syzbot

INFO: task kmmpd-loop3:7692 blocked for more than 168 seconds.
      Not tainted 6.12.0-rc7-syzkaller-00125-gcfaaa7d010d1 #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kmmpd-loop3     state:D stack:27224 pid:7692  tgid:7692  ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5328 [inline]
 __schedule+0x184f/0x4c30 kernel/sched/core.c:6693
 __schedule_loop kernel/sched/core.c:6770 [inline]
 schedule+0x14b/0x320 kernel/sched/core.c:6785
 io_schedule+0x8d/0x110 kernel/sched/core.c:7577
 bit_wait_io+0x12/0xd0 kernel/sched/wait_bit.c:209
 __wait_on_bit+0xb2/0x2f0 kernel/sched/wait_bit.c:49
 out_of_line_wait_on_bit+0x1d5/0x260 kernel/sched/wait_bit.c:64
 wait_on_buffer include/linux/buffer_head.h:414 [inline]
 write_mmp_block_thawed+0x422/0x5b0 fs/ext4/mmp.c:52
 write_mmp_block+0x13f/0x3a0 fs/ext4/mmp.c:67
 kmmpd+0x424/0xaa0 fs/ext4/mmp.c:178
 kthread+0x2f2/0x390 kernel/kthread.c:389
 ret_from_fork+0x4d/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>

Showing all locks held in the system:
3 locks held by kworker/u8:1/12:
1 lock held by khungtaskd/30:
 #0: ffffffff8e937da0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:337 [inline]
 #0: ffffffff8e937da0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #0: ffffffff8e937da0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x2a0 kernel/locking/lockdep.c:6720
2 locks held by kworker/0:1H/40:
3 locks held by kworker/u8:3/53:
4 locks held by kworker/u9:0/54:
 #0: ffff8880338de148 ((wq_completion)hci1){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3204 [inline]
 #0: ffff8880338de148 ((wq_completion)hci1){+.+.}-{0:0}, at: process_scheduled_works+0x93b/0x1850 kernel/workqueue.c:3310
 #1: ffffc90000bf7d00 ((work_completion)(&hdev->cmd_sync_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3205 [inline]
 #1: ffffc90000bf7d00 ((work_completion)(&hdev->cmd_sync_work)){+.+.}-{0:0}, at: process_scheduled_works+0x976/0x1850 kernel/workqueue.c:3310
 #2: ffff8880636d0d80 (&hdev->req_lock){+.+.}-{3:3}, at: hci_cmd_sync_work+0x1ec/0x400 net/bluetooth/hci_sync.c:331