linstor: enable discard for Linstor storage pools (apache#9770)

* linstor: enable discard for Linstor storage pools

All Linstor storage backends support discard, so it can be safely enabled.

* linstor: enable discard for Linstor storage pools CHANGELOG.md

Author: rp-

plugins/hypervisors/kvm/src/main/java/com/cloud/hypervisor/kvm/resource/LibvirtComputingResource.java

@@ -3458,6 +3458,9 @@ public int compare(final DiskTO arg0, final DiskTO arg1) {
                     else {
                         disk.defBlockBasedDisk(physicalDisk.getPath(), devId, diskBusType);
                     }
+                    if (pool.getType() == StoragePoolType.Linstor) {
+                        disk.setDiscard(DiscardType.UNMAP);
+                    }
                 } else {
                     if (volume.getType() == Volume.Type.DATADISK && !(isWindowsTemplate && isUefiEnabled)) {
                         disk.defFileBasedDisk(physicalDisk.getPath(), devId, diskBusTypeData, DiskDef.DiskFmtType.QCOW2);
@@ -3808,6 +3811,9 @@ public synchronized String attachOrDetachDisk(final Connect conn,
                     diskdef.defFileBasedDisk(attachingDisk.getPath(), devId, busT, DiskDef.DiskFmtType.QCOW2);
                 } else if (attachingDisk.getFormat() == PhysicalDiskFormat.RAW) {
                     diskdef.defBlockBasedDisk(attachingDisk.getPath(), devId, busT);
+                    if (attachingPool.getType() == StoragePoolType.Linstor) {
+                        diskdef.setDiscard(DiscardType.UNMAP);
+                    }
                 }
                 if (bytesReadRate != null && bytesReadRate > 0) {
                     diskdef.setBytesReadRate(bytesReadRate);

plugins/hypervisors/kvm/src/main/java/com/cloud/hypervisor/kvm/storage/KVMStorageProcessor.java

@@ -1493,6 +1493,9 @@ protected synchronized void attachOrDetachDisk(final Connect conn, final boolean
                     diskdef.defFileBasedDisk(attachingDisk.getPath(), devId, busT, DiskDef.DiskFmtType.QCOW2);
                 } else if (attachingDisk.getFormat() == PhysicalDiskFormat.RAW) {
                     diskdef.defBlockBasedDisk(attachingDisk.getPath(), devId, busT);
+                    if (attachingPool.getType() == StoragePoolType.Linstor) {
+                        diskdef.setDiscard(DiscardType.UNMAP);
+                    }
                 }
 
                 if (encryptDetails != null) {

plugins/storage/volume/linstor/CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to Linstor CloudStack plugin will be documented in this file
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [2024-10-04]
+
+### Added
+
+- Enable qemu discard="unmap" for Linstor block disks
+
 ## [2024-08-27]
 
 ### Changed