loop0: detected capacity change from 0 to 1024
============================================
WARNING: possible recursive locking detected
syzkaller #0 Not tainted
--------------------------------------------
syz.0.0/5321 is trying to acquire lock:
ffff888050a5c108 (&HFSPLUS_I(inode)->extents_lock){+.+.}-{4:4}, at: hfsplus_file_extend+0x1f8/0x1ba0 fs/hfsplus/extents.c:453

but task is already holding lock:
ffff888050a5f048 (&HFSPLUS_I(inode)->extents_lock){+.+.}-{4:4}, at: hfsplus_file_extend+0x1f8/0x1ba0 fs/hfsplus/extents.c:453

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

       CPU0
       ----
  lock(&HFSPLUS_I(inode)->extents_lock);
  lock(&HFSPLUS_I(inode)->extents_lock);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

4 locks held by syz.0.0/5321:
 #0: ffff8880121e0420 (sb_writers#12){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:508
 #1: ffff888050a5f238 (&sb->s_type->i_mutex_key#20){+.+.}-{4:4}, at: inode_lock_killable include/linux/fs.h:985 [inline]
 #1: ffff888050a5f238 (&sb->s_type->i_mutex_key#20){+.+.}-{4:4}, at: do_truncate+0x171/0x220 fs/open.c:63
 #2: ffff888050a5f048 (&HFSPLUS_I(inode)->extents_lock){+.+.}-{4:4}, at: hfsplus_file_extend+0x1f8/0x1ba0 fs/hfsplus/extents.c:453
 #3: ffff888032bba0b0 (&tree->tree_lock/1){+.+.}-{4:4}, at: hfsplus_find_init+0x168/0x290 fs/hfsplus/bfind.c:28

stack backtrace:
CPU: 0 UID: 0 PID: 5321 Comm: syz.0.0 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_deadlock_bug+0x28b/0x2a0 kernel/locking/lockdep.c:3041
 check_deadlock kernel/locking/lockdep.c:3093 [inline]
 validate_chain+0x1a3f/0x2140 kernel/locking/lockdep.c:3895
 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237
 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
 __mutex_lock_common kernel/locking/mutex.c:598 [inline]
 __mutex_lock+0x187/0x1350 kernel/locking/mutex.c:760
 hfsplus_file_extend+0x1f8/0x1ba0 fs/hfsplus/extents.c:453
 hfsplus_bmap_reserve+0x122/0x500 fs/hfsplus/btree.c:358
 __hfsplus_ext_write_extent+0x28d/0x5b0 fs/hfsplus/extents.c:104
 __hfsplus_ext_cache_extent+0x89/0xe30 fs/hfsplus/extents.c:186
 hfsplus_ext_read_extent fs/hfsplus/extents.c:218 [inline]
 hfsplus_file_extend+0x437/0x1ba0 fs/hfsplus/extents.c:457
 hfsplus_get_block+0x40a/0x15d0 fs/hfsplus/extents.c:245
 __block_write_begin_int+0x6b5/0x1900 fs/buffer.c:2145
 block_write_begin fs/buffer.c:2256 [inline]
 cont_write_begin+0x789/0xb50 fs/buffer.c:2594
 hfsplus_write_begin+0x66/0xb0 fs/hfsplus/inode.c:48
 cont_expand_zero fs/buffer.c:2522 [inline]
 cont_write_begin+0x2fd/0xb50 fs/buffer.c:2584
 hfsplus_write_begin+0x66/0xb0 fs/hfsplus/inode.c:48
 generic_cont_expand_simple+0x13f/0x210 fs/buffer.c:2485
 hfsplus_setattr+0x169/0x270 fs/hfsplus/inode.c:260
 notify_change+0xc1a/0xf40 fs/attr.c:546
 do_truncate+0x1a4/0x220 fs/open.c:68
 vfs_truncate+0x493/0x520 fs/open.c:118
 do_sys_truncate+0xdb/0x190 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+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f2a1618f6c9
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:00007f2a17113038 EFLAGS: 00000246 ORIG_RAX: 000000000000004c
RAX: ffffffffffffffda RBX: 00007f2a163e5fa0 RCX: 00007f2a1618f6c9
RDX: 0000000000000000 RSI: 00000000001fefff RDI: 0000200000000280
RBP: 00007f2a16211f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2a163e6038 R14: 00007f2a163e5fa0 R15: 00007ffddfa6cb38
 </TASK>