fix(btrfs): fixing duplicate UUID issue with btrfs

btrfs, like xfs, needs to generate a new UUID for the
cloned volumes. All the devices with the same UUID will be treated
same for btrfs, so here generating the new UUID for the cloned volumes
using btrfstune command.

Signed-off-by: Pawan <pawan@mayadata.io>

pkg/zfs/btrfs_util.go

@@ -0,0 +1,42 @@
+/*
+Copyright 2020 The OpenEBS Authors
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package zfs
+
+import (
+	"k8s.io/klog"
+	"os/exec"
+)
+
+/*
+* We have to generate a new UUID for the cloned volumes with btrfs filesystem
+* otherwise system will mount the same volume if UUID is same. Here, since cloned
+* volume refers to the same block because of the way ZFS clone works, it will
+* also have the same UUID.
+ */
+func btrfsGenerateUuid(volume string) error {
+	device := ZFS_DEVPATH + volume
+
+	// for mounting the cloned volume for btrfs, a new UUID has to be generated
+	cmd := exec.Command("btrfstune", "-f", "-u", device)
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		klog.Errorf("btrfs: uuid generate failed %s error: %s", volume, string(out))
+		return err
+	}
+	klog.Infof("btrfs: generated UUID for the cloned volume %s \n %v", volume, string(out))
+	return nil
+}