rbd: add SetSnapshot (re)implementing rbd_snap_set

Signed-off-by: oct28.yjkim <oct28.yjkim@gmail.com>

rbd/rbd.go

@@ -916,6 +916,22 @@ func (image *Image) GetId() (string, error) {
 
 }
 
+// SetSnapshot updates the rbd image (not the Snapshot) such that the snapshot
+// is the source of readable data.
+//
+// Implements:
+//  int rbd_snap_set(rbd_image_t image, const char *snapname);
+func (image *Image) SetSnapshot(snapname string) error {
+	if err := image.validate(imageIsOpen); err != nil {
+		return err
+	}
+
+	c_snapname := C.CString(snapname)
+	defer C.free(unsafe.Pointer(c_snapname))
+
+	return getError(C.rbd_snap_set(image.image, c_snapname))
+}
+
 // GetTrashList returns a slice of TrashInfo structs, containing information about all RBD images
 // currently residing in the trash.
 func GetTrashList(ioctx *rados.IOContext) ([]TrashInfo, error) {

rbd/snapshot.go

@@ -149,6 +149,7 @@ func (snapshot *Snapshot) IsProtected() (bool, error) {
 
 // Set updates the rbd image (not the Snapshot) such that the snapshot
 // is the source of readable data.
+// This method is deprecated. Refer the SetSnapshot method of the Image type instead.
 //
 // Implements:
 //  int rbd_snap_set(rbd_image_t image, const char *snapname);
@@ -157,10 +158,7 @@ func (snapshot *Snapshot) Set() error {
 		return err
 	}
 
-	c_snapname := C.CString(snapshot.name)
-	defer C.free(unsafe.Pointer(c_snapname))
-
-	return getError(C.rbd_snap_set(snapshot.image.image, c_snapname))
+	return snapshot.image.SetSnapshot(snapshot.name)
 }
 
 // GetSnapTimestamp returns the timestamp of a snapshot for an image.

rbd/snapshot_test.go

@@ -94,6 +94,9 @@ func TestErrorSnapshotNoName(t *testing.T) {
 	_, err = snapshot.IsProtected()
 	assert.Equal(t, err, ErrSnapshotNoName)
 
+	err = img.SetSnapshot(snapshot.name)
+	assert.Equal(t, err, ErrImageNotOpen)
+
 	err = snapshot.Set()
 	assert.Equal(t, err, ErrSnapshotNoName)