Separate the codebase for XL and FS format.json related code (#5317)

cmd/format-fs.go

@@ -0,0 +1,226 @@
+/*
+ * Minio Cloud Storage, (C) 2017 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package cmd
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"os"
+	"time"
+
+	errors2 "github.com/minio/minio/pkg/errors"
+	"github.com/minio/minio/pkg/lock"
+)
+
+// FS format version strings.
+const (
+	formatBackendFS   = "fs"
+	formatFSVersionV1 = "1"
+)
+
+// formatFSV1 - structure holds format version '1'.
+type formatFSV1 struct {
+	formatMetaV1
+	FS struct {
+		Version string `json:"version"`
+	} `json:"fs"`
+}
+
+// Used to detect the version of "fs" format.
+type formatFSVersionDetect struct {
+	FS struct {
+		Version string `json:"version"`
+	} `json:"fs"`
+}
+
+// Returns the latest "fs" format.
+func newFormatFSV1() (format *formatFSV1) {
+	f := &formatFSV1{}
+	f.Version = formatMetaVersionV1
+	f.Format = formatBackendFS
+	f.FS.Version = formatFSVersionV1
+	return f
+}
+
+// Save to fs format.json
+func formatFSSave(f *os.File, data interface{}) error {
+	b, err := json.Marshal(data)
+	if err != nil {
+		return errors2.Trace(err)
+	}
+	if err = f.Truncate(0); err != nil {
+		return errors2.Trace(err)
+	}
+	if _, err = f.Seek(0, io.SeekStart); err != nil {
+		return err
+	}
+	_, err = f.Write(b)
+	if err != nil {
+		return errors2.Trace(err)
+	}
+	return nil
+}
+
+// Returns the field formatMetaV1.Format i.e the string "fs" which is never likely to change.
+// We do not use this function in XL to get the format as the file is not fcntl-locked on XL.
+func formatMetaGetFormatBackendFS(r io.ReadSeeker) (string, error) {
+	format := &formatMetaV1{}
+	if err := jsonLoadFromSeeker(r, format); err != nil {
+		return "", err
+	}
+	if format.Version == formatMetaVersionV1 {
+		return format.Format, nil
+	}
+	return "", fmt.Errorf(`format.Version expected: %s, got: %s`, formatMetaVersionV1, format.Version)
+}
+
+// Returns formatFS.FS.Version
+func formatFSGetVersion(r io.ReadSeeker) (string, error) {
+	format := &formatFSVersionDetect{}
+	if err := jsonLoadFromSeeker(r, format); err != nil {
+		return "", err
+	}
+	return format.FS.Version, nil
+}
+
+// Migrate the "fs" backend.
+// Migration should happen when formatFSV1.FS.Version changes. This version
+// can change when there is a change to the struct formatFSV1.FS or if there
+// is any change in the backend file system tree structure.
+func formatFSMigrate(wlk *lock.LockedFile) error {
+	// Add any migration code here in case we bump format.FS.Version
+
+	// Make sure that the version is what we expect after the migration.
+	version, err := formatFSGetVersion(wlk)
+	if err != nil {
+		return err
+	}
+	if version != formatFSVersionV1 {
+		return fmt.Errorf(`%s file: expected FS version: %s, found FS version: %s`, formatConfigFile, formatFSVersionV1, version)
+	}
+	return nil
+}
+
+// Creates a new format.json if unformatted.
+func createFormatFS(fsFormatPath string) error {
+	// Attempt a write lock on formatConfigFile `format.json`
+	// file stored in minioMetaBucket(.minio.sys) directory.
+	lk, err := lock.TryLockedOpenFile(fsFormatPath, os.O_RDWR|os.O_CREATE, 0600)
+	if err != nil {
+		return errors2.Trace(err)
+	}
+	// Close the locked file upon return.
+	defer lk.Close()
+
+	fi, err := lk.Stat()
+	if err != nil {
+		return errors2.Trace(err)
+	}
+	if fi.Size() != 0 {
+		// format.json already got created because of another minio process's createFormatFS()
+		return nil
+	}
+
+	return formatFSSave(lk.File, newFormatFSV1())
+}
+
+// This function returns a read-locked format.json reference to the caller.
+// The file descriptor should be kept open throughout the life
+// of the process so that another minio process does not try to
+// migrate the backend when we are actively working on the backend.
+func initFormatFS(fsPath string) (rlk *lock.RLockedFile, err error) {
+	fsFormatPath := pathJoin(fsPath, minioMetaBucket, formatConfigFile)
+	// Any read on format.json should be done with read-lock.
+	// Any write on format.json should be done with write-lock.
+	for {
+		isEmpty := false
+		rlk, err := lock.RLockedOpenFile(fsFormatPath)
+		if err == nil {
+			// format.json can be empty in a rare condition when another
+			// minio process just created the file but could not hold lock
+			// and write to it.
+			var fi os.FileInfo
+			fi, err = rlk.Stat()
+			if err != nil {
+				return nil, errors2.Trace(err)
+			}
+			isEmpty = fi.Size() == 0
+		}
+		if os.IsNotExist(err) || isEmpty {
+			if err == nil {
+				rlk.Close()
+			}
+			// Fresh disk - create format.json
+			err = createFormatFS(fsFormatPath)
+			if err == lock.ErrAlreadyLocked {
+				// Lock already present, sleep and attempt again.
+				// Can happen in a rare situation when a parallel minio process
+				// holds the lock and creates format.json
+				time.Sleep(100 * time.Millisecond)
+				continue
+			}
+			if err != nil {
+				return nil, errors2.Trace(err)
+			}
+			// After successfully creating format.json try to hold a read-lock on
+			// the file.
+			continue
+		}
+		if err != nil {
+			return nil, errors2.Trace(err)
+		}
+
+		formatBackend, err := formatMetaGetFormatBackendFS(rlk)
+		if err != nil {
+			return nil, errors2.Trace(err)
+		}
+		if formatBackend != formatBackendFS {
+			return nil, fmt.Errorf(`%s file: expected format-type: %s, found: %s`, formatConfigFile, formatBackendFS, formatBackend)
+		}
+		version, err := formatFSGetVersion(rlk)
+		if err != nil {
+			return nil, err
+		}
+		if version != formatFSVersionV1 {
+			// Format needs migration
+			rlk.Close()
+			// Hold write lock during migration so that we do not disturb any
+			// minio processes running in parallel.
+			wlk, err := lock.TryLockedOpenFile(fsFormatPath, os.O_RDWR, 0)
+			if err == lock.ErrAlreadyLocked {
+				// Lock already present, sleep and attempt again.
+				wlk.Close()
+				time.Sleep(100 * time.Millisecond)
+				continue
+			}
+			if err != nil {
+				return nil, err
+			}
+			err = formatFSMigrate(wlk)
+			wlk.Close()
+			if err != nil {
+				// Migration failed, bail out so that the user can observe what happened.
+				return nil, err
+			}
+			// Successfully migrated, now try to hold a read-lock on format.json
+			continue
+		}
+
+		return rlk, nil
+	}
+}

cmd/format-fs_test.go

@@ -0,0 +1,102 @@
+/*
+ * Minio Cloud Storage, (C) 2017 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package cmd
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+// TestFSFormatFS - tests initFormatFS, formatMetaGetFormatBackendFS, formatFSGetVersion.
+func TestFSFormatFS(t *testing.T) {
+	// Prepare for testing
+	disk := filepath.Join(globalTestTmpDir, "minio-"+nextSuffix())
+	defer os.RemoveAll(disk)
+
+	fsFormatPath := pathJoin(disk, minioMetaBucket, formatConfigFile)
+
+	// Assign a new UUID.
+	uuid := mustGetUUID()
+
+	// Initialize meta volume, if volume already exists ignores it.
+	if err := initMetaVolumeFS(disk, uuid); err != nil {
+		t.Fatal(err)
+	}
+
+	rlk, err := initFormatFS(disk)
+	if err != nil {
+		t.Fatal(err)
+	}
+	rlk.Close()
+
+	// Do the basic sanity checks to check if initFormatFS() did its job.
+	f, err := os.OpenFile(fsFormatPath, os.O_RDWR, 0)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer f.Close()
+
+	format, err := formatMetaGetFormatBackendFS(f)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if format != formatBackendFS {
+		t.Fatalf(`expected: %s, got: %s`, formatBackendFS, format)
+	}
+	version, err := formatFSGetVersion(f)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if version != formatFSVersionV1 {
+		t.Fatalf(`expected: %s, got: %s`, formatFSVersionV1, version)
+	}
+
+	// Corrupt the format.json file and test the functions.
+	// formatMetaGetFormatBackendFS, formatFSGetVersion, initFormatFS should return errors.
+	if err = f.Truncate(0); err != nil {
+		t.Fatal(err)
+	}
+	if _, err = f.WriteString("b"); err != nil {
+		t.Fatal(err)
+	}
+
+	if _, err = formatMetaGetFormatBackendFS(f); err == nil {
+		t.Fatal("expected to fail")
+	}
+	if _, err = formatFSGetVersion(rlk); err == nil {
+		t.Fatal("expected to fail")
+	}
+	if _, err = initFormatFS(disk); err == nil {
+		t.Fatal("expected to fail")
+	}
+
+	// With unknown formatMetaV1.Version formatMetaGetFormatBackendFS, initFormatFS should return error.
+	if err = f.Truncate(0); err != nil {
+		t.Fatal(err)
+	}
+	// Here we set formatMetaV1.Version to "2"
+	if _, err = f.WriteString(`{"version":"2","format":"fs","fs":{"version":"1"}}`); err != nil {
+		t.Fatal(err)
+	}
+	if _, err = formatMetaGetFormatBackendFS(f); err == nil {
+		t.Fatal("expected to fail")
+	}
+	if _, err = initFormatFS(disk); err == nil {
+		t.Fatal("expected to fail")
+	}
+}

cmd/format-meta.go

@@ -0,0 +1,52 @@
+/*
+ * Minio Cloud Storage, (C) 2017 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package cmd
+
+// Format related consts
+const (
+	// Format config file carries backend format specific details.
+	formatConfigFile = "format.json"
+
+	// Format config tmp file carries backend format.
+	formatConfigFileTmp = "format.json.tmp"
+)
+
+const (
+	// Version of the formatMetaV1
+	formatMetaVersionV1 = "1"
+)
+
+// format.json currently has the format:
+// {
+//   "version": "1",
+//   "format": "XXXXX",
+//   "XXXXX": {
+//
+//   }
+// }
+// Here "XXXXX" depends on the backend, currently we have "fs" and "xl" implementations.
+// formatMetaV1 should be inherited by backend format structs. Please look at format-fs.go
+// and format-xl.go for details.
+
+// Ideally we will never have a situation where we will have to change the
+// fields of this struct and deal with related migration.
+type formatMetaV1 struct {
+	// Version of the format config.
+	Version string `json:"version"`
+	// Format indicates the backend format type, supports two values 'xl' and 'fs'.
+	Format string `json:"format"`
+}

cmd/format-xl.go

@@ -20,168 +20,30 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
-	"io"
-	"io/ioutil"
 	"reflect"
 	"sync"
-
-	errors2 "github.com/minio/minio/pkg/errors"
-	"github.com/minio/minio/pkg/lock"
 )
 
-// fsFormat - structure holding 'fs' format.
-type fsFormat struct {
-	Version string `json:"version"`
-}
-
-// FS format version strings.
 const (
+	// Represents XL backend.
+	formatBackendXL = "xl"
+
+	// formatXLV1.XL.Version
+	formatXLVersionV1 = "1"
+)
+
 // Represents the current backend disk structure
 // version under `.minio.sys` and actual data namespace.
-
-	// formatConfigV1.fsFormat.Version
-	fsFormatBackendV1 = "1"
-)
-
-// xlFormat - structure holding 'xl' format.
-type xlFormat struct {
+// formatXLV1 - structure holds format config version '1'.
+type formatXLV1 struct {
+	formatMetaV1
+	XL struct {
 		Version string `json:"version"` // Version of 'xl' format.
 		Disk    string `json:"disk"`    // Disk field carries assigned disk uuid.
 		// JBOD field carries the input disk order generated the first
 		// time when fresh disks were supplied.
 		JBOD []string `json:"jbod"`
-}
-
-// XL format version strings.
-const (
-	// Represents the current backend disk structure
-	// version under `.minio.sys` and actual data namespace.
-
-	// formatConfigV1.xlFormat.Version
-	xlFormatBackendV1 = "1"
-)
-
-// formatConfigV1 - structure holds format config version '1'.
-type formatConfigV1 struct {
-	Version string `json:"version"` // Version of the format config.
-	// Format indicates the backend format type, supports two values 'xl' and 'fs'.
-	Format string    `json:"format"`
-	FS     *fsFormat `json:"fs,omitempty"` // FS field holds fs format.
-	XL     *xlFormat `json:"xl,omitempty"` // XL field holds xl format.
-}
-
-// Format json file.
-const (
-	// Format config file carries backend format specific details.
-	formatConfigFile = "format.json"
-
-	// Format config tmp file carries backend format.
-	formatConfigFileTmp = "format.json.tmp"
-)
-
-// `format.json` version value.
-const (
-	// formatConfigV1.Version represents the version string
-	// of the current structure and its fields in `format.json`.
-	formatFileV1 = "1"
-
-	// Future `format.json` structure changes should have
-	// its own version and should be subsequently listed here.
-)
-
-// Constitutes `format.json` backend name.
-const (
-	// Represents FS backend.
-	formatBackendFS = "fs"
-
-	// Represents XL backend.
-	formatBackendXL = "xl"
-)
-
-// CheckFS if the format is FS and is valid with right values
-// returns appropriate errors otherwise.
-func (f *formatConfigV1) CheckFS() error {
-	// Validate if format config version is v1.
-	if f.Version != formatFileV1 {
-		return fmt.Errorf("Unknown format file version '%s'", f.Version)
-	}
-
-	// Validate if we have the expected format.
-	if f.Format != formatBackendFS {
-		return fmt.Errorf("FS backend format required. Found '%s'", f.Format)
-	}
-
-	// Check if format is currently supported.
-	if f.FS.Version != fsFormatBackendV1 {
-		return fmt.Errorf("Unknown backend FS format version '%s'", f.FS.Version)
-	}
-
-	// Success.
-	return nil
-}
-
-// LoadFormat - loads format config v1, returns `errUnformattedDisk`
-// if reading format.json fails with io.EOF.
-func (f *formatConfigV1) LoadFormat(lk *lock.LockedFile) error {
-	_, err := f.ReadFrom(lk)
-	if errors2.Cause(err) == io.EOF {
-		// No data on disk `format.json` still empty
-		// treat it as unformatted disk.
-		return errors2.Trace(errUnformattedDisk)
-	}
-	return err
-}
-
-func (f *formatConfigV1) WriteTo(lk *lock.LockedFile) (n int64, err error) {
-	// Serialize to prepare to write to disk.
-	var fbytes []byte
-	fbytes, err = json.Marshal(f)
-	if err != nil {
-		return 0, errors2.Trace(err)
-	}
-	if err = lk.Truncate(0); err != nil {
-		return 0, errors2.Trace(err)
-	}
-	_, err = lk.Write(fbytes)
-	if err != nil {
-		return 0, errors2.Trace(err)
-	}
-	return int64(len(fbytes)), nil
-}
-
-func (f *formatConfigV1) ReadFrom(lk *lock.LockedFile) (n int64, err error) {
-	var fbytes []byte
-	fi, err := lk.Stat()
-	if err != nil {
-		return 0, errors2.Trace(err)
-	}
-	fbytes, err = ioutil.ReadAll(io.NewSectionReader(lk, 0, fi.Size()))
-	if err != nil {
-		return 0, errors2.Trace(err)
-	}
-	if len(fbytes) == 0 {
-		return 0, errors2.Trace(io.EOF)
-	}
-	// Decode `format.json`.
-	if err = json.Unmarshal(fbytes, f); err != nil {
-		return 0, errors2.Trace(err)
-	}
-	return int64(len(fbytes)), nil
-}
-
-func newFSFormat() (format *formatConfigV1) {
-	return newFSFormatV1()
-}
-
-// newFSFormatV1 - initializes new formatConfigV1 with FS format info.
-func newFSFormatV1() (format *formatConfigV1) {
-	return &formatConfigV1{
-		Version: formatFileV1,
-		Format:  formatBackendFS,
-		FS: &fsFormat{
-			Version: fsFormatBackendV1,
-		},
-	}
+	} `json:"xl"` // XL field holds xl format.
 }
 
 /*
@@ -271,7 +133,7 @@ func formatErrsSummary(errs []error) (formatCount, unformattedDiskCount,
 }
 
 // loadAllFormats - load all format config from all input disks in parallel.
-func loadAllFormats(bootstrapDisks []StorageAPI) ([]*formatConfigV1, []error) {
+func loadAllFormats(bootstrapDisks []StorageAPI) ([]*formatXLV1, []error) {
 	// Initialize sync waitgroup.
 	var wg = &sync.WaitGroup{}
 
@@ -279,7 +141,7 @@ func loadAllFormats(bootstrapDisks []StorageAPI) ([]*formatConfigV1, []error) {
 	var sErrs = make([]error, len(bootstrapDisks))
 
 	// Initialize format configs.
-	var formatConfigs = make([]*formatConfigV1, len(bootstrapDisks))
+	var formats = make([]*formatXLV1, len(bootstrapDisks))
 
 	// Make a volume entry on all underlying storage disks.
 	for index, disk := range bootstrapDisks {
@@ -291,12 +153,12 @@ func loadAllFormats(bootstrapDisks []StorageAPI) ([]*formatConfigV1, []error) {
 		// Make a volume inside a go-routine.
 		go func(index int, disk StorageAPI) {
 			defer wg.Done()
-			formatConfig, lErr := loadFormat(disk)
+			format, lErr := loadFormat(disk)
 			if lErr != nil {
 				sErrs[index] = lErr
 				return
 			}
-			formatConfigs[index] = formatConfig
+			formats[index] = format
 		}(index, disk)
 	}
 
@@ -306,11 +168,11 @@ func loadAllFormats(bootstrapDisks []StorageAPI) ([]*formatConfigV1, []error) {
 	for _, err := range sErrs {
 		if err != nil {
 			// Return all formats and errors.
-			return formatConfigs, sErrs
+			return formats, sErrs
 		}
 	}
 	// Return all formats and nil
-	return formatConfigs, sErrs
+	return formats, sErrs
 }
 
 // genericFormatCheckXL - validates and returns error.
@@ -318,7 +180,7 @@ func loadAllFormats(bootstrapDisks []StorageAPI) ([]*formatConfigV1, []error) {
 // if (any disk is corrupt) return error // phase2
 // if (jbod inconsistent) return error // phase2
 // if (disks not recognized) // Always error.
-func genericFormatCheckXL(formatConfigs []*formatConfigV1, sErrs []error) (err error) {
+func genericFormatCheckXL(formats []*formatXLV1, sErrs []error) (err error) {
 	// Calculate the errors.
 	var (
 		errCorruptFormatCount = 0
@@ -342,20 +204,20 @@ func genericFormatCheckXL(formatConfigs []*formatConfigV1, sErrs []error) (err e
 	}
 
 	// Calculate read quorum.
-	readQuorum := len(formatConfigs) / 2
+	readQuorum := len(formats) / 2
 
 	// Validate the err count under read quorum.
-	if errCount > len(formatConfigs)-readQuorum {
+	if errCount > len(formats)-readQuorum {
 		return errXLReadQuorum
 	}
 
 	// Check if number of corrupted format under read quorum
-	if errCorruptFormatCount > len(formatConfigs)-readQuorum {
+	if errCorruptFormatCount > len(formats)-readQuorum {
 		return errCorruptedFormat
 	}
 
 	// Validates if format and JBOD are consistent across all disks.
-	if err = checkFormatXL(formatConfigs); err != nil {
+	if err = checkFormatXL(formats); err != nil {
 		return err
 	}
 
@@ -366,15 +228,15 @@ func genericFormatCheckXL(formatConfigs []*formatConfigV1, sErrs []error) (err e
 // isSavedUUIDInOrder - validates if disk uuid is present and valid in all
 // available format config JBOD. This function also validates if the disk UUID
 // is always available on all JBOD under the same order.
-func isSavedUUIDInOrder(uuid string, formatConfigs []*formatConfigV1) bool {
+func isSavedUUIDInOrder(uuid string, formats []*formatXLV1) bool {
 	var orderIndexes []int
 	// Validate each for format.json for relevant uuid.
-	for _, formatConfig := range formatConfigs {
-		if formatConfig == nil {
+	for _, format := range formats {
+		if format == nil {
 			continue
 		}
 		// Validate if UUID is present in JBOD.
-		uuidIndex := findDiskIndex(uuid, formatConfig.XL.JBOD)
+		uuidIndex := findDiskIndex(uuid, format.XL.JBOD)
 		if uuidIndex == -1 {
 			// UUID not found.
 			errorIf(errDiskNotFound, "Disk %s not found in JBOD list", uuid)
@@ -398,15 +260,15 @@ func isSavedUUIDInOrder(uuid string, formatConfigs []*formatConfigV1) bool {
 }
 
 // checkDisksConsistency - checks if all disks are consistent with all JBOD entries on all disks.
-func checkDisksConsistency(formatConfigs []*formatConfigV1) error {
-	var disks = make([]string, len(formatConfigs))
+func checkDisksConsistency(formats []*formatXLV1) error {
+	var disks = make([]string, len(formats))
 	// Collect currently available disk uuids.
-	for index, formatConfig := range formatConfigs {
-		if formatConfig == nil {
+	for index, format := range formats {
+		if format == nil {
 			disks[index] = ""
 			continue
 		}
-		disks[index] = formatConfig.XL.Disk
+		disks[index] = format.XL.Disk
 	}
 	// Validate collected uuids and verify JBOD.
 	for _, uuid := range disks {
@@ -414,7 +276,7 @@ func checkDisksConsistency(formatConfigs []*formatConfigV1) error {
 			continue
 		}
 		// Is uuid present on all JBOD ?.
-		if !isSavedUUIDInOrder(uuid, formatConfigs) {
+		if !isSavedUUIDInOrder(uuid, formats) {
 			return fmt.Errorf("%s disk not found in JBOD", uuid)
 		}
 	}
@@ -422,17 +284,17 @@ func checkDisksConsistency(formatConfigs []*formatConfigV1) error {
 }
 
 // checkJBODConsistency - validate xl jbod order if they are consistent.
-func checkJBODConsistency(formatConfigs []*formatConfigV1) error {
+func checkJBODConsistency(formats []*formatXLV1) error {
 	var sentinelJBOD []string
 	// Extract first valid JBOD.
-	for _, format := range formatConfigs {
+	for _, format := range formats {
 		if format == nil {
 			continue
 		}
 		sentinelJBOD = format.XL.JBOD
 		break
 	}
-	for _, format := range formatConfigs {
+	for _, format := range formats {
 		if format == nil {
 			continue
 		}
@@ -458,14 +320,14 @@ func findDiskIndex(disk string, jbod []string) int {
 // format-config. If assignUUIDs is true, it assigns UUIDs to disks
 // with missing format configurations in the reference configuration.
 func reorderDisks(bootstrapDisks []StorageAPI,
-	formatConfigs []*formatConfigV1, assignUUIDs bool) (*formatConfigV1,
+	formats []*formatXLV1, assignUUIDs bool) (*formatXLV1,
 	[]StorageAPI, error) {
 
 	// Pick first non-nil format-cfg as reference
-	var refCfg *formatConfigV1
-	for _, formatConfig := range formatConfigs {
-		if formatConfig != nil {
-			refCfg = formatConfig
+	var refCfg *formatXLV1
+	for _, format := range formats {
+		if format != nil {
+			refCfg = format
 			break
 		}
 	}
@@ -476,7 +338,7 @@ func reorderDisks(bootstrapDisks []StorageAPI,
 
 	// construct reordered disk slice
 	var newDisks = make([]StorageAPI, len(bootstrapDisks))
-	for fIndex, format := range formatConfigs {
+	for fIndex, format := range formats {
 		if format == nil {
 			continue
 		}
@@ -501,7 +363,7 @@ func reorderDisks(bootstrapDisks []StorageAPI,
 }
 
 // loadFormat - loads format.json from disk.
-func loadFormat(disk StorageAPI) (format *formatConfigV1, err error) {
+func loadFormat(disk StorageAPI) (format *formatXLV1, err error) {
 	buf, err := disk.ReadAll(minioMetaBucket, formatConfigFile)
 	if err != nil {
 		// 'file not found' and 'volume not found' as
@@ -523,7 +385,7 @@ func loadFormat(disk StorageAPI) (format *formatConfigV1, err error) {
 	}
 
 	// Try to decode format json into formatConfigV1 struct.
-	format = &formatConfigV1{}
+	format = &formatXLV1{}
 	if err = json.Unmarshal(buf, format); err != nil {
 		return nil, err
 	}
@@ -535,23 +397,20 @@ func loadFormat(disk StorageAPI) (format *formatConfigV1, err error) {
 // collectNSaveNewFormatConfigs - creates new format configs based on
 // the reference config and saves it on all disks, this is to be
 // called from healFormatXL* functions.
-func collectNSaveNewFormatConfigs(referenceConfig *formatConfigV1,
+func collectNSaveNewFormatConfigs(referenceConfig *formatXLV1,
 	orderedDisks []StorageAPI) error {
 
 	// Collect new format configs that need to be written.
-	var newFormatConfigs = make([]*formatConfigV1, len(orderedDisks))
+	var newFormatConfigs = make([]*formatXLV1, len(orderedDisks))
 	for index := range orderedDisks {
 		// New configs are generated since we are going
 		// to re-populate across all disks.
-		config := &formatConfigV1{
-			Version: referenceConfig.Version,
-			Format:  referenceConfig.Format,
-			XL: &xlFormat{
-				Version: referenceConfig.XL.Version,
-				Disk:    referenceConfig.XL.JBOD[index],
-				JBOD:    referenceConfig.XL.JBOD,
-			},
-		}
+		config := &formatXLV1{}
+		config.Version = referenceConfig.Version
+		config.Format = referenceConfig.Format
+		config.XL.Version = referenceConfig.XL.Version
+		config.XL.Disk = referenceConfig.XL.JBOD[index]
+		config.XL.JBOD = referenceConfig.XL.JBOD
 		newFormatConfigs[index] = config
 	}
 
@@ -568,11 +427,11 @@ func collectNSaveNewFormatConfigs(referenceConfig *formatConfigV1,
 // unexpected errors as regular errors can be ignored since there
 // might be enough quorum to be operational.  Heals only fresh disks.
 func healFormatXLFreshDisks(storageDisks []StorageAPI,
-	formatConfigs []*formatConfigV1) error {
+	formats []*formatXLV1) error {
 
 	// Reorder the disks based on the JBOD order.
 	referenceConfig, orderedDisks, err := reorderDisks(storageDisks,
-		formatConfigs, true)
+		formats, true)
 	if err != nil {
 		return err
 	}
@@ -581,7 +440,7 @@ func healFormatXLFreshDisks(storageDisks []StorageAPI,
 	// We need to make sure we have kept the previous order
 	// and allowed fresh disks to be arranged anywhere.
 	// Following block facilitates to put fresh disks.
-	for index, format := range formatConfigs {
+	for index, format := range formats {
 		// Format is missing so we go through ordered disks.
 		if format == nil {
 			// At this point when disk is missing the fresh disk
@@ -624,9 +483,9 @@ func collectUnAssignedDisks(storageDisks, orderedDisks []StorageAPI) (
 // Inspect the content of all disks to guess the right order according
 // to the format files. The right order is represented in orderedDisks
 func reorderDisksByInspection(orderedDisks, storageDisks []StorageAPI,
-	formatConfigs []*formatConfigV1) ([]StorageAPI, error) {
+	formats []*formatXLV1) ([]StorageAPI, error) {
 
-	for index, format := range formatConfigs {
+	for index, format := range formats {
 		if format != nil {
 			continue
 		}
@@ -681,11 +540,11 @@ func reorderDisksByInspection(orderedDisks, storageDisks []StorageAPI,
 
 // Heals corrupted format json in all disks
 func healFormatXLCorruptedDisks(storageDisks []StorageAPI,
-	formatConfigs []*formatConfigV1) error {
+	formats []*formatXLV1) error {
 
 	// Reorder the disks based on the JBOD order.
 	referenceConfig, orderedDisks, err := reorderDisks(storageDisks,
-		formatConfigs, true)
+		formats, true)
 	if err != nil {
 		return err
 	}
@@ -693,7 +552,7 @@ func healFormatXLCorruptedDisks(storageDisks []StorageAPI,
 	// For disks with corrupted formats, inspect the disks
 	// contents to guess the disks order
 	orderedDisks, err = reorderDisksByInspection(orderedDisks, storageDisks,
-		formatConfigs)
+		formats)
 	if err != nil {
 		return err
 	}
@@ -721,7 +580,7 @@ func loadFormatXL(bootstrapDisks []StorageAPI, readQuorum int) (disks []StorageA
 	var unformattedDisksFoundCnt = 0
 	var diskNotFoundCount = 0
 	var corruptedDisksFoundCnt = 0
-	formatConfigs := make([]*formatConfigV1, len(bootstrapDisks))
+	formats := make([]*formatXLV1, len(bootstrapDisks))
 
 	// Try to load `format.json` bootstrap disks.
 	for index, disk := range bootstrapDisks {
@@ -729,7 +588,7 @@ func loadFormatXL(bootstrapDisks []StorageAPI, readQuorum int) (disks []StorageA
 			diskNotFoundCount++
 			continue
 		}
-		var formatXL *formatConfigV1
+		var formatXL *formatXLV1
 		formatXL, err = loadFormat(disk)
 		if err != nil {
 			if err == errUnformattedDisk {
@@ -745,7 +604,7 @@ func loadFormatXL(bootstrapDisks []StorageAPI, readQuorum int) (disks []StorageA
 			return nil, err
 		}
 		// Save valid formats.
-		formatConfigs[index] = formatXL
+		formats[index] = formatXL
 	}
 
 	// If all disks indicate that 'format.json' is not available return 'errUnformattedDisk'.
@@ -760,59 +619,59 @@ func loadFormatXL(bootstrapDisks []StorageAPI, readQuorum int) (disks []StorageA
 	}
 
 	// Validate the format configs read are correct.
-	if err = checkFormatXL(formatConfigs); err != nil {
+	if err = checkFormatXL(formats); err != nil {
 		return nil, err
 	}
 	// Erasure code requires disks to be presented in the same
 	// order each time.
-	_, orderedDisks, err := reorderDisks(bootstrapDisks, formatConfigs,
+	_, orderedDisks, err := reorderDisks(bootstrapDisks, formats,
 		false)
 	return orderedDisks, err
 }
 
-func checkFormatXLValue(formatXL *formatConfigV1) error {
+func checkFormatXLValue(formatXL *formatXLV1) error {
 	// Validate format version and format type.
-	if formatXL.Version != formatFileV1 {
+	if formatXL.Version != formatMetaVersionV1 {
 		return fmt.Errorf("Unsupported version of backend format [%s] found", formatXL.Version)
 	}
 	if formatXL.Format != formatBackendXL {
 		return fmt.Errorf("Unsupported backend format [%s] found", formatXL.Format)
 	}
-	if formatXL.XL.Version != "1" {
+	if formatXL.XL.Version != formatXLVersionV1 {
 		return fmt.Errorf("Unsupported XL backend format found [%s]", formatXL.XL.Version)
 	}
 	return nil
 }
 
-func checkFormatXLValues(formatConfigs []*formatConfigV1) (int, error) {
-	for i, formatXL := range formatConfigs {
+func checkFormatXLValues(formats []*formatXLV1) (int, error) {
+	for i, formatXL := range formats {
 		if formatXL == nil {
 			continue
 		}
 		if err := checkFormatXLValue(formatXL); err != nil {
 			return i, err
 		}
-		if len(formatConfigs) != len(formatXL.XL.JBOD) {
+		if len(formats) != len(formatXL.XL.JBOD) {
 			return i, fmt.Errorf("Number of disks %d did not match the backend format %d",
-				len(formatConfigs), len(formatXL.XL.JBOD))
+				len(formats), len(formatXL.XL.JBOD))
 		}
 	}
 	return -1, nil
 }
 
 // checkFormatXL - verifies if format.json format is intact.
-func checkFormatXL(formatConfigs []*formatConfigV1) error {
-	if _, err := checkFormatXLValues(formatConfigs); err != nil {
+func checkFormatXL(formats []*formatXLV1) error {
+	if _, err := checkFormatXLValues(formats); err != nil {
 		return err
 	}
-	if err := checkJBODConsistency(formatConfigs); err != nil {
+	if err := checkJBODConsistency(formats); err != nil {
 		return err
 	}
-	return checkDisksConsistency(formatConfigs)
+	return checkDisksConsistency(formats)
 }
 
 // saveFormatXL - populates `format.json` on disks in its order.
-func saveFormatXL(storageDisks []StorageAPI, formats []*formatConfigV1) error {
+func saveFormatXL(storageDisks []StorageAPI, formats []*formatXLV1) error {
 	var errs = make([]error, len(storageDisks))
 	var wg = &sync.WaitGroup{}
 	// Write `format.json` to all disks.
@@ -821,7 +680,7 @@ func saveFormatXL(storageDisks []StorageAPI, formats []*formatConfigV1) error {
 			continue
 		}
 		wg.Add(1)
-		go func(index int, disk StorageAPI, format *formatConfigV1) {
+		go func(index int, disk StorageAPI, format *formatXLV1) {
 			defer wg.Done()
 
 			// Marshal and write to disk.
@@ -862,45 +721,37 @@ func saveFormatXL(storageDisks []StorageAPI, formats []*formatConfigV1) error {
 	return nil
 }
 
-// initFormatXL - save XL format configuration on all disks.
-func initFormatXL(storageDisks []StorageAPI) (err error) {
-	// Initialize jbods.
-	var jbod = make([]string, len(storageDisks))
+// Return a slice of format, to be used to format uninitialized disks.
+func newFormatXLV1(diskCount int) []*formatXLV1 {
+	var jbod = make([]string, diskCount)
 
-	// Initialize formats.
-	var formats = make([]*formatConfigV1, len(storageDisks))
+	var formats = make([]*formatXLV1, diskCount)
 
-	// Initialize `format.json`.
-	for index, disk := range storageDisks {
-		if disk == nil {
-			continue
-		}
-		// Allocate format config.
-		formats[index] = &formatConfigV1{
-			Version: formatFileV1,
-			Format:  formatBackendXL,
-			XL: &xlFormat{
-				Version: xlFormatBackendV1,
-				Disk:    mustGetUUID(),
-			},
-		}
-		jbod[index] = formats[index].XL.Disk
+	for i := 0; i < diskCount; i++ {
+		format := &formatXLV1{}
+		format.Version = formatMetaVersionV1
+		format.Format = formatBackendXL
+		format.XL.Version = formatXLVersionV1
+		format.XL.Disk = mustGetUUID()
+		formats[i] = format
+		jbod[i] = formats[i].XL.Disk
 	}
 
 	// Update the jbod entries.
-	for index, disk := range storageDisks {
-		if disk == nil {
-			continue
-		}
-		// Save jbod.
-		formats[index].XL.JBOD = jbod
+	for i := 0; i < diskCount; i++ {
+		formats[i].XL.JBOD = jbod
 	}
 
+	return formats
+}
+
+// initFormatXL - save XL format configuration on all disks.
+func initFormatXL(storageDisks []StorageAPI) (err error) {
 	// Initialize meta volume, if volume already exists ignores it.
 	if err := initMetaVolume(storageDisks); err != nil {
 		return fmt.Errorf("Unable to initialize '.minio.sys' meta volume, %s", err)
 	}
 
 	// Save formats `format.json` across all disks.
-	return saveFormatXL(storageDisks, formats)
+	return saveFormatXL(storageDisks, newFormatXLV1(len(storageDisks)))
 }

cmd/format-xl_test.go

@@ -18,54 +18,46 @@ package cmd
 
 import (
 	"bytes"
-	"errors"
 	"os"
-	"path/filepath"
 	"testing"
 
-	errors2 "github.com/minio/minio/pkg/errors"
 	"github.com/minio/minio/pkg/hash"
-	"github.com/minio/minio/pkg/lock"
 )
 
 // generates a valid format.json for XL backend.
-func genFormatXLValid() []*formatConfigV1 {
+func genFormatXLValid() []*formatXLV1 {
 	jbod := make([]string, 8)
-	formatConfigs := make([]*formatConfigV1, 8)
+	formatConfigs := make([]*formatXLV1, 8)
 	for index := range jbod {
 		jbod[index] = mustGetUUID()
 	}
 	for index := range jbod {
-		formatConfigs[index] = &formatConfigV1{
-			Version: formatFileV1,
-			Format:  formatBackendXL,
-			XL: &xlFormat{
-				Version: xlFormatBackendV1,
-				Disk:    jbod[index],
-				JBOD:    jbod,
-			},
-		}
+		format := &formatXLV1{}
+		format.Version = formatMetaVersionV1
+		format.Format = formatBackendXL
+		format.XL.Version = formatXLVersionV1
+		format.XL.Disk = jbod[index]
+		format.XL.JBOD = jbod
+		formatConfigs[index] = format
 	}
 	return formatConfigs
 }
 
 // generates a invalid format.json version for XL backend.
-func genFormatXLInvalidVersion() []*formatConfigV1 {
+func genFormatXLInvalidVersion() []*formatXLV1 {
 	jbod := make([]string, 8)
-	formatConfigs := make([]*formatConfigV1, 8)
+	formatConfigs := make([]*formatXLV1, 8)
 	for index := range jbod {
 		jbod[index] = mustGetUUID()
 	}
 	for index := range jbod {
-		formatConfigs[index] = &formatConfigV1{
-			Version: formatFileV1,
-			Format:  formatBackendXL,
-			XL: &xlFormat{
-				Version: xlFormatBackendV1,
-				Disk:    jbod[index],
-				JBOD:    jbod,
-			},
-		}
+		format := &formatXLV1{}
+		format.Version = formatMetaVersionV1
+		format.Format = formatBackendXL
+		format.XL.Version = formatXLVersionV1
+		format.XL.Disk = jbod[index]
+		format.XL.JBOD = jbod
+		formatConfigs[index] = format
 	}
 	// Corrupt version numbers.
 	formatConfigs[0].Version = "2"
@@ -74,46 +66,42 @@ func genFormatXLInvalidVersion() []*formatConfigV1 {
 }
 
 // generates a invalid format.json version for XL backend.
-func genFormatXLInvalidFormat() []*formatConfigV1 {
+func genFormatXLInvalidFormat() []*formatXLV1 {
 	jbod := make([]string, 8)
-	formatConfigs := make([]*formatConfigV1, 8)
+	formatConfigs := make([]*formatXLV1, 8)
 	for index := range jbod {
 		jbod[index] = mustGetUUID()
 	}
 	for index := range jbod {
-		formatConfigs[index] = &formatConfigV1{
-			Version: formatFileV1,
-			Format:  formatBackendXL,
-			XL: &xlFormat{
-				Version: xlFormatBackendV1,
-				Disk:    jbod[index],
-				JBOD:    jbod,
-			},
+		format := &formatXLV1{}
+		format.Version = formatMetaVersionV1
+		format.Format = formatBackendXL
+		format.XL.Version = formatXLVersionV1
+		format.XL.Disk = jbod[index]
+		format.XL.JBOD = jbod
+		formatConfigs[index] = format
 	}
-	}
-	// Corrupt version numbers.
+	// Corrupt format.
 	formatConfigs[0].Format = "lx"
 	formatConfigs[3].Format = "lx"
 	return formatConfigs
 }
 
 // generates a invalid format.json version for XL backend.
-func genFormatXLInvalidXLVersion() []*formatConfigV1 {
+func genFormatXLInvalidXLVersion() []*formatXLV1 {
 	jbod := make([]string, 8)
-	formatConfigs := make([]*formatConfigV1, 8)
+	formatConfigs := make([]*formatXLV1, 8)
 	for index := range jbod {
 		jbod[index] = mustGetUUID()
 	}
 	for index := range jbod {
-		formatConfigs[index] = &formatConfigV1{
-			Version: formatFileV1,
-			Format:  formatBackendXL,
-			XL: &xlFormat{
-				Version: xlFormatBackendV1,
-				Disk:    jbod[index],
-				JBOD:    jbod,
-			},
-		}
+		format := &formatXLV1{}
+		format.Version = formatMetaVersionV1
+		format.Format = formatBackendXL
+		format.XL.Version = formatXLVersionV1
+		format.XL.Disk = jbod[index]
+		format.XL.JBOD = jbod
+		formatConfigs[index] = format
 	}
 	// Corrupt version numbers.
 	formatConfigs[0].XL.Version = "10"
@@ -121,51 +109,47 @@ func genFormatXLInvalidXLVersion() []*formatConfigV1 {
 	return formatConfigs
 }
 
-func genFormatFS() *formatConfigV1 {
-	return &formatConfigV1{
-		Version: formatFileV1,
-		Format:  formatBackendFS,
-	}
+func genFormatFS() *formatXLV1 {
+	format := &formatXLV1{}
+	format.Version = formatMetaVersionV1
+	format.Format = formatBackendFS
+	return format
 }
 
 // generates a invalid format.json version for XL backend.
-func genFormatXLInvalidJBODCount() []*formatConfigV1 {
+func genFormatXLInvalidJBODCount() []*formatXLV1 {
 	jbod := make([]string, 7)
-	formatConfigs := make([]*formatConfigV1, 8)
+	formatConfigs := make([]*formatXLV1, 8)
 	for index := range jbod {
 		jbod[index] = mustGetUUID()
 	}
 	for index := range jbod {
-		formatConfigs[index] = &formatConfigV1{
-			Version: formatFileV1,
-			Format:  formatBackendXL,
-			XL: &xlFormat{
-				Version: xlFormatBackendV1,
-				Disk:    jbod[index],
-				JBOD:    jbod,
-			},
-		}
+		format := &formatXLV1{}
+		format.Version = formatMetaVersionV1
+		format.Format = formatBackendXL
+		format.XL.Version = formatXLVersionV1
+		format.XL.Disk = jbod[index]
+		format.XL.JBOD = jbod
+		formatConfigs[index] = format
 	}
 	return formatConfigs
 }
 
 // generates a invalid format.json JBOD for XL backend.
-func genFormatXLInvalidJBOD() []*formatConfigV1 {
+func genFormatXLInvalidJBOD() []*formatXLV1 {
 	jbod := make([]string, 8)
-	formatConfigs := make([]*formatConfigV1, 8)
+	formatConfigs := make([]*formatXLV1, 8)
 	for index := range jbod {
 		jbod[index] = mustGetUUID()
 	}
 	for index := range jbod {
-		formatConfigs[index] = &formatConfigV1{
-			Version: formatFileV1,
-			Format:  formatBackendXL,
-			XL: &xlFormat{
-				Version: xlFormatBackendV1,
-				Disk:    jbod[index],
-				JBOD:    jbod,
-			},
-		}
+		format := &formatXLV1{}
+		format.Version = formatMetaVersionV1
+		format.Format = formatBackendXL
+		format.XL.Version = formatXLVersionV1
+		format.XL.Disk = jbod[index]
+		format.XL.JBOD = jbod
+		formatConfigs[index] = format
 	}
 	for index := range jbod {
 		jbod[index] = mustGetUUID()
@@ -177,22 +161,20 @@ func genFormatXLInvalidJBOD() []*formatConfigV1 {
 }
 
 // generates a invalid format.json Disk UUID for XL backend.
-func genFormatXLInvalidDisks() []*formatConfigV1 {
+func genFormatXLInvalidDisks() []*formatXLV1 {
 	jbod := make([]string, 8)
-	formatConfigs := make([]*formatConfigV1, 8)
+	formatConfigs := make([]*formatXLV1, 8)
 	for index := range jbod {
 		jbod[index] = mustGetUUID()
 	}
 	for index := range jbod {
-		formatConfigs[index] = &formatConfigV1{
-			Version: formatFileV1,
-			Format:  formatBackendXL,
-			XL: &xlFormat{
-				Version: xlFormatBackendV1,
-				Disk:    jbod[index],
-				JBOD:    jbod,
-			},
-		}
+		format := &formatXLV1{}
+		format.Version = formatMetaVersionV1
+		format.Format = formatBackendXL
+		format.XL.Version = formatXLVersionV1
+		format.XL.Disk = jbod[index]
+		format.XL.JBOD = jbod
+		formatConfigs[index] = format
 	}
 	// Make disk 5 and disk 8 have inconsistent disk uuid's.
 	formatConfigs[4].XL.Disk = mustGetUUID()
@@ -201,22 +183,20 @@ func genFormatXLInvalidDisks() []*formatConfigV1 {
 }
 
 // generates a invalid format.json Disk UUID in wrong order for XL backend.
-func genFormatXLInvalidDisksOrder() []*formatConfigV1 {
+func genFormatXLInvalidDisksOrder() []*formatXLV1 {
 	jbod := make([]string, 8)
-	formatConfigs := make([]*formatConfigV1, 8)
+	formatConfigs := make([]*formatXLV1, 8)
 	for index := range jbod {
 		jbod[index] = mustGetUUID()
 	}
 	for index := range jbod {
-		formatConfigs[index] = &formatConfigV1{
-			Version: formatFileV1,
-			Format:  formatBackendXL,
-			XL: &xlFormat{
-				Version: xlFormatBackendV1,
-				Disk:    jbod[index],
-				JBOD:    jbod,
-			},
-		}
+		format := &formatXLV1{}
+		format.Version = formatMetaVersionV1
+		format.Format = formatBackendXL
+		format.XL.Version = formatXLVersionV1
+		format.XL.Disk = jbod[index]
+		format.XL.JBOD = jbod
+		formatConfigs[index] = format
 	}
 	// Re order jbod for failure case.
 	var jbod1 = make([]string, 8)
@@ -459,7 +439,7 @@ func TestFormatXLReorderByInspection(t *testing.T) {
 //  - invalid JBOD
 //  - invalid Disk uuid
 func TestFormatXL(t *testing.T) {
-	formatInputCases := [][]*formatConfigV1{
+	formatInputCases := [][]*formatXLV1{
 		genFormatXLValid(),
 		genFormatXLInvalidVersion(),
 		genFormatXLInvalidFormat(),
@@ -470,7 +450,7 @@ func TestFormatXL(t *testing.T) {
 		genFormatXLInvalidDisksOrder(),
 	}
 	testCases := []struct {
-		formatConfigs []*formatConfigV1
+		formatConfigs []*formatXLV1
 		shouldPass    bool
 	}{
 		{
@@ -525,22 +505,20 @@ func TestSavedUUIDOrder(t *testing.T) {
 		shouldPass bool
 	}, 8)
 	jbod := make([]string, 8)
-	formatConfigs := make([]*formatConfigV1, 8)
+	formatConfigs := make([]*formatXLV1, 8)
 	for index := range jbod {
 		jbod[index] = mustGetUUID()
 		uuidTestCases[index].uuid = jbod[index]
 		uuidTestCases[index].shouldPass = true
 	}
 	for index := range jbod {
-		formatConfigs[index] = &formatConfigV1{
-			Version: formatFileV1,
-			Format:  formatBackendXL,
-			XL: &xlFormat{
-				Version: xlFormatBackendV1,
-				Disk:    jbod[index],
-				JBOD:    jbod,
-			},
-		}
+		format := &formatXLV1{}
+		format.Version = formatMetaVersionV1
+		format.Format = formatBackendXL
+		format.XL.Version = formatXLVersionV1
+		format.XL.Disk = jbod[index]
+		format.XL.JBOD = jbod
+		formatConfigs[index] = format
 	}
 	// Re order jbod for failure case.
 	var jbod1 = make([]string, 8)
@@ -653,172 +631,18 @@ func TestGenericFormatCheckXL(t *testing.T) {
 		t.Fatalf("Should fail here")
 	}
 	errs = []error{nil}
-	if err := genericFormatCheckXL([]*formatConfigV1{genFormatFS()}, errs); err == nil {
+	format := &formatXLV1{}
+	format.Version = formatMetaVersionV1
+	format.Format = formatBackendFS
+	if err := genericFormatCheckXL([]*formatXLV1{format}, errs); err == nil {
 		t.Fatalf("Should fail here")
 	}
 	errs = []error{errFaultyDisk}
-	if err := genericFormatCheckXL([]*formatConfigV1{genFormatFS()}, errs); err == nil {
+	if err := genericFormatCheckXL([]*formatXLV1{format}, errs); err == nil {
 		t.Fatalf("Should fail here")
 	}
 }
 
-// TestFSCheckFormatFSErr - test loadFormatFS loading older format.
-func TestFSCheckFormatFSErr(t *testing.T) {
-	// Prepare for testing
-	disk := filepath.Join(globalTestTmpDir, "minio-"+nextSuffix())
-	defer os.RemoveAll(disk)
-
-	// Assign a new UUID.
-	uuid := mustGetUUID()
-
-	// Initialize meta volume, if volume already exists ignores it.
-	if err := initMetaVolumeFS(disk, uuid); err != nil {
-		t.Fatal(err)
-	}
-
-	testCases := []struct {
-		format         *formatConfigV1
-		formatWriteErr error
-		formatCheckErr error
-		shouldPass     bool
-	}{
-		{
-			format: &formatConfigV1{
-				Version: formatFileV1,
-				Format:  formatBackendFS,
-				FS: &fsFormat{
-					Version: fsFormatBackendV1,
-				},
-			},
-			formatCheckErr: nil,
-			shouldPass:     true,
-		},
-		{
-			format: &formatConfigV1{
-				Version: formatFileV1,
-				Format:  formatBackendFS,
-				FS: &fsFormat{
-					Version: "10",
-				},
-			},
-			formatCheckErr: errors.New("Unknown backend FS format version '10'"),
-			shouldPass:     false,
-		},
-		{
-			format: &formatConfigV1{
-				Version: formatFileV1,
-				Format:  "garbage",
-				FS: &fsFormat{
-					Version: fsFormatBackendV1,
-				},
-			},
-			formatCheckErr: errors.New("FS backend format required. Found 'garbage'"),
-		},
-		{
-			format: &formatConfigV1{
-				Version: "-1",
-				Format:  formatBackendFS,
-				FS: &fsFormat{
-					Version: fsFormatBackendV1,
-				},
-			},
-			formatCheckErr: errors.New("Unknown format file version '-1'"),
-		},
-	}
-
-	fsFormatPath := pathJoin(disk, minioMetaBucket, formatConfigFile)
-	for i, testCase := range testCases {
-		lk, err := lock.LockedOpenFile((fsFormatPath), os.O_RDWR|os.O_CREATE, 0600)
-		if err != nil {
-			t.Fatal(err)
-		}
-		_, err = testCase.format.WriteTo(lk)
-		lk.Close()
-		if err != nil {
-			t.Fatalf("Test %d: Expected nil, got %s", i+1, err)
-		}
-
-		lk, err = lock.LockedOpenFile((fsFormatPath), os.O_RDWR|os.O_CREATE, 0600)
-		if err != nil {
-			t.Fatal(err)
-		}
-
-		formatCfg := &formatConfigV1{}
-		_, err = formatCfg.ReadFrom(lk)
-		lk.Close()
-		if err != nil {
-			t.Fatal(err)
-		}
-		err = formatCfg.CheckFS()
-		if err != nil && testCase.shouldPass {
-			t.Errorf("Test %d: Should not fail with unexpected %s, expected nil", i+1, err)
-		}
-		if err == nil && !testCase.shouldPass {
-			t.Errorf("Test %d: Should fail with expected %s, got nil", i+1, testCase.formatCheckErr)
-		}
-		if err != nil && !testCase.shouldPass {
-			if errors2.Cause(err).Error() != testCase.formatCheckErr.Error() {
-				t.Errorf("Test %d: Should fail with expected %s, got %s", i+1, testCase.formatCheckErr, err)
-			}
-		}
-	}
-}
-
-// TestFSCheckFormatFS - test loadFormatFS with healty and faulty disks
-func TestFSCheckFormatFS(t *testing.T) {
-	// Prepare for testing
-	disk := filepath.Join(globalTestTmpDir, "minio-"+nextSuffix())
-	defer os.RemoveAll(disk)
-
-	// Assign a new UUID.
-	uuid := mustGetUUID()
-
-	// Initialize meta volume, if volume already exists ignores it.
-	if err := initMetaVolumeFS(disk, uuid); err != nil {
-		t.Fatal(err)
-	}
-
-	fsFormatPath := pathJoin(disk, minioMetaBucket, formatConfigFile)
-	lk, err := lock.LockedOpenFile((fsFormatPath), os.O_RDWR|os.O_CREATE, 0600)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	format := newFSFormatV1()
-	_, err = format.WriteTo(lk)
-	lk.Close()
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	// Loading corrupted format file
-	file, err := os.OpenFile((fsFormatPath), os.O_APPEND|os.O_WRONLY|os.O_CREATE, 0666)
-	if err != nil {
-		t.Fatal("Should not fail here", err)
-	}
-	file.Write([]byte{'b'})
-	file.Close()
-
-	lk, err = lock.LockedOpenFile((fsFormatPath), os.O_RDWR|os.O_CREATE, 0600)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	format = &formatConfigV1{}
-	_, err = format.ReadFrom(lk)
-	lk.Close()
-	if err == nil {
-		t.Fatal("Should return an error here")
-	}
-
-	// Loading format file from disk not found.
-	os.RemoveAll(disk)
-	_, err = lock.LockedOpenFile((fsFormatPath), os.O_RDONLY, 0600)
-	if err != nil && !os.IsNotExist(err) {
-		t.Fatal("Should return 'format.json' does not exist, but got", err)
-	}
-}
-
 func TestLoadFormatXLErrs(t *testing.T) {
 	nDisks := 16
 	fsDirs, err := getRandomDisks(nDisks)

cmd/fs-v1-metadata.go

@@ -24,7 +24,6 @@ import (
 	pathutil "path"
 	"sort"
 	"strings"
-	"time"
 
 	"github.com/minio/minio/pkg/errors"
 	"github.com/minio/minio/pkg/lock"
@@ -269,97 +268,6 @@ func newFSMetaV1() (fsMeta fsMetaV1) {
 	return fsMeta
 }
 
-// Check if disk has already a valid format, holds a read lock and
-// upon success returns it to the caller to be closed.
-func checkLockedValidFormatFS(fsPath string) (*lock.RLockedFile, error) {
-	fsFormatPath := pathJoin(fsPath, minioMetaBucket, formatConfigFile)
-
-	rlk, err := lock.RLockedOpenFile((fsFormatPath))
-	if err != nil {
-		if os.IsNotExist(err) {
-			// If format.json not found then
-			// its an unformatted disk.
-			return nil, errors.Trace(errUnformattedDisk)
-		}
-		return nil, errors.Trace(err)
-	}
-
-	var format = &formatConfigV1{}
-	if err = format.LoadFormat(rlk.LockedFile); err != nil {
-		rlk.Close()
-		return nil, err
-	}
-
-	// Check format FS.
-	if err = format.CheckFS(); err != nil {
-		rlk.Close()
-		return nil, err
-	}
-
-	//  Always return read lock here and should be closed by the caller.
-	return rlk, errors.Trace(err)
-}
-
-// Creates a new format.json if unformatted.
-func createFormatFS(fsPath string) error {
-	fsFormatPath := pathJoin(fsPath, minioMetaBucket, formatConfigFile)
-
-	// Attempt a write lock on formatConfigFile `format.json`
-	// file stored in minioMetaBucket(.minio.sys) directory.
-	lk, err := lock.TryLockedOpenFile((fsFormatPath), os.O_RDWR|os.O_CREATE, 0600)
-	if err != nil {
-		return errors.Trace(err)
-	}
-	// Close the locked file upon return.
-	defer lk.Close()
-
-	// Load format on disk, checks if we are unformatted
-	// writes the new format.json
-	var format = &formatConfigV1{}
-	err = format.LoadFormat(lk)
-	if errors.Cause(err) == errUnformattedDisk {
-		_, err = newFSFormat().WriteTo(lk)
-		return err
-	}
-	return err
-}
-
-func initFormatFS(fsPath string) (rlk *lock.RLockedFile, err error) {
-	// This loop validates format.json by holding a read lock and
-	// proceeds if disk unformatted to hold non-blocking WriteLock
-	// If for some reason non-blocking WriteLock fails and the error
-	// is lock.ErrAlreadyLocked i.e some other process is holding a
-	// lock we retry in the loop again.
-	for {
-		// Validate the `format.json` for expected values.
-		rlk, err = checkLockedValidFormatFS(fsPath)
-		switch {
-		case err == nil:
-			// Holding a read lock ensures that any write lock operation
-			// is blocked if attempted in-turn avoiding corruption on
-			// the backend disk.
-			return rlk, nil
-		case errors.Cause(err) == errUnformattedDisk:
-			if err = createFormatFS(fsPath); err != nil {
-				// Existing write locks detected.
-				if errors.Cause(err) == lock.ErrAlreadyLocked {
-					// Lock already present, sleep and attempt again.
-					time.Sleep(100 * time.Millisecond)
-					continue
-				}
-
-				// Unexpected error, return.
-				return nil, err
-			}
-
-			// Loop will continue to attempt a read-lock on `format.json`.
-		default:
-			// Unhandled error return.
-			return nil, err
-		}
-	}
-}
-
 // Return if the part info in uploadedParts and CompleteParts are same.
 func isPartsSame(uploadedParts []objectPartInfo, CompleteParts []CompletePart) bool {
 	if len(uploadedParts) != len(CompleteParts) {

cmd/utils.go

@@ -263,3 +263,11 @@ func NewCustomHTTPTransport() http.RoundTripper {
 		DisableCompression:    true,
 	}
 }
+
+// Load the json (typically from disk file).
+func jsonLoadFromSeeker(r io.ReadSeeker, data interface{}) error {
+	if _, err := r.Seek(0, io.SeekStart); err != nil {
+		return err
+	}
+	return json.NewDecoder(r).Decode(data)
+}

cmd/utils_test.go

@@ -17,6 +17,7 @@
 package cmd
 
 import (
+	"bytes"
 	"encoding/json"
 	"errors"
 	"io/ioutil"
@@ -363,3 +364,19 @@ func TestContains(t *testing.T) {
 		}
 	}
 }
+
+// Test jsonLoadFromSeeker.
+func TestJSONLoadFromSeeker(t *testing.T) {
+	format := newFormatFSV1()
+	b, err := json.Marshal(format)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var gotFormat formatFSV1
+	if err = jsonLoadFromSeeker(bytes.NewReader(b), &gotFormat); err != nil {
+		t.Fatal(err)
+	}
+	if *format != gotFormat {
+		t.Fatal("jsonLoadFromSeeker() failed to decode json")
+	}
+}