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.0.17/5949 is trying to acquire lock:
ffff88802bc1a0b0 (&tree->tree_lock/1){+.+.}-{3:3}, at: hfs_find_init+0x17e/0x1f0 fs/hfs/bfind.c:-1

but task is already holding lock:
ffff88802bc1a0b0 (&tree->tree_lock/1){+.+.}-{3:3}, at: hfs_find_init+0x17e/0x1f0 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.0.17/5949:
 #0: ffff88802bc18418 (sb_writers#13){.+.+}-{0:0}, at: do_sys_ftruncate+0x281/0x3d0 fs/open.c:191
 #1: ffff88802c4c8938 (&sb->s_type->i_mutex_key#20){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:804 [inline]
 #1: ffff88802c4c8938 (&sb->s_type->i_mutex_key#20){+.+.}-{3:3}, at: do_truncate+0x187/0x220 fs/open.c:64
 #2: ffff88802c4c8778 (&HFS_I(inode)->extents_lock){+.+.}-{3:3}, at: hfs_extend_file+0xdb/0x1220 fs/hfs/extent.c:397
 #3: ffff88802bc1a0b0 (&tree->tree_lock/1){+.+.}-{3:3}, at: hfs_find_init+0x17e/0x1f0 fs/hfs/bfind.c:-1
 #4: ffff8880280000f8 (&HFS_I(tree->inode)->extents_lock){+.+.}-{3:3}, at: hfs_extend_file+0xdb/0x1220 fs/hfs/extent.c:397

stack backtrace:
CPU: 0 PID: 5949 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
 check_deadlock kernel/locking/lockdep.c:3062 [inline]
 validate_chain kernel/locking/lockdep.c:3856 [inline]
 __lock_acquire+0x5d40/0x7c80 kernel/locking/lockdep.c:5137
 lock_acquire+0x197/0x410 kernel/locking/lockdep.c:5754
 __mutex_lock_common kernel/locking/mutex.c:603 [inline]
 __mutex_lock+0x129/0xcc0 kernel/locking/mutex.c:747
 hfs_find_init+0x17e/0x1f0 fs/hfs/bfind.c:-1
 hfs_ext_read_extent fs/hfs/extent.c:200 [inline]
 hfs_extend_file+0x2ef/0x1220 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+0x317/0x1220 fs/hfs/extent.c:401
 hfs_get_block+0x3d8/0xbd0 fs/hfs/extent.c:353
 __block_write_begin_int+0x566/0x1ad0 fs/buffer.c:2124
 __block_write_begin fs/buffer.c:2173 [inline]
 block_write_begin+0x9a/0x1e0 fs/buffer.c:2234
 cont_write_begin+0x5c8/0x7e0 fs/buffer.c:2591
 hfs_write_begin+0x8b/0xd0 fs/hfs/inode.c:58
 cont_expand_zero fs/buffer.c:2518 [inline]
 cont_write_begin+0x2ad/0x7e0 fs/buffer.c:2581
 hfs_write_begin+0x8b/0xd0 fs/hfs/inode.c:58
 hfs_file_truncate+0x191/0x9b0 fs/hfs/extent.c:494
 hfs_inode_setattr+0x4af/0x6e0 fs/hfs/inode.c:659
 notify_change+0xb0d/0xe10 fs/attr.c:499
 do_truncate+0x19b/0x220 fs/open.c:66
 do_sys_ftruncate+0x325/0x3d0 fs/open.c:194
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fd82d58f749
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:00007ffcf9284228 EFLAGS: 00000246 ORIG_RAX: 000000000000004d
RAX: ffffffffffffffda RBX: 00007fd82d7e5fa0 RCX: 00007fd82d58f749
RDX: 0000000000000000 RSI: 0000000008800000 RDI: 0000000000000004
RBP: 00007fd82d613f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd82d7e5fa0 R14: 00007fd82d7e5fa0 R15: 0000000000000002
 </TASK>