list-disks doesn't correctly work when using partitions for osd backends

[Andrey Grebennikov]

In full-nvme solution it makes sense to run multiple osds working on with the same nvme device.
IN order to achieve this it is necessary to use partitions when provisioning osds. However list-disks action doesn't list all possible partitions but rather shows disks only.

use-case:
pre-created 4 partitions on /dev/disk/by-dname/osd:
ubuntu@infra1:~/k8s-vxflex$ juju run --unit ceph-osd/0 'ls /dev/disk/by-dname'
nvme1n1
nvme1n1-part1
nvme1n1-part2
nvme1n1-part3
osd
osd-part1
osd-part2
osd-part3
osd-part4
sda

And osds are created on top of osd-partX partitions.
However list-disks only shows block devices themselves:

ubuntu@infra1:~/k8s-vxflex$ juju run-action ceph-osd/0 list-disks --wait
unit-ceph-osd-0:
  id: e5d80a12-0d73-4977-8c32-8c84bda3f4fb
  results:
    blacklist: '[]'
    disks: '[''/dev/sda'', ''/dev/nvme0n1'']'
    non-pristine: '[''/dev/nvme0n1'']'
  status: completed

[Alex Kavanagh (ajkavanagh)]

The culprit function is in charms.ceph lib/ceph/utils.py:

def unmounted_disks():
    """List of unmounted block devices on the current host."""
    disks = []
    context = pyudev.Context()
    for device in context.list_devices(DEVTYPE='disk'):
        if device['SUBSYSTEM'] == 'block':
            matched = False
            for block_type in [u'dm', u'loop', u'ram', u'nbd']:
                if block_type in device.device_node:
                    matched = True
            if matched:
                continue
            disks.append(device.device_node)
    log("Found disks: {}".format(disks))
    return [disk for disk in disks if not is_device_mounted(disk)]

It would either need to learn about partitions, or the calling function in ceph-osd would need to call another library that would add in partitions.