kvm: align NVMe-oF adaptor stubs with the Fibre Channel adaptor

NVMe-TCP is a different carrier for the same array operations, so the NVMe-oF
storage adaptor should only diverge from MultipathSCSIAdapterBase where the
transport genuinely differs. Several unimplemented methods threw
UnsupportedOperationException where the Fibre Channel adaptor returns a benign
value, which means a caller that degrades gracefully on Fibre Channel aborts on
NVMe-TCP:

  * deletePhysicalDisk(): FC returns false. Namespaces are created and destroyed
    by the storage provider, so a host-side delete is simply not handled here;
    throwing from a cleanup path is worse than reporting that.
  * createTemplateFromDisk(), listPhysicalDisks(): FC returns null.
  * createFolder(): FC logs and returns true. Block storage has no directory
    structure, so this is a no-op rather than an error.

createPhysicalDisk(), createDiskFromTemplate() and createDiskFromTemplateBacking()
still throw, because the Fibre Channel adaptor throws for those too.

createTemplateFromDirectDownloadFile() also still throws, but the message now
states the limitation instead of reading as an oversight. The Fibre Channel
implementation resolves the downloaded file with destPool.getPhysicalDisk(),
which on this adaptor requires a "type=NVMETCP;address=..." path and therefore
cannot describe a plain local file. Supporting it needs a separate way to present
the local file as the copy source, which is left for follow-up rather than
guessed at here.

No functional change to the connect/disconnect paths. The comment on
disconnectPhysicalDisk() is updated because it described connections as
host-group scoped, which is no longer how NVMe-TCP volumes are connected, and to
record why the host-side no-op is correct: the kernel drops the namespace when
the target removes the connection, whereas Fibre Channel must flush its
device-mapper entry.

Signed-off-by: Eugenio Grosso <eugenio.grosso@gmail.com>
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Author: Eugenio Grosso

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

@@ -267,8 +267,9 @@ private void rescanAllControllers() {
 
     @Override
     public boolean disconnectPhysicalDisk(String volumePath, KVMStoragePool pool) {
-        // NVMe-oF: the kernel drops the namespace as soon as the target
-        // removes the host(-group) connection. No host-side action needed.
+        // NVMe-oF: the kernel drops the namespace as soon as the target removes
+        // this host's connection, so there is no host-side map to tear down the way
+        // Fibre Channel must flush its device-mapper entry.
         return true;
     }
 
@@ -286,7 +287,11 @@ public boolean disconnectPhysicalDiskByPath(String localPath) {
 
     @Override
     public boolean deletePhysicalDisk(String uuid, KVMStoragePool pool, Storage.ImageFormat format) {
-        throw new UnsupportedOperationException("Deletion of NVMe namespaces is the storage provider's responsibility");
+        // Namespaces are created and destroyed by the storage provider, never from the
+        // host. Report "not handled here" instead of throwing, so a caller on a cleanup
+        // path behaves the same as it does on the Fibre Channel adapter.
+        LOGGER.info("deletePhysicalDisk({}) not handled by the NVMe-oF adapter; the storage provider owns namespace deletion", uuid);
+        return false;
     }
 
     @Override
@@ -297,12 +302,15 @@ public KVMPhysicalDisk createPhysicalDisk(String name, KVMStoragePool pool, Phys
 
     @Override
     public KVMPhysicalDisk createTemplateFromDisk(KVMPhysicalDisk disk, String name, QemuImg.PhysicalDiskFormat format, long size, KVMStoragePool destPool) {
-        throw new UnsupportedOperationException("Unimplemented method 'createTemplateFromDisk'");
+        LOGGER.info("createTemplateFromDisk not supported on NVMe-oF pools");
+        return null;
     }
 
     @Override
     public List<KVMPhysicalDisk> listPhysicalDisks(String storagePoolUuid, KVMStoragePool pool) {
-        throw new UnsupportedOperationException("Unimplemented method 'listPhysicalDisks'");
+        // The array owns the namespace inventory; it is not enumerable from the host.
+        LOGGER.info("listPhysicalDisks not supported on NVMe-oF pool {}", storagePoolUuid);
+        return null;
     }
 
     @Override
@@ -376,7 +384,13 @@ public KVMPhysicalDisk createDiskFromTemplateBacking(KVMPhysicalDisk template, S
 
     @Override
     public KVMPhysicalDisk createTemplateFromDirectDownloadFile(String templateFilePath, String destTemplatePath, KVMStoragePool destPool, Storage.ImageFormat format, int timeout) {
-        throw new UnsupportedOperationException("Unimplemented method 'createTemplateFromDirectDownloadFile'");
+        // Not supported yet. The equivalent Fibre Channel path resolves the downloaded
+        // file through destPool.getPhysicalDisk(), which on this adapter requires a
+        // "type=NVMETCP;address=..." volume path and so cannot describe a plain local
+        // file. Supporting direct-download templates needs a separate way to present
+        // the local file as the copy source.
+        throw new UnsupportedOperationException(
+                "Direct download templates are not supported on NVMe-oF pools; register the template via secondary storage instead");
     }
 
     @Override
@@ -386,12 +400,15 @@ public boolean refresh(KVMStoragePool pool) {
 
     @Override
     public boolean createFolder(String uuid, String path) {
-        throw new UnsupportedOperationException("Unimplemented method 'createFolder'");
+        return createFolder(uuid, path, null);
     }
 
     @Override
     public boolean createFolder(String uuid, String path, String localPath) {
-        throw new UnsupportedOperationException("Unimplemented method 'createFolder'");
+        // Block storage has no directory structure to create. Succeed rather than
+        // throw, matching the Fibre Channel adapter.
+        LOGGER.info("createFolder({}, {}, {}) is a no-op on NVMe-oF pools", uuid, path, localPath);
+        return true;
     }
 
     /**