INFO: task syz.4.3105:18108 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.4.3105      state:D stack:25128 pid:18108 tgid:18107 ppid:16676  task_flags:0x400140 flags:0x00004004
Call Trace:
 <TASK>
 __schedule+0x1798/0x4cc0
 schedule+0x165/0x360
 wb_wait_for_completion+0x15f/0x260
 sync_inodes_sb+0x1bb/0xa10
 __iterate_supers+0x13d/0x290
 ksys_sync+0x94/0x150
 __ia32_sys_sync+0xe/0x20
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f218a98ebe9
RSP: 002b:00007f218b7a2038 EFLAGS: 00000246 ORIG_RAX: 00000000000000a2
RAX: ffffffffffffffda RBX: 00007f218abb5fa0 RCX: 00007f218a98ebe9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007f218abb5fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f218abb6038 R14: 00007f218abb5fa0 R15: 00007fffb945c6c8
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/34:
 #0: ffffffff8e139ea0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180
3 locks held by kworker/u9:5/3721:
 #0: ffff888100727948 ((wq_completion)writeback){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0
 #1: ffffc90021d7fbc0 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0
 #2: ffff888107fc80e0 (&type->s_umount_key#50){++++}-{4:4}, at: super_trylock_shared+0x20/0xf0
2 locks held by getty/5672:
 #0: ffff888026a090a0 (&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
1 lock held by sshd/5774:
5 locks held by kworker/u8:5/9332:
 #0: ffff88801b2f7148 ((wq_completion)netns){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0
 #1: ffffc90002f2fbc0 (net_cleanup_work){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0
 #2: ffffffff8f52ae30 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0xf7/0x800
 #3: ffffffff8f537c88 (rtnl_mutex){+.+.}-{4:4}, at: default_device_exit_batch+0xdc/0x890
 #4: ffffffff8e13f938 (rcu_state.exp_mutex){+.+.}-{4:4}, at: synchronize_rcu_expedited+0x2f6/0x730
1 lock held by syz.2.2016/14415:
 #0: ffff888107fc8428 (sb_writers#12){.+.+}-{0:0}, at: vfs_write+0x211/0xb30
3 locks held by kworker/u9:12/16062:
 #0: ffff888100727948 ((wq_completion)writeback){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0
 #1: ffffc90003507bc0 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0
 #2: ffff888106b660e0 (&type->s_umount_key#50){++++}-{4:4}, at: super_trylock_shared+0x20/0xf0
3 locks held by kworker/u10:30/17891:
 #0: ffff88801a489148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0
 #1: ffffc90002d3fbc0 ((linkwatch_work).work){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0
 #2: ffffffff8f537c88 (rtnl_mutex){+.+.}-{4:4}, at: linkwatch_event+0xe/0x60
2 locks held by syz.6.3095/18022:
 #0: ffff888109ca30f8 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x247/0x320
 #1: ffff888106b66428 (sb_writers#12){.+.+}-{0:0}, at: vfs_write+0x211/0xb30
2 locks held by bch-rebalance/l/18032:
2 locks held by syz.4.3105/18108:
 #0: ffff888107fc80e0 (&type->s_umount_key#50){++++}-{4:4}, at: super_lock+0x2a9/0x3b0
 #1: ffff888107fca7d0 (&bdi->wb_switch_rwsem){+.+.}-{4:4}, at: sync_inodes_sb+0x19f/0xa10
1 lock held by syz.5.3116/18189:
 #0: ffffffff8e13f938 (rcu_state.exp_mutex){+.+.}-{4:4}, at: synchronize_rcu_expedited+0x3b9/0x730
2 locks held by syz-executor/18765:
 #0: ffffffff8fa58190 (&ops->srcu#2){.+.+}-{0:0}, at: rtnl_link_ops_get+0x23/0x250
 #1: ffffffff8f537c88 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_newlink+0x8db/0x1c70

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

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+0x3fc/0x770
 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: 18032 Comm: bch-rebalance/l 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
RIP: 0010:stack_trace_consume_entry+0xb/0x280
Code: cc cc cc cc cc e8 f5 0d cd 09 0f 1f 44 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 55 41 57 41 56 41 55 <41> 54 53 48 83 ec 18 48 ba 00 00 00 00 00 fc ff df 4c 8d 47 10 4c
RSP: 0018:ffffc90002d5e8a0 EFLAGS: 00000282
RAX: ffffffff82189a9b RBX: ffffc90002d5e980 RCX: 6f36793d09eadf00
RDX: 0000000000000001 RSI: ffffffff82189a9b RDI: ffffc90002d5e980
RBP: ffffc90002d5e950 R08: ffffc90002d5f050 R09: 0000000000000000
R10: ffffc90002d5e918 R11: ffffffff81ac3910 R12: ffff888021975640
R13: 1ffff920005abd44 R14: ffffffff81ac3910 R15: ffffc90002d5e8c8
FS:  0000000000000000(0000) GS:ffff8881a3c1c000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055d983e8e043 CR3: 000000000df36000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 arch_stack_walk+0x110/0x150
 stack_trace_save+0x9c/0xe0
 save_stack+0xf5/0x1f0
 __set_page_owner+0x8d/0x4a0
 post_alloc_hook+0x240/0x2a0
 get_page_from_freelist+0x21e4/0x22c0
 __alloc_frozen_pages_noprof+0x181/0x370
 alloc_pages_mpol+0x232/0x4a0
 allocate_slab+0x8a/0x370
 ___slab_alloc+0xbeb/0x1410
 __kmalloc_cache_noprof+0x296/0x3d0
 bch2_move_extent+0x3ac/0x1bb0
 do_rebalance_extent+0x8f0/0x1fe0
 bch2_rebalance_thread+0x126a/0x1f80
 kthread+0x711/0x8a0
 ret_from_fork+0x3fc/0x770
 ret_from_fork_asm+0x1a/0x30
 </TASK>
