fix(xfs): clearing the xfs log before generating UUID (#64)

xfs_admin command to generate the new UUID for the cloned
volume fails without returning error if there is log available
in the filesystem :

ERROR: The filesystem has valuable metadata changes in a log that needs to
be replayed.  Mount the filesystem to replay the log, and unmount it before
re-running xfs_admin.  If you are unable to mount the filesystem, then use
the xfs_repair -L option to destroy the log and attempt a repair.
Note that destroying the log may cause corruption -- please attempt a mount
of the filesystem before doing this.

No UUID will be generated in this case and application can not mount the volume.

Here mounting the filesystem to the temp location with "nouuid" mount option first
so that it can replay the logs first and system is in clean state and then unmount it
and after that generating the UUID with the xfs_admin command.

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

pkg/zfs/xfs_util.go

@@ -0,0 +1,90 @@
+/*
+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 (
+	"os"
+	"os/exec"
+
+	"github.com/Sirupsen/logrus"
+	"strings"
+)
+
+func xfs_temp_mount(volume string) error {
+	device := ZFS_DEVPATH + volume
+	pvol := strings.Split(volume, "/")
+
+	// create a temporary directory to mount the xfs file system
+	tmpdir := "/tmp/" + pvol[1]
+	err := os.Mkdir(tmpdir, 0755)
+	if err != nil {
+		logrus.Errorf("xfs: failed to create tmpdir %s error: %s", tmpdir, err.Error())
+		return err
+	}
+
+	// mount with nouuid, so that it can play the log
+	cmd := exec.Command("mount", "-o", "nouuid", device, tmpdir)
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		logrus.Errorf("xfs: failed to mount volume %s=>%s error: %s", device, tmpdir, string(out))
+		return err
+	}
+
+	// log has been replayed, unmount the volume
+	cmd = exec.Command("umount", tmpdir)
+	out, err = cmd.CombinedOutput()
+	if err != nil {
+		logrus.Errorf("xfs: failed to umount tmpdir %s error: %s", tmpdir, string(out))
+		return err
+	}
+
+	// remove the directory
+	err = os.Remove(tmpdir)
+	if err != nil {
+		logrus.Errorf("xfs: failed to remove tmpdir %s error: %s", tmpdir, err.Error())
+		return err
+	}
+	return nil
+}
+
+/*
+* We have to generate a new UUID for the cloned volumes with xfs filesystem
+* otherwise system won't let anyone mount it 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.
+* There might be something there in the xfs log, we have to clear them
+* so that filesystem is clean and we can generate the UUID for it.
+ */
+func xfs_generate_uuid(volume string) error {
+	device := ZFS_DEVPATH + volume
+
+	// temporary mount the volume with nouuid to replay the logs
+	err := xfs_temp_mount(volume)
+	if err != nil {
+		return err
+	}
+
+	// for mounting the cloned volume for xfs, a new UUID has to be generated
+	cmd := exec.Command("xfs_admin", "-U", "generate", device)
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		logrus.Errorf("xfs: uuid generate failed %s error: %s", volume, string(out))
+		return err
+	}
+	logrus.Infof("xfs: generated UUID for the cloned volume %s \n %v", volume, string(out))
+	return nil
+}

pkg/zfs/zfs_util.go

@@ -362,14 +362,7 @@ func CreateClone(vol *apis.ZFSVolume) error {
 	}
 
 	if vol.Spec.FsType == "xfs" {
-		// for mounting the cloned volume for xfs, a new UUID has to be generated
-		device := ZFS_DEVPATH + volume
-		cmd := exec.Command("xfs_admin", "-U", "generate", device)
-		out, err := cmd.CombinedOutput()
-		if err != nil {
-			logrus.Errorf("zfspv: Clone XFS uuid generate failed error: %s", string(out))
-			return err
-		}
+		return xfs_generate_uuid(volume)
 	}
 	return nil
 }