+0x14e/0x190
       ____sys_sendmsg+0x54e/0x850
       ___sys_sendmsg+0x2a5/0x360
       __x64_sys_sendmsg+0x1b1/0x290
       do_syscall_64+0x166/0x520
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  fs_reclaim --> slab_mutex --> &sb->s_type->i_mutex_key#3/1

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&sb->s_type->i_mutex_key#3/1);
                               lock(slab_mutex);
                               lock(&sb->s_type->i_mutex_key#3/1);
  lock(fs_reclaim);

 *** DEADLOCK ***

locks held by syz.1.9668/17155: 4, last CPU#1:
 #0: ffffffff914f05a8 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40
 #1: ffff88811ba12128 (&dev->mutex){....}-{4:4}, at: devlink_get_from_attrs_lock+0x34a/0x490
 #2: ffff88811baf1258 (&devlink->lock_key){+.+.}-{4:4}, at: devlink_get_from_attrs_lock+0x360/0x490
 #3: ffff88811461ac90 (&sb->s_type->i_mutex_key#3/1){+.+.}-{4:4}, at: start_dirop+0x4f/0x90

stack backtrace:
CPU: 1 UID: 0 PID: 17155 Comm: syz.1.9668 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150
 print_circular_bug+0x2e2/0x300
 check_noncircular+0x12f/0x150
 __lock_acquire+0x164c/0x2de0
 lock_acquire+0x115/0x350
 fs_reclaim_acquire+0x71/0x100
 kmem_cache_alloc_lru_noprof+0x65/0x5f0
 __d_alloc+0x37/0x820
 d_alloc+0x4b/0x190
 lookup_one_qstr_excl+0xd8/0x360
 start_dirop+0x5c/0x90
 simple_start_creating+0xcc/0x110
 debugfs_start_creating+0xca/0x1b0
 debugfs_create_dir+0x24/0x350
 nsim_fib_create+0x752/0xae0
 nsim_dev_reload_up+0x3ea/0x880
 devlink_reload+0x40b/0x7f0
 devlink_nl_reload_doit+0xa96/0xc80
 genl_family_rcv_msg_doit+0x233/0x340
 genl_rcv_msg+0x614/0x7a0
 netlink_rcv_skb+0x226/0x4a0
 genl_rcv+0x28/0x40
 netlink_unicast+0x8ef/0xa80
 netlink_sendmsg+0x7f0/0xb20
 sock_sendmsg_nosec+0x14e/0x190
 ____sys_sendmsg+0x54e/0x850
 ___sys_sendmsg+0x2a5/0x360
 __x64_sys_sendmsg+0x1b1/0x290
 do_syscall_64+0x166/0x520
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f485af9f559
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f485bf4e028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f485b225fa0 RCX: 00007f485af9f559
RDX: 0000000000000000 RSI: 0000200000000080 RDI: 0000000000000004
RBP: 00007f485b036b20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f485b226038 R14: 00007f485b225fa0 R15: 00007fff08e820c8
 </TASK>
