Buffer I/O error on dev loop0, logical block 1, lost async page write
INFO: task syz-executor5:17644 blocked for more than 120 seconds.
      Not tainted 4.9.93-geba1ffe #3
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor5   D28392 17644   3842 0x20020004
 ffff8801d491b000 0000000000000000 ffff8801ce5b6f40 ffffffff84429800
 ffff8801db221b98 ffff8801d73a7930 ffffffff838c4a7d 1ffff1003ae74f1a
 ffffffff85351d98 0000000041b58ab3 00ffffff841a4608 ffff8801db222468
Call Trace:
 [<ffffffff838c607f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3556
 [<ffffffff838d2491>] schedule_timeout+0x861/0xf70 kernel/time/timer.c:1768
 [<ffffffff838c425a>] io_schedule_timeout+0x1ba/0x390 kernel/sched/core.c:5178
 [<ffffffff838c74c9>] io_schedule include/linux/sched.h:460 [inline]
 [<ffffffff838c74c9>] bit_wait_io+0x19/0xa0 kernel/sched/wait.c:582
 [<ffffffff838c6c13>] __wait_on_bit+0x93/0x120 kernel/sched/wait.c:383
 [<ffffffff81431dd0>] wait_on_page_bit+0x130/0x140 mm/filemap.c:802
 [<ffffffff81431fa1>] wait_on_page_writeback include/linux/pagemap.h:526 [inline]
 [<ffffffff81431fa1>] __filemap_fdatawait_range+0x1c1/0x290 mm/filemap.c:453
 [<ffffffff8143bec3>] filemap_fdatawait_keep_errors+0x63/0x80 mm/filemap.c:511
 [<ffffffff81617a30>] fdatawait_one_bdev+0x50/0x70 fs/sync.c:94
 [<ffffffff81632f2c>] iterate_bdevs+0x10c/0x260 fs/block_dev.c:1978
 [<ffffffff81618311>] sys_sync+0xe1/0x170 fs/sync.c:116
 [<ffffffff81006da7>] do_syscall_32_irqs_on arch/x86/entry/common.c:325 [inline]
 [<ffffffff81006da7>] do_fast_syscall_32+0x2f7/0x870 arch/x86/entry/common.c:387
 [<ffffffff838d7050>] entry_SYSENTER_compat+0x90/0xa2 arch/x86/entry/entry_64_compat.S:137

Showing all locks held in the system:
2 locks held by khungtaskd/515:
 #0:  (rcu_read_lock){......}, at: [<ffffffff813643fc>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff813643fc>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81423bb0>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
1 lock held by rsyslogd/3647:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815d562c>] __fdget_pos+0xac/0xd0 fs/file.c:781
2 locks held by getty/3743:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff838d3b22>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff82007e42>] n_tty_read+0x202/0x16b0 drivers/tty/n_tty.c:2133
3 locks held by kworker/u4:6/10939:
 #0:  ("writeback"){++++.+}, at: [<ffffffff8118ab9e>] work_static include/linux/workqueue.h:186 [inline]
 #0:  ("writeback"){++++.+}, at: [<ffffffff8118ab9e>] set_work_data kernel/workqueue.c:617 [inline]
 #0:  ("writeback"){++++.+}, at: [<ffffffff8118ab9e>] set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0:  ("writeback"){++++.+}, at: [<ffffffff8118ab9e>] process_one_work+0x6ee/0x1500 kernel/workqueue.c:2085
 #1:  ((&(&wb->dwork)->work)){+.+.+.}, at: [<ffffffff8118abd8>] process_one_work+0x728/0x1500 kernel/workqueue.c:2089
 #2:  (&type->s_umount_key#29){++++..}, at: [<ffffffff81579f40>] trylock_super+0x20/0xf0 fs/super.c:393
1 lock held by syz-executor5/17644:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff81632ee8>] iterate_bdevs+0xc8/0x260 fs/block_dev.c:1976

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

NMI backtrace for cpu 1
CPU: 1 PID: 515 Comm: khungtaskd Not tainted 4.9.93-geba1ffe #3
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d901fd08 ffffffff81d9c2b9 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810b7d90 ffff8801d901fd40
 ffffffff81da75f7 0000000000000001 0000000000000000 0000000000000002
Call Trace:
 [<ffffffff81d9c2b9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d9c2b9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81da75f7>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81da758a>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810b7e94>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81364994>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81364994>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81364994>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81364994>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119ab4d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff838d5b1c>] 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: 0 Comm: swapper/0 Not tainted 4.9.93-geba1ffe #3
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffffffff84429800 task.stack: ffffffff84400000
RIP: 0010:[<ffffffff81148e61>] 
c [<ffffffff81148e61>] __read_once_size include/linux/compiler.h:243 [inline]
RIP: 0010:[<ffffffff81148e61>] 
c [<ffffffff81148e61>] atomic_read arch/x86/include/asm/atomic.h:26 [inline]
RIP: 0010:[<ffffffff81148e61>] 
c [<ffffffff81148e61>] static_key_count include/linux/jump_label.h:174 [inline]
RIP: 0010:[<ffffffff81148e61>] 
c [<ffffffff81148e61>] static_key_false include/linux/jump_label.h:184 [inline]
RIP: 0010:[<ffffffff81148e61>] 
c [<ffffffff81148e61>] trace_softirq_raise include/trace/events/irq.h:155 [inline]
RIP: 0010:[<ffffffff81148e61>] 
c [<ffffffff81148e61>] __raise_softirq_irqoff kernel/softirq.c:443 [inline]
RIP: 0010:[<ffffffff81148e61>] 
c [<ffffffff81148e61>] raise_softirq_irqoff+0x11/0x1e0 kernel/softirq.c:417
RSP: 0018:ffff8801db207f78  EFLAGS: 00000046
RAX: 0000000000000000 RBX: ffff8801db221b80 RCX: 1ffffffff084227c
RDX: 1ffff1003b64449b RSI: ffffffff81e03cbb RDI: 0000000000000007
RBP: ffff8801db207f98 R08: 0000000000000001 R09: 000000000000000c
R10: ffffed0043fffa01 R11: 0000000000000001 R12: ffffffff84429800
R13: ffff8801db200000 R14: ffffffff84429800 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fb6932f2000 CR3: 00000001ba4b8000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff8801db221b80
c ffffffff84429800
c ffff8801db200000
c ffffffff84429800
c
 ffff8801db207fd0
c ffffffff811cdfd1
c ffffffff84429800
c ffffffff84211840
c
 0000000000000000
c 0000000000000000
c ffffffff84a3a008
c ffff8801db207fe8
c
Call Trace:
 <IRQ> 
d [<ffffffff811cdfd1>] scheduler_ipi+0x291/0x4e0 kernel/sched/core.c:1853
 [<ffffffff838da0dc>] __smp_reschedule_interrupt arch/x86/kernel/smp.c:262 [inline]
 [<ffffffff838da0dc>] smp_reschedule_interrupt+0x6c/0x90 arch/x86/kernel/smp.c:269
 [<ffffffff838d7c50>] reschedule_interrupt+0xa0/0xb0 arch/x86/entry/entry_64.S:671
 <EOI> 
d [<ffffffff838d4586>] ? native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:53
 [<ffffffff838d3bc5>] arch_safe_halt arch/x86/include/asm/paravirt.h:104 [inline]
 [<ffffffff838d3bc5>] default_idle+0x55/0x360 arch/x86/kernel/process.c:295
 [<ffffffff81069fa0>] arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:286
 [<ffffffff838d49e5>] default_idle_call+0x45/0x60 kernel/sched/idle.c:97
 [<ffffffff81220765>] cpuidle_idle_call kernel/sched/idle.c:155 [inline]
 [<ffffffff81220765>] cpu_idle_loop kernel/sched/idle.c:248 [inline]
 [<ffffffff81220765>] cpu_startup_entry+0x2b5/0x380 kernel/sched/idle.c:303
 [<ffffffff838c184c>] rest_init+0x183/0x189 init/main.c:409
 [<ffffffff84a73943>] start_kernel+0x67e/0x6b2 init/main.c:664
 [<ffffffff84a7229a>] x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:196
 [<ffffffff84a723db>] x86_64_start_kernel+0x13f/0x162 arch/x86/kernel/head64.c:177
Code: 
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c