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-executor0:3842 blocked for more than 120 seconds.
      Not tainted 4.9.109-ga4230be #48
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor0   D26872  3842      1 0x00000004
 ffff8801d71e4800 0000000000000000 ffff8801d6ff1f80 ffff8801d9a39800
 ffff8801db321c18 ffff8801d4ecfb40 ffffffff839e8a8d 0000000000000002
 0000000041b58ab3 ffffffff843b9d9b 00ffffff81221500 ffff8801db3224e8
Call Trace:
 [<ffffffff839ea08f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3557
 [<ffffffff81602ad9>] wb_wait_for_completion+0x149/0x1b0 fs/fs-writeback.c:221
 [<ffffffff81602d47>] __writeback_inodes_sb_nr+0x207/0x300 fs/fs-writeback.c:2310
 [<ffffffff81602e97>] writeback_inodes_sb_nr fs/fs-writeback.c:2327 [inline]
 [<ffffffff81602e97>] writeback_inodes_sb+0x27/0x30 fs/fs-writeback.c:2342
 [<ffffffff8161aa53>] __sync_filesystem fs/sync.c:35 [inline]
 [<ffffffff8161aa53>] sync_filesystem+0x93/0x240 fs/sync.c:63
 [<ffffffff815794e5>] generic_shutdown_super+0x75/0x300 fs/super.c:423
 [<ffffffff81579e1f>] kill_block_super+0x9f/0x120 fs/super.c:1127
 [<ffffffff8157a195>] deactivate_locked_super+0x75/0xd0 fs/super.c:310
 [<ffffffff8157aba1>] deactivate_super+0x91/0xd0 fs/super.c:341
 [<ffffffff815dcee2>] cleanup_mnt+0xb2/0x160 fs/namespace.c:1134
 [<ffffffff815dd016>] __cleanup_mnt+0x16/0x20 fs/namespace.c:1141
 [<ffffffff8119832c>] 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
 [<ffffffff839f9993>] 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: [<ffffffff8136662c>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136662c>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81425cb7>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
1 lock held by rsyslogd/3687:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815d803c>] __fdget_pos+0xac/0xd0 fs/file.c:781
2 locks held by getty/3782:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839f7b32>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff8211fce2>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2133
1 lock held by syz-executor0/3842:
 #0:  (&type->s_umount_key#46){+.+...}, at: [<ffffffff8157ab99>] deactivate_super+0x89/0xd0 fs/super.c:340
1 lock held by init/11399:
 #0:  (tty_mutex){+.+.+.}, at: [<ffffffff82119d8c>] tty_open_by_driver drivers/tty/tty_io.c:2047 [inline]
 #0:  (tty_mutex){+.+.+.}, at: [<ffffffff82119d8c>] tty_open+0x46c/0xe20 drivers/tty/tty_io.c:2125
1 lock held by init/11400:
 #0:  (tty_mutex){+.+.+.}, at: [<ffffffff82119d8c>] tty_open_by_driver drivers/tty/tty_io.c:2047 [inline]
 #0:  (tty_mutex){+.+.+.}, at: [<ffffffff82119d8c>] tty_open+0x46c/0xe20 drivers/tty/tty_io.c:2125
1 lock held by init/11401:
 #0:  (tty_mutex){+.+.+.}, at: [<ffffffff82119d8c>] tty_open_by_driver drivers/tty/tty_io.c:2047 [inline]
 #0:  (tty_mutex){+.+.+.}, at: [<ffffffff82119d8c>] tty_open+0x46c/0xe20 drivers/tty/tty_io.c:2125
1 lock held by init/11402:
 #0:  (tty_mutex){+.+.+.}, at: [<ffffffff82119d8c>] tty_open_by_driver drivers/tty/tty_io.c:2047 [inline]
 #0:  (tty_mutex){+.+.+.}, at: [<ffffffff82119d8c>] tty_open+0x46c/0xe20 drivers/tty/tty_io.c:2125
1 lock held by init/11403:
 #0:  (tty_mutex){+.+.+.}, at: [<ffffffff82119d8c>] tty_open_by_driver drivers/tty/tty_io.c:2047 [inline]
 #0:  (tty_mutex){+.+.+.}, at: [<ffffffff82119d8c>] tty_open+0x46c/0xe20 drivers/tty/tty_io.c:2125

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

NMI backtrace for cpu 1
CPU: 1 PID: 519 Comm: khungtaskd Not tainted 4.9.109-ga4230be #48
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d8fbfd08 ffffffff81eb3e29 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810b9580 ffff8801d8fbfd40
 ffffffff81ebf127 0000000000000001 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb3e29>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb3e29>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebf127>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebf0ba>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810b9684>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81366bc4>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81366bc4>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81366bc4>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81366bc4>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119d04d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839f9b5c>] 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: 4643 Comm: kworker/0:3 Not tainted 4.9.109-ga4230be #48
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events_power_efficient gc_worker
c
task: ffff880182af6000 task.stack: ffff880182a78000
RIP: 0010:[<ffffffff8122eeff>] 
c [<ffffffff8122eeff>] trace_hardirqs_off_caller+0x6f/0x280 kernel/locking/lockdep.c:2756
RSP: 0018:ffff880182a7fb98  EFLAGS: 00000002
RAX: dffffc0000000000 RBX: ffff880182af6000 RCX: 1ffffffff0886480
RDX: 0000000000000004 RSI: ffffffff831f2da7 RDI: ffff880182af68c4
RBP: ffff880182a7fbb0 R08: ffff880182af6938 R09: 0000000000000001
R10: ffff880182af6000 R11: 1ffff1003055ed22 R12: ffff880182af6000
R13: ffffffff831f2dbd R14: ffffffff84c65928 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fceb6676000 CR3: 00000001b7859000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 0000000000000293
c dffffc0000000000
c ffffffff84c65920
c ffff880182a7fbc0
c
 ffffffff8122f11d
c ffff880182a7fc40
c ffffffff831f2dbd
c ffffffff831f2d06
c
 ffffffff864ef2f8
c ffffffff864ef240
c fffffbfff08c1200
c 00000200c7d09d00
c
Call Trace:
 [<ffffffff8122f11d>] trace_hardirqs_off+0xd/0x10 kernel/locking/lockdep.c:2781
 [<ffffffff831f2dbd>] seqcount_lockdep_reader_access include/linux/seqlock.h:79 [inline]
 [<ffffffff831f2dbd>] read_seqcount_begin include/linux/seqlock.h:163 [inline]
 [<ffffffff831f2dbd>] nf_conntrack_get_ht include/net/netfilter/nf_conntrack.h:325 [inline]
 [<ffffffff831f2dbd>] gc_worker+0x14d/0x620 net/netfilter/nf_conntrack_core.c:968
 [<ffffffff8118d121>] process_one_work+0x7e1/0x1500 kernel/workqueue.c:2092
 [<ffffffff8118df16>] worker_thread+0xd6/0x10a0 kernel/workqueue.c:2226
 [<ffffffff8119d04d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839f9b5c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Code: 
c00 
c00 
c8b 
c3d 
c44 
c1c 
c64 
c03 
c85 
cff 
c0f 
c84 
c70 
c01 
c00 
c00 
c65 
c4c 
c8b 
c24 
c25 
cc0 
c7d 
c01 
c00 
c49 
c8d 
cbc 
c24 
cc4 
c08 
c00 
c00 
c48 
cb8 
c00 
c00 
c00 
c00 
c00 
cfc 
cff 
cdf 
c<48> 
c89 
cfa 
c48 
cc1 
cea 
c03 
c0f 
cb6 
c14 
c02 
c48 
c89 
cf8 
c83 
ce0 
c07 
c83 
cc0 
c03 
c38 
c