INFO: task syz-executor5:16223 blocked for more than 120 seconds.
      Not tainted 4.9.77-ge12a9c4 #18
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor5   D28144 16223   5135 0x00000004
 ffff8801c8964800 ffff8801cd177480 ffff8801d867b9c0 ffff8801c8966000
 ffff8801db221b98 ffff8801b37076d0 ffffffff838a1b9b 0000000041b58ab3
 ffffffff84193178 00ffffff8123bda0 ffff8801db222468 ffff8801db222490
Call Trace:
 [<ffffffff838a313f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3550
 [<ffffffff838af29c>] schedule_timeout+0x56c/0x10b0 kernel/time/timer.c:1768
 [<ffffffff838a134e>] io_schedule_timeout+0x1be/0x390 kernel/sched/core.c:5172
 [<ffffffff838a4aae>] do_wait_for_common kernel/sched/completion.c:75 [inline]
 [<ffffffff838a4aae>] __wait_for_common kernel/sched/completion.c:93 [inline]
 [<ffffffff838a4aae>] wait_for_common_io kernel/sched/completion.c:107 [inline]
 [<ffffffff838a4aae>] wait_for_completion_io+0x20e/0x2e0 kernel/sched/completion.c:155
 [<ffffffff81cdaabb>] submit_bio_wait+0x11b/0x180 block/bio.c:885
 [<ffffffff81d0dc67>] blkdev_issue_flush+0x157/0x220 block/blk-flush.c:518
 [<ffffffff81629ed5>] blkdev_fsync+0x85/0xb0 fs/block_dev.c:378
 [<ffffffff8161583a>] vfs_fsync_range+0x10a/0x250 fs/sync.c:195
 [<ffffffff816159a9>] vfs_fsync+0x29/0x30 fs/sync.c:209
 [<ffffffff824b2313>] __loop_update_dio+0x453/0x5d0 drivers/block/loop.c:207
 [<ffffffff824b7282>] loop_set_dio drivers/block/loop.c:1323 [inline]
 [<ffffffff824b7282>] lo_ioctl+0x13a2/0x1990 drivers/block/loop.c:1377
 [<ffffffff81d3731a>] __blkdev_driver_ioctl block/ioctl.c:294 [inline]
 [<ffffffff81d3731a>] blkdev_ioctl+0x4aa/0x1a60 block/ioctl.c:590
 [<ffffffff8162bd9e>] block_ioctl+0xde/0x120 fs/block_dev.c:1688
 [<ffffffff815adeba>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff815adeba>] do_vfs_ioctl+0x1aa/0x1140 fs/ioctl.c:679
 [<ffffffff815aeedf>] SYSC_ioctl fs/ioctl.c:694 [inline]
 [<ffffffff815aeedf>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 [<ffffffff838b2c2e>] entry_SYSCALL_64_fastpath+0x29/0xe8

Showing all locks held in the system:
2 locks held by khungtaskd/514:
 #0:  (rcu_read_lock){......}, at: [<ffffffff81372d85>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff81372d85>] watchdog+0x125/0xa70 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81237f00>] debug_show_all_locks+0x70/0x280 kernel/locking/lockdep.c:4336
1 lock held by rsyslogd/3193:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815d31ff>] __fdget_pos+0x9f/0xc0 fs/file.c:781
2 locks held by getty/3322:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff838b0e12>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff82009514>] n_tty_read+0x1f4/0x16c0 drivers/tty/n_tty.c:2133
1 lock held by syz-executor5/16223:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff824b5f6f>] lo_ioctl+0x8f/0x1990 drivers/block/loop.c:1337
1 lock held by syz-executor5/16233:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff824b5f6f>] lo_ioctl+0x8f/0x1990 drivers/block/loop.c:1337

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

NMI backtrace for cpu 1
CPU: 1 PID: 514 Comm: khungtaskd Not tainted 4.9.77-ge12a9c4 #18
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d89afd00 ffffffff81d941c9 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810babe0 ffff8801d89afd38
 ffffffff81d9f2ed 0000000000000001 0000000000000000 ffff8801cc49cc18
Call Trace:
 [<ffffffff81d941c9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d941c9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81d9f2ed>] nmi_cpu_backtrace+0xfd/0x120 lib/nmi_backtrace.c:99
 [<ffffffff81d9f427>] nmi_trigger_cpumask_backtrace+0x117/0x190 lib/nmi_backtrace.c:60
 [<ffffffff810bacd4>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81373350>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81373350>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81373350>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81373350>] watchdog+0x6f0/0xa70 kernel/hung_task.c:239
 [<ffffffff8119a6fd>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff838b2f69>] ret_from_fork+0x59/0x70 arch/x86/entry/entry_64.S:466
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at pc 0xffffffff838b1886