INFO: task loop4:8213 blocked for more than 140 seconds.
      Not tainted 4.9.112-gf540ce0 #60
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
loop4           D27080  8213      2 0x00000000
 ffff8801919fe000 ffff880199718a80 ffff8801cf9d8a80 ffff8801919fc800
 ffff8801db321c18 ffff8801cd6cedf0 ffffffff839e907d 0000000041b58ab3
 ffffffff843c3728 ffffffff812361d0 0000000000000000 ffff8801db3224e8
Call Trace:
 [<ffffffff839ea67f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3557
 [<ffffffff839f6a91>] schedule_timeout+0x861/0xf70 kernel/time/timer.c:1768
 [<ffffffff839e885a>] io_schedule_timeout+0x1ba/0x390 kernel/sched/core.c:5180
 [<ffffffff81e5132c>] io_schedule include/linux/sched.h:460 [inline]
 [<ffffffff81e5132c>] bt_get.isra.8+0x27c/0x780 block/blk-mq-tag.c:141
 [<ffffffff81e5223c>] __blk_mq_get_tag block/blk-mq-tag.c:163 [inline]
 [<ffffffff81e5223c>] blk_mq_get_tag+0xac/0x220 block/blk-mq-tag.c:192
 [<ffffffff81e4196a>] __blk_mq_alloc_request+0x2a/0xaa0 block/blk-mq.c:196
 [<ffffffff81e43d6b>] blk_mq_map_request.isra.38+0x3ab/0x900 block/blk-mq.c:1207
 [<ffffffff81e4c1b6>] blk_sq_make_request+0x1d6/0x1220 block/blk-mq.c:1374
 [<ffffffff81e1f08e>] generic_make_request+0x20e/0x9b0 block/blk-core.c:2055
 [<ffffffff81e1f8e0>] submit_bio+0xb0/0x460 block/blk-core.c:2126
 [<ffffffff81643a5a>] dio_bio_submit fs/direct-io.c:420 [inline]
 [<ffffffff81643a5a>] do_blockdev_direct_IO+0x35da/0x5a80 fs/direct-io.c:1301
 [<ffffffff81645fa5>] __blockdev_direct_IO+0xa5/0xd0 fs/direct-io.c:1360
 [<ffffffff8162fb50>] blkdev_direct_IO+0xa0/0xd0 fs/block_dev.c:183
 [<ffffffff8143e870>] generic_file_read_iter+0x660/0x1a90 mm/filemap.c:1951
 [<ffffffff81632755>] blkdev_read_iter+0x105/0x170 fs/block_dev.c:1738
 [<ffffffff825cd463>] lo_rw_aio+0x6b3/0x8a0 drivers/block/loop.c:506
 [<ffffffff825cda27>] do_req_filebacked drivers/block/loop.c:543 [inline]
 [<ffffffff825cda27>] loop_handle_cmd drivers/block/loop.c:1698 [inline]
 [<ffffffff825cda27>] loop_queue_work+0x3d7/0x2320 drivers/block/loop.c:1710
 [<ffffffff8119d499>] kthread_worker_fn+0x249/0x6b0 kernel/kthread.c:627
 [<ffffffff8119d0bd>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839fa11c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373

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/3673:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839f8122>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff8211edc2>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142

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

NMI backtrace for cpu 0
CPU: 0 PID: 519 Comm: khungtaskd Not tainted 4.9.112-gf540ce0 #60
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d8607d08 ffffffff81eb3249 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810b9bd0 ffff8801d8607d40
 ffffffff81ebe547 0000000000000000 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb3249>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb3249>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebe547>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebe4da>] 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
 [<ffffffff8119d0bd>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839fa11c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 13825 Comm: syz-executor3 Not tainted 4.9.112-gf540ce0 #60
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d3708000 task.stack: ffff8801a45c0000
RIP: 0010:[<ffffffff814a11c5>] 
c [<ffffffff814a11c5>] pcpu_alloc_area+0x255/0xd10 mm/percpu.c:565
RSP: 0018:ffff8801a45c77a8  EFLAGS: 00000002
RAX: 0000000000000007 RBX: 0000000000025844 RCX: ffffc9000c915000
RDX: 0000000000000000 RSI: ffffffff814a11a7 RDI: dffffc0000000000
RBP: ffff8801a45c7900 R08: ffff8801a45c7988 R09: 0000000000000001
R10: ffff8801d3708000 R11: 1ffff1003a6e1127 R12: 0000000000000000
R13: 0000000000079c69 R14: 0000000000025848 R15: ffffc90000589c6c
FS:  00007f1baf069700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f193dfa8000 CR3: 00000001d013a000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffed003aa9ce21
c ffffffff85b2d6c0
c 1ffff100348b8f07
c ffff8801d54e70d0
c
 00000003a45c77e8
c 0000001001005a5b
c ffff8801d54e7108
c ffff8801d54e70d4
c
 ffff8801a45c7988
c ffffffff84737580
c ffff8801a45c7900
c fffffffc00000001
c
Call Trace:
 [<ffffffff814a36dc>] pcpu_alloc+0x2bc/0xad0 mm/percpu.c:954
 [<ffffffff814a3f44>] __alloc_percpu+0x24/0x30 mm/percpu.c:1079
 [<ffffffff815dc76a>] alloc_vfsmnt+0x12a/0x7f0 fs/namespace.c:221
 [<ffffffff815de214>] clone_mnt+0x74/0xb40 fs/namespace.c:1031
 [<ffffffff815e30ef>] copy_tree+0x32f/0x810 fs/namespace.c:1793
 [<ffffffff8160f644>] propagate_one+0x434/0x7e0 fs/pnode.c:267
 [<ffffffff8161093a>] propagate_mnt+0x18a/0x3d0 fs/pnode.c:317
 [<ffffffff815e3ffd>] attach_recursive_mnt+0x4ed/0x8f0 fs/namespace.c:2022
 [<ffffffff815e456f>] graft_tree+0x16f/0x1f0 fs/namespace.c:2122
 [<ffffffff815e6f2f>] do_loopback fs/namespace.c:2243 [inline]
 [<ffffffff815e6f2f>] do_mount+0x1f5f/0x2740 fs/namespace.c:2829
 [<ffffffff815e80ee>] SYSC_mount fs/namespace.c:3051 [inline]
 [<ffffffff815e80ee>] SyS_mount+0xfe/0x110 fs/namespace.c:3028
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839f9f53>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: 
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c48 
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c<38> 
cd0 
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c01 
c