Merge pull request #3631 from ddebroy/inline1

Enhancements for inline volume migration

1 files changed, 30 insertions, 14 deletions

diff --git a/contributors/design-proposals/storage/csi-migration.md b/contributors/design-proposals/storage/csi-migration.md
index 2dc03170..52b6ff16 100644
--- a/contributors/design-proposals/storage/csi-migration.md
+++ b/contributors/design-proposals/storage/csi-migration.md
@@ -179,6 +179,9 @@ type CSITranslator interface {
   // by the `Driver` field in the CSI Source. The input PV object will not be modified.
   TranslateCSIPVToInTree(pv *v1.PersistentVolume) (*v1.PersistentVolume, error) {
 
+  // TranslateInTreeInlineVolumeToPVSpec takes an inline intree volume and will translate
+  // the in-tree volume source to a PersistentVolumeSpec containing a CSIPersistentVolumeSource
+  TranslateInTreeInlineVolumeToPVSpec(volume *v1.Volume) (*v1.PersistentVolumeSpec, error) {
 
   // IsMigratableByName tests whether there is Migration logic for the in-tree plugin
   // for the given `pluginName`
@@ -187,11 +190,9 @@ type CSITranslator interface {
   // GetCSINameFromIntreeName maps the name of a CSI driver to its in-tree version
   GetCSINameFromIntreeName(pluginName string) (string, error) {
 
-
   // IsPVMigratable tests whether there is Migration logic for the given Persistent Volume
   IsPVMigratable(pv *v1.PersistentVolume) bool {
 
-
   // IsInlineMigratable tests whether there is Migration logic for the given Inline Volume
   IsInlineMigratable(vol *v1.Volume) bool {
 }
@@ -236,34 +237,49 @@ with the in-tree plugin, the VolumeAttachment object becomes orphaned.
 
 ### In-line Volumes
 
-In-line controller calls are a special case because there is no PV. In this case
-we will translate the volume source and copy it to the field
-VolumeAttachment.Spec.Source.VolumeAttachmentSource.InlineVolumeSource. The
-VolumeAttachment name must be made with the CSI Translated version of the
+In-line controller calls are a special case because there is no PV. In this case,
+we will translate the in-line Volume into a PersistentVolumeSpec using
+plugin-specific translation logic in the CSI translation library method,
+`TranslateInTreeInlineVolumeToPVSpec`. The resulting PersistentVolumeSpec will
+be stored in a new field `VolumeAttachment.Spec.Source.VolumeAttachmentSource.InlineVolumeSpec`.
+
+The plugin-specific CSI translation logic invoked by `TranslateInTreeInlineVolumeToPVSpec`
+will need to populate the `CSIPersistentVolumeSource` field along with appropriate
+values for `AccessModes` and `MountOptions` fields in
+`VolumeAttachment.Spec.Source.VolumeAttachmentSource.InlineVolumeSpec`. Since
+`AccessModes` and `MountOptions` are not specified for inline volumes, default values
+for these fields suitable for the CSI plugin will need to be populated in addition
+to translation logic to populate `CSIPersistentVolumeSource`.
+
+The VolumeAttachment name must be made with the CSI translated version of the
 VolumeSource in order for it to be discoverable by Detach and WaitForAttach
 (described in more detail below).
 
-The CSI Attacher will have to be modified to also check this location for a
-source as well as checking for the `pvName`. Only one of the two may be
-specified.
+The CSI Attacher will have to be modified to also check for `InlineVolumeSpec`
+besides the `PersistentVolumeName`. Only one of the two may be specified. If `PersistentVolumeName`
+is empty and `InlineVolumeSpec` is set, the CSI Attacher will not look for
+an associated PV in it's PV informer cache as it implies the inline volume scenario
+(where no PVs are created).
+
+The CSI Attacher will have access to all the data it requires for handling in-line
+volumes attachment (through the CSI plugins) from fields in the `InlineVolumeSpec`.
 
 The new VolumeAttachmentSource API will look as such:
 ```
 // VolumeAttachmentSource represents a volume that should be attached.
-// Right now only PersistenVolumes can be attached via external attacher,
-// in future we may allow also inline volumes in pods.
+// Inline volumes and Persistent volumes can be attached via external attacher.
 // Exactly one member can be set.
 type VolumeAttachmentSource struct {
 	// Name of the persistent volume to attach.
 	// +optional
 	PersistentVolumeName *string `json:"persistentVolumeName,omitempty" protobuf:"bytes,1,opt,name=persistentVolumeName"`
 
-	// Translated VolumeSource from a pod to a CSIPersistentVolumeSource
-	// to support shimming of in-tree inline volumes to a CSI backend.
+	// A PersistentVolumeSpec whose fields contain translated data from a pod's inline
+	// VolumeSource to support shimming of in-tree inline volumes to a CSI backend.
 	// This field is alpha-level and is only honored by servers that
 	// enable the CSIMigration feature.
 	// +optional
-	InlineCSIVolumeSource *v1.CSIPersistentVolumeSource `json:"inlineCSIVolumeSource,omitempty" protobuf:"bytes,2,opt,name=inlineCSIVolumeSource"`
+	InlineVolumeSpec *v1.PersistentVolumeSpec `json:"inlineVolumeSpec,omitempty" protobuf:"bytes,2,opt,name=inlineVolumeSpec"`
 }
 ```