Set FS type from LINSTOR properties during mounts

If a user restores a volume from a snapshot, the file system type of the
restored volume may not match the requested FS type of the storage class. This
may happen if for example the snapshot was taken from an xfs volume, but the
new StorageClass is configured to provision ext4 volumes. We then would try
to call "mount -t ext4" on a xfs-formatted block device, leading to a failure
mode where the volume is created fine, but you cannot make use of it.

To fix this, instead of taking the FS type directly from Kubernetes, we use
the existing LINSTOR FsType property to determine what fs type is actually
on the volume. Only if this information is not provided (possible with very
old snapshots or some other funky setups), we fall back to the information
provided by Kubernetes.

One alternative would be to disallow such mixing of filesystem types
completely, ensuring when a volume is restored from a snapshot that old and new
volume have matching FS type in Kubernetes. This would permanently lock in some
users to their initial choice of FS, so we instead chose the option that allows
for gradual migration to a new StorageClass/FS.

Signed-off-by: Moritz Wanzenböck <[email protected]>

CHANGELOG.md

@@ -6,6 +6,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- Set the FS type during mount operations based on the FS type stored in LINSTOR.
+
 ## [1.7.0] - 2025-02-13
 
 ### Added

pkg/driver/driver.go

@@ -342,13 +342,31 @@ func (d Driver) NodePublishVolume(ctx context.Context, req *csi.NodePublishVolum
 
 	volCtx.MountOptions = append(volCtx.MountOptions, "_netdev")
 
+	publishCtx := PublishContextFromMap(req.GetPublishContext())
+	if publishCtx == nil {
+		assignment, err := d.Assignments.FindAssignmentOnNode(ctx, req.GetVolumeId(), d.nodeID)
+		if err != nil {
+			return nil, status.Errorf(codes.Internal, "NodePublishVolume failed for %s: %v", req.GetVolumeId(), err)
+		}
+
+		if assignment == nil {
+			return nil, status.Errorf(codes.NotFound, "NodePublishVolume failed for %s: assignment not found", req.GetVolumeId())
+		}
+
+		publishCtx = &PublishContext{
+			DevicePath: assignment.Path,
+		}
+	}
+
 	var fsType string
 
 	if block := req.GetVolumeCapability().GetBlock(); block != nil {
 		volCtx.MountOptions = []string{"bind"}
 	}
 
-	if mnt := req.GetVolumeCapability().GetMount(); mnt != nil {
+	if publishCtx.FsType != "" {
+		fsType = publishCtx.FsType
+	} else if mnt := req.GetVolumeCapability().GetMount(); mnt != nil {
 		volCtx.MountOptions = append(volCtx.MountOptions, mnt.GetMountFlags()...)
 		fsType = "ext4"
 		if mnt.FsType != "" {
@@ -362,22 +380,6 @@ func (d Driver) NodePublishVolume(ctx context.Context, req *csi.NodePublishVolum
 		volCtx.MountOptions = append(volCtx.MountOptions, "nouuid")
 	}
 
-	publishCtx := PublishContextFromMap(req.GetPublishContext())
-	if publishCtx == nil {
-		assignment, err := d.Assignments.FindAssignmentOnNode(ctx, req.GetVolumeId(), d.nodeID)
-		if err != nil {
-			return nil, status.Errorf(codes.Internal, "NodePublishVolume failed for %s: %v", req.GetVolumeId(), err)
-		}
-
-		if assignment == nil {
-			return nil, status.Errorf(codes.NotFound, "NodePublishVolume failed for %s: assignment not found", req.GetVolumeId())
-		}
-
-		publishCtx = &PublishContext{
-			DevicePath: assignment.Path,
-		}
-	}
-
 	ro := req.GetReadonly() || req.GetVolumeCapability().GetAccessMode().GetMode() == csi.VolumeCapability_AccessMode_MULTI_NODE_READER_ONLY
 
 	err = d.Mounter.Mount(ctx, publishCtx.DevicePath, req.GetTargetPath(), fsType, ro, volCtx.MountOptions)
@@ -683,6 +685,7 @@ func (d Driver) ControllerPublishVolume(ctx context.Context, req *csi.Controller
 	return &csi.ControllerPublishVolumeResponse{
 		PublishContext: (&PublishContext{
 			DevicePath: devPath,
+			FsType:     existingVolume.FsType,
 		}).ToMap(),
 	}, nil
 }

pkg/driver/publish_context.go

@@ -7,9 +7,11 @@ import (
 const (
 	PublishContextMarker = linstor.ParameterNamespace + "/uses-publish-context"
 	DevicePath           = linstor.ParameterNamespace + "/device-path"
+	FsType               = linstor.ParameterNamespace + "/fs-type"
 )
 
 type PublishContext struct {
+	FsType     string
 	DevicePath string
 }
 
@@ -21,12 +23,14 @@ func PublishContextFromMap(ctx map[string]string) *PublishContext {
 
 	return &PublishContext{
 		DevicePath: ctx[DevicePath],
+		FsType:     ctx[FsType],
 	}
 }
 
 func (p *PublishContext) ToMap() map[string]string {
 	return map[string]string{
 		PublishContextMarker: "true",
 		DevicePath:           p.DevicePath,
+		FsType:               p.FsType,
 	}
 }