Expose virtual size of backing images

This commit adds virtualSize to the BackingImageStatus and
BackingImageFileInfo structs, and thus to the BackingImage and
BackingImageManager CRDs.  We can see how this works in practice by
creating a new backing image downloaded from a URL, then periodically
running `kubectl -n longhorn-system get lhbi`.  I'm using
https://download.opensuse.org/distribution/leap/15.5/appliances/openSUSE-Leap-15.5-Minimal-VM.x86_64-Cloud.qcow2
in the example below.

Initially, when the download is just started, before the file size is known:

```
> kubectl -n longhorn-system get lhbi/default-image-7mplj
NAME                  UUID       SOURCETYPE   SIZE        VIRTUALSIZE   AGE
default-image-7mplj   6d5a98b0   download     0           0             9s
```

A little later, while the download is running:

```
> kubectl -n longhorn-system get lhbi/default-image-7mplj
NAME                  UUID       SOURCETYPE   SIZE        VIRTUALSIZE   AGE
default-image-7mplj   6d5a98b0   download     255701504   0             3m33s
```

Finally, once the download is complete:

```
> kubectl -n longhorn-system get lhbi/default-image-7mplj
NAME                  UUID       SOURCETYPE   SIZE        VIRTUALSIZE   AGE
default-image-7mplj   6d5a98b0   download     255701504   821035008     4m26s
```

Compare size and virtualSize above with the image downloaded manually:

```
> wget https://download.opensuse.org/distribution/leap/15.5/appliances/openSUSE-Leap-15.5-Minimal-VM.x86_64-Cloud.qcow2
[...]

> ls -l openSUSE-Leap-15.5-Minimal-VM.x86_64-Cloud.qcow2
-rw-r--r-- 1 tserong users 255701504 Dec 19 23:26 openSUSE-Leap-15.5-Minimal-VM.x86_64-Cloud.qcow2

> qemu-img info openSUSE-Leap-15.5-Minimal-VM.x86_64-Cloud.qcow2 | grep virtual
virtual size: 783 MiB (821035008 bytes)
```

Related issue: longhorn/longhorn#7923

Signed-off-by: Tim Serong <tserong@suse.com>
(cherry picked from commit d438e9b)

controller/backing_image_controller.go

@@ -666,6 +666,16 @@ func (bic *BackingImageController) syncBackingImageFileInfo(bi *longhorn.Backing
 				return fmt.Errorf("found mismatching size %v reported by backing image manager %v in disk %v, the size recorded in status is %v", info.Size, bim.Name, bim.Spec.DiskUUID, bi.Status.Size)
 			}
 		}
+		if info.VirtualSize > 0 {
+			if bi.Status.VirtualSize == 0 {
+				bi.Status.VirtualSize = info.VirtualSize
+				bic.eventRecorder.Eventf(bi, corev1.EventTypeNormal, constant.EventReasonUpdate, "Set virtualSize to %v", bi.Status.VirtualSize)
+			}
+			if bi.Status.VirtualSize != info.VirtualSize {
+				return fmt.Errorf("found mismatching virtualSize %v reported by backing image manager %v in disk %v, the virtualSize recorded in status is %v",
+					info.VirtualSize, bim.Name, bim.Spec.DiskUUID, bi.Status.VirtualSize)
+			}
+		}
 	}
 
 	for diskUUID := range bi.Status.DiskFileStatusMap {

engineapi/backing_image_manager.go

@@ -54,9 +54,10 @@ func (c *BackingImageManagerClient) parseBackingImageFileInfo(bi *bimapi.Backing
 		return nil
 	}
 	return &longhorn.BackingImageFileInfo{
-		Name: bi.Name,
-		UUID: bi.UUID,
-		Size: bi.Size,
+		Name:        bi.Name,
+		UUID:        bi.UUID,
+		Size:        bi.Size,
+		VirtualSize: bi.VirtualSize,
 
 		State:                longhorn.BackingImageState(bi.Status.State),
 		CurrentChecksum:      bi.Status.CurrentChecksum,

k8s/crds.yaml

@@ -314,6 +314,9 @@ spec:
                       type: string
                     uuid:
                       type: string
+                    virtualSize:
+                      format: int64
+                      type: integer
                   type: object
                 nullable: true
                 type: object
@@ -412,6 +415,10 @@ spec:
       jsonPath: .status.size
       name: Size
       type: string
+    - description: The virtual size of the image (may be larger than file size)
+      jsonPath: .status.virtualSize
+      name: VirtualSize
+      type: string
     - jsonPath: .metadata.creationTimestamp
       name: Age
       type: date
@@ -479,6 +486,10 @@ spec:
                 type: integer
               uuid:
                 type: string
+              virtualSize:
+                description: Virtual size of image, which may be larger than physical size. Will be zero until known (e.g. while a backing image is uploading)
+                format: int64
+                type: integer
             type: object
         type: object
     served: true

k8s/pkg/apis/longhorn/v1beta2/backingimage.go

@@ -56,6 +56,9 @@ type BackingImageStatus struct {
 	UUID string `json:"uuid"`
 	// +optional
 	Size int64 `json:"size"`
+	// Virtual size of image, which may be larger than physical size. Will be zero until known (e.g. while a backing image is uploading)
+	// +optional
+	VirtualSize int64 `json:"virtualSize"`
 	// +optional
 	Checksum string `json:"checksum"`
 	// +optional
@@ -74,6 +77,7 @@ type BackingImageStatus struct {
 // +kubebuilder:printcolumn:name="UUID",type=string,JSONPath=`.status.uuid`,description="The system generated UUID"
 // +kubebuilder:printcolumn:name="SourceType",type=string,JSONPath=`.spec.sourceType`,description="The source of the backing image file data"
 // +kubebuilder:printcolumn:name="Size",type=string,JSONPath=`.status.size`,description="The backing image file size in each disk"
+// +kubebuilder:printcolumn:name="VirtualSize",type=string,JSONPath=`.status.virtualSize`,description="The virtual size of the image (may be larger than file size)"
 // +kubebuilder:printcolumn:name="Age",type=date,JSONPath=`.metadata.creationTimestamp`
 
 // BackingImage is where Longhorn stores backing image object.

k8s/pkg/apis/longhorn/v1beta2/backingimagemanager.go

@@ -20,6 +20,8 @@ type BackingImageFileInfo struct {
 	// +optional
 	Size int64 `json:"size"`
 	// +optional
+	VirtualSize int64 `json:"virtualSize"`
+	// +optional
 	State BackingImageState `json:"state"`
 	// +optional
 	CurrentChecksum string `json:"currentChecksum"`