b_state=0x00000029, b_size=512
device loop0 blocksize: 4096
__find_get_block_slow() failed. block=1, b_blocknr=8
b_state=0x00000029, b_size=512
device loop0 blocksize: 4096
INFO: task syz-executor0:28007 blocked for more than 140 seconds.
      Not tainted 4.9.119-g9dc978d #23
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor0   D27928 28007      1 0x00000004
 ffff8801c2470000 0000000000000000 ffff8801a7b40a80 ffff8801d99b3000
 ffff8801db221c18 ffff8801b54c7b40 ffffffff839ebdcd 0000000000000002
 0000000041b58ab3 ffffffff843bc37b 00ffffff81221590 ffff8801db2224e8
Call Trace:
 [<ffffffff839ed3cf>] schedule+0x7f/0x1b0 kernel/sched/core.c:3553
 [<ffffffff81603039>] wb_wait_for_completion+0x149/0x1b0 fs/fs-writeback.c:221
 [<ffffffff816032a7>] __writeback_inodes_sb_nr+0x207/0x300 fs/fs-writeback.c:2310
 [<ffffffff816033f7>] writeback_inodes_sb_nr fs/fs-writeback.c:2327 [inline]
 [<ffffffff816033f7>] writeback_inodes_sb+0x27/0x30 fs/fs-writeback.c:2342
 [<ffffffff8161afb3>] __sync_filesystem fs/sync.c:35 [inline]
 [<ffffffff8161afb3>] sync_filesystem+0x93/0x240 fs/sync.c:63
 [<ffffffff815799e5>] generic_shutdown_super+0x75/0x300 fs/super.c:423
 [<ffffffff8157a31f>] kill_block_super+0x9f/0x120 fs/super.c:1127
 [<ffffffff8157a695>] deactivate_locked_super+0x75/0xd0 fs/super.c:310
 [<ffffffff8157b0a1>] deactivate_super+0x91/0xd0 fs/super.c:341
 [<ffffffff815dd442>] cleanup_mnt+0xb2/0x160 fs/namespace.c:1134
 [<ffffffff815dd576>] __cleanup_mnt+0x16/0x20 fs/namespace.c:1141
 [<ffffffff8119838c>] task_work_run+0x10c/0x180 kernel/task_work.c:116
 [<ffffffff8100559c>] tracehook_notify_resume include/linux/tracehook.h:191 [inline]
 [<ffffffff8100559c>] exit_to_usermode_loop+0xfc/0x120 arch/x86/entry/common.c:161
 [<ffffffff810064d4>] prepare_exit_to_usermode arch/x86/entry/common.c:191 [inline]
 [<ffffffff810064d4>] syscall_return_slowpath arch/x86/entry/common.c:260 [inline]
 [<ffffffff810064d4>] do_syscall_64+0x364/0x490 arch/x86/entry/common.c:287
 [<ffffffff839fccd3>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Showing all locks held in the system:
2 locks held by khungtaskd/519:
 #0:  (rcu_read_lock){......}, at: [<ffffffff813667bc>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff813667bc>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81426027>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by getty/3685:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839fae72>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff821208d2>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
1 lock held by syz-executor0/28007:
 #0:  (&type->s_umount_key#46){+.+...}, at: [<ffffffff8157b099>] deactivate_super+0x89/0xd0 fs/super.c:340
1 lock held by init/31003:
 #0:  (tty_mutex){+.+.+.}, at: [<ffffffff8211acdc>] tty_open_by_driver drivers/tty/tty_io.c:2047 [inline]
 #0:  (tty_mutex){+.+.+.}, at: [<ffffffff8211acdc>] tty_open+0x46c/0xe20 drivers/tty/tty_io.c:2125
1 lock held by init/31004:
 #0:  (tty_mutex){+.+.+.}, at: [<ffffffff8211acdc>] tty_open_by_driver drivers/tty/tty_io.c:2047 [inline]
 #0:  (tty_mutex){+.+.+.}, at: [<ffffffff8211acdc>] tty_open+0x46c/0xe20 drivers/tty/tty_io.c:2125
1 lock held by init/31005:
 #0:  (tty_mutex){+.+.+.}, at: [<ffffffff8211acdc>] tty_open_by_driver drivers/tty/tty_io.c:2047 [inline]
 #0:  (tty_mutex){+.+.+.}, at: [<ffffffff8211acdc>] tty_open+0x46c/0xe20 drivers/tty/tty_io.c:2125
1 lock held by init/31006:
 #0:  (tty_mutex){+.+.+.}, at: [<ffffffff8211acdc>] tty_open_by_driver drivers/tty/tty_io.c:2047 [inline]
 #0:  (tty_mutex){+.+.+.}, at: [<ffffffff8211acdc>] tty_open+0x46c/0xe20 drivers/tty/tty_io.c:2125
1 lock held by init/31007:
 #0:  (tty_mutex){+.+.+.}, at: [<ffffffff8211acdc>] tty_open_by_driver drivers/tty/tty_io.c:2047 [inline]
 #0:  (tty_mutex){+.+.+.}, at: [<ffffffff8211acdc>] tty_open+0x46c/0xe20 drivers/tty/tty_io.c:2125

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

NMI backtrace for cpu 1
CPU: 1 PID: 519 Comm: khungtaskd Not tainted 4.9.119-g9dc978d #23
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d8b67d08 ffffffff81eb4be9 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810b9bd0 ffff8801d8b67d40
 ffffffff81ebfee7 0000000000000001 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb4be9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb4be9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebfee7>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebfe7a>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810b9cd4>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81366d54>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81366d54>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81366d54>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81366d54>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119d0ed>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839fce9c>] 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: 31002 Comm: init Not tainted 4.9.119-g9dc978d #23
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801ce836000 task.stack: ffff880196c40000
RIP: 0010:[<ffffffff81ee3d6c>] 
c [<ffffffff81ee3d6c>] rdtsc arch/x86/include/asm/msr.h:165 [inline]
RIP: 0010:[<ffffffff81ee3d6c>] 
c [<ffffffff81ee3d6c>] rdtsc_ordered arch/x86/include/asm/msr.h:192 [inline]
RIP: 0010:[<ffffffff81ee3d6c>] 
c [<ffffffff81ee3d6c>] delay_tsc+0x4c/0xc0 arch/x86/lib/delay.c:60
RSP: 0018:ffff880196c47500  EFLAGS: 00000046
RAX: 0000000049efd2a2 RBX: 0000030049efd22f RCX: 0000000000000000
RDX: 0000000000000300 RSI: ffffffff81f1c62b RDI: ffffffff83e2e3e0
RBP: ffff880196c47520 R08: ffff8801ce836938 R09: 0000000000000001
R10: ffff8801ce836000 R11: 1ffff10039d06d22 R12: 0000030049efca87
R13: 00000000000008fd R14: 0000000000000000 R15: fffffbfff0c955d9
FS:  00007fb5553607a0(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f19b43a2188 CR3: 00000001b0caa000 CR4: 00000000001606f0
DR0: 0000000020000000 DR1: 00000000200000c0 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Stack:
 ffffffff864aae80
c 000000000000270e
c 0000000000000020
c fffffbfff0c95617
c
 ffff880196c47530
c ffffffff81ee3c91
c ffff880196c47580
c ffffffff8215324f
c
 ffff880196c475b8
c ffffffff864aaec8
c ffffffff864ab0ba
c ffffffff864aae80
c
Call Trace:
 [<ffffffff81ee3c91>] __delay arch/x86/lib/delay.c:160 [inline]
 [<ffffffff81ee3c91>] __const_udelay+0x31/0x40 arch/x86/lib/delay.c:174
 [<ffffffff8215324f>] wait_for_xmitr+0x6f/0x1e0 drivers/tty/serial/8250/8250_port.c:2006
 [<ffffffff821533df>] serial8250_console_putchar+0x1f/0x60 drivers/tty/serial/8250/8250_port.c:3104
 [<ffffffff8213bc09>] uart_console_write+0x59/0xf0 drivers/tty/serial/serial_core.c:1859
 [<ffffffff8215f5f8>] serial8250_console_write+0x528/0x820 drivers/tty/serial/8250/8250_port.c:3170
 [<ffffffff8214c15f>] univ8250_console_write+0x5f/0x70 drivers/tty/serial/8250/8250_core.c:594
 [<ffffffff8125bcad>] call_console_drivers.isra.18.constprop.28+0x1ad/0x360 kernel/printk/printk.c:1589
 [<ffffffff8125eaaf>] console_unlock+0x42f/0xb40 kernel/printk/printk.c:2449
 [<ffffffff8125fef7>] console_device+0x97/0xc0 kernel/printk/printk.c:2557
 [<ffffffff8211af8a>] tty_lookup_driver drivers/tty/tty_io.c:2003 [inline]
 [<ffffffff8211af8a>] tty_open_by_driver drivers/tty/tty_io.c:2048 [inline]
 [<ffffffff8211af8a>] tty_open+0x71a/0xe20 drivers/tty/tty_io.c:2125
 [<ffffffff8157f21d>] chrdev_open+0x22d/0x4c0 fs/char_dev.c:392
 [<ffffffff8156a103>] do_dentry_open+0x703/0xc80 fs/open.c:766
 [<ffffffff8156d8ec>] vfs_open+0x11c/0x210 fs/open.c:879
 [<ffffffff815a4a28>] do_last fs/namei.c:3410 [inline]
 [<ffffffff815a4a28>] path_openat+0x758/0x3590 fs/namei.c:3534
 [<ffffffff815abb27>] do_filp_open+0x197/0x270 fs/namei.c:3568
 [<ffffffff8156e2fd>] do_sys_open+0x30d/0x5c0 fs/open.c:1072
 [<ffffffff8156e5dd>] SYSC_open fs/open.c:1090 [inline]
 [<ffffffff8156e5dd>] SyS_open+0x2d/0x40 fs/open.c:1085
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839fccd3>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: 
cae 
ce8 
c0f 
c31 
c48 
cc1 
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c20 
c48 
c09 
cc2 
c49 
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cd4 
ceb 
c16 
cf3 
c90 
cbf 
c01 
c00 
c00 
c00 
ce8 
ca3 
c81 
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cff 
ce8 
cfe 
c89 
c03 
c00 
c44 
c39 
cf0 
c75 
c36 
c0f 
cae 
ce8 
c0f 
c31 
c<48> 
cc1 
ce2 
c20 
c48 
c89 
cd3 
c48 
c09 
cc3 
c48 
c89 
cd8 
c4c 
c29 
ce0 
c4c 
c39 
ce8 
c73 
c24 
c