cephfs admin: add flagSet interface and mergeFlags function

To prepare for multiple flags types, we create a flagSet interface and
break out the functionality that was in Update into a per-type method
and then the common "merger" function.

Signed-off-by: John Mulligan <jmulligan@redhat.com>

cephfs/admin/flags.go

@@ -2,17 +2,37 @@
 
 package admin
 
+// For APIs that accept extra sets of "boolean" flags we may end up wanting
+// multiple different sets of supported flags. Example: most rm functions
+// accept a force flag, but only subvolume delete has retain snapshots.
+// To make this somewhat uniform in the admin package we define a utility
+// interface and helper function to merge flags with naming options.
+
+type flagSet interface {
+	flags() map[string]bool
+}
+
 type commonRmFlags struct {
 	force bool
 }
 
-func (f commonRmFlags) Update(m map[string]string) map[string]interface{} {
-	o := make(map[string]interface{})
-	for k, v := range m {
-		o[k] = v
-	}
+func (f commonRmFlags) flags() map[string]bool {
+	o := make(map[string]bool)
 	if f.force {
 		o["force"] = true
 	}
 	return o
 }
+
+// mergeFlags combines a set of key-value settings with any type implementing
+// the flagSet interface.
+func mergeFlags(m map[string]string, f flagSet) map[string]interface{} {
+	o := make(map[string]interface{})
+	for k, v := range m {
+		o[k] = v
+	}
+	for k, v := range f.flags() {
+		o[k] = v
+	}
+	return o
+}

cephfs/admin/subvolume.go

@@ -109,7 +109,7 @@ func (fsa *FSAdmin) rmSubVolume(volume, group, name string, o commonRmFlags) err
 	if group != NoGroup {
 		m["group_name"] = group
 	}
-	return fsa.marshalMgrCommand(o.Update(m)).noData().End()
+	return fsa.marshalMgrCommand(mergeFlags(m, o)).noData().End()
 }
 
 type subVolumeResizeFields struct {
@@ -287,7 +287,7 @@ func (fsa *FSAdmin) rmSubVolumeSnapshot(volume, group, subvolume, name string, o
 	if group != NoGroup {
 		m["group_name"] = group
 	}
-	return fsa.marshalMgrCommand(o.Update(m)).noData().End()
+	return fsa.marshalMgrCommand(mergeFlags(m, o)).noData().End()
 }
 
 // ListSubVolumeSnapshots returns a listing of snapshots for a given subvolume.

cephfs/admin/subvolumegroup.go

@@ -80,12 +80,12 @@ func (fsa *FSAdmin) ForceRemoveSubVolumeGroup(volume, name string) error {
 }
 
 func (fsa *FSAdmin) rmSubVolumeGroup(volume, name string, o commonRmFlags) error {
-	res := fsa.marshalMgrCommand(o.Update(map[string]string{
+	res := fsa.marshalMgrCommand(mergeFlags(map[string]string{
 		"prefix":     "fs subvolumegroup rm",
 		"vol_name":   volume,
 		"group_name": name,
 		"format":     "json",
-	}))
+	}, o))
 	return res.noData().End()
 }