linstor: Provide /dev/drbd/by-res/ resource paths to CloudStack

Instead of using the basic /dev/drbd1000 minor number block device path,
provide CloudStack with the actual resource path, that can also be linked
back to the CloudStack volume.path

Author: rp-

plugins/storage/volume/linstor/CHANGELOG.md

@@ -5,22 +5,24 @@ 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).
 
-## [2025-10-03]
+## [2025-12-18]
 
 ### Changed
+- Provide /dev/drbd/by-res/ resource paths to CloudStack for usage.
+
+## [2025-10-03]
 
+### Changed
 - Revert qcow2 snapshot now use sparse/discard options to convert on thin devices.
 
 ## [2025-08-05]
 
 ### Fixed
-
 - getVolumeStats wasn't correctly working if multiple Linstor clusters/primary storages are used.
 
 ## [2025-07-01]
 
 ### Fixed
-
 - Regression in 4.19.3 and 4.21.0 with templates from snapshots
 
 ## [2025-05-07]
@@ -31,25 +33,21 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [2025-03-13]
 
 ### Fixed
-
 - Implemented missing delete datastore, to correctly cleanup on datastore removal
 
 ## [2025-02-21]
 
 ### Fixed
-
 - Always try to delete cs-...-rst resource before doing a snapshot backup
 
 ## [2025-01-27]
 
 ### Fixed
-
 - Use of multiple primary storages on the same linstor controller
 
 ## [2025-01-20]
 
 ### Fixed
-
 - Volume snapshots on zfs used the wrong dataset path to hide/unhide snapdev
 
 ## [2024-12-19]
@@ -60,13 +58,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [2024-12-13]
 
 ### Fixed
-
 - Linstor heartbeat check now also ask linstor-controller if there is no connection between nodes
 
 ## [2024-12-11]
 
 ### Fixed
-
 - Only set allow-two-primaries if a live migration is performed
 
 ## [2024-10-28]
@@ -79,17 +75,14 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [2024-10-14]
 
 ### Added
-
 - Support for ISO direct download to primary storage
 
 ## [2024-10-04]
 
 ### Added
-
 - Enable qemu discard="unmap" for Linstor block disks
 
 ## [2024-08-27]
 
 ### Changed
-
 - Allow two primaries(+protocol c) is now set on resource-connection level instead of rd

plugins/storage/volume/linstor/src/main/java/com/cloud/hypervisor/kvm/storage/LinstorStorageAdaptor.java

@@ -232,7 +232,7 @@ public KVMPhysicalDisk createPhysicalDisk(String name, KVMStoragePool pool, Qemu
             makeResourceAvailable(api, foundRscName, false);
 
             if (!resources.isEmpty() && !resources.get(0).getVolumes().isEmpty()) {
-                final String devPath = resources.get(0).getVolumes().get(0).getDevicePath();
+                final String devPath = LinstorUtil.getDevicePathFromResource(resources.get(0));
                 logger.info("Linstor: Created drbd device: " + devPath);
                 final KVMPhysicalDisk kvmDisk = new KVMPhysicalDisk(devPath, name, pool);
                 kvmDisk.setFormat(QemuImg.PhysicalDiskFormat.RAW);
@@ -455,8 +455,9 @@ public boolean disconnectPhysicalDisk(Map<String, String> volumeToDisconnect)
     private Optional<ResourceWithVolumes> getResourceByPathOrName(
             final List<ResourceWithVolumes> resources, String path) {
         return resources.stream()
-            .filter(rsc -> getLinstorRscName(path).equalsIgnoreCase(rsc.getName()) || rsc.getVolumes().stream()
-                .anyMatch(v -> path.equals(v.getDevicePath())))
+            .filter(rsc -> getLinstorRscName(path).equalsIgnoreCase(rsc.getName()) ||
+                    path.equals(LinstorUtil.formatDrbdByResDevicePath(rsc.getName())) ||
+                    rsc.getVolumes().stream().anyMatch(v -> path.equals(v.getDevicePath())))
             .findFirst();
     }
 

plugins/storage/volume/linstor/src/main/java/org/apache/cloudstack/storage/datastore/util/LinstorUtil.java

@@ -264,6 +264,16 @@ public static boolean areResourcesDiskless(DevelopersApi api, String rscName, Co
         return false;
     }
 
+    /**
+     * Format the device path for DRBD resources.
+     * @param rscName
+     * @return
+     */
+    public static String formatDrbdByResDevicePath(String rscName)
+    {
+        return String.format("/dev/drbd/by-res/%s/0", rscName);
+    }
+
     /**
      * Try to get the device path for the given resource name.
      * This could be made a bit more direct after java-linstor api is fixed for layer data subtypes.
@@ -283,12 +293,7 @@ public static String getDevicePath(DevelopersApi api, String rscName) throws Api
                 null);
         for (ResourceWithVolumes rsc : resources) {
             if (!rsc.getVolumes().isEmpty()) {
-                // CloudStack resource always only have 1 volume
-                String devicePath = rsc.getVolumes().get(0).getDevicePath();
-                if (devicePath != null && !devicePath.isEmpty()) {
-                    LOGGER.debug("getDevicePath: {} -> {}", rscName, devicePath);
-                    return devicePath;
-                }
+                return LinstorUtil.getDevicePathFromResource(rsc);
             }
         }
 
@@ -297,6 +302,24 @@ public static String getDevicePath(DevelopersApi api, String rscName) throws Api
         throw new CloudRuntimeException("Linstor: " + errMsg);
     }
 
+    /**
+     * Check if the resource has DRBD or not and deliver the correct device path.
+     * @param rsc
+     * @return
+     */
+    public static String getDevicePathFromResource(ResourceWithVolumes rsc) {
+        if (!rsc.getVolumes().isEmpty()) {
+            // CloudStack resource always only have 1 volume
+            if (rsc.getLayerObject().getDrbd() != null) {
+                return formatDrbdByResDevicePath(rsc.getName());
+            } else {
+                return rsc.getVolumes().get(0).getDevicePath();
+            }
+        }
+        throw new CloudRuntimeException(
+                String.format("getDevicePath: Resource %s/%s doesn't have volumes", rsc.getNodeName(), rsc.getName()));
+    }
+
     public static ApiCallRcList applyAuxProps(DevelopersApi api, String rscName, String dispName, String vmName)
             throws ApiException
     {