INFO: task syz.3.1705:10537 blocked for more than 143 seconds.
      Tainted: G             L      syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.3.1705      state:D stack:27304 pid:10537 tgid:10535 ppid:6807   task_flags:0x400040 flags:0x00080002
Call Trace:
 <TASK>
 __schedule+0x17d9/0x56c0
 schedule+0x164/0x2b0
 schedule_preempt_disabled+0x13/0x30
 __mutex_lock+0x7bf/0x1550
 write_threads+0x39d/0x5a0
 nfsctl_transaction_write+0x10f/0x160
 vfs_write+0x296/0xba0
 ksys_write+0x150/0x270
 do_syscall_64+0x174/0x580
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f7ca299de99
RSP: 002b:00007f7ca3783028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f7ca2c26090 RCX: 00007f7ca299de99
RDX: 0000000000000002 RSI: 00002000000002c0 RDI: 0000000000000005
RBP: 00007f7ca2a33eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f7ca2c26128 R14: 00007f7ca2c26090 R15: 00007fff639517a8
 </TASK>

Showing all locks held in the system:
2 locks held by kworker/0:1/10:
 #0: ffff88812103b160 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x2d/0x160
 #1: ffff888121024440 (psi_seq){-.-.}-{0:0}, at: psi_task_switch+0x57/0x7d0
1 lock held by khungtaskd/35:
 #0: ffffffff8eb59c60 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180
2 locks held by kworker/u12:0/55:
 #0: ffff88816ce3f940 ((wq_completion)nbd1-recv){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0
 #1: ffffc90000bf7c40 ((work_completion)(&args->work)){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0
2 locks held by getty/5434:
 #0: ffff88810d6350a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70
 #1: ffffc900034732e8 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x45a/0x1360
2 locks held by kworker/1:4/5672:
 #0: ffff88810006b140 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0
 #1: ffffc90004f5fc40 ((work_completion)(&m->mpeg_thread)){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0
3 locks held by syz.3.1705/10536:
 #0: ffff888177b252f0 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x246/0x320
 #1: ffff8881ac00e450 (sb_writers#21){.+.+}-{0:0}, at: vfs_write+0x22b/0xba0
 #2: ffffffff8ee8e620 (nfsd_mutex){+.+.}-{4:4}, at: write_ports+0xb5/0xd10
3 locks held by syz.3.1705/10537:
 #0: ffff8881787262f0 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x246/0x320
 #1: ffff8881ac00e450 (sb_writers#21){.+.+}-{0:0}, at: vfs_write+0x22b/0xba0
 #2: ffffffff8ee8e620 (nfsd_mutex){+.+.}-{4:4}, at: write_threads+0x39d/0x5a0
2 locks held by kworker/u12:1/10914:
 #0: ffff88816ce3f940 ((wq_completion)nbd1-recv){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0
 #1: ffffc9000409fc40 ((work_completion)(&args->work)){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0
2 locks held by kworker/u12:2/12778:
 #0: ffff88816ce3f940 ((wq_completion)nbd1-recv){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0
 #1: ffffc9000439fc40 ((work_completion)(&args->work)){+.+.}-{0:0}, at: process_scheduled_works+0xa20/0x14e0

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

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 35 Comm: khungtaskd Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150
 nmi_cpu_backtrace+0x274/0x2d0
 nmi_trigger_cpumask_backtrace+0x17a/0x380
 sys_info+0x135/0x170
 watchdog+0xfd7/0x1030
 kthread+0x388/0x470
 ret_from_fork+0x514/0xb70
 ret_from_fork_asm+0x1a/0x30
 </TASK>
