INFO: task syz-executor3:17413 blocked for more than 140 seconds.
      Not tainted 4.9.121-g681e57b #25
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor3   D29496 17413  11029 0x00000004
 ffff88019b3c4800 ffff8801b9e1ea00 ffff8801d47b8000 ffff880199920000
 ffff8801db321c18 ffff8801d52df908 ffffffff839eedcd 0000000000000002
 0000000041b58ab3 ffffffff843bbbe4 00ffffff81223400 ffff8801db3224e8
Call Trace:
 [<ffffffff839f03cf>] schedule+0x7f/0x1b0 kernel/sched/core.c:3553
 [<ffffffff81605d69>] wb_wait_for_completion+0x149/0x1b0 fs/fs-writeback.c:221
 [<ffffffff81605fd7>] __writeback_inodes_sb_nr+0x207/0x300 fs/fs-writeback.c:2310
 [<ffffffff81606127>] writeback_inodes_sb_nr fs/fs-writeback.c:2327 [inline]
 [<ffffffff81606127>] writeback_inodes_sb+0x27/0x30 fs/fs-writeback.c:2342
 [<ffffffff8161dce3>] __sync_filesystem fs/sync.c:35 [inline]
 [<ffffffff8161dce3>] sync_filesystem+0x93/0x240 fs/sync.c:63
 [<ffffffff81636f7c>] fsync_bdev+0x8c/0xc0 fs/block_dev.c:216
 [<ffffffff81e5bda0>] blkdev_flushbuf block/ioctl.c:427 [inline]
 [<ffffffff81e5bda0>] blkdev_ioctl+0xb30/0x1a70 block/ioctl.c:512
 [<ffffffff81635e1e>] block_ioctl+0xde/0x120 fs/block_dev.c:1688
 [<ffffffff815b5e0c>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff815b5e0c>] file_ioctl fs/ioctl.c:493 [inline]
 [<ffffffff815b5e0c>] do_vfs_ioctl+0x1ac/0x11a0 fs/ioctl.c:677
 [<ffffffff815b6e8f>] SYSC_ioctl fs/ioctl.c:694 [inline]
 [<ffffffff815b6e8f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839ffcd3>] 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: [<ffffffff8136862c>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136862c>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81427e98>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by getty/3777:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839fde72>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff82123b32>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
1 lock held by syz-executor3/17413:
 #0:  (&type->s_umount_key#39){++++..}, at: [<ffffffff8157df69>] get_super.part.9+0x119/0x1f0 fs/super.c:665
1 lock held by syz-executor3/17418:
 #0:  (&type->s_umount_key#39){++++..}, at: [<ffffffff8157df69>] get_super.part.9+0x119/0x1f0 fs/super.c:665
1 lock held by syz-executor6/17414:
 #0:  (&type->s_umount_key#39){++++..}, at: [<ffffffff8157df69>] get_super.part.9+0x119/0x1f0 fs/super.c:665
1 lock held by syz-executor6/17422:
 #0:  (&type->s_umount_key#39){++++..}, at: [<ffffffff8157df69>] get_super.part.9+0x119/0x1f0 fs/super.c:665
1 lock held by syz-executor1/17453:
 #0:  (&type->s_umount_key#39){++++..}, at: [<ffffffff8157df69>] get_super.part.9+0x119/0x1f0 fs/super.c:665
1 lock held by syz-executor1/17464:
 #0:  (&type->s_umount_key#39){++++..}, at: [<ffffffff8157df69>] get_super.part.9+0x119/0x1f0 fs/super.c:665
1 lock held by syz-executor1/17494:
 #0:  (&type->s_umount_key#39){++++..}, at: [<ffffffff8157df69>] get_super.part.9+0x119/0x1f0 fs/super.c:665
1 lock held by syz-executor1/17495:
 #0:  (&type->s_umount_key#39){++++..}, at: [<ffffffff8157df69>] get_super.part.9+0x119/0x1f0 fs/super.c:665

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

NMI backtrace for cpu 1
CPU: 1 PID: 519 Comm: khungtaskd Not tainted 4.9.121-g681e57b #25
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d868fd08 ffffffff81eb7e29 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810b9fa0 ffff8801d868fd40
 ffffffff81ec3137 0000000000000001 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb7e29>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb7e29>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ec3137>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ec30ca>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810ba0a4>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81368bc4>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81368bc4>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81368bc4>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81368bc4>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119ef5d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839ffe9c>] 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: 4828 Comm: kworker/u4:6 Not tainted 4.9.121-g681e57b #25
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: writeback wb_workfn
c (flush-7:0)
c
task: ffff88019a2a4800 task.stack: ffff88019a328000
RIP: 0010:[<ffffffff812328ef>] 
c [<ffffffff812328ef>] arch_local_irq_restore arch/x86/include/asm/paravirt.h:768 [inline]
RIP: 0010:[<ffffffff812328ef>] 
c [<ffffffff812328ef>] lock_is_held+0xff/0x140 kernel/locking/lockdep.c:3796
RSP: 0018:ffff88019a32f550  EFLAGS: 00000246
RAX: 0000000000000007 RBX: 0000000000000246 RCX: ffff88019a2a4800
RDX: 0000000000000000 RSI: ffffffff846df460 RDI: 0000000000000246
RBP: ffff88019a32f568 R08: ffff88019a2a5138 R09: 0000000000000001
R10: 0000000000000000 R11: 1ffff10033454a22 R12: ffff88019a2a4800
R13: 0000000000000000 R14: 00000000000001cc R15: ffff8801d63214c8
FS:  0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f505a39e000 CR3: 00000001cb5ad000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff88019a2a4800
c 0000000000000000
c ffffffff83ca4be0
c ffff88019a32f5a0
c
 ffffffff811bd43f
c ffff88019a2a4800
c ffffffff83ca4be0
c 00000000000001cc
c
 0000000000000000
c ffff8801d63214c8
c ffff88019a32f5e0
c ffffffff811bd535
c
Call Trace:
 [<ffffffff811bd43f>] ___might_sleep+0x1ff/0x260 kernel/sched/core.c:7954
 [<ffffffff811bd535>] __might_sleep+0x95/0x1a0 kernel/sched/core.c:7945
 [<ffffffff8143c4dd>] lock_page include/linux/pagemap.h:460 [inline]
 [<ffffffff8143c4dd>] pagecache_get_page+0x3bd/0x720 mm/filemap.c:1214
 [<ffffffff81628539>] find_or_create_page include/linux/pagemap.h:309 [inline]
 [<ffffffff81628539>] grow_dev_page fs/buffer.c:1005 [inline]
 [<ffffffff81628539>] grow_buffers fs/buffer.c:1078 [inline]
 [<ffffffff81628539>] __getblk_slow fs/buffer.c:1105 [inline]
 [<ffffffff81628539>] __getblk_gfp+0x249/0x710 fs/buffer.c:1386
 [<ffffffff8162be1d>] __bread_gfp+0x2d/0x270 fs/buffer.c:1420
 [<ffffffff818cfbdb>] sb_bread include/linux/buffer_head.h:300 [inline]
 [<ffffffff818cfbdb>] __fat_write_inode+0x2ab/0x980 fs/fat/inode.c:852
 [<ffffffff818d3e99>] fat_write_inode+0x79/0x170 fs/fat/inode.c:901
 [<ffffffff8160546d>] write_inode fs/fs-writeback.c:1180 [inline]
 [<ffffffff8160546d>] __writeback_single_inode+0x86d/0x1020 fs/fs-writeback.c:1379
 [<ffffffff8160676c>] writeback_sb_inodes+0x4ac/0xe70 fs/fs-writeback.c:1584
 [<ffffffff8160776f>] wb_writeback+0x2cf/0xbd0 fs/fs-writeback.c:1760
 [<ffffffff81610c9e>] wb_do_writeback fs/fs-writeback.c:1894 [inline]
 [<ffffffff81610c9e>] wb_workfn+0x20e/0xdb0 fs/fs-writeback.c:1930
 [<ffffffff8118eff1>] process_one_work+0x7e1/0x1500 kernel/workqueue.c:2092
 [<ffffffff8118fde6>] worker_thread+0xd6/0x10a0 kernel/workqueue.c:2226
 [<ffffffff8119ef5d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839ffe9c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Code: 
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c<0f> 
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c