syzbot

__find_get_block_slow() failed. block=1, b_blocknr=8
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
INFO: task syz-executor0:3889 blocked for more than 120 seconds.
device loop0 blocksize: 4096
      Not tainted 4.9.107-gdb2c520 #46
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
__find_get_block_slow() failed. block=1, b_blocknr=8
syz-executor0   D
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
28024  3889      1 0x00000004
 ffff8801d868c800
__find_get_block_slow() failed. block=1, b_blocknr=8
 ffff8801cd451a40b_state=0x00000029, b_size=512
 ffff8801d8576f40device loop0 blocksize: 4096
 ffff8801cb91b000
__find_get_block_slow() failed. block=1, b_blocknr=8
 ffff88018a2e7b40b_state=0x00000029, b_size=512
 ffffffff839e8c1ddevice loop0 blocksize: 4096
 0000000000000002
__find_get_block_slow() failed. block=1, b_blocknr=8
 ffffffff843b9ea3b_state=0x00000029, b_size=512
 00ffffff81221500device loop0 blocksize: 4096
 ffff8801db3224e8
__find_get_block_slow() failed. block=1, b_blocknr=8
b_state=0x00000029, b_size=512
device loop0 blocksize: 4096
 [<ffffffff839ea21f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3557
__find_get_block_slow() failed. block=1, b_blocknr=8
 [<ffffffff81602a49>] wb_wait_for_completion+0x149/0x1b0 fs/fs-writeback.c:221
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
__find_get_block_slow() failed. block=1, b_blocknr=8
 [<ffffffff81602cb7>] __writeback_inodes_sb_nr+0x207/0x300 fs/fs-writeback.c:2310
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
 [<ffffffff81602e07>] writeback_inodes_sb_nr fs/fs-writeback.c:2327 [inline]
 [<ffffffff81602e07>] writeback_inodes_sb+0x27/0x30 fs/fs-writeback.c:2342
__find_get_block_slow() failed. block=1, b_blocknr=8
 [<ffffffff8161a9c3>] __sync_filesystem fs/sync.c:35 [inline]
 [<ffffffff8161a9c3>] sync_filesystem+0x93/0x240 fs/sync.c:63
b_state=0x00000029, b_size=512
 [<ffffffff81579455>] generic_shutdown_super+0x75/0x300 fs/super.c:423
device loop0 blocksize: 4096
 [<ffffffff81579d8f>] kill_block_super+0x9f/0x120 fs/super.c:1127
__find_get_block_slow() failed. block=1, b_blocknr=8
 [<ffffffff8157a105>] deactivate_locked_super+0x75/0xd0 fs/super.c:310
b_state=0x00000029, b_size=512
 [<ffffffff8157ab11>] deactivate_super+0x91/0xd0 fs/super.c:341
device loop0 blocksize: 4096
 [<ffffffff815dce52>] cleanup_mnt+0xb2/0x160 fs/namespace.c:1134
__find_get_block_slow() failed. block=1, b_blocknr=8
 [<ffffffff815dcf86>] __cleanup_mnt+0x16/0x20 fs/namespace.c:1141
b_state=0x00000029, b_size=512
 [<ffffffff8119832c>] task_work_run+0x10c/0x180 kernel/task_work.c:116
device loop0 blocksize: 4096
 [<ffffffff8100559c>] tracehook_notify_resume include/linux/tracehook.h:191 [inline]
 [<ffffffff8100559c>] exit_to_usermode_loop+0xfc/0x120 arch/x86/entry/common.c:161
__find_get_block_slow() failed. block=1, b_blocknr=8
 [<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
b_state=0x00000029, b_size=512
 [<ffffffff839f9b13>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
device loop0 blocksize: 4096

Showing all locks held in the system:
__find_get_block_slow() failed. block=1, b_blocknr=8
2 locks held by khungtaskd/519:
b_state=0x00000029, b_size=512
 #0: 
device loop0 blocksize: 4096
 (rcu_read_lock__find_get_block_slow() failed. block=1, b_blocknr=8
){......}b_state=0x00000029, b_size=512
, at: [<ffffffff8136662c>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
, at: [<ffffffff8136662c>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock
__find_get_block_slow() failed. block=1, b_blocknr=8
){.+.+..}b_state=0x00000029, b_size=512
, at: [<ffffffff81425cb7>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
__find_get_block_slow() failed. block=1, b_blocknr=8
1 lock held by rsyslogd/3676:
b_state=0x00000029, b_size=512
 #0: 
device loop0 blocksize: 4096
 (&f->f_pos_lock){+.+.+.}__find_get_block_slow() failed. block=1, b_blocknr=8
, at: [<ffffffff815d7fac>] __fdget_pos+0xac/0xd0 fs/file.c:781
2 locks held by getty/3772:
device loop0 blocksize: 4096
 #0:  (&tty->ldisc_sem
__find_get_block_slow() failed. block=1, b_blocknr=8
){++++++}b_state=0x00000029, b_size=512
, at: [<ffffffff839f7cc2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock
__find_get_block_slow() failed. block=1, b_blocknr=8
){+.+...}b_state=0x00000029, b_size=512
, at: [<ffffffff8211fc62>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2133
1 lock held by syz-executor0/3889:
 #0: 
__find_get_block_slow() failed. block=1, b_blocknr=8
 (b_state=0x00000029, b_size=512
&type->s_umount_keydevice loop0 blocksize: 4096
#50){+.+...}, at: [<ffffffff8157ab09>] deactivate_super+0x89/0xd0 fs/super.c:340
b_state=0x00000029, b_size=512
device loop0 blocksize: 4096

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

__find_get_block_slow() failed. block=1, b_blocknr=8
NMI backtrace for cpu 1
b_state=0x00000029, b_size=512
CPU: 1 PID: 519 Comm: khungtaskd Not tainted 4.9.107-gdb2c520 #46
device loop0 blocksize: 4096
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d8697d08
__find_get_block_slow() failed. block=1, b_blocknr=8
 ffffffff81eb3da9b_state=0x00000029, b_size=512
 0000000000000000device loop0 blocksize: 4096
 0000000000000001
__find_get_block_slow() failed. block=1, b_blocknr=8
 0000000000000001b_state=0x00000029, b_size=512
 ffffffff810b96a0device loop0 blocksize: 4096
 ffff8801d8697d40
__find_get_block_slow() failed. block=1, b_blocknr=8
 0000000000000001b_state=0x00000029, b_size=512
 0000000000000000device loop0 blocksize: 4096
 0000000000000003
__find_get_block_slow() failed. block=1, b_blocknr=8
 [<ffffffff81eb3da9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb3da9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
b_state=0x00000029, b_size=512
device loop0 blocksize: 4096
 [<ffffffff81ebf0a7>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
__find_get_block_slow() failed. block=1, b_blocknr=8
b_state=0x00000029, b_size=512
 [<ffffffff81ebf03a>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
device loop0 blocksize: 4096
 [<ffffffff810b97a4>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
__find_get_block_slow() failed. block=1, b_blocknr=8
 [<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
b_state=0x00000029, b_size=512
device loop0 blocksize: 4096
 [<ffffffff8119d04d>] kthread+0x26d/0x300 kernel/kthread.c:211
__find_get_block_slow() failed. block=1, b_blocknr=8
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
 [<ffffffff839f9cdc>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
device loop0 blocksize: 4096
Sending NMI from CPU 1 to CPUs 0:
__find_get_block_slow() failed. block=1, b_blocknr=8
b_state=0x00000029, b_size=512
NMI backtrace for cpu 0
CPU: 0 PID: 4173 Comm: kworker/u4:4 Not tainted 4.9.107-gdb2c520 #46
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: writeback wb_workfn
c (flush-7:0)
c
task: ffff8801cfef8000 task.stack: ffff880181698000
RIP: 0010:[<ffffffff811bb236>] 
c [<ffffffff811bb236>] __preempt_count_sub arch/x86/include/asm/preempt.h:74 [inline]
RIP: 0010:[<ffffffff811bb236>] 
c [<ffffffff811bb236>] preempt_count_sub+0x66/0x160 kernel/sched/core.c:3285
RSP: 0018:ffff88018169f3e8  EFLAGS: 00000093
RAX: 0000000080000002 RBX: 00000000ffffffff RCX: 0000000000000000
RDX: 0000000000000002 RSI: 0000000000000001 RDI: ffffffff85b2d700
RBP: ffff88018169f3f0 R08: fffffbfff0b5efed R09: ffffffff85af7f66
R10: 0000000000000001 R11: ffffffff85af7f67 R12: 000000000000001e
R13: 000000000000001e R14: 0000000000000002 R15: ffffffff85aec6a0
FS:  0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f5e2380e000 CR3: 00000001cda5b000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff846d79e0
c ffff88018169f408
c ffffffff839f915c
c 0000000000000004
c
 ffff88018169f498
c ffffffff8125f3b1
c ffffffff85aec6a0
c ffff88010000001e
c
 ffff8801cfef8000
c ffffed0039fdf118
c ffff8801cfef88c8
c ffffffff846defa0
c
Call Trace:
 [<ffffffff839f915c>] __raw_spin_unlock include/linux/spinlock_api_smp.h:154 [inline]
 [<ffffffff839f915c>] _raw_spin_unlock+0x2c/0x50 kernel/locking/spinlock.c:183
 [<ffffffff8125f3b1>] vprintk_emit+0x241/0x790 kernel/printk/printk.c:1890
 [<ffffffff8125f928>] vprintk+0x28/0x30 kernel/printk/printk.c:1913
 [<ffffffff8125f94d>] vprintk_default+0x1d/0x30 kernel/printk/printk.c:1914
 [<ffffffff8142ca8c>] vprintk_func kernel/printk/internal.h:36 [inline]
 [<ffffffff8142ca8c>] printk+0xaf/0xd7 kernel/printk/printk.c:1975
 [<ffffffff81cba355>] __find_get_block_slow.cold.57+0x82/0xf0 fs/buffer.c:242
 [<ffffffff8162434e>] __find_get_block+0x23e/0x4c0 fs/buffer.c:1360
 [<ffffffff81625159>] __getblk_slow fs/buffer.c:1101 [inline]
 [<ffffffff81625159>] __getblk_gfp+0x189/0x710 fs/buffer.c:1386
 [<ffffffff81628afd>] __bread_gfp+0x2d/0x270 fs/buffer.c:1420
 [<ffffffff818cba4b>] sb_bread include/linux/buffer_head.h:300 [inline]
 [<ffffffff818cba4b>] __fat_write_inode+0x2ab/0x980 fs/fat/inode.c:844
 [<ffffffff818cfc59>] fat_write_inode+0x79/0x170 fs/fat/inode.c:893
 [<ffffffff8160214d>] write_inode fs/fs-writeback.c:1180 [inline]
 [<ffffffff8160214d>] __writeback_single_inode+0x86d/0x1020 fs/fs-writeback.c:1379
 [<ffffffff8160344c>] writeback_sb_inodes+0x4ac/0xe70 fs/fs-writeback.c:1584
 [<ffffffff8160444f>] wb_writeback+0x2cf/0xbd0 fs/fs-writeback.c:1760
 [<ffffffff8160d97e>] wb_do_writeback fs/fs-writeback.c:1894 [inline]
 [<ffffffff8160d97e>] wb_workfn+0x20e/0xdb0 fs/fs-writeback.c:1930
 [<ffffffff8118d121>] process_one_work+0x7e1/0x1500 kernel/workqueue.c:2092
 [<ffffffff8118df16>] worker_thread+0xd6/0x10a0 kernel/workqueue.c:2226
 [<ffffffff8119d04d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839f9cdc>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Code: 
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c75 
c1b 
c65 
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c05 
c37 
ccb 
ce5 
c7e 
c89 
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c81 
ce2 
cff 
cff 
cff 
c7f 
c39 
cd3 
c7f 
c14 
c81 
cfb 
cfe 
c00 
c00 
c00 
c76 
c71 
cf7 
cdb 
c65 
c01 
c1d 
c1a 
ccb 
ce5 
c7e 
c<5b> 
c5d 
cc3 
ce8 
c12 
cf1 
cd2 
c00 
c85 
cc0 
c74 
cf4 
c48 
cc7 
cc7 
c80 
c29 
cb9 
c85 
c48 
cb8 
c
device loop0 blocksize: 4096
__find_get_block_slow() failed. block=1, b_blocknr=8
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
__find_get_block_slow() failed. block=1, b_blocknr=8
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
__find_get_block_slow() failed. block=1, b_blocknr=8
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
__find_get_block_slow() failed. block=1, b_blocknr=8
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
__find_get_block_slow() failed. block=1, b_blocknr=8
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
__find_get_block_slow() failed. block=1, b_blocknr=8
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
__find_get_block_slow() failed. block=1, b_blocknr=8
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
__find_get_block_slow() failed. block=1, b_blocknr=8
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
__find_get_block_slow() failed. block=1, b_blocknr=8
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
__find_get_block_slow() failed. block=1, b_blocknr=8
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