Haiku KDL when unmounting FAT volume

gistfile1.txt

kdebug> message
PANIC: acquire_vnode(0xffffffffae557880, 770): node wasn't used!
kdebug> bt
stack trace for thread 4289 "w>DriveSetup"
    kernel stack: 0xffffffffb7cd4000 to 0xffffffffb7cd9000
      user stack: 0x00007f27b96cf000 to 0x00007f27b970f000
frame                       caller             <image>:function + offset
 0 ffffffffb7cd8380 (+  32) ffffffff800bdd59   <kernel_x86_64> invoke_command_trampoline(void*) + 0x19
 1 ffffffffb7cd83a0 (+  32) ffffffff80162d8b   <kernel_x86_64> arch_debug_call_with_fault_handler + 0x1d
 2 ffffffffb7cd83f0 (+  80) ffffffff800baed0   <kernel_x86_64> debug_call_with_fault_handler + 0x80
 3 ffffffffb7cd8450 (+  96) ffffffff800bdfb8   <kernel_x86_64> invoke_debugger_command + 0xf8
 4 ffffffffb7cd8490 (+  64) ffffffff800be166   <kernel_x86_64> invoke_pipe_segment(debugger_command_pipe*, int, char*) + 0x116
 5 ffffffffb7cd84e0 (+  80) ffffffff800be28c   <kernel_x86_64> invoke_debugger_command_pipe + 0x9c
 6 ffffffffb7cd8520 (+  64) ffffffff800c04f6   <kernel_x86_64> ExpressionParser::_ParseCommandPipe(int&) + 0x1e6
 7 ffffffffb7cd8560 (+  64) ffffffff800c1a5d   <kernel_x86_64> ExpressionParser::EvaluateCommand(char const*, int&) + 0x43d
 8 ffffffffb7cd8650 (+ 240) ffffffff800c208f   <kernel_x86_64> evaluate_debug_command + 0x12f
 9 ffffffffb7cd86b0 (+  96) ffffffff800bc688   <kernel_x86_64> kernel_debugger_loop(char const*, char const*, __va_list_tag*, int) + 0x1b8
10 ffffffffb7cd8710 (+  96) ffffffff800bc9ce   <kernel_x86_64> kernel_debugger_internal(char const*, char const*, __va_list_tag*, int) + 0x6e
11 ffffffffb7cd8800 (+ 240) ffffffff800bcdc7   <kernel_x86_64> panic + 0xb7
12 ffffffffb7cd8830 (+  48) ffffffff80117369   <kernel_x86_64> acquire_vnode + 0xa9
13 ffffffffb7cd8880 (+  80) ffffffff826b4602   <fat> dosfs_io(fs_volume*, fs_vnode*, void*, IORequest*) + 0xa2
14 ffffffffb7cd88d0 (+  80) ffffffff8011f866   <kernel_x86_64> vfs_vnode_io + 0x36
15 ffffffffb7cd8a40 (+ 368) ffffffff8012018e   <kernel_x86_64> vfs_write_pages + 0x9e
16 ffffffffb7cd8a60 (+  32) ffffffff8005da04   <kernel_x86_64> VMVnodeCache::Write(long, generic_io_vec const*, unsigned long, unsigned int, unsigned long*) + 0x24
17 ffffffffb7cd8a90 (+  48) ffffffff80150dde   <kernel_x86_64> PageWriteTransfer::Schedule(unsigned int) + 0x5e
18 ffffffffb7cd8da0 (+ 784) ffffffff80151732   <kernel_x86_64> vm_page_write_modified_page_range + 0x452
19 ffffffffb7cd8dc0 (+  32) ffffffff8015b9e7   <kernel_x86_64> VMCache::WriteModified() + 0x27
20 ffffffffb7cd8e20 (+  96) ffffffff826b5a97   <fat> _dosfs_fsync(vnode*) + 0x67
21 ffffffffb7cd8e60 (+  64) ffffffff8010d71e   <kernel_x86_64> free_vnode(vnode*, bool) + 0x7e
22 ffffffffb7cd8ed0 (+ 112) ffffffff80115703   <kernel_x86_64> fs_unmount(char*, int, unsigned int, bool) + 0x2c3
23 ffffffffb7cd8f20 (+  80) ffffffff8011c5c3   <kernel_x86_64> _user_unmount + 0xb3
24 ffffffffb7cd8f30 (+  16) ffffffff80164991   <kernel_x86_64> x86_64_syscall_entry + 0xfb
user iframe at 0xffffffffb7cd8f30 (end = 0xffffffffb7cd8ff8)
 rax 0x6a                  rbx 0x0                   rcx 0xca5309001c
 rdx 0xb657270860          rsi 0x0                   rdi 0x52c88cb390
 rbp 0x7f27b970ebb0         r8 0x1ff                  r9 0x0
 r10 0xca53090359          r11 0x246                 r12 0x52c86cec60
 r13 0x0                   r14 0x7f27b970eaf0        r15 0x7f27b970ec83
 rip 0xca5309001c          rsp 0x7f27b970eae8     rflags 0x246
 vector: 0x63, error code: 0x0
25 00007f27b970ebb0 (+   0) 000000ca5309001c   </boot/system/lib/libroot.so> _kern_unmount + 0x0c
26 00007f27b970ec60 (+ 176) 000000cdfb41c62c   </boot/system/apps/DriveSetup> MainWindow::_Unmount(BDiskDevice*, int) + 0x6c
27 00007f27b970ecf0 (+ 144) 000000b65723c9f9   147555:libbe.so_seg0rx@0x000000b657039000 + 0x2039f9
28 00007f27b970ed10 (+  32) 000000b65717a641   147555:libbe.so_seg0rx@0x000000b657039000 + 0x141641
29 00007f27b970ed30 (+  32) 000000ca5308f539   </boot/system/lib/libroot.so> _thread_do_exit_work (nearest) + 0x89
30 0000000000000000 (+   0) 00007fd7c3419258   <commpage> commpage_thread_exit + 0x00