IPVS: stopping master sync thread 7266 ...
INFO: task syz-executor7:15235 blocked for more than 140 seconds.
      Not tainted 4.9.113-g47bbcd6 #10
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor7   D28504 15235  12706 0x00000004
 ffff8801b7959800 ffff8801c90e5a40 ffff8801cb7439c0 ffff8801ce174800
 ffff8801db221c18 ffff88019e807b58 ffffffff839e909d 0000000000000002
 0000000041b58ab3 ffffffff843bbae3 00ffffff81221550 ffff8801db2224e8
Call Trace:
 [<ffffffff839ea69f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3553
 [<ffffffff81602c89>] wb_wait_for_completion+0x149/0x1b0 fs/fs-writeback.c:221
 [<ffffffff81608419>] sync_inodes_sb+0x1a9/0x8d0 fs/fs-writeback.c:2412
 [<ffffffff8161a543>] sync_inodes_one_sb+0x43/0x60 fs/sync.c:73
 [<ffffffff8157ce00>] iterate_supers+0x130/0x260 fs/super.c:593
 [<ffffffff8161ae52>] sys_sync+0xa2/0x170 fs/sync.c:112
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839f9f93>] 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: [<ffffffff8136675c>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136675c>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81425de7>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by getty/3774:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839f8142>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff8211ee22>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
1 lock held by syz-executor7/15235:
 #0:  (&type->s_umount_key#34){++++..}, at: [<ffffffff8157cdb1>] iterate_supers+0xe1/0x260 fs/super.c:591
1 lock held by syz-executor7/15292:
 #0:  (&type->s_umount_key#34){++++..}, at: [<ffffffff8157cdb1>] iterate_supers+0xe1/0x260 fs/super.c:591

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

NMI backtrace for cpu 1
CPU: 1 PID: 519 Comm: khungtaskd Not tainted 4.9.113-g47bbcd6 #10
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d845fd08 ffffffff81eb32a9 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810b9bd0 ffff8801d845fd40
 ffffffff81ebe5a7 0000000000000001 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb32a9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb32a9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebe5a7>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebe53a>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810b9cd4>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81366cf4>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81366cf4>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81366cf4>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81366cf4>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119d0ad>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839fa15c>] 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: 22 Comm: kworker/u4:1 Not tainted 4.9.113-g47bbcd6 #10
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: writeback wb_workfn
c (flush-7:0)
c
task: ffff8801d9bd0000 task.stack: ffff8801d9bd8000
RIP: 0010:[<ffffffff81f1ae7d>] 
c [<ffffffff81f1ae7d>] __this_cpu_preempt_check+0x1d/0x20 lib/smp_processor_id.c:63
RSP: 0018:ffff8801d9bdf640  EFLAGS: 00000096
RAX: 0000000000000000 RBX: 000000000000000d RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff81f1ad0b RDI: ffffffff83e2de20
RBP: ffff8801d9bdf640 R08: ffff8801d9bd0988 R09: 0000000000000001
R10: 0000000000000000 R11: 1ffff1003b37a12c R12: ffff8801bacbe2a0
R13: dffffc0000000000 R14: ffff8801bacbe2a0 R15: 000000000000000d
FS:  0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fd249a07000 CR3: 00000001bebf1000 CR4: 00000000001606f0
DR0: 00000000200001c0 DR1: 00000000200001c0 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Stack:
 ffff8801d9bdf690
c ffffffff816243c5
c 0000020006cc2300
c 0000000000000001
c
 ffff8801cbf8ed40
c 0000000000000001
c ffffea0006cc231c
c ffffea0006cc2300
c
 0000000000000200
c dffffc0000000000
c ffff8801d9bdf730
c ffffffff81625399
c
Call Trace:
 [<ffffffff816243c5>] lookup_bh_lru fs/buffer.c:1327 [inline]
 [<ffffffff816243c5>] __find_get_block+0x75/0x4c0 fs/buffer.c:1356
 [<ffffffff81625399>] __getblk_slow fs/buffer.c:1101 [inline]
 [<ffffffff81625399>] __getblk_gfp+0x189/0x710 fs/buffer.c:1386
 [<ffffffff81628d3d>] __bread_gfp+0x2d/0x270 fs/buffer.c:1420
 [<ffffffff818d6931>] sb_bread include/linux/buffer_head.h:300 [inline]
 [<ffffffff818d6931>] fat_clusters_flush+0x111/0x380 fs/fat/misc.c:69
 [<ffffffff818d08c2>] fat_write_inode+0xf2/0x170 fs/fat/inode.c:890
 [<ffffffff8160238d>] write_inode fs/fs-writeback.c:1180 [inline]
 [<ffffffff8160238d>] __writeback_single_inode+0x86d/0x1020 fs/fs-writeback.c:1379
 [<ffffffff8160368c>] writeback_sb_inodes+0x4ac/0xe70 fs/fs-writeback.c:1584
 [<ffffffff8160414b>] __writeback_inodes_wb+0xfb/0x1e0 fs/fs-writeback.c:1653
 [<ffffffff816048d2>] wb_writeback+0x512/0xbd0 fs/fs-writeback.c:1762
 [<ffffffff8160dbbe>] wb_do_writeback fs/fs-writeback.c:1894 [inline]
 [<ffffffff8160dbbe>] wb_workfn+0x20e/0xdb0 fs/fs-writeback.c:1930
 [<ffffffff8118d181>] process_one_work+0x7e1/0x1500 kernel/workqueue.c:2092
 [<ffffffff8118df76>] worker_thread+0xd6/0x10a0 kernel/workqueue.c:2226
 [<ffffffff8119d0ad>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839fa15c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Code: 
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c