INFO: task syz.6.1374:31755 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.6.1374      state:D stack:28760 pid:31755 tgid:31696 ppid:24831  task_flags:0x400040 flags:0x00080002
Call Trace:
 <TASK>
 __schedule+0x17b4/0x5680
 schedule+0x164/0x360
 schedule_preempt_disabled+0x13/0x30
 rwsem_down_read_slowpath+0x6d9/0x940
 down_read+0x99/0x2e0
 super_lock+0x2d6/0x3d0
 __iterate_supers+0x126/0x250
 __ia32_sys_sync+0xa0/0x120
 do_syscall_64+0x15f/0xf80
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc8a919cdd9
RSP: 002b:00007fc8aa032028 EFLAGS: 00000246 ORIG_RAX: 00000000000000a2
RAX: ffffffffffffffda RBX: 00007fc8a9416180 RCX: 00007fc8a919cdd9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007fc8a9416180 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc8a9416218 R14: 00007fc8a9416180 R15: 00007fff8170ece8
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/34:
 #0: ffffffff8e95cda0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180
2 locks held by kworker/u10:4/2288:
2 locks held by getty/5435:
 #0: ffff8881136100a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70
 #1: ffffc9000346b2e8 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x45c/0x13a0
2 locks held by syz-executor/24044:
1 lock held by syz.6.1374/31755:
 #0: ffff88817058c0d8 (&type->s_umount_key#62){++++}-{4:4}, at: super_lock+0x2d6/0x3d0
1 lock held by syz.7.1439/443:
 #0: ffff88817058c0d8 (&type->s_umount_key#62){++++}-{4:4}, at: super_lock+0x2d6/0x3d0
3 locks held by syz-executor/1252:
 #0: ffff8881bb0ba0d8 (&type->s_umount_key#56){++++}-{4:4}, at: deactivate_super+0xa9/0xe0
 #1: ffff8881b0778940 ((wq_completion)btrfs-cache){+.+.}-{0:0}, at: touch_wq_lockdep_map+0xb5/0x180
 #2: ffff88823c63aea0 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x31/0x150
1 lock held by syz.5.1493/2586:
 #0: ffff88817058c0d8 (&type->s_umount_key#62){++++}-{4:4}, at: super_lock+0x2d6/0x3d0
1 lock held by syz.5.1493/2588:
 #0: ffff88817058c0d8 (&type->s_umount_key#62){++++}-{4:4}, at: super_lock+0x2d6/0x3d0
3 locks held by kworker/u10:2/5854:
 #0: ffff88823c63aea0 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x31/0x150
 #1: ffff88823c624588 (psi_seq){-.-.}-{0:0}, at: psi_task_switch+0x53/0x880
 #2: ffff88823c626118 (&base->lock){-.-.}-{2:2}, at: __mod_timer+0x1ae/0xf30
1 lock held by syz.0.1766/6602:
 #0: ffff8881bad880d8 (&type->s_umount_key#55/1){+.+.}-{4:4}, at: alloc_super+0x28c/0xab0

=============================================

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 34 Comm: khungtaskd 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
 nmi_cpu_backtrace+0x274/0x2d0
 nmi_trigger_cpumask_backtrace+0x17a/0x300
 sys_info+0x135/0x170
 watchdog+0xfd3/0x1030
 kthread+0x388/0x470
 ret_from_fork+0x514/0xb70
 ret_from_fork_asm+0x1a/0x30
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 1252 Comm: syz-executor 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
RIP: 0010:__rcu_read_lock+0x2f/0x60
Code: 65 48 8b 1d ab 53 8d 11 48 81 c3 c4 04 00 00 48 89 d8 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df 0f b6 04 08 84 c0 75 18 ff 03 <8b> 03 3d 00 00 00 40 7d 07 5b e9 52 6d ff 09 cc 90 0f 0b 90 eb f3
RSP: 0018:ffffc9002158f8a8 EFLAGS: 00000202
RAX: 0000000000000000 RBX: ffff8881af373fc4 RCX: dffffc0000000000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff88816c416d20
RBP: 0000000000000001 R08: ffffffff82700b3c R09: ffffffff8e95cda0
R10: dffffc0000000000 R11: ffffed1020256937 R12: dffffc0000000000
R13: ffff88816c4165a0 R14: ffff88816c416d20 R15: dffffc0000000000
FS:  000055555afdf500(0000) GS:ffff8882a9293000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000559657720b28 CR3: 00000001ac228000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 kernfs_root+0x15/0x230
 kernfs_next_descendant_post+0x83/0x310
 __kernfs_remove+0x17e/0x8e0
 kernfs_remove_by_name_ns+0xc0/0x140
 sysfs_remove_group+0xfc/0x2e0
 sysfs_remove_groups+0x54/0xb0
 device_remove_attrs+0x229/0x280
 device_del+0x51f/0x8f0
 device_unregister+0x21/0xf0
 bdi_unregister+0x440/0x530
 generic_shutdown_super+0x235/0x2d0
 kill_anon_super+0x3b/0x70
 btrfs_kill_super+0x41/0x50
 deactivate_locked_super+0xbc/0x130
 cleanup_mnt+0x437/0x4d0
 task_work_run+0x1d9/0x270
 exit_to_user_mode_loop+0xed/0x480
 do_syscall_64+0x33e/0xf80
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fa3ae19e017
Code: a2 c7 05 dc 06 25 00 00 00 00 00 eb 96 e8 e1 12 00 00 90 31 f6 e9 09 00 00 00 66 0f 1f 84 00 00 00 00 00 b8 a6 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 01 c3 48 c7 c2 e8 ff ff ff f7 d8 64 89 02 b8
RSP: 002b:00007fff57e96fd8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 00007fa3ae232120 RCX: 00007fa3ae19e017
RDX: 0000000000000000 RSI: 0000000000000009 RDI: 00007fff57e97090
RBP: 00007fff57e97090 R08: 00007fff57e98090 R09: 00000000ffffffff
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fff57e98120
R13: 00007fa3ae232120 R14: 00000000000ae0b8 R15: 00007fff57e98160
 </TASK>
