What were you trying to do that didn't work?

[Machines] Failed to add a disk with "Create new" based on "Pre-formatted block device" pool

Please provide the package NVR for which bug is seen:

cockpit-machines-308-1.el9.noarch

cockpit-311.1-1.el9.x86_64

libvirt-dbus-1.4.1-5.el9.x86_64

How reproducible:

100%

Steps to reproduce

1. Prepare a VM

2. Prepare a block device by:

#dd if=/dev/zero of=/tmp/device_test bs=1G count=20
#mknod /dev/device_test b 7 80
#losetup /dev/device_test /tmp/device_test
#mkfs.ext4 /dev/device_test

3. Enter "Storage pools" page, create a new "Pre-formatted block device" pool with the device above:

Name: device_test

Type: Pre-formatted block device

Target path: /mnt/

Source path: /dev/device_test

Format: ext4

 
4. Enter the VM detail page, click "Add disk" and create a new disk with above pool.
There is an error:
 

Danger alert:Disk failed to be added

unsupported configuration: 'directory' storage format is not directly supported by QEMU, use 'dir' disk type instead

5. Go to "Storage pools" page and create volume in the above pool first, then repeat step 4, the disk will be created successfully.

Expected results

Can create new disk in step 4.

Actual results

Can not create new disk in step 4.

Additional info:

Sometimes the error is:

Danger alert:Disk failed to be added

unsupported configuration: virtual FAT storage can't be accessed in read-write mode

And creating volume first in step5 does not help.