syzbot

loop0: detected capacity change from 0 to 64
============================================
WARNING: possible recursive locking detected
syzkaller #0 Not tainted
--------------------------------------------
syz.0.17/5991 is trying to acquire lock:
ffff88803138a0b0 (&tree->tree_lock/1){+.+.}-{4:4}, at: hfs_find_init+0x18e/0x300 fs/hfs/bfind.c:-1

but task is already holding lock:
ffff88803138a0b0 (&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.0.17/5991:
 #0: ffff888033b7e420 (sb_writers#12){.+.+}-{0:0}, at: class_super_write_constructor include/linux/fs/super.h:128 [inline]
 #0: ffff888033b7e420 (sb_writers#12){.+.+}-{0:0}, at: do_ftruncate+0x47c/0x5c0 fs/open.c:195
 #1: ffff888032d39620 (&sb->s_type->i_mutex_key#25){+.+.}-{4:4}, at: inode_lock_killable include/linux/fs.h:1033 [inline]
 #1: ffff888032d39620 (&sb->s_type->i_mutex_key#25){+.+.}-{4:4}, at: do_truncate+0x18f/0x250 fs/open.c:63
 #2: ffff888032d39478 (&HFS_I(inode)->extents_lock){+.+.}-{4:4}, at: hfs_extend_file+0xf2/0x15e0 fs/hfs/extent.c:397
 #3: ffff88803138a0b0 (&tree->tree_lock/1){+.+.}-{4:4}, at: hfs_find_init+0x18e/0x300 fs/hfs/bfind.c:-1
 #4: ffff8880332a4878 (&HFS_I(tree->inode)->extents_lock){+.+.}-{4:4}, at: hfs_extend_file+0xf2/0x15e0 fs/hfs/extent.c:397

stack backtrace:
CPU: 1 UID: 0 PID: 5991 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
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+0x253f/0x2cf0 kernel/locking/lockdep.c:5237
 lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868
 __mutex_lock_common kernel/locking/mutex.c:614 [inline]
 __mutex_lock+0x19f/0x1300 kernel/locking/mutex.c:776
 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:2142
 block_write_begin fs/buffer.c:2253 [inline]
 cont_write_begin+0x737/0xae0 fs/buffer.c:2591
 hfs_write_begin+0x66/0xb0 fs/hfs/inode.c:53
 cont_expand_zero fs/buffer.c:2519 [inline]
 cont_write_begin+0x2e7/0xae0 fs/buffer.c:2581
 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:684
 notify_change+0xc1a/0xf40 fs/attr.c:556
 do_truncate+0x1c2/0x250 fs/open.c:68
 do_ftruncate+0x4db/0x5c0 fs/open.c:196
 do_sys_ftruncate fs/open.c:208 [inline]
 __do_sys_ftruncate fs/open.c:213 [inline]
 __se_sys_ftruncate fs/open.c:211 [inline]
 __x64_sys_ftruncate+0x92/0xf0 fs/open.c:211
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f94dcd9c799
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:00007fffcaf9e0d8 EFLAGS: 00000246 ORIG_RAX: 000000000000004d
RAX: ffffffffffffffda RBX: 00007f94dd015fa0 RCX: 00007f94dcd9c799
RDX: 0000000000000000 RSI: 000000000100c17a RDI: 0000000000000004
RBP: 00007f94dce32bd9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f94dd015fac R14: 00007f94dd015fa0 R15: 00007f94dd015fa0
 </TASK>