buffer_io_error: 6 callbacks suppressed
Buffer I/O error on dev loop0, logical block 0, lost async page write
INFO: task syz-executor7:5453 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-executor7   D27960  5453   5275 0x20020004
 ffff8801bcfa8000 0000000000000000 ffff8801a3759f80 ffff8801d9b73000
 ffff8801db321b98 ffff8801d705f690 ffffffff838c4a7d 1ffff1003ae0bec6
 ffffffff85317f38 0000000041b58ab3 00ffffff841a4608 ffff8801db322468
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
 [<ffffffff838c6d6e>] __wait_on_bit_lock+0xce/0x1c0 kernel/sched/wait.c:421
 [<ffffffff8143246f>] __lock_page+0xff/0x160 mm/filemap.c:934
 [<ffffffff81456ac8>] lock_page include/linux/pagemap.h:454 [inline]
 [<ffffffff81456ac8>] write_cache_pages+0x638/0xef0 mm/page-writeback.c:2214
 [<ffffffff8145745a>] generic_writepages+0xda/0x150 mm/page-writeback.c:2333
 [<ffffffff8162d37d>] blkdev_writepages+0x1d/0x30 fs/block_dev.c:1764
 [<ffffffff8145ca6f>] do_writepages+0xef/0x1d0 mm/page-writeback.c:2347
 [<ffffffff8143aae3>] __filemap_fdatawrite_range+0x1b3/0x250 mm/filemap.c:390
 [<ffffffff8143ada9>] filemap_write_and_wait_range+0x59/0xb0 mm/filemap.c:580
 [<ffffffff8162c6a6>] blkdev_fsync+0x66/0xb0 fs/block_dev.c:369
 [<ffffffff81617ccc>] vfs_fsync_range+0x10c/0x260 fs/sync.c:195
 [<ffffffff81617e92>] vfs_fsync fs/sync.c:209 [inline]
 [<ffffffff81617e92>] do_fsync+0x42/0xb0 fs/sync.c:219
 [<ffffffff81618639>] SYSC_fdatasync fs/sync.c:233 [inline]
 [<ffffffff81618639>] SyS_fdatasync+0x19/0x20 fs/sync.c:231
 [<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
2 locks held by getty/3704:
 #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/u4:2/4801:
 #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

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

NMI backtrace for cpu 0
CPU: 0 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
 ffff8801d8697d08 ffffffff81d9c2b9 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810b7d90 ffff8801d8697d40
 ffffffff81da75f7 0000000000000000 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 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at pc 0xffffffff838d4586