Buffer I/O error on dev loop0, logical block 1, lost async page write
INFO: task syz-executor6:7173 blocked for more than 120 seconds.
      Not tainted 4.9.90-gdd1e37e #66
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor6   D29472  7173   3882 0x00000004
 ffff8801ca793000 0000000000000000 ffff8801cbd8e4c0 ffffffff84429880
 ffff8801db221b98 ffff8801c9d87a10 ffffffff838a75cb 0000000041b58ab3
 ffffffff84193d90 00ffffff8123aaf0 ffff8801db222468 ffff8801db222490
Call Trace:
 [<ffffffff838a8b6f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3551
 [<ffffffff838b4b2c>] schedule_timeout+0x56c/0x10b0 kernel/time/timer.c:1768
 [<ffffffff838a6d7e>] io_schedule_timeout+0x1be/0x390 kernel/sched/core.c:5173
 [<ffffffff838a9fe9>] io_schedule include/linux/sched.h:460 [inline]
 [<ffffffff838a9fe9>] bit_wait_io+0x19/0xa0 kernel/sched/wait.c:582
 [<ffffffff838a96c7>] __wait_on_bit+0x57/0x120 kernel/sched/wait.c:383
 [<ffffffff814316e4>] wait_on_page_bit+0xf4/0x140 mm/filemap.c:802
 [<ffffffff814318f1>] wait_on_page_writeback include/linux/pagemap.h:526 [inline]
 [<ffffffff814318f1>] __filemap_fdatawait_range+0x1c1/0x2b0 mm/filemap.c:453
 [<ffffffff81431a05>] filemap_fdatawait_range+0x25/0x50 mm/filemap.c:483
 [<ffffffff816160fb>] SYSC_sync_file_range fs/sync.c:346 [inline]
 [<ffffffff816160fb>] SyS_sync_file_range+0x1bb/0x220 fs/sync.c:283
 [<ffffffff81006504>] do_syscall_64+0x1a4/0x490 arch/x86/entry/common.c:282
 [<ffffffff838b8493>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Showing all locks held in the system:
2 locks held by khungtaskd/515:
 #0:  (rcu_read_lock){......}, at: [<ffffffff81372185>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff81372185>] watchdog+0x125/0xa70 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81236c50>] debug_show_all_locks+0x70/0x280 kernel/locking/lockdep.c:4336
3 locks held by kworker/u4:3/1603:
 #0:  ("writeback"){.+.+.+}, at: [<ffffffff8118af42>] work_static include/linux/workqueue.h:186 [inline]
 #0:  ("writeback"){.+.+.+}, at: [<ffffffff8118af42>] set_work_data kernel/workqueue.c:617 [inline]
 #0:  ("writeback"){.+.+.+}, at: [<ffffffff8118af42>] set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0:  ("writeback"){.+.+.+}, at: [<ffffffff8118af42>] process_one_work+0x6f2/0x1610 kernel/workqueue.c:2085
 #1:  ((&(&wb->dwork)->work)){+.+.+.}, at: [<ffffffff8118af7c>] process_one_work+0x72c/0x1610 kernel/workqueue.c:2089
 #2:  (&type->s_umount_key#22){.+.+..}, at: [<ffffffff815790a0>] trylock_super+0x20/0x100 fs/super.c:393
1 lock held by rsyslogd/3655:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815d2f5f>] __fdget_pos+0x9f/0xc0 fs/file.c:781
2 locks held by getty/3783:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff838b66a2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff8200a6a4>] n_tty_read+0x1f4/0x16c0 drivers/tty/n_tty.c:2133

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

NMI backtrace for cpu 1
CPU: 1 PID: 515 Comm: khungtaskd Not tainted 4.9.90-gdd1e37e #66
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d8627d00 ffffffff81d94ee9 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810bb920 ffff8801d8627d38
 ffffffff81da000d 0000000000000001 0000000000000000 ffff8801cba93418
Call Trace:
 [<ffffffff81d94ee9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d94ee9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81da000d>] nmi_cpu_backtrace+0xfd/0x120 lib/nmi_backtrace.c:99
 [<ffffffff81da0147>] nmi_trigger_cpumask_backtrace+0x117/0x190 lib/nmi_backtrace.c:60
 [<ffffffff810bba14>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81372750>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81372750>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81372750>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81372750>] watchdog+0x6f0/0xa70 kernel/hung_task.c:239
 [<ffffffff8119bf4d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff838b865c>] 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 4.9.90-gdd1e37e #66
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffffffff84429880 task.stack: ffffffff84400000
RIP: 0010:[<ffffffff811cb9c3>] 
c [<ffffffff811cb9c3>] llist_del_all include/linux/llist.h:210 [inline]
RIP: 0010:[<ffffffff811cb9c3>] 
c [<ffffffff811cb9c3>] sched_ttwu_pending+0x53/0x160 kernel/sched/core.c:1792
RSP: 0018:ffff8801db207f58  EFLAGS: 00000046
RAX: 0000000000000000 RBX: ffff8801db221b80 RCX: 1ffffffff084007c
RDX: 0000000000000000 RSI: ffffffff83c18d80 RDI: ffffffff842003e0
RBP: ffff8801db207f98 R08: 0000000000000001 R09: ffff88021fffd008
R10: ffff88021fffd018 R11: ffff88021fffd010 R12: 0000000000021b80
R13: ffff8801db200000 R14: ffffffff84429880 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fdd12264000 CR3: 00000001b84e2000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff812862b7
c ffff8801db207f80
c 0000000000000046
c 0000000000021b80
c
 0000000000021b80
c ffff8801db200000
c ffffffff84429880
c 0000000000000000
c
 ffff8801db207fd0
c ffffffff811cbdb2
c ffffffff84429880
c ffffffff84200840
c
Call Trace:
 [<ffffffff811cbdb2>] scheduler_ipi+0xc2/0x4f0 kernel/sched/core.c:1845
 [<ffffffff838bcbb6>] __smp_reschedule_interrupt arch/x86/kernel/smp.c:262 [inline]
 [<ffffffff838bcbb6>] smp_reschedule_interrupt+0x66/0x80 arch/x86/kernel/smp.c:269
 [<ffffffff838ba7d0>] reschedule_interrupt+0xa0/0xb0 arch/x86/entry/entry_64.S:671
 <EOI> 
d [<ffffffff838b7116>] ? native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:53
 [<ffffffff838b6745>] arch_safe_halt arch/x86/include/asm/paravirt.h:104 [inline]
 [<ffffffff838b6745>] default_idle+0x55/0x360 arch/x86/kernel/process.c:295
 [<ffffffff8106be0a>] arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:286
 [<ffffffff838b7556>] default_idle_call+0x36/0x60 kernel/sched/idle.c:97
 [<ffffffff81225520>] cpuidle_idle_call kernel/sched/idle.c:155 [inline]
 [<ffffffff81225520>] cpu_idle_loop kernel/sched/idle.c:248 [inline]
 [<ffffffff81225520>] cpu_startup_entry+0x2b0/0x380 kernel/sched/idle.c:303
 [<ffffffff838a4214>] rest_init+0x184/0x190 init/main.c:408
 [<ffffffff84a6f8b2>] start_kernel+0x684/0x6b9 init/main.c:663
 [<ffffffff84a6e29d>] x86_64_start_reservations+0x2a/0x2c arch/x86/kernel/head64.c:196
 [<ffffffff84a6e3df>] x86_64_start_kernel+0x140/0x163 arch/x86/kernel/head64.c:177
Code: 
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c