https://github.com/cockpit-project/cockpit/issues/21760

I was investigating https://issues.redhat.com/browse/RHEL-84058 . I found that it was difficult to express desired filesystem size quantities w/ Cockpit's GUI.

It is a problem for me as the Stratis team lead. What it means is that, in general, it is a difficult math problem for the user to calculate a valid filesystem size that can be set in the Cockpit GUI. The user will frequently receive an error, since the required computations to find how to express a valid size involve reasoning about factors. The user can create filesystems, but only if the user accepts the filesystem default size, 1 TiB, i.e., does not specify a filesystem size, or calculates how to express a valid size. If the user has determined a specific size in SI units that the user wants it may be inexpressible in Cockpit's GUI. For example, 10 GiB is not expressible via the Cockpit GUI, since it is a fractional number of MB.

Seen in:

cockpit-333-1.el10

cockpit-storaged-333-1.el10

but I think all previous as well.

How reproducible is this bug?: 100%

Steps to reproduce

I. with 512B block size devices, only shows up with MB units.

1. Create a pool with 512B block size devices.
2. Create a filesystem on the pool, setting the filesystem size to some number of MB that is not divisible by 16. The error will not show up with GB or TB as any value in those units is divisible by 512. I suggest any power of 3 greater than 700, e.g, 729.
3. Observe an error from Stratis indicating that the pool is not divisible by the sector size of 512.

II. with 4096B block size devices.

1. Create a pool with 4096B block size devices.
2. Create a filesystem on the pool. Avoid the error you can obtain in I. For MB, take that 729 you tried in the previous, and multiply by 8. For GB, 20 is a good number. For TB, this bug can't be obtained, since any number of TB is divisible by 4096.
3. Observe a low-level ioctl error, as here: https://issues.redhat.com/browse/RHEL-84058 .

III. With 10 GiB

1. Try to express this value in MiB. The result is 10737.41824 MB . Cockpit will not accept this value. It can, of course, be expressed as Bytes, but Cockpit does not allow Bytes.

Expected results

  A way of expressing any valid filesystem size that I might desire.

Actual results

  There is no such way.