cleanup: move core functions to core pkg

as we are refractoring the cephfs code,
Moving all the core functions to a new folder
/pkg called core. This will make things easier
to implement. For now onwards all the core
functionalities will be added to the core
package.

Signed-off-by: Madhu Rajanna <madhupr007@gmail.com>

internal/cephfs/core/filesystem.go

@@ -0,0 +1,100 @@
+/*
+Copyright 2019 The Ceph-CSI 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 core
+
+import (
+	"context"
+	"fmt"
+
+	cerrors "github.com/ceph/ceph-csi/internal/cephfs/errors"
+	"github.com/ceph/ceph-csi/internal/util"
+	"github.com/ceph/ceph-csi/internal/util/log"
+)
+
+func (vo *VolumeOptions) getFscID(ctx context.Context) (int64, error) {
+	fsa, err := vo.conn.GetFSAdmin()
+	if err != nil {
+		log.ErrorLog(ctx, "could not get FSAdmin, can not fetch filesystem ID for %s:", vo.FsName, err)
+
+		return 0, err
+	}
+
+	volumes, err := fsa.EnumerateVolumes()
+	if err != nil {
+		log.ErrorLog(ctx, "could not list volumes, can not fetch filesystem ID for %s:", vo.FsName, err)
+
+		return 0, err
+	}
+
+	for _, vol := range volumes {
+		if vol.Name == vo.FsName {
+			return vol.ID, nil
+		}
+	}
+
+	log.ErrorLog(ctx, "failed to list volume %s", vo.FsName)
+
+	return 0, cerrors.ErrVolumeNotFound
+}
+
+func (vo *VolumeOptions) getMetadataPool(ctx context.Context) (string, error) {
+	fsa, err := vo.conn.GetFSAdmin()
+	if err != nil {
+		log.ErrorLog(ctx, "could not get FSAdmin, can not fetch metadata pool for %s:", vo.FsName, err)
+
+		return "", err
+	}
+
+	fsPoolInfos, err := fsa.ListFileSystems()
+	if err != nil {
+		log.ErrorLog(ctx, "could not list filesystems, can not fetch metadata pool for %s:", vo.FsName, err)
+
+		return "", err
+	}
+
+	for _, fspi := range fsPoolInfos {
+		if fspi.Name == vo.FsName {
+			return fspi.MetadataPool, nil
+		}
+	}
+
+	return "", fmt.Errorf("%w: could not find metadata pool for %s", util.ErrPoolNotFound, vo.FsName)
+}
+
+func (vo *VolumeOptions) getFsName(ctx context.Context) (string, error) {
+	fsa, err := vo.conn.GetFSAdmin()
+	if err != nil {
+		log.ErrorLog(ctx, "could not get FSAdmin, can not fetch filesystem name for ID %d:", vo.FscID, err)
+
+		return "", err
+	}
+
+	volumes, err := fsa.EnumerateVolumes()
+	if err != nil {
+		log.ErrorLog(ctx, "could not list volumes, can not fetch filesystem name for ID %d:", vo.FscID, err)
+
+		return "", err
+	}
+
+	for _, vol := range volumes {
+		if vol.ID == vo.FscID {
+			return vol.Name, nil
+		}
+	}
+
+	return "", fmt.Errorf("%w: fscID (%d) not found in Ceph cluster", util.ErrPoolNotFound, vo.FscID)
+}