======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.4.1066/10386 is trying to acquire lock:
ffff8881b6b680b0 (&tree->tree_lock#2/1){+.+.}-{4:4}, at: hfs_find_init+0x18e/0x300

but task is already holding lock:
ffff8881b367dbf8 (&HFS_I(tree->inode)->extents_lock){+.+.}-{4:4}, at: hfs_extend_file+0xf2/0x15e0

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&HFS_I(tree->inode)->extents_lock){+.+.}-{4:4}:
       __mutex_lock+0x19f/0x1300
       hfs_extend_file+0xf2/0x15e0
       hfs_bmap_reserve+0x107/0x430
       __hfs_ext_write_extent+0x1fa/0x470
       hfs_ext_write_extent+0x17e/0x210
       hfs_write_inode+0x117/0x960
       __writeback_single_inode+0x75a/0x11a0
       writeback_sb_inodes+0x992/0x1a20
       wb_writeback+0x456/0xb70
       wb_workfn+0x414/0xf50
       process_scheduled_works+0xb02/0x1830
       worker_thread+0xa50/0xfc0
       kthread+0x388/0x470
       ret_from_fork+0x51e/0xb90
       ret_from_fork_asm+0x1a/0x30

-> #0 (&tree->tree_lock#2/1){+.+.}-{4:4}:
       __lock_acquire+0x15a5/0x2cf0
       lock_acquire+0xf0/0x2e0
       __mutex_lock+0x19f/0x1300
       hfs_find_init+0x18e/0x300
       hfs_extend_file+0x35c/0x15e0
       hfs_bmap_reserve+0x107/0x430
       hfs_cat_create+0x20f/0x800
       hfs_mkdir+0x79/0xe0
       vfs_mkdir+0x413/0x630
       filename_mkdirat+0x285/0x510
       __se_sys_mkdirat+0x35/0x150
       do_syscall_64+0x14d/0xf80
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&HFS_I(tree->inode)->extents_lock);
                               lock(&tree->tree_lock#2/1);
                               lock(&HFS_I(tree->inode)->extents_lock);
  lock(&tree->tree_lock#2/1);

 *** DEADLOCK ***

4 locks held by syz.4.1066/10386:
 #0: ffff8881b3f76420 (sb_writers#26){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90
 #1: ffff8881b3679620 (&type->i_mutex_dir_key#16/1){+.+.}-{4:4}, at: filename_create+0x200/0x370
 #2: ffff88811777a0b0 (&tree->tree_lock#2){+.+.}-{4:4}, at: hfs_find_init+0x18e/0x300
 #3: ffff8881b367dbf8 (&HFS_I(tree->inode)->extents_lock){+.+.}-{4:4}, at: hfs_extend_file+0xf2/0x15e0

stack backtrace:
CPU: 1 UID: 0 PID: 10386 Comm: syz.4.1066 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150
 print_circular_bug+0x2e1/0x300
 check_noncircular+0x12e/0x150
 __lock_acquire+0x15a5/0x2cf0
 lock_acquire+0xf0/0x2e0
 __mutex_lock+0x19f/0x1300
 hfs_find_init+0x18e/0x300
 hfs_extend_file+0x35c/0x15e0
 hfs_bmap_reserve+0x107/0x430
 hfs_cat_create+0x20f/0x800
 hfs_mkdir+0x79/0xe0
 vfs_mkdir+0x413/0x630
 filename_mkdirat+0x285/0x510
 __se_sys_mkdirat+0x35/0x150
 do_syscall_64+0x14d/0xf80
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc7a6d9b607
Code: 00 66 90 48 89 f2 b9 00 01 00 00 48 89 fe bf 9c ff ff ff e9 db f7 ff ff 66 2e 0f 1f 84 00 00 00 00 00 90 b8 02 01 00 00 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:00007fc7a7c4ae58 EFLAGS: 00000246 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 00007fc7a7c4aee0 RCX: 00007fc7a6d9b607
RDX: 00000000000001ff RSI: 0000200000000240 RDI: 00000000ffffff9c
RBP: 0000200000000200 R08: 00002000000000c0 R09: 0000000000000000
R10: 0000200000000200 R11: 0000000000000246 R12: 0000200000000240
R13: 00007fc7a7c4aea0 R14: 0000000000000000 R15: 0000000000000000
 </TASK>
