DeviceManager: Return no error if the device not found while deleting

Discussion on issue intel#413, raised a requirement that PMEM-CSI should handle the
DeleteVolume() call for volumes that the underlined device already deleted
manually by the admin.  So for such a volume we just ignore and return no error
in DeviceManager.DeleteVolume(). This also makes DeleteVolume() idempotent.

pkg/pmem-device-manager/pmd-lvm.go

@@ -2,12 +2,14 @@ package pmdmanager
 
 import (
 	"fmt"
+	"os"
 	"strconv"
 	"strings"
 	"sync"
 
 	"github.com/intel/pmem-csi/pkg/ndctl"
 	pmemexec "github.com/intel/pmem-csi/pkg/pmem-exec"
+	"github.com/pkg/errors"
 	"k8s.io/klog"
 )
 
@@ -152,11 +154,22 @@ func (lvm *pmemLvm) DeleteDevice(name string, flush bool) error {
 	lvmMutex.Lock()
 	defer lvmMutex.Unlock()
 
-	device, err := lvm.getDevice(name)
-	if err != nil {
+	var err error
+	var device PmemDeviceInfo
+
+	if device, err = lvm.getDevice(name); err != nil {
+		if os.IsNotExist(errors.Cause(err)) {
+			return nil
+		}
 		return err
 	}
-	if err := ClearDevice(device, flush); err != nil {
+
+	if err = ClearDevice(device, flush); err != nil {
+		if os.IsNotExist(errors.Cause(err)) {
+			// Remove device from cache
+			delete(lvm.devices, name)
+			return nil
+		}
 		return err
 	}
 
@@ -194,7 +207,7 @@ func (lvm *pmemLvm) getDevice(id string) (PmemDeviceInfo, error) {
 		return dev, nil
 	}
 
-	return PmemDeviceInfo{}, fmt.Errorf("Device not found with name %s", id)
+	return PmemDeviceInfo{}, errors.Wrapf(os.ErrNotExist, "no device found with id '%s'", id)
 }
 
 func getUncachedDevice(id string, volumeGroup string) (PmemDeviceInfo, error) {

pkg/pmem-device-manager/pmd-ndctl.go

@@ -2,6 +2,7 @@ package pmdmanager
 
 import (
 	"fmt"
+	"os"
 	"sync"
 
 	"github.com/intel/pmem-csi/pkg/ndctl"
@@ -143,12 +144,18 @@ func (pmem *pmemNdctl) DeleteDevice(name string, flush bool) error {
 
 	device, err := pmem.getDevice(name)
 	if err != nil {
-		return err
+		// Assume not found device as already deleted
+		// and return no error
+		return nil
 	}
-	err = ClearDevice(device, flush)
-	if err != nil {
+	if err := ClearDevice(device, flush); err != nil {
+		// Device might have already deleted
+		if os.IsNotExist(err) {
+			return nil
+		}
 		return err
 	}
+
 	return pmem.ctx.DestroyNamespaceByName(name)
 }