cephfs: volumemounter probe

The driver will now probe for either ceph fuse/kernel every time
it's about to mount a cephfs volume.

This also affects CreateVolume/DeleteVolume where the mounting
was hard-coded to ceph kernel client till now - mounter configuration
and probing are now honored.

pkg/cephfs/driver.go

@@ -46,14 +46,6 @@ var (
 	DefaultVolumeMounter string
 )
 
-func getVolumeMounterByProbing() string {
-	if execCommandAndValidate("ceph-fuse", "--version") == nil {
-		return volumeMounter_fuse
-	} else {
-		return volumeMounter_kernel
-	}
-}
-
 func NewCephFSDriver() *cephfsDriver {
 	return &cephfsDriver{}
 }
@@ -97,7 +89,12 @@ func (fs *cephfsDriver) Run(driverName, nodeId, endpoint, volumeMounter string)
 			DefaultVolumeMounter = volumeMounter
 		}
 	} else {
-		DefaultVolumeMounter = getVolumeMounterByProbing()
+		availableMounters := getAvailableMounters()
+		if len(availableMounters) == 0 {
+			glog.Fatal("no ceph mounters found on system")
+		}
+
+		DefaultVolumeMounter = availableMounters[0]
 	}
 
 	glog.Infof("cephfs: setting default volume mounter to %s", DefaultVolumeMounter)

pkg/cephfs/nodeserver.go

@@ -134,9 +134,12 @@ func (ns *nodeServer) NodeStageVolume(ctx context.Context, req *csi.NodeStageVol
 		return nil, status.Error(codes.Internal, err.Error())
 	}
 
-	m := newMounter(volOptions)
-	glog.V(4).Infof("cephfs: mounting volume %s with %s", volId, m.name())
+	m, err := newMounter(volOptions)
+	if err != nil {
+		glog.Errorf("failed to create mounter for volume %s: %v", volId, err)
+	}
 
+	glog.V(4).Infof("cephfs: mounting volume %s with %s", volId, m.name())
 	if err = m.mount(stagingTargetPath, cr, volOptions, volId); err != nil {
 		glog.Errorf("failed to mount volume %s: %v", volId, err)
 		return nil, status.Error(codes.Internal, err.Error())

pkg/cephfs/util.go

@@ -97,23 +97,6 @@ func storeCephCredentials(volId volumeID, cr *credentials) error {
 	return nil
 }
 
-func newMounter(volOptions *volumeOptions) volumeMounter {
-	mounter := volOptions.Mounter
-
-	if mounter == "" {
-		mounter = DefaultVolumeMounter
-	}
-
-	switch mounter {
-	case volumeMounter_fuse:
-		return &fuseMounter{}
-	case volumeMounter_kernel:
-		return &kernelMounter{}
-	}
-
-	return nil
-}
-
 //
 // Controller service request validation
 //

pkg/cephfs/volume.go

@@ -60,7 +60,12 @@ func createVolume(volOptions *volumeOptions, adminCr *credentials, volId volumeI
 	// Access to cephfs's / is required
 	volOptions.RootPath = "/"
 
-	if err := mountKernel(cephRoot, adminCr, volOptions, volId); err != nil {
+	m, err := newMounter(volOptions)
+	if err != nil {
+		return fmt.Errorf("failed to create mounter: %v", err)
+	}
+
+	if err = m.mount(cephRoot, adminCr, volOptions, volId); err != nil {
 		return fmt.Errorf("error mounting ceph root: %v", err)
 	}
 
@@ -91,22 +96,28 @@ func createVolume(volOptions *volumeOptions, adminCr *credentials, volId volumeI
 	return nil
 }
 
-func purgeVolume(volId volumeID, cr *credentials, volOptions *volumeOptions) error {
-	// Root path is not set for dynamically provisioned volumes
-	volOptions.RootPath = "/"
-
+func purgeVolume(volId volumeID, adminCr *credentials, volOptions *volumeOptions) error {
 	var (
-		root            = getCephRootPath_local(volId)
+		cephRoot        = getCephRootPath_local(volId)
 		volRoot         = getCephRootVolumePath_local(volId)
 		volRootDeleting = volRoot + "-deleting"
 	)
 
-	if err := createMountPoint(root); err != nil {
+	if err := createMountPoint(cephRoot); err != nil {
 		return err
 	}
 
-	if err := mountKernel(root, cr, volOptions, volId); err != nil {
-		return err
+	// Root path is not set for dynamically provisioned volumes
+	// Access to cephfs's / is required
+	volOptions.RootPath = "/"
+
+	m, err := newMounter(volOptions)
+	if err != nil {
+		return fmt.Errorf("failed to create mounter: %v", err)
+	}
+
+	if err = m.mount(cephRoot, adminCr, volOptions, volId); err != nil {
+		return fmt.Errorf("error mounting ceph root: %v", err)
 	}
 
 	defer func() {

pkg/cephfs/volumemounter.go

@@ -20,6 +20,7 @@ import (
 	"bytes"
 	"fmt"
 	"os"
+	"os/exec"
 )
 
 const (
@@ -113,3 +114,63 @@ func unmountVolume(mountPoint string) error {
 func createMountPoint(root string) error {
 	return os.MkdirAll(root, 0750)
 }
+
+func getAvailableMounters() []string {
+	var ms []string
+
+	fuseMounterProbe := exec.Command("ceph-fuse", "--version")
+	kernelMounterProbe := exec.Command("mount.ceph")
+
+	if fuseMounterProbe.Run() == nil {
+		ms = append(ms, volumeMounter_fuse)
+	}
+
+	if kernelMounterProbe.Run() == nil {
+		ms = append(ms, volumeMounter_kernel)
+	}
+
+	return ms
+}
+
+func newMounter(volOptions *volumeOptions) (volumeMounter, error) {
+	// Get the mounter from the configuration
+
+	wantMounter := volOptions.Mounter
+
+	if wantMounter == "" {
+		wantMounter = DefaultVolumeMounter
+	}
+
+	// Verify that it's available
+
+	availableMounters := getAvailableMounters()
+	if len(availableMounters) == 0 {
+		return nil, fmt.Errorf("no ceph mounters found on system")
+	}
+
+	var chosenMounter string
+
+	for _, availMounter := range getAvailableMounters() {
+		if chosenMounter == "" {
+			if availMounter == wantMounter {
+				chosenMounter = wantMounter
+			}
+		}
+	}
+
+	if chosenMounter == "" {
+		// Otherwise pick whatever is left
+		chosenMounter = availableMounters[0]
+	}
+
+	// Create the mounter
+
+	switch chosenMounter {
+	case volumeMounter_fuse:
+		return &fuseMounter{}, nil
+	case volumeMounter_kernel:
+		return &kernelMounter{}, nil
+	}
+
+	return nil, fmt.Errorf("unknown mounter '%s'", chosenMounter)
+}