cleanup: move mount functions to new pkg

moved fuse and kernel mount functions
to a new package.

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

internal/cephfs/mounter/volumemounter.go

@@ -0,0 +1,154 @@
+/*
+Copyright 2018 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 mounter
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"os/exec"
+	"strings"
+
+	"github.com/ceph/ceph-csi/internal/cephfs/core"
+	"github.com/ceph/ceph-csi/internal/util"
+	"github.com/ceph/ceph-csi/internal/util/log"
+)
+
+var (
+	availableMounters []string
+
+	// nolint:gomnd // numbers specify Kernel versions.
+	quotaSupport = []util.KernelVersion{
+		{
+			Version:      4,
+			PatchLevel:   17,
+			SubLevel:     0,
+			ExtraVersion: 0, Distribution: "",
+			Backport: false,
+		}, // standard 4.17+ versions
+		{
+			Version:      3,
+			PatchLevel:   10,
+			SubLevel:     0,
+			ExtraVersion: 1062,
+			Distribution: ".el7",
+			Backport:     true,
+		}, // RHEL-7.7
+	}
+)
+
+func execCommandErr(ctx context.Context, program string, args ...string) error {
+	_, _, err := util.ExecCommand(ctx, program, args...)
+
+	return err
+}
+
+// Load available ceph mounters installed on system into availableMounters
+// Called from driver.go's Run().
+func LoadAvailableMounters(conf *util.Config) error {
+	// #nosec
+	fuseMounterProbe := exec.Command("ceph-fuse", "--version")
+	// #nosec
+	kernelMounterProbe := exec.Command("mount.ceph")
+
+	err := kernelMounterProbe.Run()
+	if err != nil {
+		log.ErrorLogMsg("failed to run mount.ceph %v", err)
+	} else {
+		// fetch the current running kernel info
+		release, kvErr := util.GetKernelVersion()
+		if kvErr != nil {
+			return kvErr
+		}
+
+		if conf.ForceKernelCephFS || util.CheckKernelSupport(release, quotaSupport) {
+			log.DefaultLog("loaded mounter: %s", volumeMounterKernel)
+			availableMounters = append(availableMounters, volumeMounterKernel)
+		} else {
+			log.DefaultLog("kernel version < 4.17 might not support quota feature, hence not loading kernel client")
+		}
+	}
+
+	err = fuseMounterProbe.Run()
+	if err != nil {
+		log.ErrorLogMsg("failed to run ceph-fuse %v", err)
+	} else {
+		log.DefaultLog("loaded mounter: %s", volumeMounterFuse)
+		availableMounters = append(availableMounters, volumeMounterFuse)
+	}
+
+	if len(availableMounters) == 0 {
+		return errors.New("no ceph mounters found on system")
+	}
+
+	return nil
+}
+
+type VolumeMounter interface {
+	Mount(ctx context.Context, mountPoint string, cr *util.Credentials, volOptions *core.VolumeOptions) error
+	Name() string
+}
+
+func New(volOptions *core.VolumeOptions) (VolumeMounter, error) {
+	// Get the mounter from the configuration
+
+	wantMounter := volOptions.Mounter
+
+	// Verify that it's available
+
+	var chosenMounter string
+
+	for _, availMounter := range availableMounters {
+		if availMounter == wantMounter {
+			chosenMounter = wantMounter
+
+			break
+		}
+	}
+
+	if chosenMounter == "" {
+		// Otherwise pick whatever is left
+		chosenMounter = availableMounters[0]
+		log.DebugLogMsg("requested mounter: %s, chosen mounter: %s", wantMounter, chosenMounter)
+	}
+
+	// Create the mounter
+	switch chosenMounter {
+	case volumeMounterFuse:
+		return &FuseMounter{}, nil
+	case volumeMounterKernel:
+		return &KernelMounter{}, nil
+	}
+
+	return nil, fmt.Errorf("unknown mounter '%s'", chosenMounter)
+}
+
+func BindMount(ctx context.Context, from, to string, readOnly bool, mntOptions []string) error {
+	mntOptionSli := strings.Join(mntOptions, ",")
+	if err := execCommandErr(ctx, "mount", "-o", mntOptionSli, from, to); err != nil {
+		return fmt.Errorf("failed to bind-mount %s to %s: %w", from, to, err)
+	}
+
+	if readOnly {
+		mntOptionSli = util.MountOptionsAdd(mntOptionSli, "remount")
+		if err := execCommandErr(ctx, "mount", "-o", mntOptionSli, to); err != nil {
+			return fmt.Errorf("failed read-only remount of %s: %w", to, err)
+		}
+	}
+
+	return nil
+}