Re: [syzbot] [bcachefs?] INFO: task hung in do_rmdir (6)

On Thu, Oct 24, 2024 at 05:44:29PM -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    715ca9dd687f Merge tag 'io_uring-6.12-20241019' of git://g..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=163e60a7980000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=78db40d8379956d9
> dashboard link: https://syzkaller.appspot.com/bug?extid=4128a26fb0f85ec9e76c
> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> 
> Unfortunately, I don't have any reproducer for this issue yet.
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/bf3787869b5a/disk-715ca9dd.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/b938d885bc17/vmlinux-715ca9dd.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/9c039de0dde2/bzImage-715ca9dd.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: [email protected]
> 
> INFO: task syz.4.77:6035 blocked for more than 143 seconds.
>       Not tainted 6.12.0-rc3-syzkaller-00420-g715ca9dd687f #0
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:syz.4.77        state:D stack:25024 pid:6035  tgid:6021  ppid:5239   flags:0x00000004
> Call Trace:
>  <TASK>
>  context_switch kernel/sched/core.c:5322 [inline]
>  __schedule+0x1843/0x4ae0 kernel/sched/core.c:6682
>  __schedule_loop kernel/sched/core.c:6759 [inline]
>  schedule+0x14b/0x320 kernel/sched/core.c:6774
>  schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6831
>  rwsem_down_write_slowpath+0xeee/0x13b0 kernel/locking/rwsem.c:1176
>  __down_write_common kernel/locking/rwsem.c:1304 [inline]
>  __down_write kernel/locking/rwsem.c:1313 [inline]
>  down_write_nested+0x1e0/0x220 kernel/locking/rwsem.c:1694
>  inode_lock_nested include/linux/fs.h:850 [inline]
>  do_rmdir+0x263/0x580 fs/namei.c:4387
>  __do_sys_rmdir fs/namei.c:4418 [inline]
>  __se_sys_rmdir fs/namei.c:4416 [inline]
>  __x64_sys_rmdir+0x47/0x50 fs/namei.c:4416
>  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>  do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7f271637dff9
> RSP: 002b:00007f27171e6038 EFLAGS: 00000246 ORIG_RAX: 0000000000000054
> RAX: ffffffffffffffda RBX: 00007f2716536058 RCX: 00007f271637dff9
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000100
> RBP: 00007f27163f0296 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 0000000000000000 R14: 00007f2716536058 R15: 00007ffc08a709a8
>  </TASK>
> 
> Showing all locks held in the system:
> 1 lock held by khungtaskd/30:
>  #0: ffffffff8e937e20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:337 [inline]
>  #0: ffffffff8e937e20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
>  #0: ffffffff8e937e20 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x2a0 kernel/locking/lockdep.c:6720
> 1 lock held by khugepaged/37:
>  #0: ffffffff8e9f9028 (lock#3){+.+.}-{3:3}, at: __lru_add_drain_all+0x66/0x560 mm/swap.c:843
> 3 locks held by kworker/u8:12/3110:
> 2 locks held by getty/4978:
>  #0: ffff88803374a0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
>  #1: ffffc90002f062f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x6a6/0x1e00 drivers/tty/n_tty.c:2211
> 6 locks held by syz.4.77/6025:
> 2 locks held by syz.4.77/6035:
>  #0: ffff88802b2fe420 (sb_writers#4){.+.+}-{0:0}, at: mnt_want_write+0x3f/0x90 fs/namespace.c:515
>  #1: ffff888061fdbf68 (&type->i_mutex_dir_key#3/1){+.+.}-{3:3}, at: inode_lock_nested include/linux/fs.h:850 [inline]
>  #1: ffff888061fdbf68 (&type->i_mutex_dir_key#3/1){+.+.}-{3:3}, at: do_rmdir+0x263/0x580 fs/namei.c:4387
> 1 lock held by syz-executor/6680:
>  #0: ffffffff8e93d3b8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:297 [inline]
>  #0: ffffffff8e93d3b8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x381/0x830 kernel/rcu/tree_exp.h:976
> 2 locks held by syz-executor/7146:
> 2 locks held by syz.2.238/7877:
> 
> =============================================
> 
> NMI backtrace for cpu 0
> CPU: 0 UID: 0 PID: 30 Comm: khungtaskd Not tainted 6.12.0-rc3-syzkaller-00420-g715ca9dd687f #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
> Call Trace:
>  <TASK>
>  __dump_stack lib/dump_stack.c:94 [inline]
>  dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
>  nmi_cpu_backtrace+0x49c/0x4d0 lib/nmi_backtrace.c:113
>  nmi_trigger_cpumask_backtrace+0x198/0x320 lib/nmi_backtrace.c:62
>  trigger_all_cpu_backtrace include/linux/nmi.h:162 [inline]
>  check_hung_uninterruptible_tasks kernel/hung_task.c:223 [inline]
>  watchdog+0xff4/0x1040 kernel/hung_task.c:379
>  kthread+0x2f0/0x390 kernel/kthread.c:389
>  ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
>  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
>  </TASK>
> Sending NMI from CPU 0 to CPUs 1:
> NMI backtrace for cpu 1
> CPU: 1 UID: 0 PID: 7146 Comm: syz-executor Not tainted 6.12.0-rc3-syzkaller-00420-g715ca9dd687f #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
> RIP: 0010:lock_acquire+0x1e8/0x550 kernel/locking/lockdep.c:5825
> Code: 02 00 00 41 0f 94 c1 48 8b 7c 24 20 44 89 f6 8b 54 24 1c 48 8b 4c 24 30 4c 8b 44 24 38 6a 00 6a 00 6a 00 ff 75 10 ff 74 24 48 <e8> c3 04 00 00 48 83 c4 28 48 c7 c7 40 dc 0a 8c e8 03 bf 4d 0a b8
> RSP: 0018:ffffc900038d7698 EFLAGS: 00000006
> RAX: 0000000000000001 RBX: ffffc900038d7720 RCX: 0000000000000001
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff888012601bd8
> RBP: ffffc900038d7808 R08: 0000000000000001 R09: 0000000000000000
> R10: dffffc0000000000 R11: fffffbfff2037a4e R12: 1ffff9200071aee0
> R13: dffffc0000000000 R14: 0000000000000000 R15: 0000000000000246
> FS:  00005555639f4500(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007ffe89d07e48 CR3: 000000007652c000 CR4: 00000000003526f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <NMI>
>  </NMI>
>  <TASK>
>  __raw_read_lock include/linux/rwlock_api_smp.h:150 [inline]
>  _raw_read_lock+0x36/0x50 kernel/locking/spinlock.c:228
>  ext4_es_lookup_extent+0x169/0xa90 fs/ext4/extents_status.c:1015
>  ext4_map_blocks+0x1f9/0x1960 fs/ext4/inode.c:623
>  ext4_readdir+0xb25/0x3a60 fs/ext4/dir.c:182
>  iterate_dir+0x571/0x800 fs/readdir.c:108
>  __do_sys_getdents64 fs/readdir.c:407 [inline]
>  __se_sys_getdents64+0x1d3/0x4a0 fs/readdir.c:392
>  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>  do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7f6d7fdb0193
> Code: c1 66 0f 1f 44 00 00 48 83 c4 08 48 89 ef 5b 5d e9 42 43 f8 ff 66 90 b8 ff ff ff 7f 48 39 c2 48 0f 47 d0 b8 d9 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 05 c3 0f 1f 40 00 48 c7 c2 a8 ff ff ff f7 d8
> RSP: 002b:00007fffae72a608 EFLAGS: 00000293 ORIG_RAX: 00000000000000d9
> RAX: ffffffffffffffda RBX: 0000555563a17640 RCX: 00007f6d7fdb0193
> RDX: 0000000000008000 RSI: 0000555563a17640 RDI: 0000000000000006
> RBP: 0000555563a17614 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000001000 R11: 0000000000000293 R12: ffffffffffffffa8
> R13: 0000000000000016 R14: 0000555563a17610 R15: 00007fffae72d9a0
>  </TASK>
> 
> 
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at [email protected].
> 
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> 
> If the report is already addressed, let syzbot know by replying with:
> #syz fix: exact-commit-title
> 
> If you want to overwrite report's subsystems, reply with:
> #syz set subsystems: new-subsystem
> (See the list of subsystem names on the web dashboard)
> 
> If the report is a duplicate of another one, reply with:
> #syz dup: exact-subject-of-another-report
> 
> If you want to undo deduplication, reply with:
> #syz undup

#syz set subsystems: fs