API: added method for deleting unused links

[ekakhrom-orionsoft]

Problem:
When creating a disk on a block storage domain (for example, FibreChannel), links to the disk are created on all active hosts that belong to the StoragePool of the disk being created. Further, when deleting a created disk, links to the disk are deleted only on the host with the SPM role, while incorrect links to the deleted disk remain on the other hosts.

Playback:
Environment: SA oVirt Engine, 2 hosts (Host 1 with the SPM role), a FibreChannel storage domain.
Actions:

1. Create two disks in the FibreChannel storage domain.
2. Links to these two disks are immediately created on Host 1 (SPM)

[root@host1 ~]# ls -la /rhev/data-center/77b48f64-1484-11f0-9d8c-566fd2810d4a/ab643bd9-8753-4375-8c6c-eb1fbedcf6b4/images/
total 0
…
drwxr-xr-x. 2 vdsm kvm  50 Apr 11 08:50 7c451669-9d44-4994-9711-389d5026ff36
drwxr-xr-x. 2 vdsm kvm  50 Apr 11 08:50 e394da48-7cf3-413a-b22c-7a9fc56d8985

3. After some time, links to the created disks are created on Host 2.

[root@host2 ~]# ls -la /rhev/data-center/77b48f64-1484-11f0-9d8c-566fd2810d4a/ab643bd9-8753-4375-8c6c-eb1fbedcf6b4/images/
total 0
…
drwxr-xr-x. 2 vdsm kvm  50 Apr 11 08:51 7c451669-9d44-4994-9711-389d5026ff36
drwxr-xr-x. 2 vdsm kvm  50 Apr 11 08:51 e394da48-7cf3-413a-b22c-7a9fc56d8985

4. Delete both created disks.
5. Disk links have been deleted on Host 1 (SPM).

[root@host1 ~]# ls -la /rhev/data-center/77b48f64-1484-11f0-9d8c-566fd2810d4a/ab643bd9-8753-4375-8c6c-eb1fbedcf6b4/images/
total 0
drwxr-xr-x. 4 vdsm kvm 94 Apr 11 08:52 .
drwxr-xr-x. 5 vdsm kvm 48 Apr 10 13:30 ..

6. There are still links to deleted disks on the Host 2, but they are now incorrect:

[root@host2 ~]# ls -la /rhev/data-center/77b48f64-1484-11f0-9d8c-566fd2810d4a/ab643bd9-8753-4375-8c6c-eb1fbedcf6b4/images/
total 0
…
drwxr-xr-x. 2 vdsm kvm  50 Apr 11 08:51 7c451669-9d44-4994-9711-389d5026ff36
drwxr-xr-x. 2 vdsm kvm  50 Apr 11 08:51 e394da48-7cf3-413a-b22c-7a9fc56d8985

Solution:
Added an API method on VDSM to remove unused links. When deleting a disk, the command to delete unused links is invoked for all active hosts that are associated with the StoragePool of the disk being deleted.

Playback (after solved issue):
Environment: SA oVirt Engine, 2 hosts (Host 1 with the SPM role), a FibreChannel storage domain.
Actions:

1. Create two disks in the FibreChannel storage domain.
2. Links to these two disks are immediately created on Host 1 (SPM)

[root@host1 ~]#  ls -la /rhev/data-center/77b48f64-1484-11f0-9d8c-566fd2810d4a/ab643bd9-8753-4375-8c6c-eb1fbedcf6b4/images/
total 0
…
drwxr-xr-x. 2 vdsm kvm  50 Apr 15 07:18 2a1bff81-1474-44a1-8cd2-ca39b0b498e7
drwxr-xr-x. 2 vdsm kvm  50 Apr 15 07:18 311450d6-854c-4a56-84fe-4ce7bb432b86

3. After some time, links to the created disks are created on Host 2

 [root@host2 ~]# ls -la /rhev/data-center/77b48f64-1484-11f0-9d8c-566fd2810d4a/ab643bd9-8753-4375-8c6c-eb1fbedcf6b4/images/
total 0
…
drwxr-xr-x. 2 vdsm kvm  50 Apr 15 07:18 311450d6-854c-4a56-84fe-4ce7bb432b86
drwxr-xr-x. 2 vdsm kvm  50 Apr 15 07:18 2a1bff81-1474-44a1-8cd2-ca39b0b498e7

4. Delete both created disks.
5. Disk links have been deleted on Host 1 (SPM).

[root@host1 ~]# ls -la /rhev/data-center/77b48f64-1484-11f0-9d8c-566fd2810d4a/ab643bd9-8753-4375-8c6c-eb1fbedcf6b4/images/
total 0
drwxr-xr-x. 4 vdsm kvm 94 Apr 11 08:52 .
drwxr-xr-x. 5 vdsm kvm 48 Apr 10 13:30 ..

6. Disk links have been deleted on Host 2.

 [root@host2 ~]# ls -la /rhev/data-center/77b48f64-1484-11f0-9d8c-566fd2810d4a/ab643bd9-8753-4375-8c6c-eb1fbedcf6b4/images/
total 0
drwxr-xr-x. 2 vdsm kvm  50 Apr 11 08:52 .
drwxr-xr-x. 2 vdsm kvm  50 Apr 11 13:30 ..

Attention!
This PR should be applied only after applying PR on the VDSM:
oVirt/ovirt-engine#1009

Are you the owner of the code you are sending in, or do you have permission of the owner?

Yes