INFO: task kworker/u10:1:36 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u10:1   state:D stack:21080 pid:36    tgid:36    ppid:2      task_flags:0x4208060 flags:0x00080000
Workqueue: writeback wb_workfn (flush-7:8)
Call Trace:
 <TASK>
 __schedule+0x17b4/0x5680
 schedule+0x164/0x360
 schedule_preempt_disabled+0x13/0x30
 rwsem_down_write_slowpath+0x883/0x1080
 down_write+0x1bc/0x200
 f2fs_issue_checkpoint+0x437/0x790
 f2fs_balance_fs_bg+0x576/0x990
 f2fs_write_node_pages+0x158/0x700
 do_writepages+0x32e/0x550
 __writeback_single_inode+0x133/0x10e0
 writeback_sb_inodes+0x979/0x19d0
 __writeback_inodes_wb+0x111/0x240
 wb_writeback+0x459/0xb00
 wb_workfn+0xb12/0xf10
 process_scheduled_works+0xb5d/0x1860
 worker_thread+0xa53/0xfc0
 kthread+0x388/0x470
 ret_from_fork+0x514/0xb70
 ret_from_fork_asm+0x1a/0x30
 </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
4 locks held by kworker/u10:1/36:
 #0: ffff888162aa0140 ((wq_completion)writeback){+.+.}-{0:0}, at: process_scheduled_works+0xa35/0x1860
 #1: ffffc90000ac7c40 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_scheduled_works+0xa70/0x1860
 #2: ffff88810b7340d8 (&type->s_umount_key#64){++++}-{4:4}, at: super_trylock_shared+0x20/0xf0
 #3: ffff888113e194b8 (&sbi->gc_lock){+.+.}-{4:4}, at: f2fs_issue_checkpoint+0x437/0x790
2 locks held by getty/5441:
 #0: ffff888174b2b0a0 (&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
3 locks held by kworker/0:4/5669:
 #0: ffff88810006b140 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0xa35/0x1860
 #1: ffffc90004de7c40 (free_ipc_work){+.+.}-{0:0}, at: process_scheduled_works+0xa70/0x1860
 #2: ffffffff8e9630a8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: synchronize_rcu_expedited+0x2d0/0x770
3 locks held by syz.8.841/14107:
2 locks held by syz-executor/16020:
 #0: ffffffff8fdd0140 (rtnl_mutex){+.+.}-{4:4}, at: tun_chr_close+0x3e/0x1c0
 #1: ffffffff8e9630a8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: synchronize_rcu_expedited+0x38d/0x770
1 lock held by syz.8.1168/17439:
 #0: ffff88810b7340d8 (&type->s_umount_key#64){++++}-{4:4}, at: super_lock+0x289/0x3d0

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

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: 18578 Comm: syz.9.1328 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:check_preemption_disabled+0x2a/0xe0
Code: 55 41 57 41 56 53 65 8b 05 b7 af 90 07 65 8b 0d ac af 90 07 f7 c1 ff ff ff 7f 74 0c 5b 41 5e 41 5f 5d e9 49 d9 02 00 cc 9c 59 <f7> c1 00 02 00 00 74 ea 65 4c 8b 3d 5e af 90 07 41 f6 47 2f 04 74
RSP: 0018:ffffc90007b7f410 EFLAGS: 00000046
RAX: 0000000000000001 RBX: 0000000000000000 RCX: 0000000000000046
RDX: 0000000000000000 RSI: ffffffff8dfc1e24 RDI: ffffffff8c28b4e0
RBP: ffffffff8176e256 R08: 0000000000000000 R09: 0000000000000000
R10: ffffc90007b7f5f8 R11: ffffffff81b0da30 R12: 0000000000000002
R13: ffffffff8e95cda0 R14: 0000000000000000 R15: 0000000000000246
FS:  00007fe922f3f6c0(0000) GS:ffff8882a9290000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f89a05cb620 CR3: 000000010c2ae000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 lock_acquire+0xcd/0x350
 unwind_next_frame+0xc3/0x2550
 arch_stack_walk+0x11b/0x150
 stack_trace_save+0xa9/0x100
 save_stack+0x122/0x230
 __reset_page_owner+0x71/0x1f0
 free_pages_prepare+0x936/0xaa0
 __free_contig_range_common+0x174/0x340
 free_pages_bulk+0x48/0x120
 vfree+0x254/0x320
 kcov_close+0x28/0x50
 __fput+0x44f/0xa60
 task_work_run+0x1d9/0x270
 do_exit+0x70f/0x22c0
 do_group_exit+0x21b/0x2d0
 get_signal+0x1284/0x1330
 arch_do_signal_or_restart+0xbc/0x830
 exit_to_user_mode_loop+0x86/0x480
 do_syscall_64+0x33e/0xf80
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fe921f5d60e
Code: Unable to access opcode bytes at 0x7fe921f5d5e4.
RSP: 002b:00007fe922f3eda8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: 0000000001092000 RBX: 00007fe922f3f6c0 RCX: 00007fe921f5d60e
RDX: 00000000013bd7ef RSI: 00007fe917c00000 RDI: 0000000000000006
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000006
R13: 00007fe922f3eee0 R14: 00007fe922f3eea0 R15: 00007fe917c00000
 </TASK>
