kvm: apply rbd_default_data_pool when creating volumes from templates on RBD

[bhouse-nexthop]

Description

RBD erasure-coded (EC) pool support (#9808) taught the KVM agent to honor the rbd_default_data_pool storage-pool detail, but only in two places:

• KVMPhysicalDisk.RBDStringBuilder() — the qemu-img URI builder
• createPhysicalDisk() — blank volume creation (routes RBD creates to the QemuImg path when a data pool is set)

It was not applied to createDiskFromTemplateOnRBD(), which creates ROOT volumes from a template using rados-java (rbd.clone() / rbd.create()) directly. Those calls build a Rados connection that sets mon_host, key and client_mount_timeout but never rbd_default_data_pool, so the resulting image is created without a data pool.

Net effect: every volume cloned from a template onto an EC-backed primary storage has all of its data objects written to the replicated metadata pool instead of the erasure-coded data pool. This silently defeats EC and consumes ~3x raw space for those volumes. Blank data disks on the same pool are correct, which makes the inconsistency easy to miss.

This was observed in production: of the VMs on an EC primary storage, the template-derived ROOT volumes had no data_pool (rbd info shows no data_pool: line and lacks the data-pool feature), while blank DATADISKs and the template base images themselves were correct.

Fix

In createDiskFromTemplateOnRBD, read the destination pool's rbd_default_data_pool detail once and, when present, confSet it on the Rados connection beforeconnect() — in both the same-cluster clone/copy branch and the cross-cluster copy branch. librbd then uses it as the default data pool when the new image is created, so template-derived volumes get data_pool set, exactly like blank volumes already do. This mirrors how RBDStringBuilder injects the same key for the qemu-img path.

StringdataPool = (destDetails == null) ? null : destDetails.get(KVMPhysicalDisk.RBD_DEFAULT_DATA_POOL);
...
if (dataPool != null) {
r.confSet(KVMPhysicalDisk.RBD_DEFAULT_DATA_POOL, dataPool);
}
r.connect();

No behavior change for non-EC pools (dataPool == null → no-op).

Types of changes

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

• Root cause reproduced live: deploying a VM from a template onto an EC primary storage produced a ROOT clone with no data_pool (parent base snapshot in the metadata pool); the data-pool feature was absent.
• Confirmed the working paths (template seed via qemu-img, blank DATADISK create) already set the data pool, isolating the gap to the rados-java clone/create path.
• Code-path traced to Add support to RBD erasure code pools #9808, which did not touch createDiskFromTemplateOnRBD.

[DaanHoogland]

@blueorangutan package

[blueorangutan]

@DaanHoogland a [SL] Jenkins job has been kicked to build packages. It will be bundled with KVM, XenServer and VMware SystemVM templates. I'll keep you posted as I make progress.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 17.67%. Comparing base (21b2025) to head (aaa2a61).
⚠️ Report is 70 commits behind head on 4.22.

Files with missing lines	Patch %	Lines
.../hypervisor/kvm/storage/LibvirtStorageAdaptor.java	0.00%	8 Missing ⚠️

Additional details and impacted files

@@ Coverage Diff @@## 4.22 #13361 +/- ##
============================================
- Coverage 17.67% 17.67% -0.01% + Complexity 15792 15789 -3 
============================================
Files 5922 5922 Lines 533165 533173 +8 Branches 65208 65211 +3 ============================================
- Hits 94242 94224 -18 - Misses 428276 428305 +29 + Partials 10647 10644 -3 

Flag	Coverage Δ
uitests	3.69% <ø> (ø)
unittests	18.74% <0.00%> (-0.01%)	⬇️

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[blueorangutan]

Packaging result [SF]: ✔️ el8 ✔️ el9 ✔️ el10 ✔️ debian ✔️ suse15. SL-JID 18262

[DaanHoogland]

@blueorangutan test

[blueorangutan]

@DaanHoogland a [SL] Trillian-Jenkins test job (ol8 mgmt + kvm-ol8) has been kicked to run smoke tests

[blueorangutan]

[SF] Trillian test result (tid-16344)
Environment: kvm-ol8 (x2), zone: Advanced Networking with Mgmt server ol8
Total time taken: 50505 seconds
Marvin logs: https://github.com/blueorangutan/acs-prs/releases/download/trillian/pr13361-t16344-kvm-ol8.zip
Smoke tests completed. 149 look OK, 0 have errors, 0 did not run
Only failed and skipped tests results shown below:

Test	Result	Time (s)	Test File

[DaanHoogland]

clgtm

[bhouse-nexthop]

@vladimirpetrov@sureshanaparti please make sure this gets into 4.22.2