EXT4-fs (loop4): VFS: Can't find ext4 filesystem
INFO: task syz-executor.4:4488 blocked for more than 140 seconds.
      Not tainted 4.9.155+ #27
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.4  D28976  4488   4196 0x00000004
 ffff8801cbf28000 0000000000000000 ffff8801db721000 ffff8801da6b2f80
 ffff8801db721018 ffff8801cbe0fc48 ffffffff82806806 ffffffff815cc960
 0000000000000000 ffff8801cbf288b0 0000000000000006 ffff8801db7218f0
Call Trace:
 [<ffffffff82807d92>] schedule+0x92/0x1c0 kernel/sched/core.c:3553
 [<ffffffff82808733>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3586
 [<ffffffff8280a68d>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff8280a68d>] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621
 [<ffffffff815cc42b>] blkdev_put+0x2b/0x560 fs/block_dev.c:1629
 [<ffffffff815cc9eb>] blkdev_close+0x8b/0xb0 fs/block_dev.c:1678
 [<ffffffff81512344>] __fput+0x274/0x720 fs/file_table.c:208
 [<ffffffff81512876>] ____fput+0x16/0x20 fs/file_table.c:244
 [<ffffffff8113cf88>] task_work_run+0x108/0x180 kernel/task_work.c:116
 [<ffffffff81003deb>] tracehook_notify_resume include/linux/tracehook.h:191 [inline]
 [<ffffffff81003deb>] exit_to_usermode_loop+0x13b/0x160 arch/x86/entry/common.c:162
 [<ffffffff81005907>] prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline]
 [<ffffffff81005907>] syscall_return_slowpath arch/x86/entry/common.c:263 [inline]
 [<ffffffff81005907>] do_syscall_64+0x3f7/0x570 arch/x86/entry/common.c:290
 [<ffffffff82816a93>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Showing all locks held in the system:
2 locks held by khungtaskd/24:
 #0:  (rcu_read_lock){......}, at: [<ffffffff8131bbab>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8131bbab>] watchdog+0x11b/0xa40 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff813fea8f>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4336
1 lock held by rsyslogd/1902:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff8156f2f8>] __fdget_pos+0xa8/0xd0 fs/file.c:781
2 locks held by getty/2029:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff82814b83>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff81d3982e>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156
1 lock held by syz-executor.4/4488:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff815cc42b>] blkdev_put+0x2b/0x560 fs/block_dev.c:1629
2 locks held by syz-executor.4/4491:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff815cadcb>] __blkdev_put+0xbb/0x840 fs/block_dev.c:1587
 #1:  (loop_ctl_mutex){+.+.+.}, at: [<ffffffff81deef4e>] lo_release+0x1e/0x190 drivers/block/loop.c:1641
2 locks held by syz-executor.3/4492:
 #0:  (loop_ctl_mutex/1){+.+.+.}, at: [<ffffffff81dea975>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1404
 #1:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff81b1076f>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189
2 locks held by blkid/4490:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff815cadcb>] __blkdev_put+0xbb/0x840 fs/block_dev.c:1587
 #1:  (loop_ctl_mutex){+.+.+.}, at: [<ffffffff81deef4e>] lo_release+0x1e/0x190 drivers/block/loop.c:1641
1 lock held by blkid/4494:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff815cb65e>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273

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

NMI backtrace for cpu 1
CPU: 1 PID: 24 Comm: khungtaskd Not tainted 4.9.155+ #27
 ffff8801d9907cd0 ffffffff81b47871 0000000000000001 0000000000000000
 0000000000000001 ffffffff81097301 00000000003fff7d ffff8801d9907d08
 ffffffff81b52afc 0000000000000001 0000000000000000 0000000000000001
Call Trace:
 [<ffffffff81b47871>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81b47871>] dump_stack+0xc1/0x120 lib/dump_stack.c:51
 [<ffffffff81b52afc>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81b52a84>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60
 [<ffffffff81097494>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff8131c087>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff8131c087>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff8131c087>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff8131c087>] watchdog+0x5f7/0xa40 kernel/hung_task.c:239
 [<ffffffff81142028>] kthread+0x278/0x310 kernel/kthread.c:211
 [<ffffffff82816c5c>] 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 skipped: idling at pc 0xffffffff82815692