syzbot

         option from the mount to silence this warning.
=======================================================
hfs: unable to locate alternate MDB
hfs: continuing without an alternate MDB
============================================
WARNING: possible recursive locking detected
syzkaller #0 Not tainted
--------------------------------------------
syz.0.17/6066 is trying to acquire lock:
ffff888028b5a0a0 (&tree->tree_lock/1){+.+.}-{4:4}, at: hfs_find_init+0x18e/0x300 fs/hfs/bfind.c:-1

but task is already holding lock:
ffff888028b5a0a0 (&tree->tree_lock/1){+.+.}-{4:4}, at: hfs_find_init+0x18e/0x300 fs/hfs/bfind.c:-1

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&tree->tree_lock/1);
  lock(&tree->tree_lock/1);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

5 locks held by syz.0.17/6066:
 #0: ffff888028b58480 (sb_writers#12){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:499
 #1: ffff888025dc18c0 (&sb->s_type->i_mutex_key#23){+.+.}-{4:4}, at: inode_lock_killable include/linux/fs.h:1032 [inline]
 #1: ffff888025dc18c0 (&sb->s_type->i_mutex_key#23){+.+.}-{4:4}, at: do_truncate+0x18f/0x250 fs/open.c:63
 #2: ffff888025dc16e8 (&HFS_I(inode)->extents_lock){+.+.}-{4:4}, at: hfs_extend_file+0xf2/0x15e0 fs/hfs/extent.c:397
 #3: ffff888028b5a0a0 (&tree->tree_lock/1){+.+.}-{4:4}, at: hfs_find_init+0x18e/0x300 fs/hfs/bfind.c:-1
 #4: ffff888025dc0128 (&HFS_I(tree->inode)->extents_lock){+.+.}-{4:4}, at: hfs_extend_file+0xf2/0x15e0 fs/hfs/extent.c:397

stack backtrace:
CPU: 0 UID: 0 PID: 6066 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_deadlock_bug+0x279/0x290 kernel/locking/lockdep.c:3041
 check_deadlock kernel/locking/lockdep.c:3093 [inline]
 validate_chain kernel/locking/lockdep.c:3895 [inline]
 __lock_acquire+0x253f/0x2cf0 kernel/locking/lockdep.c:5237
 lock_acquire+0x106/0x330 kernel/locking/lockdep.c:5868
 __mutex_lock_common kernel/locking/rtmutex_api.c:533 [inline]
 mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:552
 hfs_find_init+0x18e/0x300 fs/hfs/bfind.c:-1
 hfs_ext_read_extent fs/hfs/extent.c:200 [inline]
 hfs_extend_file+0x35c/0x15e0 fs/hfs/extent.c:401
 hfs_bmap_reserve+0x107/0x430 fs/hfs/btree.c:269
 __hfs_ext_write_extent+0x1fa/0x470 fs/hfs/extent.c:121
 __hfs_ext_cache_extent+0x6b/0x9b0 fs/hfs/extent.c:174
 hfs_ext_read_extent fs/hfs/extent.c:202 [inline]
 hfs_extend_file+0x39b/0x15e0 fs/hfs/extent.c:401
 hfs_get_block+0x412/0xc50 fs/hfs/extent.c:353
 __block_write_begin_int+0x6c6/0x1910 fs/buffer.c:2145
 block_write_begin fs/buffer.c:2256 [inline]
 cont_write_begin+0x737/0xae0 fs/buffer.c:2594
 hfs_write_begin+0x66/0xb0 fs/hfs/inode.c:53
 cont_expand_zero fs/buffer.c:2522 [inline]
 cont_write_begin+0x2e7/0xae0 fs/buffer.c:2584
 hfs_write_begin+0x66/0xb0 fs/hfs/inode.c:53
 hfs_file_truncate+0x1cf/0xb70 fs/hfs/extent.c:495
 hfs_inode_setattr+0x4a9/0x670 fs/hfs/inode.c:666
 notify_change+0xc18/0xf60 fs/attr.c:546
 do_truncate+0x1c2/0x250 fs/open.c:68
 vfs_truncate+0x4b4/0x540 fs/open.c:118
 do_sys_truncate+0xf1/0x1c0 fs/open.c:141
 __do_sys_truncate fs/open.c:153 [inline]
 __se_sys_truncate fs/open.c:151 [inline]
 __x64_sys_truncate+0x5b/0x70 fs/open.c:151
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fccb138acb9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe1470ca38 EFLAGS: 00000246 ORIG_RAX: 000000000000004c
RAX: ffffffffffffffda RBX: 00007fccb1605fa0 RCX: 00007fccb138acb9
RDX: 0000000000000000 RSI: 0000000001001bfc RDI: 0000200000000040
RBP: 00007fccb13f8bf7 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fccb1605fac R14: 00007fccb1605fa0 R15: 00007fccb1605fa0
 </TASK>
------------[ cut here ]------------
rtmutex deadlock detected
WARNING: kernel/locking/rtmutex.c:1674 at rt_mutex_handle_deadlock+0x21/0xb0 kernel/locking/rtmutex.c:1674, CPU#0: syz.0.17/6066
Modules linked in:
CPU: 0 UID: 0 PID: 6066 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:rt_mutex_handle_deadlock+0x21/0xb0 kernel/locking/rtmutex.c:1674
Code: 90 90 90 90 90 90 90 90 90 41 57 41 56 41 55 41 54 53 83 ff dd 0f 85 81 00 00 00 48 89 f7 e8 96 39 01 00 48 8d 3d 5f 8c 2f 04 <67> 48 0f b9 3a 4c 8d 3d 00 00 00 00 65 48 8b 1d c3 69 05 07 4c 8d
RSP: 0018:ffffc90003c16c30 EFLAGS: 00010286
RAX: 0000000080000000 RBX: ffffc90003c16cc0 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8b5f6240 RDI: ffffffff8f1e9290
RBP: ffffc90003c16dc8 R08: ffffffff8f1b6f77 R09: 1ffffffff1e36dee
R10: dffffc0000000000 R11: fffffbfff1e36def R12: 1ffff92000782d94
R13: ffffffff8aef00ed R14: ffff888028b5a048 R15: dffffc0000000000
FS:  000055558bf25500(0000) GS:ffff8881268d9000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055d588562138 CR3: 0000000040f94000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 __rt_mutex_slowlock kernel/locking/rtmutex.c:1734 [inline]
 __rt_mutex_slowlock_locked kernel/locking/rtmutex.c:1760 [inline]
 rt_mutex_slowlock+0x6c0/0x710 kernel/locking/rtmutex.c:1800
 __rt_mutex_lock kernel/locking/rtmutex.c:1815 [inline]
 __mutex_lock_common kernel/locking/rtmutex_api.c:534 [inline]
 mutex_lock_nested+0x168/0x1d0 kernel/locking/rtmutex_api.c:552
 hfs_find_init+0x18e/0x300 fs/hfs/bfind.c:-1
 hfs_ext_read_extent fs/hfs/extent.c:200 [inline]
 hfs_extend_file+0x35c/0x15e0 fs/hfs/extent.c:401
 hfs_bmap_reserve+0x107/0x430 fs/hfs/btree.c:269
 __hfs_ext_write_extent+0x1fa/0x470 fs/hfs/extent.c:121
 __hfs_ext_cache_extent+0x6b/0x9b0 fs/hfs/extent.c:174
 hfs_ext_read_extent fs/hfs/extent.c:202 [inline]
 hfs_extend_file+0x39b/0x15e0 fs/hfs/extent.c:401
 hfs_get_block+0x412/0xc50 fs/hfs/extent.c:353
 __block_write_begin_int+0x6c6/0x1910 fs/buffer.c:2145
 block_write_begin fs/buffer.c:2256 [inline]
 cont_write_begin+0x737/0xae0 fs/buffer.c:2594
 hfs_write_begin+0x66/0xb0 fs/hfs/inode.c:53
 cont_expand_zero fs/buffer.c:2522 [inline]
 cont_write_begin+0x2e7/0xae0 fs/buffer.c:2584
 hfs_write_begin+0x66/0xb0 fs/hfs/inode.c:53
 hfs_file_truncate+0x1cf/0xb70 fs/hfs/extent.c:495
 hfs_inode_setattr+0x4a9/0x670 fs/hfs/inode.c:666
 notify_change+0xc18/0xf60 fs/attr.c:546
 do_truncate+0x1c2/0x250 fs/open.c:68
 vfs_truncate+0x4b4/0x540 fs/open.c:118
 do_sys_truncate+0xf1/0x1c0 fs/open.c:141
 __do_sys_truncate fs/open.c:153 [inline]
 __se_sys_truncate fs/open.c:151 [inline]
 __x64_sys_truncate+0x5b/0x70 fs/open.c:151
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fccb138acb9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe1470ca38 EFLAGS: 00000246 ORIG_RAX: 000000000000004c
RAX: ffffffffffffffda RBX: 00007fccb1605fa0 RCX: 00007fccb138acb9
RDX: 0000000000000000 RSI: 0000000001001bfc RDI: 0000200000000040
RBP: 00007fccb13f8bf7 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fccb1605fac R14: 00007fccb1605fa0 R15: 00007fccb1605fa0
 </TASK>
----------------
Code disassembly (best guess):
   0:	90                   	nop
   1:	90                   	nop
   2:	90                   	nop
   3:	90                   	nop
   4:	90                   	nop
   5:	90                   	nop
   6:	90                   	nop
   7:	90                   	nop
   8:	90                   	nop
   9:	41 57                	push   %r15
   b:	41 56                	push   %r14
   d:	41 55                	push   %r13
   f:	41 54                	push   %r12
  11:	53                   	push   %rbx
  12:	83 ff dd             	cmp    $0xffffffdd,%edi
  15:	0f 85 81 00 00 00    	jne    0x9c
  1b:	48 89 f7             	mov    %rsi,%rdi
  1e:	e8 96 39 01 00       	call   0x139b9
  23:	48 8d 3d 5f 8c 2f 04 	lea    0x42f8c5f(%rip),%rdi        # 0x42f8c89
* 2a:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2f:	4c 8d 3d 00 00 00 00 	lea    0x0(%rip),%r15        # 0x36
  36:	65 48 8b 1d c3 69 05 	mov    %gs:0x70569c3(%rip),%rbx        # 0x7056a01
  3d:	07
  3e:	4c                   	rex.WR
  3f:	8d                   	.byte 0x8d