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.0.17/5935 is trying to acquire lock:
ffff8880355700a0 (&tree->tree_lock/1){+.+.}-{4:4}, at: hfs_find_init+0x18d/0x300 fs/hfs/bfind.c:-1

but task is already holding lock:
ffff8880355700a0 (&tree->tree_lock/1){+.+.}-{4:4}, at: hfs_find_init+0x18d/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.0.17/5935:
 #0: ffff888035b0c500 (sb_writers#12){.+.+}-{0:0}, at: class_super_write_constructor include/linux/fs/super.h:130 [inline]
 #0: ffff888035b0c500 (sb_writers#12){.+.+}-{0:0}, at: do_ftruncate+0x480/0x590 fs/open.c:193
 #1: ffff88803528b670 (&sb->s_type->i_mutex_key#24){+.+.}-{4:4}, at: inode_lock_killable include/linux/fs.h:1029 [inline]
 #1: ffff88803528b670 (&sb->s_type->i_mutex_key#24){+.+.}-{4:4}, at: do_truncate+0x18f/0x250 fs/open.c:63
 #2: ffff88803528b498 (&HFS_I(inode)->extents_lock){+.+.}-{4:4}, at: hfs_extend_file+0xf9/0x1680 fs/hfs/extent.c:397
 #3: ffff8880355700a0 (&tree->tree_lock/1){+.+.}-{4:4}, at: hfs_find_init+0x18d/0x300 fs/hfs/bfind.c:-1
 #4: ffff88803528c818 (&HFS_I(tree->inode)->extents_lock){+.+.}-{4:4}, at: hfs_extend_file+0xf9/0x1680 fs/hfs/extent.c:397

stack backtrace:
CPU: 1 UID: 0 PID: 5935 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
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+0x24df/0x2ce0 kernel/locking/lockdep.c:5237
 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
 __mutex_lock_common kernel/locking/rtmutex_api.c:559 [inline]
 mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:578
 hfs_find_init+0x18d/0x300 fs/hfs/bfind.c:-1
 hfs_ext_read_extent fs/hfs/extent.c:200 [inline]
 hfs_extend_file+0x35f/0x1680 fs/hfs/extent.c:401
 hfs_bmap_reserve+0x108/0x430 fs/hfs/btree.c:269
 __hfs_ext_write_extent+0x1fc/0x470 fs/hfs/extent.c:121
 __hfs_ext_cache_extent+0x6e/0x9b0 fs/hfs/extent.c:174
 hfs_ext_read_extent fs/hfs/extent.c:202 [inline]
 hfs_extend_file+0x3a0/0x1680 fs/hfs/extent.c:401
 hfs_get_block+0x401/0xbe0 fs/hfs/extent.c:353
 __block_write_begin_int+0x6c2/0x1900 fs/buffer.c:2123
 block_write_begin fs/buffer.c:2234 [inline]
 cont_write_begin+0x71b/0xac0 fs/buffer.c:2596
 hfs_write_begin+0x66/0xb0 fs/hfs/inode.c:54
 cont_expand_zero fs/buffer.c:2524 [inline]
 cont_write_begin+0x2d6/0xac0 fs/buffer.c:2586
 hfs_write_begin+0x66/0xb0 fs/hfs/inode.c:54
 hfs_file_truncate+0x1cf/0xb60 fs/hfs/extent.c:495
 hfs_inode_setattr+0x49a/0x6c0 fs/hfs/inode.c:669
 notify_change+0xbb8/0xec0 fs/attr.c:556
 do_truncate+0x1c2/0x250 fs/open.c:68
 do_ftruncate+0x4e0/0x590 fs/open.c:194
 ksys_ftruncate fs/open.c:206 [inline]
 __do_sys_ftruncate fs/open.c:211 [inline]
 __se_sys_ftruncate fs/open.c:209 [inline]
 __x64_sys_ftruncate+0x8f/0xe0 fs/open.c:209
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f25dfc6de59
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:00007ffcd4e5f158 EFLAGS: 00000246 ORIG_RAX: 000000000000004d
RAX: ffffffffffffffda RBX: 00007f25dfef5fa0 RCX: 00007f25dfc6de59
RDX: 0000000000000000 RSI: 0000000006000000 RDI: 0000000000000004
RBP: 00007f25dfd03e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f25dfef5fac R14: 00007f25dfef5fa0 R15: 00007f25dfef5fa0
 </TASK>
------------[ cut here ]------------
rtmutex deadlock detected
WARNING: kernel/locking/rtmutex.c:1698 at rt_mutex_handle_deadlock+0x21/0xb0 kernel/locking/rtmutex.c:1698, CPU#0: syz.0.17/5935
Modules linked in:
CPU: 0 UID: 0 PID: 5935 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:rt_mutex_handle_deadlock+0x21/0xb0 kernel/locking/rtmutex.c:1698
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 16 40 01 00 48 8d 3d 0f 2d 6f 04 <67> 48 0f b9 3a 4c 8d 3d 00 00 00 00 65 48 8b 1d 43 8d 59 07 4c 8d
RSP: 0018:ffffc9000402ed10 EFLAGS: 00010286
RAX: 0000000080000000 RBX: 00000000ffffffdd RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8bca5f60 RDI: ffffffff8fb2dfc0
RBP: ffffc9000402eea8 R08: ffffffff8faf74f7 R09: 1ffffffff1f5ee9e
R10: dffffc0000000000 R11: fffffbfff1f5ee9f R12: 1ffff92000805db0
R13: ffffffff8b43acf2 R14: ffff888035570048 R15: dffffc0000000000
FS:  000055555befd500(0000) GS:ffff888125c4c000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fe304b6e286 CR3: 0000000041a5e000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 __rt_mutex_slowlock kernel/locking/rtmutex.c:1760 [inline]
 __rt_mutex_slowlock_locked kernel/locking/rtmutex.c:1787 [inline]
 rt_mutex_slowlock+0x73c/0x780 kernel/locking/rtmutex.c:1827
 __rt_mutex_lock kernel/locking/rtmutex.c:1842 [inline]
 __mutex_lock_common kernel/locking/rtmutex_api.c:560 [inline]
 mutex_lock_nested+0x168/0x1d0 kernel/locking/rtmutex_api.c:578
 hfs_find_init+0x18d/0x300 fs/hfs/bfind.c:-1
 hfs_ext_read_extent fs/hfs/extent.c:200 [inline]
 hfs_extend_file+0x35f/0x1680 fs/hfs/extent.c:401
 hfs_bmap_reserve+0x108/0x430 fs/hfs/btree.c:269
 __hfs_ext_write_extent+0x1fc/0x470 fs/hfs/extent.c:121
 __hfs_ext_cache_extent+0x6e/0x9b0 fs/hfs/extent.c:174
 hfs_ext_read_extent fs/hfs/extent.c:202 [inline]
 hfs_extend_file+0x3a0/0x1680 fs/hfs/extent.c:401
 hfs_get_block+0x401/0xbe0 fs/hfs/extent.c:353
 __block_write_begin_int+0x6c2/0x1900 fs/buffer.c:2123
 block_write_begin fs/buffer.c:2234 [inline]
 cont_write_begin+0x71b/0xac0 fs/buffer.c:2596
 hfs_write_begin+0x66/0xb0 fs/hfs/inode.c:54
 cont_expand_zero fs/buffer.c:2524 [inline]
 cont_write_begin+0x2d6/0xac0 fs/buffer.c:2586
 hfs_write_begin+0x66/0xb0 fs/hfs/inode.c:54
 hfs_file_truncate+0x1cf/0xb60 fs/hfs/extent.c:495
 hfs_inode_setattr+0x49a/0x6c0 fs/hfs/inode.c:669
 notify_change+0xbb8/0xec0 fs/attr.c:556
 do_truncate+0x1c2/0x250 fs/open.c:68
 do_ftruncate+0x4e0/0x590 fs/open.c:194
 ksys_ftruncate fs/open.c:206 [inline]
 __do_sys_ftruncate fs/open.c:211 [inline]
 __se_sys_ftruncate fs/open.c:209 [inline]
 __x64_sys_ftruncate+0x8f/0xe0 fs/open.c:209
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f25dfc6de59
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:00007ffcd4e5f158 EFLAGS: 00000246 ORIG_RAX: 000000000000004d
RAX: ffffffffffffffda RBX: 00007f25dfef5fa0 RCX: 00007f25dfc6de59
RDX: 0000000000000000 RSI: 0000000006000000 RDI: 0000000000000004
RBP: 00007f25dfd03e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f25dfef5fac R14: 00007f25dfef5fa0 R15: 00007f25dfef5fa0
 </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 16 40 01 00       	call   0x14039
  23:	48 8d 3d 0f 2d 6f 04 	lea    0x46f2d0f(%rip),%rdi        # 0x46f2d39
* 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 43 8d 59 	mov    %gs:0x7598d43(%rip),%rbx        # 0x7598d81
  3d:	07
  3e:	4c                   	rex.WR
  3f:	8d                   	.byte 0x8d