INFO: task syz.6.728:13449 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.6.728       state:D stack:25128 pid:13449 tgid:13448 ppid:11418  task_flags:0x400140 flags:0x00004006
Call Trace:
 <TASK>
 __schedule+0x1798/0x4cc0
 schedule+0x165/0x360
 schedule_preempt_disabled+0x13/0x30
 rwsem_down_read_slowpath+0x5fd/0x8f0
 down_read+0x98/0x2e0
 super_lock+0x2a9/0x3b0
 __iterate_supers+0x126/0x290
 drop_caches_sysctl_handler+0x97/0x170
 proc_sys_call_handler+0x4c6/0x700
 iter_file_splice_write+0x975/0x10e0
 direct_splice_actor+0x101/0x160
 splice_direct_to_actor+0x5a8/0xcc0
 do_splice_direct+0x181/0x270
 do_sendfile+0x4da/0x7e0
 __se_sys_sendfile64+0x13e/0x190
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fdd1518ec29
RSP: 002b:00007fdd1603e038 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007fdd153d5fa0 RCX: 00007fdd1518ec29
RDX: 0000000000000000 RSI: 0000000000000006 RDI: 0000000000000007
RBP: 00007fdd15211e41 R08: 0000000000000000 R09: 0000000000000000
R10: 000000000000023b R11: 0000000000000246 R12: 0000000000000000
R13: 00007fdd153d6038 R14: 00007fdd153d5fa0 R15: 00007fff4cef9df8
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/34:
 #0: ffffffff8e13a0e0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180
2 locks held by getty/5671:
 #0: ffff888021feb0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70
 #1: ffffc900029062f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x43e/0x1400
2 locks held by syz-executor/6076:
2 locks held by syz.6.728/13449:
 #0: ffff8881256dc428 (sb_writers#3){.+.+}-{0:0}, at: direct_splice_actor+0x49/0x160
 #1: ffff8880291460e0 (&type->s_umount_key#69){++++}-{4:4}, at: super_lock+0x2a9/0x3b0
1 lock held by syz.3.1159/15716:
 #0: ffff8880291460e0 (&type->s_umount_key#69){++++}-{4:4}, at: super_lock+0x2a9/0x3b0
2 locks held by syz.2.1178/15760:

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

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 34 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT(full) 
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+0x189/0x250
 nmi_cpu_backtrace+0x39e/0x3d0
 nmi_trigger_cpumask_backtrace+0x17a/0x300
 watchdog+0xf93/0xfe0
 kthread+0x711/0x8a0
 ret_from_fork+0x439/0x7d0
 ret_from_fork_asm+0x1a/0x30
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 5882 Comm: kworker/u8:4 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Workqueue: bat_events batadv_nc_worker
RIP: 0010:__lock_acquire+0x449/0xd20
Code: b6 e9 44 0f 44 ea 44 8b a7 e8 0a 00 00 41 8d 4c 24 ff 83 f9 ff bd ff ff ff ff 0f 4c e9 ff c5 45 8d 7c 24 01 49 ff cc 44 89 f9 <83> c1 fe 78 44 44 89 e3 81 e3 ff ff ff 7f 83 f9 31 73 1d 48 8d 0c
RSP: 0018:ffffc900044bf840 EFLAGS: 00000046
RAX: 0000000000040783 RBX: 0000000000000001 RCX: 0000000000000002
RDX: 0000000000000003 RSI: 0000000000000000 RDI: ffff888021cf3980
RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffff8b484277
R10: dffffc0000000000 R11: fffffbfff1f474e7 R12: 0000000000000000
R13: 0000000000000003 R14: ffff888021cf44c0 R15: 0000000000000002
FS:  0000000000000000(0000) GS:ffff8881a3c13000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffcb520fe18 CR3: 0000000106018000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 lock_acquire+0x120/0x360
 _raw_spin_lock_bh+0x36/0x50
 batadv_nc_purge_paths+0xe7/0x3b0
 batadv_nc_worker+0x369/0x610
 process_scheduled_works+0xae1/0x17b0
 worker_thread+0x8a0/0xda0
 kthread+0x711/0x8a0
 ret_from_fork+0x439/0x7d0
 ret_from_fork_asm+0x1a/0x30
 </TASK>
