syzbot

loop0: detected capacity change from 0 to 1024
============================================
WARNING: possible recursive locking detected
syzkaller #0 Not tainted
--------------------------------------------
syz.0.17/4426 is trying to acquire lock:
ffff88807b261548 (&HFSPLUS_I(inode)->extents_lock){+.+.}-{3:3}, at: hfsplus_get_block+0x3a1/0x15a0 fs/hfsplus/extents.c:260

but task is already holding lock:
ffff88807b262988 (&HFSPLUS_I(inode)->extents_lock){+.+.}-{3:3}, at: hfsplus_file_extend+0x1cd/0x1a50 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

4 locks held by syz.0.17/4426:
 #0: ffff88807b6d4460 (sb_writers#13){.+.+}-{0:0}, at: mnt_want_write+0x3d/0x90 fs/namespace.c:402
 #1: ffff88807b262b80 (&sb->s_type->i_mutex_key#21){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:758 [inline]
 #1: ffff88807b262b80 (&sb->s_type->i_mutex_key#21){+.+.}-{3:3}, at: do_truncate+0x198/0x240 fs/open.c:63
 #2: ffff88807b262988 (&HFSPLUS_I(inode)->extents_lock){+.+.}-{3:3}, at: hfsplus_file_extend+0x1cd/0x1a50 fs/hfsplus/extents.c:455
 #3: ffff88807d10f8f8 (&sbi->alloc_mutex){+.+.}-{3:3}, at: hfsplus_block_allocate+0x92/0x8a0 fs/hfsplus/bitmap.c:35

stack backtrace:
CPU: 0 PID: 4426 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x24e lib/dump_stack.c:106
 __lock_acquire+0x123e/0x7d10 kernel/locking/lockdep.c:-1
 lock_acquire+0x1bb/0x4a0 kernel/locking/lockdep.c:5662
 __mutex_lock_common kernel/locking/mutex.c:603 [inline]
 __mutex_lock+0x12d/0xaf0 kernel/locking/mutex.c:747
 hfsplus_get_block+0x3a1/0x15a0 fs/hfsplus/extents.c:260
 block_read_full_folio+0x3e6/0xf00 fs/buffer.c:2271
 filemap_read_folio+0x16b/0x770 mm/filemap.c:2490
 do_read_cache_folio+0x2a0/0x760 mm/filemap.c:3659
 do_read_cache_page+0x32/0x220 mm/filemap.c:3701
 read_mapping_page include/linux/pagemap.h:793 [inline]
 hfsplus_block_allocate+0xdc/0x8a0 fs/hfsplus/bitmap.c:37
 hfsplus_file_extend+0xb1f/0x1a50 fs/hfsplus/extents.c:466
 hfsplus_get_block+0x430/0x15a0 fs/hfsplus/extents.c:245
 __block_write_begin_int+0x55d/0x1a80 fs/buffer.c:1991
 __block_write_begin fs/buffer.c:2041 [inline]
 block_write_begin+0x96/0x1e0 fs/buffer.c:2102
 cont_write_begin+0x5ea/0x800 fs/buffer.c:2456
 hfsplus_write_begin+0x87/0xd0 fs/hfsplus/inode.c:52
 cont_expand_zero fs/buffer.c:2383 [inline]
 cont_write_begin+0x2ad/0x800 fs/buffer.c:2446
 hfsplus_write_begin+0x87/0xd0 fs/hfsplus/inode.c:52
 generic_cont_expand_simple+0x13d/0x200 fs/buffer.c:2347
 hfsplus_setattr+0x165/0x280 fs/hfsplus/inode.c:283
 notify_change+0xc74/0xf40 fs/attr.c:499
 do_truncate+0x1ac/0x240 fs/open.c:65
 vfs_truncate+0x262/0x2f0 fs/open.c:111
 do_sys_truncate+0xf2/0x1c0 fs/open.c:134
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f969bf9c819
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:00007ffd0d24f7a8 EFLAGS: 00000246 ORIG_RAX: 000000000000004c
RAX: ffffffffffffffda RBX: 00007f969c215fa0 RCX: 00007f969bf9c819
RDX: 0000000000000000 RSI: 000000000000fffe RDI: 0000200000000040
RBP: 00007f969c032c91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f969c215fac R14: 00007f969c215fa0 R15: 00007f969c215fa0
 </TASK>