zfs: ability to specify sources for zfsGet

fix use for Placeholder, leave rest as previous behavior

zfs/diff.go

@@ -248,7 +248,7 @@ func IsPlaceholder(p *DatasetPath, placeholderPropertyValue string) (isPlacehold
 
 // for nonexistent FS, isPlaceholder == false && err == nil
 func ZFSIsPlaceholderFilesystem(p *DatasetPath) (isPlaceholder bool, err error) {
-	props, err := ZFSGet(p, []string{ZREPL_PLACEHOLDER_PROPERTY_NAME})
+	props, err := zfsGet(p.ToString(), []string{ZREPL_PLACEHOLDER_PROPERTY_NAME}, sourceLocal)
 	if err == io.ErrUnexpectedEOF {
 		// interpret this as an early exit of the zfs binary due to the fs not existing
 		return false, nil

zfs/replication_history.go

@@ -24,13 +24,13 @@ func ZFSGetReplicationCursor(fs *DatasetPath) (*FilesystemVersion, error) {
 
 func ZFSSetReplicationCursor(fs *DatasetPath, snapname string) (guid uint64, err error) {
 	snapPath := fmt.Sprintf("%s@%s", fs.ToString(), snapname)
-	propsSnap, err := zfsGet(snapPath, []string{"createtxg", "guid"})
+	propsSnap, err := zfsGet(snapPath, []string{"createtxg", "guid"}, sourceAny)
 	if err != nil {
 		return 0, err
 	}
 	snapGuid, err := strconv.ParseUint(propsSnap.Get("guid"), 10, 64)
 	bookmarkPath := fmt.Sprintf("%s#%s", fs.ToString(), ReplicationCursorBookmarkName)
-	propsBookmark, err := zfsGet(bookmarkPath, []string{"createtxg"})
+	propsBookmark, err := zfsGet(bookmarkPath, []string{"createtxg"}, sourceAny)
 	_, bookmarkNotExistErr := err.(*DatasetDoesNotExist)
 	if err != nil && !bookmarkNotExistErr {
 		return 0, err

zfs/zfs.go

@@ -487,7 +487,7 @@ func zfsSet(path string, props *ZFSProperties) (err error) {
 }
 
 func ZFSGet(fs *DatasetPath, props []string) (*ZFSProperties, error) {
-	return zfsGet(fs.ToString(), props)
+	return zfsGet(fs.ToString(), props, sourceAny)
 }
 
 var zfsGetDatasetDoesNotExistRegexp = regexp.MustCompile(`^cannot open '(\S+)': (dataset does not exist|no such pool or dataset)`)
@@ -498,8 +498,30 @@ type DatasetDoesNotExist struct {
 
 func (d *DatasetDoesNotExist) Error() string { return fmt.Sprintf("dataset %q does not exist", d.Path) }
 
-func zfsGet(path string, props []string) (*ZFSProperties, error) {
-	args := []string{"get", "-Hp", "-o", "property,value", strings.Join(props, ","), path}
+type zfsPropertySource uint
+
+const (
+	sourceLocal zfsPropertySource = 1 << iota
+	sourceDefault
+	sourceInherited
+	sourceNone
+	sourceTemporary
+
+	sourceAny zfsPropertySource = ^zfsPropertySource(0)
+)
+
+func (s zfsPropertySource) zfsGetSourceFieldPrefixes() []string {
+	prefixes := make([]string, 0, 5)
+	if s&sourceLocal != 0 {prefixes = append(prefixes, "local")}
+	if s&sourceDefault != 0 {prefixes = append(prefixes, "default")}
+	if s&sourceInherited != 0 {prefixes = append(prefixes, "inherited")}
+	if s&sourceNone != 0 {prefixes = append(prefixes, "-")}
+	if s&sourceTemporary != 0 { prefixes = append(prefixes, "temporary")}
+	return prefixes
+}
+
+func zfsGet(path string, props []string, allowedSources zfsPropertySource) (*ZFSProperties, error) {
+	args := []string{"get", "-Hp", "-o", "property,value,source", strings.Join(props, ","), path}
 	cmd := exec.Command(ZFS_BINARY, args...)
 	stdout, err := cmd.Output()
 	if err != nil {
@@ -524,12 +546,20 @@ func zfsGet(path string, props []string) (*ZFSProperties, error) {
 	res := &ZFSProperties{
 		make(map[string]string, len(lines)),
 	}
+	allowedPrefixes := allowedSources.zfsGetSourceFieldPrefixes()
 	for _, line := range lines[:len(lines)-1] {
-		fields := strings.Fields(line)
-		if len(fields) != 2 {
-			return nil, fmt.Errorf("zfs get did not return property value pairs")
+		fields := strings.FieldsFunc(line, func(r rune) bool {
+			return r == '\t'
+		})
+		if len(fields) != 3 {
+			return nil, fmt.Errorf("zfs get did not return property,value,source tuples")
 		}
+		for _, p := range allowedPrefixes {
+			if strings.HasPrefix(fields[2],p) {
 				res.m[fields[0]] = fields[1]
+				break
+			}
+		}
 	}
 	return res, nil
 }

zfs/zfs_test.go

@@ -30,3 +30,41 @@ func TestDatasetPathTrimNPrefixComps(t *testing.T) {
 	p.TrimNPrefixComps((1))
 	assert.True(t, p.Empty(), "empty trimming shouldn't do harm")
 }
+
+func TestZFSPropertySource(t *testing.T) {
+
+	tcs := []struct{
+		in zfsPropertySource
+		exp []string
+	}{
+		{
+			in: sourceAny,
+			exp: []string{"local", "default", "inherited", "-", "temporary"},
+		},
+		{
+			in: sourceTemporary,
+			exp: []string{"temporary"},
+		},
+		{
+			in: sourceLocal|sourceInherited,
+			exp: []string{"local", "inherited"},
+		},
+	}
+
+	toSet := func(in []string) map[string]struct{} {
+		m := make(map[string]struct{}, len(in))
+		for _, s := range in {
+			m[s] = struct{}{}
+		}
+		return m
+	}
+
+	for _, tc := range tcs {
+
+		res := tc.in.zfsGetSourceFieldPrefixes()
+		resSet := toSet(res)
+		expSet := toSet(tc.exp)
+		assert.Equal(t, expSet, resSet)
+	}
+
+}