EXT4-fs (loop3): VFS: Can't find ext4 filesystem
INFO: task kworker/u4:6:5002 blocked for more than 120 seconds.
      Not tainted 4.9.101-gaef17a5 #29
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/u4:6    D25672  5002      2 0x00000000
Workqueue: events_unbound flush_to_ldisc
 ffff880188f09800 0000000000000000 ffff88018a834000 ffff8801d45ec800
 ffff8801db321b98 ffff880188f278c8 ffffffff839e39bd ffff880188f0a0c8
 ffffed00311e1418 ffff880188f09800 00fffc0000000000 ffff8801db322468
Call Trace:
 [<ffffffff839e4fbf>] schedule+0x7f/0x1b0 kernel/sched/core.c:3557
 [<ffffffff839e5943>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3590
 [<ffffffff839e9dc6>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff839e9dc6>] mutex_lock_nested+0x326/0x870 kernel/locking/mutex.c:621
 [<ffffffff8211a500>] commit_echoes+0x120/0x1b0 drivers/tty/n_tty.c:764
 [<ffffffff82123158>] n_tty_receive_char_fast drivers/tty/n_tty.c:1418 [inline]
 [<ffffffff82123158>] n_tty_receive_buf_fast drivers/tty/n_tty.c:1578 [inline]
 [<ffffffff82123158>] __receive_buf drivers/tty/n_tty.c:1613 [inline]
 [<ffffffff82123158>] n_tty_receive_buf_common+0x1878/0x2300 drivers/tty/n_tty.c:1711
 [<ffffffff82123c13>] n_tty_receive_buf2+0x33/0x40 drivers/tty/n_tty.c:1746
 [<ffffffff8212970f>] tty_ldisc_receive_buf+0xaf/0x190 drivers/tty/tty_buffer.c:455
 [<ffffffff8212a713>] receive_buf drivers/tty/tty_buffer.c:474 [inline]
 [<ffffffff8212a713>] flush_to_ldisc+0x253/0x370 drivers/tty/tty_buffer.c:533
 [<ffffffff8118ae71>] process_one_work+0x7e1/0x1500 kernel/workqueue.c:2092
 [<ffffffff8118bc66>] worker_thread+0xd6/0x10a0 kernel/workqueue.c:2226
 [<ffffffff8119ad9d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839f4a5c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373

Showing all locks held in the system:
2 locks held by khungtaskd/518:
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136477c>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136477c>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81423c90>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by rs:main Q:Reg/3671:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815d57ac>] __fdget_pos+0xac/0xd0 fs/file.c:781
 #1:  (sb_writers#3){.+.+.+}, at: [<ffffffff8157050e>] file_start_write include/linux/fs.h:2640 [inline]
 #1:  (sb_writers#3){.+.+.+}, at: [<ffffffff8157050e>] vfs_write+0x3ae/0x530 fs/read_write.c:556
2 locks held by getty/3770:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839f2a62>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff8211cd32>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2133
6 locks held by kworker/u4:6/5002:
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118ad7e>] work_static include/linux/workqueue.h:186 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118ad7e>] set_work_data kernel/workqueue.c:617 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118ad7e>] set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118ad7e>] process_one_work+0x6ee/0x1500 kernel/workqueue.c:2085
 #1:  ((&buf->work)){+.+...}, at: [<ffffffff8118adb8>] process_one_work+0x728/0x1500 kernel/workqueue.c:2089
 #2:  (&tty->ldisc_sem){++++++}, at: [<ffffffff82127ee0>] tty_ldisc_ref+0x20/0x80 drivers/tty/tty_ldisc.c:296
 #3:  (&port->buf.lock/1){+.+...}, at: [<ffffffff8212a546>] flush_to_ldisc+0x86/0x370 drivers/tty/tty_buffer.c:505
 #4:  (&o_tty->termios_rwsem/1){++++..}, at: [<ffffffff8212196b>] n_tty_receive_buf_common+0x8b/0x2300 drivers/tty/n_tty.c:1674
 #5:  (&ldata->output_lock){+.+...}, at: [<ffffffff8211a500>] commit_echoes+0x120/0x1b0 drivers/tty/n_tty.c:764

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

NMI backtrace for cpu 1
CPU: 1 PID: 518 Comm: khungtaskd Not tainted 4.9.101-gaef17a5 #29
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d85b7d08 ffffffff81eb1009 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810b7da0 ffff8801d85b7d40
 ffffffff81ebc307 0000000000000001 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb1009>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb1009>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebc307>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebc29a>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810b7ea4>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81364d14>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81364d14>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81364d14>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81364d14>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119ad9d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839f4a5c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 20934 Comm: syz-executor4 Not tainted 4.9.101-gaef17a5 #29
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801b8e61800 task.stack: ffff880193e00000
RIP: 0010:[<ffffffff82118bf2>] 
c [<ffffffff82118bf2>] echo_buf drivers/tty/n_tty.c:146 [inline]
RIP: 0010:[<ffffffff82118bf2>] 
c [<ffffffff82118bf2>] __process_echoes+0x5e2/0x780 drivers/tty/n_tty.c:734
RSP: 0018:ffff880193e07980  EFLAGS: 00000202
RAX: 000000000000088a RBX: ffffc9000ef5e000 RCX: ffffc90006152000
RDX: ffffc9000ef5faea RSI: ffffffff82118bdf RDI: ffffc9000ef5faea
RBP: ffff880193e079e8 R08: ffff8801b8e62138 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 00000005b4b1988a
R13: 0000000000000183 R14: dffffc0000000000 R15: 00000005b4b1988a
FS:  00007fb3d1e7c700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000007a9b10 CR3: 00000001935fd000 CR4: 00000000001606f0
DR0: 00000000200001c0 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Stack:
 ffff880193e079c0
c 0000000000000000
c ffffc9000ef60278
c ffffed003af36185
c
 ffff8801d79b0c2c
c ffffc9000ef5e020
c 0000000000001f00
c ffff8801d79b0880
c
 ffffc9000ef60300
c ffffc9000ef5e000
c dffffc0000000000
c ffffc9000ef5e020
c
Call Trace:
 [<ffffffff82122614>] flush_echoes drivers/tty/n_tty.c:801 [inline]
 [<ffffffff82122614>] __receive_buf drivers/tty/n_tty.c:1617 [inline]
 [<ffffffff82122614>] n_tty_receive_buf_common+0xd34/0x2300 drivers/tty/n_tty.c:1711
 [<ffffffff82123c50>] n_tty_receive_buf+0x30/0x40 drivers/tty/n_tty.c:1740
 [<ffffffff8211406f>] tiocsti drivers/tty/tty_io.c:2314 [inline]
 [<ffffffff8211406f>] tty_ioctl+0xc8f/0x2270 drivers/tty/tty_io.c:2905
 [<ffffffff815b052c>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff815b052c>] file_ioctl fs/ioctl.c:493 [inline]
 [<ffffffff815b052c>] do_vfs_ioctl+0x1ac/0x11a0 fs/ioctl.c:677
 [<ffffffff815b15af>] SYSC_ioctl fs/ioctl.c:694 [inline]
 [<ffffffff815b15af>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839f4893>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: 
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c