loop0: detected capacity change from 0 to 1024
hfsplus: b-tree write err: -5, ino 2
============================================
WARNING: possible recursive locking detected
syzkaller #0 Not tainted
--------------------------------------------
syz.0.838/12916 is trying to acquire lock:
ffff88804044f8f8 (&HFSPLUS_I(inode)->extents_lock){+.+.}-{4:4}, at: hfsplus_get_block+0x3a0/0x1670 fs/hfsplus/extents.c:260

but task is already holding lock:
ffff88804050f8f8 (&HFSPLUS_I(inode)->extents_lock){+.+.}-{4:4}, at: hfsplus_file_extend+0x215/0x1d70 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

5 locks held by syz.0.838/12916:
 #0: ffff88802b880d28 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x252/0x320 fs/file.c:1261
 #1: ffff88803c67e480 (sb_writers#17){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2710 [inline]
 #1: ffff88803c67e480 (sb_writers#17){.+.+}-{0:0}, at: vfs_write+0x22d/0xba0 fs/read_write.c:684
 #2: ffff88804050fb58 (&sb->s_type->i_mutex_key#27){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:1028 [inline]
 #2: ffff88804050fb58 (&sb->s_type->i_mutex_key#27){+.+.}-{4:4}, at: generic_file_write_iter+0x11f/0x690 mm/filemap.c:4464
 #3: ffff88804050f8f8 (&HFSPLUS_I(inode)->extents_lock){+.+.}-{4:4}, at: hfsplus_file_extend+0x215/0x1d70 fs/hfsplus/extents.c:453
 #4: ffff8880282678e8 (&sbi->alloc_mutex){+.+.}-{4:4}, at: hfsplus_block_allocate+0xa7/0xce0 fs/hfsplus/bitmap.c:35

stack backtrace:
CPU: 0 UID: 0 PID: 12916 Comm: syz.0.838 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
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/rtmutex_api.c:533 [inline]
 mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:552
 hfsplus_get_block+0x3a0/0x1670 fs/hfsplus/extents.c:260
 block_read_full_folio+0x29f/0x830 fs/buffer.c:2417
 filemap_read_folio+0x137/0x3b0 mm/filemap.c:2501
 do_read_cache_folio+0x2bf/0x560 mm/filemap.c:4106
 do_read_cache_page mm/filemap.c:4172 [inline]
 read_cache_page+0x5d/0x170 mm/filemap.c:4181
 read_mapping_page include/linux/pagemap.h:1011 [inline]
 hfsplus_block_allocate+0xf3/0xce0 fs/hfsplus/bitmap.c:37
 hfsplus_file_extend+0xb2d/0x1d70 fs/hfsplus/extents.c:464
 hfsplus_get_block+0x42e/0x1670 fs/hfsplus/extents.c:245
 __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
 hfsplus_write_begin+0x66/0xb0 fs/hfsplus/inode.c:48
 generic_perform_write+0x2af/0x8b0 mm/filemap.c:4324
 generic_file_write_iter+0x14b/0x690 mm/filemap.c:4467
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x629/0xba0 fs/read_write.c:688
 ksys_write+0x156/0x270 fs/read_write.c:740
 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: 0033:0x7f1128b8c819
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:00007f1126dde028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f1128e05fa0 RCX: 00007f1128b8c819
RDX: 0000000000000012 RSI: 0000200000003a80 RDI: 0000000000000005
RBP: 00007f1128c22c91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f1128e06038 R14: 00007f1128e05fa0 R15: 00007ffd665de518
 </TASK>