INFO: task syz-executor:6718 blocked for more than 143 seconds.
      Not tainted 6.15.0-rc5-syzkaller-00275-gbec6f00f120e #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor    state:D stack:21656 pid:6718  tgid:6718  ppid:1      task_flags:0x400140 flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x168f/0x4c70 kernel/sched/core.c:6767
 __schedule_loop kernel/sched/core.c:6845 [inline]
 schedule+0x165/0x360 kernel/sched/core.c:6860
 wb_wait_for_completion+0x15f/0x260 fs/fs-writeback.c:216
 __writeback_inodes_sb_nr+0x1f6/0x250 fs/fs-writeback.c:2747
 sync_filesystem+0xa3/0x230 fs/sync.c:54
 generic_shutdown_super+0x6f/0x2c0 fs/super.c:621
 bch2_kill_sb+0x41/0x50 fs/bcachefs/fs.c:2620
 deactivate_locked_super+0xb9/0x130 fs/super.c:473
 cleanup_mnt+0x425/0x4c0 fs/namespace.c:1431
 task_work_run+0x1d1/0x260 kernel/task_work.c:227
 resume_user_mode_work+0x5e/0x80 include/linux/resume_user_mode.h:50
 exit_to_user_mode_loop kernel/entry/common.c:114 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0x9a/0x120 kernel/entry/common.c:218
 do_syscall_64+0x103/0x210 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fde8358fc97
RSP: 002b:00007ffe12bd74c8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 00007fde8361089d RCX: 00007fde8358fc97
RDX: 0000000000000000 RSI: 0000000000000009 RDI: 00007ffe12bd7580
RBP: 00007ffe12bd7580 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000ffffffff R11: 0000000000000246 R12: 00007ffe12bd8610
R13: 00007fde8361089d R14: 0000000000032248 R15: 00007ffe12bd8650
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/31:
 #0: ffffffff8df3b860 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 #0: ffffffff8df3b860 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline]
 #0: ffffffff8df3b860 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6764
3 locks held by kworker/u8:3/53:
3 locks held by kworker/u8:4/64:
2 locks held by kworker/u8:6/3478:
 #0: ffff8881412e1948 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3213 [inline]
 #0: ffff8881412e1948 ((wq_completion)writeback){+.+.}-{0:0}, at: process_scheduled_works+0x9b1/0x17a0 kernel/workqueue.c:3319
 #1: ffffc9000bfc7c60 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3214 [inline]
 #1: ffffc9000bfc7c60 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x9ec/0x17a0 kernel/workqueue.c:3319
2 locks held by getty/5578:
 #0: ffff888034bda0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc90002ffe2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x43e/0x1400 drivers/tty/n_tty.c:2222
1 lock held by syz-executor/6718:
 #0: ffff8880612520e0 (&type->s_umount_key#84){+.+.}-{4:4}, at: __super_lock fs/super.c:56 [inline]
 #0: ffff8880612520e0 (&type->s_umount_key#84){+.+.}-{4:4}, at: __super_lock_excl fs/super.c:71 [inline]
 #0: ffff8880612520e0 (&type->s_umount_key#84){+.+.}-{4:4}, at: deactivate_super+0xa9/0xe0 fs/super.c:505
1 lock held by syz-executor/9765:
1 lock held by syz.8.489/10144:
2 locks held by syz.2.494/10176:
4 locks held by syz.6.495/10181:
1 lock held by udevadm/10184:

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

NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 31 Comm: khungtaskd Not tainted 6.15.0-rc5-syzkaller-00275-gbec6f00f120e #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 nmi_cpu_backtrace+0x39e/0x3d0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x17a/0x300 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:158 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:274 [inline]
 watchdog+0xfee/0x1030 kernel/hung_task.c:437
 kthread+0x70e/0x8a0 kernel/kthread.c:464
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 10189 Comm: syz.4.492 Not tainted 6.15.0-rc5-syzkaller-00275-gbec6f00f120e #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:io_serial_in+0x77/0xc0 drivers/tty/serial/8250/8250_port.c:409
Code: e8 0e 2c 89 fc 44 89 f9 d3 e3 49 83 c6 40 4c 89 f0 48 c1 e8 03 42 80 3c 20 00 74 08 4c 89 f7 e8 df fa e8 fc 41 03 1e 89 da ec <0f> b6 c0 5b 41 5c 41 5e 41 5f c3 cc cc cc cc cc 44 89 f9 80 e1 07
RSP: 0018:ffffc900042eee70 EFLAGS: 00000002
RAX: 1ffffffff3362f00 RBX: 00000000000003fd RCX: 0000000000000000
RDX: 00000000000003fd RSI: 0000000000007776 RDI: 0000000000007777
RBP: ffffffff99b17c10 R08: ffff888023e28237 R09: 1ffff110047c5046
R10: dffffc0000000000 R11: ffffffff8536a2e0 R12: dffffc0000000000
R13: 0000000000000000 R14: ffffffff99b17980 R15: 0000000000000000
FS:  00007f54ad48b6c0(0000) GS:ffff888126100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f54ad46ad58 CR3: 000000006f84c000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 serial_in drivers/tty/serial/8250/8250.h:137 [inline]
 serial_lsr_in drivers/tty/serial/8250/8250.h:159 [inline]
 wait_for_lsr+0x19e/0x2f0 drivers/tty/serial/8250/8250_port.c:2098
 fifo_wait_for_lsr drivers/tty/serial/8250/8250_port.c:3348 [inline]
 serial8250_console_fifo_write drivers/tty/serial/8250/8250_port.c:3371 [inline]
 serial8250_console_write+0x134c/0x1ba0 drivers/tty/serial/8250/8250_port.c:3456
 console_emit_next_record kernel/printk/printk.c:3138 [inline]
 console_flush_all+0x725/0xc40 kernel/printk/printk.c:3226
 __console_flush_and_unlock kernel/printk/printk.c:3285 [inline]
 console_unlock+0xc4/0x270 kernel/printk/printk.c:3325
 vprintk_emit+0x5b7/0x7a0 kernel/printk/printk.c:2450
 _printk+0xcf/0x120 kernel/printk/printk.c:2475
 __ext4_error_inode+0x4b4/0x4f0 fs/ext4/super.c:843
 __ext4_check_dir_entry+0x6e3/0x8a0 fs/ext4/dir.c:120
 dx_make_map fs/ext4/namei.c:1297 [inline]
 do_split+0x5df/0x1e60 fs/ext4/namei.c:1950
 make_indexed_dir+0xc41/0x1200 fs/ext4/namei.c:2330
 ext4_add_entry+0xaa8/0xc20 fs/ext4/namei.c:2437
 ext4_add_nondir+0x93/0x270 fs/ext4/namei.c:2786
 ext4_mknod+0x2fd/0x4b0 fs/ext4/namei.c:2866
 vfs_mknod+0x37c/0x3c0 fs/namei.c:4228
 do_mknodat+0x385/0x4d0 fs/namei.c:-1
 __do_sys_mknod fs/namei.c:4311 [inline]
 __se_sys_mknod fs/namei.c:4309 [inline]
 __x64_sys_mknod+0x8c/0xa0 fs/namei.c:4309
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f54ac58e969
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f54ad48b038 EFLAGS: 00000246 ORIG_RAX: 0000000000000085
RAX: ffffffffffffffda RBX: 00007f54ac7b5fa0 RCX: 00007f54ac58e969
RDX: 0000000000000708 RSI: 0000000000002000 RDI: 0000200000001940
RBP: 00007f54ac610ab1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f54ac7b5fa0 R15: 00007ffcb3817fd8
 </TASK>