INFO: task syz-executor3:13952 blocked for more than 120 seconds.
      Not tainted 4.9.64-gfbb7468 #94
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor3   D28736 13952   3506 0x00000004
 ffff8801c6150000 ffff8801cb8a24c0 ffff8801ca2def40 ffff8801ce090000
 ffff8801db321418 ffff8801ce3279b0 ffffffff83897fdb ffffffff812395a0
 ffffe8ffffd03d00 00ff8801ce327a70 ffff8801db321d40 ffff8801db321d68
Call Trace:
 [<ffffffff8389957f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3540
 [<ffffffff838a57b3>] schedule_timeout+0x643/0x1220 kernel/time/timer.c:1770
 [<ffffffff8389778e>] io_schedule_timeout+0x1be/0x390 kernel/sched/core.c:5162
 [<ffffffff8389a9f9>] io_schedule include/linux/sched.h:460 [inline]
 [<ffffffff8389a9f9>] bit_wait_io+0x19/0xa0 kernel/sched/wait.c:582
 [<ffffffff8389a0d7>] __wait_on_bit+0x57/0x120 kernel/sched/wait.c:383
 [<ffffffff8142f574>] wait_on_page_bit+0xf4/0x140 mm/filemap.c:802
 [<ffffffff8142f781>] wait_on_page_writeback include/linux/pagemap.h:526 [inline]
 [<ffffffff8142f781>] __filemap_fdatawait_range+0x1c1/0x2b0 mm/filemap.c:453
 [<ffffffff814396e3>] filemap_fdatawait_keep_errors+0x63/0x80 mm/filemap.c:511
 [<ffffffff81611d20>] fdatawait_one_bdev+0x50/0x70 fs/sync.c:94
 [<ffffffff8162d3a9>] iterate_bdevs+0x109/0x260 fs/block_dev.c:1978
 [<ffffffff816125f1>] sys_sync+0xe1/0x170 fs/sync.c:116
 [<ffffffff838a9785>] entry_SYSCALL_64_fastpath+0x23/0xc6

Showing all locks held in the system:
2 locks held by khungtaskd/514:
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136fed5>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136fed5>] watchdog+0x125/0xa70 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81235700>] debug_show_all_locks+0x70/0x280 kernel/locking/lockdep.c:4336
2 locks held by getty/3217:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff838a79a2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff82001b14>] n_tty_read+0x1f4/0x16c0 drivers/tty/n_tty.c:2133
3 locks held by kworker/u4:5/3814:
 #0:  ("writeback"){++++.+}, at: [<ffffffff81187719>] __write_once_size include/linux/compiler.h:272 [inline]
 #0:  ("writeback"){++++.+}, at: [<ffffffff81187719>] atomic64_set arch/x86/include/asm/atomic64_64.h:33 [inline]
 #0:  ("writeback"){++++.+}, at: [<ffffffff81187719>] atomic_long_set include/asm-generic/atomic-long.h:56 [inline]
 #0:  ("writeback"){++++.+}, at: [<ffffffff81187719>] set_work_data kernel/workqueue.c:616 [inline]
 #0:  ("writeback"){++++.+}, at: [<ffffffff81187719>] set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline]
 #0:  ("writeback"){++++.+}, at: [<ffffffff81187719>] process_one_work+0x6a9/0x15f0 kernel/workqueue.c:2083
 #1:  ((&(&wb->dwork)->work)){+.+.+.}, at: [<ffffffff8118774b>] process_one_work+0x6db/0x15f0 kernel/workqueue.c:2087
 #2:  (&type->s_umount_key#28){.+.+..}, at: [<ffffffff81575cd0>] trylock_super+0x20/0x100 fs/super.c:393
1 lock held by syz-executor3/13952:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8162d368>] iterate_bdevs+0xc8/0x260 fs/block_dev.c:1976
1 lock held by syz-executor3/13959:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8162d368>] iterate_bdevs+0xc8/0x260 fs/block_dev.c:1976
1 lock held by syz-executor6/13985:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8162d368>] iterate_bdevs+0xc8/0x260 fs/block_dev.c:1976
1 lock held by syz-executor6/14007:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8162d368>] iterate_bdevs+0xc8/0x260 fs/block_dev.c:1976
1 lock held by syz-executor2/14002:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8162a2bc>] __blkdev_get+0x10c/0xd50 fs/block_dev.c:1268
1 lock held by syz-executor2/14011:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8162a2bc>] __blkdev_get+0x10c/0xd50 fs/block_dev.c:1268
1 lock held by syz-executor2/14016:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8162a2bc>] __blkdev_get+0x10c/0xd50 fs/block_dev.c:1268
1 lock held by syz-executor2/14023:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8162a2bc>] __blkdev_get+0x10c/0xd50 fs/block_dev.c:1268
1 lock held by syz-executor7/14006:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8162a2bc>] __blkdev_get+0x10c/0xd50 fs/block_dev.c:1268
1 lock held by syz-executor7/14018:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8162a2bc>] __blkdev_get+0x10c/0xd50 fs/block_dev.c:1268
1 lock held by syz-executor5/14042:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8162a2bc>] __blkdev_get+0x10c/0xd50 fs/block_dev.c:1268
1 lock held by syz-executor5/14053:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8162a2bc>] __blkdev_get+0x10c/0xd50 fs/block_dev.c:1268

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

NMI backtrace for cpu 1
CPU: 1 PID: 514 Comm: khungtaskd Not tainted 4.9.64-gfbb7468 #94
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d8f8fd00 ffffffff81d90429 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810ba170 ffff8801d8f8fd38
 ffffffff81d9b54d 0000000000000001 0000000000000000 ffff8801d1300418
Call Trace:
 [<ffffffff81d90429>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d90429>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81d9b54d>] nmi_cpu_backtrace+0xfd/0x120 lib/nmi_backtrace.c:99
 [<ffffffff81d9b687>] nmi_trigger_cpumask_backtrace+0x117/0x190 lib/nmi_backtrace.c:60
 [<ffffffff810ba264>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff813704a0>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff813704a0>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff813704a0>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff813704a0>] watchdog+0x6f0/0xa70 kernel/hung_task.c:239
 [<ffffffff811985dd>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff838a9a2a>] ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:433
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at pc 0xffffffff838a8416