21.10 PR: https://github.com/truenas/middleware/pull/7593

12.0 PR: https://github.com/truenas/middleware/pull/7566

Recreated the issue in TrueNAS-12.0-U3. I have included screenshots and a debug. When I click Save it gives the error provided below. When I close the error window  the UI has stayed on the window where I was creating the child_dataset. I go to Storage -> Pools and the child dataset has been created.

The error is:

CallError

[EFAULT] Failed to mount dataset: failed to create mountpoint: Read-only file system
Error: concurrent.futures.process._RemoteTraceback:
"""
Traceback (most recent call last):
File "/usr/local/lib/python3.8/site-packages/middlewared/plugins/zfs.py", line 875, in mount
dataset.mount()
File "libzfs.pyx", line 391, in libzfs.ZFS._exit_
File "/usr/local/lib/python3.8/site-packages/middlewared/plugins/zfs.py", line 875, in mount
dataset.mount()
File "libzfs.pyx", line 3534, in libzfs.ZFSDataset.mount
libzfs.ZFSException: failed to create mountpoint: Read-only file system

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/usr/local/lib/python3.8/concurrent/futures/process.py", line 239, in _process_worker
r = call_item.fn(*call_item.args, **call_item.kwargs)
File "/usr/local/lib/python3.8/site-packages/middlewared/worker.py", line 94, in main_worker
res = MIDDLEWARE._run(*call_args)
File "/usr/local/lib/python3.8/site-packages/middlewared/worker.py", line 45, in _run
return self._call(name, serviceobj, methodobj, args, job=job)
File "/usr/local/lib/python3.8/site-packages/middlewared/worker.py", line 39, in _call
return methodobj(*params)
File "/usr/local/lib/python3.8/site-packages/middlewared/worker.py", line 39, in _call
return methodobj(*params)
File "/usr/local/lib/python3.8/site-packages/middlewared/schema.py", line 977, in nf
return f(*args, **kwargs)
File "/usr/local/lib/python3.8/site-packages/middlewared/plugins/zfs.py", line 878, in mount
raise CallError(f'Failed to mount dataset: {e}')
middlewared.service_exception.CallError: [EFAULT] Failed to mount dataset: failed to create mountpoint: Read-only file system
"""

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
File "/usr/local/lib/python3.8/site-packages/middlewared/main.py", line 137, in call_method
result = await self.middleware._call(message['method'], serviceobj, methodobj, params, app=self,
File "/usr/local/lib/python3.8/site-packages/middlewared/main.py", line 1195, in _call
return await methodobj(*prepared_call.args)
File "/usr/local/lib/python3.8/site-packages/middlewared/service.py", line 465, in create
rv = await self.middleware._call(
File "/usr/local/lib/python3.8/site-packages/middlewared/main.py", line 1195, in _call
return await methodobj(*prepared_call.args)
File "/usr/local/lib/python3.8/site-packages/middlewared/schema.py", line 973, in nf
return await f(*args, **kwargs)
File "/usr/local/lib/python3.8/site-packages/middlewared/plugins/pool.py", line 3036, in do_create
await self.middleware.call('zfs.dataset.mount', data['name'])
File "/usr/local/lib/python3.8/site-packages/middlewared/main.py", line 1238, in call
return await self._call(
File "/usr/local/lib/python3.8/site-packages/middlewared/main.py", line 1203, in _call
return await self._call_worker(name, *prepared_call.args)
File "/usr/local/lib/python3.8/site-packages/middlewared/main.py", line 1209, in _call_worker
return await self.run_in_proc(main_worker, name, args, job)
File "/usr/local/lib/python3.8/site-packages/middlewared/main.py", line 1136, in run_in_proc
return await self.run_in_executor(self.__procpool, method, *args, **kwargs)
File "/usr/local/lib/python3.8/site-packages/middlewared/main.py", line 1110, in run_in_executor
return await loop.run_in_executor(pool, functools.partial(method, *args, **kwargs))
middlewared.service_exception.CallError: [EFAULT] Failed to mount dataset: failed to create mountpoint: Read-only file system

Thank you for the report, .

Can you please attach a debug file to this ticket? To generate a debug file on TrueNAS CORE, log in to the TrueNAS web interface, go to System > Advanced, then click Save Debug and wait for the file to download to your local system. In TrueNAS SCALE, this option is in System Settings > Advanced.

Expected Behavior

Do not allow creation of a dataset (and any other items) by disabling the option or displaying a dialog (instead of opening the form).