b_state=0x00000029, b_size=512
device loop0 blocksize: 4096
__find_get_block_slow() failed. block=1, b_blocknr=8
b_state=0x00000029, b_size=512
device loop0 blocksize: 4096
INFO: task syz-executor0:3845 blocked for more than 120 seconds.
      Not tainted 4.9.107-gdb2c520 #46
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor0   D28008  3845      1 0x00000004
 ffff8801d8660000 ffff8801c9294fc0 ffff8801d6fc6f40 ffff880186518000
 ffff8801db221c18 ffff88019024fb40 ffffffff839e8c1d 0000000000000002
 0000000041b58ab3 ffffffff843b9ea3 00ffffff81221500 ffff8801db2224e8
Call Trace:
 [<ffffffff839ea21f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3557
 [<ffffffff81602a49>] wb_wait_for_completion+0x149/0x1b0 fs/fs-writeback.c:221
 [<ffffffff81602cb7>] __writeback_inodes_sb_nr+0x207/0x300 fs/fs-writeback.c:2310
 [<ffffffff81602e07>] writeback_inodes_sb_nr fs/fs-writeback.c:2327 [inline]
 [<ffffffff81602e07>] writeback_inodes_sb+0x27/0x30 fs/fs-writeback.c:2342
 [<ffffffff8161a9c3>] __sync_filesystem fs/sync.c:35 [inline]
 [<ffffffff8161a9c3>] sync_filesystem+0x93/0x240 fs/sync.c:63
 [<ffffffff81579455>] generic_shutdown_super+0x75/0x300 fs/super.c:423
 [<ffffffff81579d8f>] kill_block_super+0x9f/0x120 fs/super.c:1127
 [<ffffffff8157a105>] deactivate_locked_super+0x75/0xd0 fs/super.c:310
 [<ffffffff8157ab11>] deactivate_super+0x91/0xd0 fs/super.c:341
 [<ffffffff815dce52>] cleanup_mnt+0xb2/0x160 fs/namespace.c:1134
 [<ffffffff815dcf86>] __cleanup_mnt+0x16/0x20 fs/namespace.c:1141
 [<ffffffff8119832c>] task_work_run+0x10c/0x180 kernel/task_work.c:116
 [<ffffffff8100559c>] tracehook_notify_resume include/linux/tracehook.h:191 [inline]
 [<ffffffff8100559c>] exit_to_usermode_loop+0xfc/0x120 arch/x86/entry/common.c:161
 [<ffffffff810064d4>] prepare_exit_to_usermode arch/x86/entry/common.c:191 [inline]
 [<ffffffff810064d4>] syscall_return_slowpath arch/x86/entry/common.c:260 [inline]
 [<ffffffff810064d4>] do_syscall_64+0x364/0x490 arch/x86/entry/common.c:287
 [<ffffffff839f9b13>] 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: [<ffffffff8136662c>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136662c>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81425cb7>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by getty/3785:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839f7cc2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff8211fc62>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2133
1 lock held by syz-executor0/3845:
 #0:  (&type->s_umount_key#47){++++..}, at: [<ffffffff8157ab09>] deactivate_super+0x89/0xd0 fs/super.c:340
1 lock held by init/12086:
 #0:  (tty_mutex){+.+.+.}, at: [<ffffffff82119d0c>] tty_open_by_driver drivers/tty/tty_io.c:2047 [inline]
 #0:  (tty_mutex){+.+.+.}, at: [<ffffffff82119d0c>] tty_open+0x46c/0xe20 drivers/tty/tty_io.c:2125
1 lock held by init/12087:
 #0:  (tty_mutex){+.+.+.}, at: [<ffffffff82119d0c>] tty_open_by_driver drivers/tty/tty_io.c:2047 [inline]
 #0:  (tty_mutex){+.+.+.}, at: [<ffffffff82119d0c>] tty_open+0x46c/0xe20 drivers/tty/tty_io.c:2125
1 lock held by init/12088:
 #0:  (tty_mutex){+.+.+.}, at: [<ffffffff82119d0c>] tty_open_by_driver drivers/tty/tty_io.c:2047 [inline]
 #0:  (tty_mutex){+.+.+.}, at: [<ffffffff82119d0c>] tty_open+0x46c/0xe20 drivers/tty/tty_io.c:2125
1 lock held by init/12089:
 #0:  (tty_mutex){+.+.+.}, at: [<ffffffff82119d0c>] tty_open_by_driver drivers/tty/tty_io.c:2047 [inline]
 #0:  (tty_mutex){+.+.+.}, at: [<ffffffff82119d0c>] tty_open+0x46c/0xe20 drivers/tty/tty_io.c:2125
1 lock held by init/12090:
 #0:  (tty_mutex){+.+.+.}, at: [<ffffffff82119d0c>] tty_open_by_driver drivers/tty/tty_io.c:2047 [inline]
 #0:  (tty_mutex){+.+.+.}, at: [<ffffffff82119d0c>] tty_open+0x46c/0xe20 drivers/tty/tty_io.c:2125

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

NMI backtrace for cpu 1
CPU: 1 PID: 519 Comm: khungtaskd Not tainted 4.9.107-gdb2c520 #46
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d850fd08 ffffffff81eb3da9 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810b96a0 ffff8801d850fd40
 ffffffff81ebf0a7 0000000000000001 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb3da9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb3da9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebf0a7>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebf03a>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810b97a4>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81366bc4>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81366bc4>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81366bc4>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81366bc4>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119d04d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839f9cdc>] 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: 3687 Comm: rs:main Q:Reg Not tainted 4.9.107-gdb2c520 #46
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801c684b000 task.stack: ffff8801c1d40000
RIP: 0010:[<ffffffff81230a4f>] 
c [<ffffffff81230a4f>] arch_local_irq_restore arch/x86/include/asm/paravirt.h:768 [inline]
RIP: 0010:[<ffffffff81230a4f>] 
c [<ffffffff81230a4f>] lock_is_held+0xff/0x140 kernel/locking/lockdep.c:3796
RSP: 0018:ffff8801c1d47428  EFLAGS: 00000246
RAX: 0000000000000007 RBX: 0000000000000246 RCX: ffff8801d5d40690
RDX: 0000000000000000 RSI: ffffffff846def20 RDI: 0000000000000246
RBP: ffff8801c1d47440 R08: ffff8801c684b988 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801c684b000
R13: 0000000000000000 R14: 00000000000000a1 R15: 000000000000157d
FS:  00007f9ef2587700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000129d0f8 CR3: 00000001cba63000 CR4: 00000000001606f0
DR0: 0000000020000000 DR1: 0000000020000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Stack:
 ffff8801c684b000
c 0000000000000000
c ffffffff83d02640
c ffff8801c1d47478
c
 ffffffff811bb4f7
c ffff8801c684b000
c ffffffff83d02640
c 00000000000000a1
c
 0000000000000000
c 000000000000157d
c ffff8801c1d474b8
c ffffffff811bb625
c
Call Trace:
 [<ffffffff811bb4f7>] ___might_sleep+0x1c7/0x260 kernel/sched/core.c:7958
 [<ffffffff811bb625>] __might_sleep+0x95/0x1a0 kernel/sched/core.c:7949
 [<ffffffff81806b73>] __ext4_journal_get_write_access+0x33/0x90 fs/ext4/ext4_jbd2.c:161
 [<ffffffff8174f143>] ext4_reserve_inode_write+0xe3/0x180 fs/ext4/inode.c:5501
 [<ffffffff8177e41b>] ext4_orphan_del+0x20b/0x7b0 fs/ext4/namei.c:2822
 [<ffffffff8175496f>] ext4_truncate+0xbcf/0x12c0 fs/ext4/inode.c:4277
 [<ffffffff8175694b>] ext4_truncate_failed_write fs/ext4/truncate.h:15 [inline]
 [<ffffffff8175694b>] ext4_da_write_begin+0x4eb/0x1020 fs/ext4/inode.c:3015
 [<ffffffff81435c91>] generic_perform_write+0x301/0x510 mm/filemap.c:2740
 [<ffffffff8143d722>] __generic_file_write_iter+0x352/0x540 mm/filemap.c:2865
 [<ffffffff8172cea3>] ext4_file_write_iter+0x463/0xd90 fs/ext4/file.c:165
 [<ffffffff8156ead0>] new_sync_write fs/read_write.c:496 [inline]
 [<ffffffff8156ead0>] __vfs_write+0x3e0/0x580 fs/read_write.c:509
 [<ffffffff815728c7>] vfs_write+0x187/0x530 fs/read_write.c:557
 [<ffffffff815766f9>] SYSC_write fs/read_write.c:604 [inline]
 [<ffffffff815766f9>] SyS_write+0xd9/0x1c0 fs/read_write.c:596
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839f9b13>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: 
cfa 
c48 
cc1 
cea 
c03 
c0f 
cb6 
c14 
c02 
c48 
c89 
cf8 
c83 
ce0 
c07 
c83 
cc0 
c03 
c38 
cd0 
c7c 
c04 
c84 
cd2 
c75 
c3a 
c41 
cc7 
c84 
c24 
cc4 
c08 
c00 
c00 
c00 
c00 
c00 
c00 
c48 
c89 
cdf 
c57 
c9d 
c<0f> 
c1f 
c44 
c00 
c00 
c5b 
c44 
c89 
ce8 
c41 
c5c 
c41 
c5d 
c5d 
cc3 
c41 
cbd 
c01 
c00 
c00 
c00 
c