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

@@ -2,6 +2,7 @@ package pmdmanager
 
 import (
 	"fmt"
+	"os"
 	"strconv"
 	"strings"
 	"sync"
@@ -157,6 +158,11 @@ func (lvm *pmemLvm) DeleteDevice(name string, flush bool) error {
 		return err
 	}
 	if err := ClearDevice(device, flush); err != nil {
+		if os.IsNotExist(err) {
+			// Remove device from cache
+			delete(lvm.devices, name)
+			return nil
+		}
 		return err
 	}
 

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)
 }