======================================================
WARNING: possible circular locking dependency detected
6.16.0-rc3-syzkaller-00159-g223e2288f4b8-dirty #0 Not tainted
------------------------------------------------------
kworker/u10:2/40 is trying to acquire lock:
ffff888021f0b358 (&disk->open_mutex){+.+.}-{4:4}, at: __del_gendisk+0x129/0x9e0

but task is already holding lock:
ffff888021f05188 (&set->update_nr_hwq_lock){++++}-{4:4}, at: del_gendisk+0xe0/0x160

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&set->update_nr_hwq_lock){++++}-{4:4}:
       lock_acquire+0x120/0x360
       down_write+0x96/0x1f0
       blk_mq_update_nr_hw_queues+0x3b/0x14c0
       nbd_start_device+0x16c/0xac0
       nbd_genl_connect+0x1250/0x1930
       genl_family_rcv_msg_doit+0x215/0x300
       genl_rcv_msg+0x60e/0x790
       netlink_rcv_skb+0x208/0x470
       genl_rcv+0x28/0x40
       netlink_unicast+0x75b/0x8d0
       netlink_sendmsg+0x805/0xb30
       __sock_sendmsg+0x21c/0x270
       ____sys_sendmsg+0x505/0x830
       ___sys_sendmsg+0x21f/0x2a0
       __x64_sys_sendmsg+0x19b/0x260
       do_syscall_64+0xfa/0x3b0
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&nbd->config_lock){+.+.}-{4:4}:
       lock_acquire+0x120/0x360
       __mutex_lock+0x182/0xe80
       refcount_dec_and_mutex_lock+0x30/0xa0
       nbd_config_put+0x2c/0x790
       nbd_release+0xfe/0x140
       bdev_release+0x536/0x650
       blkdev_release+0x15/0x20
       __fput+0x44c/0xa70
       fput_close_sync+0x119/0x200
       __x64_sys_close+0x7f/0x110
       do_syscall_64+0xfa/0x3b0
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&disk->open_mutex){+.+.}-{4:4}:
       validate_chain+0xb9b/0x2140
       __lock_acquire+0xab9/0xd20
       lock_acquire+0x120/0x360
       __mutex_lock+0x182/0xe80
       __del_gendisk+0x129/0x9e0
       del_gendisk+0xe8/0x160
       nbd_dev_remove_work+0x47/0xe0
       process_scheduled_works+0xae1/0x17b0
       worker_thread+0x8a0/0xda0
       kthread+0x711/0x8a0
       ret_from_fork+0x3fc/0x770
       ret_from_fork_asm+0x1a/0x30

other info that might help us debug this:

Chain exists of:
  &disk->open_mutex --> &nbd->config_lock --> &set->update_nr_hwq_lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  rlock(&set->update_nr_hwq_lock);
                               lock(&nbd->config_lock);
                               lock(&set->update_nr_hwq_lock);
  lock(&disk->open_mutex);

 *** DEADLOCK ***

3 locks held by kworker/u10:2/40:
 #0: ffff888021efe148 ((wq_completion)nbd-del){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0
 #1: ffffc900006efbc0 ((work_completion)(&nbd->remove_work)){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0
 #2: ffff888021f05188 (&set->update_nr_hwq_lock){++++}-{4:4}, at: del_gendisk+0xe0/0x160

stack backtrace:
CPU: 1 UID: 0 PID: 40 Comm: kworker/u10:2 Not tainted 6.16.0-rc3-syzkaller-00159-g223e2288f4b8-dirty #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Workqueue: nbd-del nbd_dev_remove_work
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250
 print_circular_bug+0x2ee/0x310
 check_noncircular+0x134/0x160
 validate_chain+0xb9b/0x2140
 __lock_acquire+0xab9/0xd20
 lock_acquire+0x120/0x360
 __mutex_lock+0x182/0xe80
 __del_gendisk+0x129/0x9e0
 del_gendisk+0xe8/0x160
 nbd_dev_remove_work+0x47/0xe0
 process_scheduled_works+0xae1/0x17b0
 worker_thread+0x8a0/0xda0
 kthread+0x711/0x8a0
 ret_from_fork+0x3fc/0x770
 ret_from_fork_asm+0x1a/0x30
 </TASK>
