loop4: detected capacity change from 0 to 1024
============================================
WARNING: possible recursive locking detected
syzkaller #0 Not tainted
--------------------------------------------
syz.4.5/4307 is trying to acquire lock:
ffff88807752bdc8 (&HFSPLUS_I(inode)->extents_lock){+.+.}-{3:3}, at: hfsplus_get_block+0x39b/0x1530 fs/hfsplus/extents.c:260

but task is already holding lock:
ffff88807752d8c8 (&HFSPLUS_I(inode)->extents_lock){+.+.}-{3:3}, at: hfsplus_file_extend+0x1b3/0x1950 fs/hfsplus/extents.c:455

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.4.5/4307:
 #0: ffff888076cdf270 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2bf/0x370 fs/file.c:1056
 #1: ffff888076202460 (sb_writers#13){.+.+}-{0:0}, at: vfs_writev fs/read_write.c:927 [inline]
 #1: ffff888076202460 (sb_writers#13){.+.+}-{0:0}, at: do_writev+0x238/0x410 fs/read_write.c:971
 #2: ffff88807752dac0 (&sb->s_type->i_mutex_key#22){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:787 [inline]
 #2: ffff88807752dac0 (&sb->s_type->i_mutex_key#22){+.+.}-{3:3}, at: generic_file_write_iter+0x7e/0x1b0 mm/filemap.c:3941
 #3: ffff88807752d8c8 (&HFSPLUS_I(inode)->extents_lock){+.+.}-{3:3}, at: hfsplus_file_extend+0x1b3/0x1950 fs/hfsplus/extents.c:455
 #4: ffff8880761ee8f8 (&sbi->alloc_mutex){+.+.}-{3:3}, at: hfsplus_block_allocate+0x91/0x900 fs/hfsplus/bitmap.c:35

stack backtrace:
CPU: 1 PID: 4307 Comm: syz.4.5 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
 __lock_acquire+0x1227/0x7c60 kernel/locking/lockdep.c:-1
 lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623
 __mutex_lock_common+0x1eb/0x2390 kernel/locking/mutex.c:596
 __mutex_lock kernel/locking/mutex.c:729 [inline]
 mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
 hfsplus_get_block+0x39b/0x1530 fs/hfsplus/extents.c:260
 block_read_full_page+0x2e8/0xd10 fs/buffer.c:2290
 do_read_cache_page+0x8a1/0x1030 mm/filemap.c:-1
 read_mapping_page include/linux/pagemap.h:515 [inline]
 hfsplus_block_allocate+0xf4/0x900 fs/hfsplus/bitmap.c:37
 hfsplus_file_extend+0xa8e/0x1950 fs/hfsplus/extents.c:466
 hfsplus_get_block+0x40e/0x1530 fs/hfsplus/extents.c:245
 get_more_blocks fs/direct-io.c:673 [inline]
 do_direct_IO fs/direct-io.c:959 [inline]
 do_blockdev_direct_IO fs/direct-io.c:1276 [inline]
 __blockdev_direct_IO+0x146d/0x3c90 fs/direct-io.c:1368
 blockdev_direct_IO include/linux/fs.h:3345 [inline]
 hfsplus_direct_IO+0x119/0x220 fs/hfsplus/inode.c:135
 generic_file_direct_write+0x22c/0x490 mm/filemap.c:3687
 __generic_file_write_iter+0x2b1/0x4e0 mm/filemap.c:3869
 generic_file_write_iter+0xa6/0x1b0 mm/filemap.c:3944
 do_iter_readv_writev+0x497/0x600 fs/read_write.c:-1
 do_iter_write+0x205/0x7b0 fs/read_write.c:855
 vfs_writev fs/read_write.c:928 [inline]
 do_writev+0x254/0x410 fs/read_write.c:971
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f2d4be88749
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:00007f2d4a0ce038 EFLAGS: 00000246 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 00007f2d4c0df090 RCX: 00007f2d4be88749
RDX: 0000000000000001 RSI: 0000200000000140 RDI: 0000000000000009
RBP: 00007f2d4bf0cf91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2d4c0df128 R14: 00007f2d4c0df090 R15: 00007ffd767c18f8
 </TASK>