INFO: task syz-executor6:13385 blocked for more than 120 seconds.
      Not tainted 4.4.107-g610c835 #12
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor6   D ffff8801c658f988 28944 13385   3572 0x00000004
 ffff8801c658f988 ffffffff81234260 ffff8801ceaf0898 0000000000000023
 ffff8801ceaf0000 ffffffff842b7600 ffff8801db21f878 ffff8801db21f8a0
 ffff8801db21ef98 ffff8801ceaf2f80 ffff8801ceaf0000 ffff8801c6588000
Call Trace:
 [<ffffffff83765d3a>] schedule+0x9a/0x1c0 kernel/sched/core.c:3351
 [<ffffffff83770fd1>] schedule_timeout+0x3a1/0x970 kernel/time/timer.c:1508
 [<ffffffff83763cbe>] io_schedule_timeout+0x1be/0x390 kernel/sched/core.c:4932
 [<ffffffff83766feb>] io_schedule include/linux/sched.h:447 [inline]
 [<ffffffff83766feb>] bit_wait_io+0x1b/0xc0 kernel/sched/wait.c:595
 [<ffffffff8376672c>] __wait_on_bit+0x8c/0x140 kernel/sched/wait.c:395
 [<ffffffff81419fd5>] wait_on_page_bit+0x1e5/0x210 mm/filemap.c:758
 [<ffffffff8141a1c3>] wait_on_page_writeback include/linux/pagemap.h:530 [inline]
 [<ffffffff8141a1c3>] __filemap_fdatawait_range+0x1c3/0x2e0 mm/filemap.c:410
 [<ffffffff81422893>] filemap_fdatawait_keep_errors+0x63/0x80 mm/filemap.c:468
 [<ffffffff815bbe80>] fdatawait_one_bdev+0x50/0x70 fs/sync.c:94
 [<ffffffff815d5799>] iterate_bdevs+0x109/0x260 fs/block_dev.c:1832
 [<ffffffff815bc751>] sys_sync+0xe1/0x170 fs/sync.c:116
 [<ffffffff83773d36>] entry_SYSCALL_64_fastpath+0x16/0x76
1 lock held by syz-executor6/13385:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff815d5758>] iterate_bdevs+0xc8/0x260 fs/block_dev.c:1830
Sending NMI to all CPUs:
NMI backtrace for cpu 0
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.4.107-g610c835 #12
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffffffff84214840 task.stack: ffffffff84200000
RIP: 0010:[<ffffffff810cf516>]  [<ffffffff810cf516>] native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:49
RSP: 0018:ffffffff84207da0  EFLAGS: 00000246
RAX: 0000000000000007 RBX: ffffffff847d6708 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffffffff842150ac
RBP: ffffffff84207da0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007febd9ecb9b8 CR3: 00000000b65c5000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff84207dd8 ffffffff81027d75 ffffffff84208000 ffffffff847d6708
 0000000000000000 0000000000000000 dffffc0000000000 ffffffff84207de8
 ffffffff810292ea ffffffff84207e00 ffffffff8121e338 ffffffff84208000
Call Trace:
 [<ffffffff81027d75>] arch_safe_halt arch/x86/include/asm/paravirt.h:117 [inline]
 [<ffffffff81027d75>] default_idle+0x55/0x3c0 arch/x86/kernel/process.c:291
 [<ffffffff810292ea>] arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:282
 [<ffffffff8121e338>] default_idle_call+0x48/0x70 kernel/sched/idle.c:93
 [<ffffffff8121ea45>] cpuidle_idle_call kernel/sched/idle.c:157 [inline]
 [<ffffffff8121ea45>] cpu_idle_loop kernel/sched/idle.c:253 [inline]
 [<ffffffff8121ea45>] cpu_startup_entry+0x605/0x820 kernel/sched/idle.c:301
 [<ffffffff83760d89>] rest_init+0x189/0x190 init/main.c:409
 [<ffffffff8481a80c>] start_kernel+0x6b4/0x6e9 init/main.c:680
 [<ffffffff84819312>] x86_64_start_reservations+0x2a/0x2c arch/x86/kernel/head64.c:196
 [<ffffffff84819454>] x86_64_start_kernel+0x140/0x163 arch/x86/kernel/head64.c:185
Code: 00 00 00 00 00 55 48 89 e5 fa 5d c3 66 0f 1f 84 00 00 00 00 00 55 48 89 e5 fb 5d c3 66 0f 1f 84 00 00 00 00 00 55 48 89 e5 fb f4 <5d> c3 0f 1f 84 00 00 00 00 00 55 48 89 e5 f4 5d c3 66 0f 1f 84 
NMI backtrace for cpu 1
CPU: 1 PID: 485 Comm: khungtaskd Not tainted 4.4.107-g610c835 #12
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800bb945f00 task.stack: ffff8800bac18000
RIP: 0010:[<ffffffff810c32e7>]  [<ffffffff810c32e7>] native_apic_mem_write arch/x86/include/asm/apic.h:94 [inline]
RIP: 0010:[<ffffffff810c32e7>]  [<ffffffff810c32e7>] __default_send_IPI_dest_field arch/x86/include/asm/ipi.h:119 [inline]
RIP: 0010:[<ffffffff810c32e7>]  [<ffffffff810c32e7>] _flat_send_IPI_mask arch/x86/kernel/apic/apic_flat_64.c:61 [inline]
RIP: 0010:[<ffffffff810c32e7>]  [<ffffffff810c32e7>] flat_send_IPI_mask+0xf7/0x1a0 arch/x86/kernel/apic/apic_flat_64.c:69
RSP: 0018:ffff8800bac1fcb8  EFLAGS: 00000046
RAX: 0000000003000000 RBX: 0000000000000c00 RCX: 0000000000000000
RDX: 0000000000000c00 RSI: 0000000000000000 RDI: ffffffffff5fb300
RBP: ffff8800bac1fce0 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000246
R13: 0000000000000003 R14: ffffffff8426abe0 R15: 0000000000000002
FS:  0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000001d67000 CR3: 00000000b65c5000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff8426abe0 ffffffff847e8600 00000000000194a0 0000000000000040
 dffffc0000000000 ffff8800bac1fd00 ffffffff810b8e1b ffffffff839f53e0
 0000000000000003 ffff8800bac1fd60 ffffffff81d0f4d7 ffffffff81417c73
Call Trace:
 [<ffffffff810b8e1b>] nmi_raise_cpu_backtrace+0x5b/0x70 arch/x86/kernel/apic/hw_nmi.c:33
 [<ffffffff81d0f4d7>] nmi_trigger_all_cpu_backtrace+0x4a7/0x550 lib/nmi_backtrace.c:85
 [<ffffffff810b8eb4>] arch_trigger_all_cpu_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 [<ffffffff81365a7a>] trigger_all_cpu_backtrace include/linux/nmi.h:44 [inline]
 [<ffffffff81365a7a>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81365a7a>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81365a7a>] watchdog+0x6fa/0xae0 kernel/hung_task.c:238
 [<ffffffff8118dea8>] kthread+0x268/0x300 kernel/kthread.c:211
 [<ffffffff837740ef>] ret_from_fork+0x3f/0x70 arch/x86/entry/entry_64.S:468
Code: b3 5f ff f6 c4 10 75 e1 44 89 e8 c1 e0 18 89 04 25 10 b3 5f ff 44 89 fa 09 da 80 cf 04 41 83 ff 02 0f 44 d3 89 14 25 00 b3 5f ff <41> f7 c4 00 02 00 00 74 1a e8 3b 09 17 00 4c 89 e7 57 9d 0f 1f