fs: Add safe locking semantics for format.json (#4523)

This patch also reverts previous changes which were
merged for migration to the newer disk format. We will
be bringing these changes in subsequent releases. But
we wish to add protection in this release such that
future release migrations are protected.

Revert "fs: Migration should handle bucketConfigs as regular objects. (#4482)"
This reverts commit 976870a391.

Revert "fs: Migrate object metadata to objects directory. (#4195)"
This reverts commit 76f4f20609.

cmd/format-config-v1.go

@@ -33,6 +33,15 @@ type fsFormat struct {
 	Version string `json:"version"`
 }
 
+// FS format version strings.
+const (
+	// 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 {
 	Version string `json:"version"` // Version of 'xl' format.
@@ -42,6 +51,15 @@ type xlFormat struct {
 	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.
@@ -51,6 +69,68 @@ type formatConfigV1 struct {
 	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 errorCause(err) == io.EOF {
+		// No data on disk `format.json` still empty
+		// treat it as unformatted disk.
+		return traceError(errUnformattedDisk)
+	}
+	return err
+}
+
 func (f *formatConfigV1) WriteTo(lk *lock.LockedFile) (n int64, err error) {
 	// Serialize to prepare to write to disk.
 	var fbytes []byte
@@ -88,6 +168,21 @@ func (f *formatConfigV1) ReadFrom(lk *lock.LockedFile) (n int64, err error) {
 	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,
+		},
+	}
+}
+
 /*
 
 All disks online
@@ -811,10 +906,10 @@ func loadFormatXL(bootstrapDisks []StorageAPI, readQuorum int) (disks []StorageA
 
 func checkFormatXLValue(formatXL *formatConfigV1) error {
 	// Validate format version and format type.
-	if formatXL.Version != "1" {
+	if formatXL.Version != formatFileV1 {
 		return fmt.Errorf("Unsupported version of backend format [%s] found", formatXL.Version)
 	}
-	if formatXL.Format != "xl" {
+	if formatXL.Format != formatBackendXL {
 		return fmt.Errorf("Unsupported backend format [%s] found", formatXL.Format)
 	}
 	if formatXL.XL.Version != "1" {
@@ -916,10 +1011,10 @@ func initFormatXL(storageDisks []StorageAPI) (err error) {
 		}
 		// Allocate format config.
 		formats[index] = &formatConfigV1{
-			Version: "1",
+			Version: formatFileV1,
-			Format:  "xl",
+			Format:  formatBackendXL,
 			XL: &xlFormat{
-				Version: "1",
+				Version: xlFormatBackendV1,
 				Disk:    mustGetUUID(),
 			},
 		}

cmd/format-config-v1_test.go

@@ -18,7 +18,12 @@ package cmd
 
 import (
 	"bytes"
+	"errors"
+	"os"
+	"path/filepath"
 	"testing"
+
+	"github.com/minio/minio/pkg/lock"
 )
 
 // generates a valid format.json for XL backend.
@@ -30,10 +35,10 @@ func genFormatXLValid() []*formatConfigV1 {
 	}
 	for index := range jbod {
 		formatConfigs[index] = &formatConfigV1{
-			Version: "1",
+			Version: formatFileV1,
-			Format:  "xl",
+			Format:  formatBackendXL,
 			XL: &xlFormat{
-				Version: "1",
+				Version: xlFormatBackendV1,
 				Disk:    jbod[index],
 				JBOD:    jbod,
 			},
@@ -51,10 +56,10 @@ func genFormatXLInvalidVersion() []*formatConfigV1 {
 	}
 	for index := range jbod {
 		formatConfigs[index] = &formatConfigV1{
-			Version: "1",
+			Version: formatFileV1,
-			Format:  "xl",
+			Format:  formatBackendXL,
 			XL: &xlFormat{
-				Version: "1",
+				Version: xlFormatBackendV1,
 				Disk:    jbod[index],
 				JBOD:    jbod,
 			},
@@ -75,10 +80,10 @@ func genFormatXLInvalidFormat() []*formatConfigV1 {
 	}
 	for index := range jbod {
 		formatConfigs[index] = &formatConfigV1{
-			Version: "1",
+			Version: formatFileV1,
-			Format:  "xl",
+			Format:  formatBackendXL,
 			XL: &xlFormat{
-				Version: "1",
+				Version: xlFormatBackendV1,
 				Disk:    jbod[index],
 				JBOD:    jbod,
 			},
@@ -99,10 +104,10 @@ func genFormatXLInvalidXLVersion() []*formatConfigV1 {
 	}
 	for index := range jbod {
 		formatConfigs[index] = &formatConfigV1{
-			Version: "1",
+			Version: formatFileV1,
-			Format:  "xl",
+			Format:  formatBackendXL,
 			XL: &xlFormat{
-				Version: "1",
+				Version: xlFormatBackendV1,
 				Disk:    jbod[index],
 				JBOD:    jbod,
 			},
@@ -116,8 +121,8 @@ func genFormatXLInvalidXLVersion() []*formatConfigV1 {
 
 func genFormatFS() *formatConfigV1 {
 	return &formatConfigV1{
-		Version: "1",
+		Version: formatFileV1,
-		Format:  "fs",
+		Format:  formatBackendFS,
 	}
 }
 
@@ -130,10 +135,10 @@ func genFormatXLInvalidJBODCount() []*formatConfigV1 {
 	}
 	for index := range jbod {
 		formatConfigs[index] = &formatConfigV1{
-			Version: "1",
+			Version: formatFileV1,
-			Format:  "xl",
+			Format:  formatBackendXL,
 			XL: &xlFormat{
-				Version: "1",
+				Version: xlFormatBackendV1,
 				Disk:    jbod[index],
 				JBOD:    jbod,
 			},
@@ -151,10 +156,10 @@ func genFormatXLInvalidJBOD() []*formatConfigV1 {
 	}
 	for index := range jbod {
 		formatConfigs[index] = &formatConfigV1{
-			Version: "1",
+			Version: formatFileV1,
-			Format:  "xl",
+			Format:  formatBackendXL,
 			XL: &xlFormat{
-				Version: "1",
+				Version: xlFormatBackendV1,
 				Disk:    jbod[index],
 				JBOD:    jbod,
 			},
@@ -178,10 +183,10 @@ func genFormatXLInvalidDisks() []*formatConfigV1 {
 	}
 	for index := range jbod {
 		formatConfigs[index] = &formatConfigV1{
-			Version: "1",
+			Version: formatFileV1,
-			Format:  "xl",
+			Format:  formatBackendXL,
 			XL: &xlFormat{
-				Version: "1",
+				Version: xlFormatBackendV1,
 				Disk:    jbod[index],
 				JBOD:    jbod,
 			},
@@ -202,10 +207,10 @@ func genFormatXLInvalidDisksOrder() []*formatConfigV1 {
 	}
 	for index := range jbod {
 		formatConfigs[index] = &formatConfigV1{
-			Version: "1",
+			Version: formatFileV1,
-			Format:  "xl",
+			Format:  formatBackendXL,
 			XL: &xlFormat{
-				Version: "1",
+				Version: xlFormatBackendV1,
 				Disk:    jbod[index],
 				JBOD:    jbod,
 			},
@@ -240,10 +245,10 @@ func prepareFormatXLHealFreshDisks(obj ObjectLayer) ([]StorageAPI, error) {
 	// Remove the content of export dir 10 but preserve .minio.sys because it is automatically
 	// created when minio starts
 	for i := 3; i <= 5; i++ {
-		if err = xl.storageDisks[i].DeleteFile(".minio.sys", "format.json"); err != nil {
+		if err = xl.storageDisks[i].DeleteFile(minioMetaBucket, formatConfigFile); err != nil {
 			return []StorageAPI{}, err
 		}
-		if err = xl.storageDisks[i].DeleteFile(".minio.sys", "tmp"); err != nil {
+		if err = xl.storageDisks[i].DeleteFile(minioMetaBucket, "tmp"); err != nil {
 			return []StorageAPI{}, err
 		}
 		if err = xl.storageDisks[i].DeleteFile(bucket, object+"/xl.json"); err != nil {
@@ -361,19 +366,19 @@ func TestFormatXLHealCorruptedDisks(t *testing.T) {
 	}
 
 	// Now, remove two format files.. Load them and reorder
-	if err = xl.storageDisks[3].DeleteFile(".minio.sys", "format.json"); err != nil {
+	if err = xl.storageDisks[3].DeleteFile(minioMetaBucket, formatConfigFile); err != nil {
 		t.Fatal(err)
 	}
-	if err = xl.storageDisks[11].DeleteFile(".minio.sys", "format.json"); err != nil {
+	if err = xl.storageDisks[11].DeleteFile(minioMetaBucket, formatConfigFile); err != nil {
 		t.Fatal(err)
 	}
 
 	// Remove the content of export dir 10 but preserve .minio.sys because it is automatically
 	// created when minio starts
-	if err = xl.storageDisks[10].DeleteFile(".minio.sys", "format.json"); err != nil {
+	if err = xl.storageDisks[10].DeleteFile(minioMetaBucket, formatConfigFile); err != nil {
 		t.Fatal(err)
 	}
-	if err = xl.storageDisks[10].DeleteFile(".minio.sys", "tmp"); err != nil {
+	if err = xl.storageDisks[10].DeleteFile(minioMetaBucket, "tmp"); err != nil {
 		t.Fatal(err)
 	}
 	if err = xl.storageDisks[10].DeleteFile(bucket, object+"/xl.json"); err != nil {
@@ -434,10 +439,10 @@ func TestFormatXLReorderByInspection(t *testing.T) {
 	}
 
 	// Now, remove two format files.. Load them and reorder
-	if err = xl.storageDisks[3].DeleteFile(".minio.sys", "format.json"); err != nil {
+	if err = xl.storageDisks[3].DeleteFile(minioMetaBucket, formatConfigFile); err != nil {
 		t.Fatal(err)
 	}
-	if err = xl.storageDisks[5].DeleteFile(".minio.sys", "format.json"); err != nil {
+	if err = xl.storageDisks[5].DeleteFile(minioMetaBucket, formatConfigFile); err != nil {
 		t.Fatal(err)
 	}
 
@@ -555,10 +560,10 @@ func TestSavedUUIDOrder(t *testing.T) {
 	}
 	for index := range jbod {
 		formatConfigs[index] = &formatConfigV1{
-			Version: "1",
+			Version: formatFileV1,
-			Format:  "xl",
+			Format:  formatBackendXL,
 			XL: &xlFormat{
-				Version: "1",
+				Version: xlFormatBackendV1,
 				Disk:    jbod[index],
 				JBOD:    jbod,
 			},
@@ -682,6 +687,163 @@ func TestGenericFormatCheckXL(t *testing.T) {
 	}
 }
 
+// TestFSCheckFormatFSErr - test loadFormatFS loading older format.
+func TestFSCheckFormatFSErr(t *testing.T) {
+	// Prepare for testing
+	disk := filepath.Join(globalTestTmpDir, "minio-"+nextSuffix())
+	defer 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(preparePath(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(preparePath(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 errorCause(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 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(preparePath(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(preparePath(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(preparePath(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.
+	removeAll(disk)
+	_, err = lock.LockedOpenFile(preparePath(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)
@@ -749,7 +911,7 @@ func TestLoadFormatXLErrs(t *testing.T) {
 
 	// disks 0..10 returns unformatted disk
 	for i := 0; i <= 10; i++ {
-		if err = xl.storageDisks[i].DeleteFile(".minio.sys", "format.json"); err != nil {
+		if err = xl.storageDisks[i].DeleteFile(minioMetaBucket, formatConfigFile); err != nil {
 			t.Fatal(err)
 		}
 	}
@@ -873,7 +1035,7 @@ func TestHealFormatXLCorruptedDisksErrs(t *testing.T) {
 	}
 	xl = obj.(*xlObjects)
 	for i := 0; i <= 15; i++ {
-		if err = xl.storageDisks[i].DeleteFile(".minio.sys", "format.json"); err != nil {
+		if err = xl.storageDisks[i].DeleteFile(minioMetaBucket, formatConfigFile); err != nil {
 			t.Fatal(err)
 		}
 	}
@@ -894,7 +1056,7 @@ func TestHealFormatXLCorruptedDisksErrs(t *testing.T) {
 	}
 	xl = obj.(*xlObjects)
 	for i := 0; i <= 15; i++ {
-		if err = xl.storageDisks[i].AppendFile(".minio.sys", "format.json", []byte("corrupted data")); err != nil {
+		if err = xl.storageDisks[i].AppendFile(minioMetaBucket, formatConfigFile, []byte("corrupted data")); err != nil {
 			t.Fatal(err)
 		}
 	}
@@ -998,7 +1160,7 @@ func TestHealFormatXLFreshDisksErrs(t *testing.T) {
 	}
 	xl = obj.(*xlObjects)
 	for i := 0; i <= 15; i++ {
-		if err = xl.storageDisks[i].DeleteFile(".minio.sys", "format.json"); err != nil {
+		if err = xl.storageDisks[i].DeleteFile(minioMetaBucket, formatConfigFile); err != nil {
 			t.Fatal(err)
 		}
 	}

cmd/fs-v1-helpers.go

@@ -134,6 +134,7 @@ func fsStat(statLoc string) (os.FileInfo, error) {
 	if err != nil {
 		return nil, traceError(err)
 	}
+
 	return fi, nil
 }
 
@@ -142,12 +143,13 @@ func fsStat(statLoc string) (os.FileInfo, error) {
 func fsStatDir(statDir string) (os.FileInfo, error) {
 	fi, err := fsStat(statDir)
 	if err != nil {
-		if os.IsNotExist(errorCause(err)) {
+		err = errorCause(err)
+		if os.IsNotExist(err) {
 			return nil, traceError(errVolumeNotFound)
-		} else if os.IsPermission(errorCause(err)) {
+		} else if os.IsPermission(err) {
 			return nil, traceError(errVolumeAccessDenied)
 		}
-		return nil, err
+		return nil, traceError(err)
 	}
 
 	if !fi.IsDir() {
@@ -161,16 +163,17 @@ func fsStatDir(statDir string) (os.FileInfo, error) {
 func fsStatFile(statFile string) (os.FileInfo, error) {
 	fi, err := fsStat(statFile)
 	if err != nil {
-		if os.IsNotExist(errorCause(err)) {
+		err = errorCause(err)
+		if os.IsNotExist(err) {
 			return nil, traceError(errFileNotFound)
-		} else if os.IsPermission(errorCause(err)) {
+		} else if os.IsPermission(err) {
 			return nil, traceError(errFileAccessDenied)
-		} else if isSysErrNotDir(errorCause(err)) {
+		} else if isSysErrNotDir(err) {
 			return nil, traceError(errFileAccessDenied)
-		} else if isSysErrPathNotFound(errorCause(err)) {
+		} else if isSysErrPathNotFound(err) {
 			return nil, traceError(errFileNotFound)
 		}
-		return nil, err
+		return nil, traceError(err)
 	}
 	if fi.IsDir() {
 		return nil, traceError(errFileAccessDenied)

cmd/fs-v1-metadata.go

@@ -18,16 +18,14 @@ package cmd
 
 import (
 	"encoding/json"
-	"errors"
-	"fmt"
 	"io"
 	"io/ioutil"
 	"os"
 	pathutil "path"
 	"sort"
 	"strings"
+	"time"
 
-	"github.com/minio/minio-go/pkg/set"
 	"github.com/minio/minio/pkg/lock"
 	"github.com/minio/minio/pkg/mimedb"
 	"github.com/tidwall/gjson"
@@ -37,8 +35,6 @@ import (
 const (
 	// fs.json object metadata.
 	fsMetaJSONFile = "fs.json"
-	// format.json FS format metadata.
-	fsFormatJSONFile = "format.json"
 )
 
 // FS metadata constants.
@@ -52,9 +48,6 @@ const (
 	// FS backend meta format.
 	fsMetaFormat = "fs"
 
-	// FS backend format version.
-	fsFormatVersion = fsFormatV2
-
 	// Add more constants here.
 )
 
@@ -257,14 +250,6 @@ func (m *fsMetaV1) ReadFrom(lk *lock.LockedFile) (n int64, err error) {
 	return int64(len(fsMetaBuf)), nil
 }
 
-// FS format version strings.
-const (
-	fsFormatV1 = "1" // Previous format.
-	fsFormatV2 = "2" // Current format.
-	// Proceed to add "3" when we
-	// change the backend format in future.
-)
-
 // newFSMetaV1 - initializes new fsMetaV1.
 func newFSMetaV1() (fsMeta fsMetaV1) {
 	fsMeta = fsMetaV1{}
@@ -274,167 +259,107 @@ func newFSMetaV1() (fsMeta fsMetaV1) {
 	return fsMeta
 }
 
-// newFSFormatV2 - initializes new formatConfigV1 with FS format version 2.
+// Check if disk has already a valid format, holds a read lock and
-func newFSFormatV2() (format *formatConfigV1) {
+// upon success returns it to the caller to be closed.
-	return &formatConfigV1{
+func checkLockedValidFormatFS(fsPath string) (*lock.RLockedFile, error) {
-		Version: "1",
+	fsFormatPath := pathJoin(fsPath, minioMetaBucket, formatConfigFile)
-		Format:  "fs",
-		FS: &fsFormat{
-			Version: fsFormatV2,
-		},
-	}
-}
 
-// Checks if input format is version 1 and 2.
+	rlk, err := lock.RLockedOpenFile(preparePath(fsFormatPath))
-func isFSValidFormat(formatCfg *formatConfigV1) bool {
+	if err != nil {
-	// Supported format versions.
+		if os.IsNotExist(err) {
-	var supportedFormatVersions = []string{
+			// If format.json not found then
-		fsFormatV1,
+			// its an unformatted disk.
-		fsFormatV2,
+			return nil, traceError(errUnformattedDisk)
-		// New supported versions here.
-	}
-
-	// Check for supported format versions.
-	for _, version := range supportedFormatVersions {
-		if formatCfg.FS.Version == version {
-			return true
 		}
+		return nil, traceError(err)
 	}
-	return false
+
+	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, traceError(err)
 }
 
-// errFSFormatOld- old fs format.
+// Writes the new format.json if unformatted,
-var errFSFormatOld = errors.New("old FS format found")
+// otherwise closes the input locked file
+// and returns any error.
+func writeFormatFS(lk *lock.LockedFile) error {
+	// Close the locked file upon return.
+	defer lk.Close()
 
-// Checks if the loaded `format.json` is valid and
+	// Load format on disk, checks if we are unformatted
-// is expected to be of the requested version.
+	// writes the new format.json
-func checkFormatFS(format *formatConfigV1, formatVersion string) error {
+	var format = &formatConfigV1{}
-	if format == nil {
+	err := format.LoadFormat(lk)
-		return errUnexpected
+	if errorCause(err) == errUnformattedDisk {
-	}
+		_, err = newFSFormat().WriteTo(lk)
-
-	// Validate if we have the same format.
-	if format.Format != "fs" {
-		return fmt.Errorf("Unable to recognize backend format, Disk is not in FS format. %s", format.Format)
-	}
-
-	// Check if format is currently supported.
-	if !isFSValidFormat(format) {
-		return errCorruptedFormat
-	}
-
-	// Check for format version is current.
-	if format.FS.Version != formatVersion {
-		return errFSFormatOld
-	}
-
-	return nil
-}
-
-// This is just kept as reference, there is no sanity
-// check for FS format in version "1".
-func checkFormatSanityFSV1(fsPath string) error {
-	return nil
-}
-
-// Check for sanity of FS format in version "2".
-func checkFormatSanityFSV2(fsPath string) error {
-	buckets, err := readDir(pathJoin(fsPath, minioMetaBucket, bucketConfigPrefix))
-	if err != nil && err != errFileNotFound {
 		return err
 	}
-
-	// Attempt to validate all the buckets have a sanitized backend.
-	for _, bucket := range buckets {
-		entries, rerr := readDir(pathJoin(fsPath, minioMetaBucket, bucketConfigPrefix, bucket))
-		if rerr != nil {
-			return rerr
-		}
-
-		var expectedConfigs = append(bucketMetadataConfigs, objectMetaPrefix+"/")
-		entriesSet := set.CreateStringSet(entries...)
-		expectedConfigsSet := set.CreateStringSet(expectedConfigs...)
-
-		// Entries found shouldn't be more than total
-		// expected config directories, files.
-		if len(entriesSet) > len(expectedConfigsSet) {
-			return errCorruptedFormat
-		}
-
-		// Look for the difference between entries and the
-		// expected config set, resulting entries if they
-		// intersect with original entries set we know
-		// that the backend has unexpected files.
-		if !entriesSet.Difference(expectedConfigsSet).IsEmpty() {
-			return errCorruptedFormat
-		}
-	}
-	return nil
-}
-
-// Check for sanity of FS format for a given version.
-func checkFormatSanityFS(fsPath string, fsFormatVersion string) (err error) {
-	switch fsFormatVersion {
-	case fsFormatV2:
-		err = checkFormatSanityFSV2(fsPath)
-	default:
-		err = errCorruptedFormat
-	}
 	return err
 }
 
-// Initializes a new `format.json` if not present, validates `format.json`
-// if already present and migrates to newer version if necessary. Returns
-// the final format version.
 func initFormatFS(fsPath, fsUUID string) (err error) {
-	fsFormatPath := pathJoin(fsPath, minioMetaBucket, fsFormatJSONFile)
+	fsFormatPath := pathJoin(fsPath, minioMetaBucket, formatConfigFile)
 
-	// fsFormatJSONFile - format.json file stored in minioMetaBucket(.minio.sys) directory.
+	// Once the filesystem has initialized hold the read lock for
-	lk, err := lock.LockedOpenFile(preparePath(fsFormatPath), os.O_RDWR|os.O_CREATE, 0600)
+	// the life time of the server. This is done to ensure that under
-	if err != nil {
+	// shared backend mode for FS, remote servers do not migrate
-		return traceError(err)
+	// or cause changes on backend format.
-	}
-	defer lk.Close()
 
-	var format = &formatConfigV1{}
+	// This loop validates format.json by holding a read lock and
-	_, err = format.ReadFrom(lk)
+	// proceeds if disk unformatted to hold non-blocking WriteLock
-	// For all unexpected errors, we return.
+	// If for some reason non-blocking WriteLock fails and the error
-	if err != nil && errorCause(err) != io.EOF {
+	// is lock.ErrAlreadyLocked i.e some other process is holding a
-		return traceError(fmt.Errorf("Unable to load 'format.json', %s", err))
+	// lock we retry in the loop again.
-	}
+	var rlk *lock.RLockedFile
+	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.
+			_ = rlk // Hold the lock on `format.json` until server dies.
+			return nil
+		case errorCause(err) == errUnformattedDisk:
+			// Attempt a write lock on formatConfigFile `format.json`
+			// file stored in minioMetaBucket(.minio.sys) directory.
+			var lk *lock.LockedFile
+			lk, err = lock.TryLockedOpenFile(preparePath(fsFormatPath), os.O_RDWR|os.O_CREATE, 0600)
+			if err != nil {
+				// Existing write locks detected.
+				if err == lock.ErrAlreadyLocked {
+					// Lock already present, sleep and attempt again.
+					time.Sleep(100 * time.Millisecond)
+					continue
+				}
 
-	// If we couldn't read anything, The disk is unformatted.
+				// Unexpected error, return.
-	if errorCause(err) == io.EOF {
+				return traceError(err)
-		err = errUnformattedDisk
+			}
-		format = newFSFormatV2()
+
-	} else {
+			// Write new format.
-		// Validate loaded `format.json`.
+			if err = writeFormatFS(lk); err != nil {
-		err = checkFormatFS(format, fsFormatVersion)
+				return err
-		if err != nil && err != errFSFormatOld {
+			}
-			return traceError(fmt.Errorf("Unable to validate 'format.json', %s", err))
+			// Loop will continue to attempt a
+			// read-lock on `format.json` .
+		default:
+			// Unhandled error return.
+			return err
 		}
 	}
-
-	// Disk is in old format migrate object metadata.
-	if err == errFSFormatOld {
-		if merr := migrateFSObject(fsPath, fsUUID); merr != nil {
-			return merr
-		}
-
-		// Initialize format v2.
-		format = newFSFormatV2()
-	}
-
-	// Rewrite or write format.json depending on if disk
-	// unformatted and if format is old.
-	if err == errUnformattedDisk || err == errFSFormatOld {
-		if _, err = format.WriteTo(lk); err != nil {
-			return traceError(fmt.Errorf("Unable to initialize 'format.json', %s", err))
-		}
-	}
-
-	// Check for sanity.
-	return checkFormatSanityFS(fsPath, format.FS.Version)
 }
 
 // Return if the part info in uploadedParts and completeParts are same.

cmd/fs-v1-metadata_test.go

@@ -58,7 +58,7 @@ func TestReadFSMetadata(t *testing.T) {
 	}
 
 	// Construct the full path of fs.json
-	fsPath := pathJoin(bucketMetaPrefix, bucketName, objectMetaPrefix, objectName, "fs.json")
+	fsPath := pathJoin(bucketMetaPrefix, bucketName, objectName, "fs.json")
 	fsPath = pathJoin(fs.fsPath, minioMetaBucket, fsPath)
 
 	rlk, err := fs.rwPool.Open(fsPath)
@@ -95,7 +95,7 @@ func TestWriteFSMetadata(t *testing.T) {
 	}
 
 	// Construct the full path of fs.json
-	fsPath := pathJoin(bucketMetaPrefix, bucketName, objectMetaPrefix, objectName, "fs.json")
+	fsPath := pathJoin(bucketMetaPrefix, bucketName, objectName, "fs.json")
 	fsPath = pathJoin(fs.fsPath, minioMetaBucket, fsPath)
 
 	rlk, err := fs.rwPool.Open(fsPath)

cmd/fs-v1-multipart.go

@@ -759,7 +759,7 @@ func (fs fsObjects) CompleteMultipartUpload(bucket string, object string, upload
 
 	// Wait for any competing PutObject() operation on bucket/object, since same namespace
 	// would be acquired for `fs.json`.
-	fsMetaPath := pathJoin(fs.fsPath, minioMetaBucket, bucketMetaPrefix, bucket, objectMetaPrefix, object, fsMetaJSONFile)
+	fsMetaPath := pathJoin(fs.fsPath, minioMetaBucket, bucketMetaPrefix, bucket, object, fsMetaJSONFile)
 	metaFile, err := fs.rwPool.Create(fsMetaPath)
 	if err != nil {
 		fs.rwPool.Close(fsMetaPathMultipart)

cmd/fs-v1.go

@@ -24,7 +24,6 @@ import (
 	"io"
 	"io/ioutil"
 	"os"
-	"os/signal"
 	"path"
 	"path/filepath"
 	"sort"
@@ -74,144 +73,15 @@ func initMetaVolumeFS(fsPath, fsUUID string) error {
 
 }
 
-// Migrate FS object is a place holder code for all
-// FS format migrations.
-func migrateFSObject(fsPath, fsUUID string) (err error) {
-	// Writing message here is important for servers being upgraded.
-	log.Println("Please do not stop the server.")
-
-	ch := make(chan os.Signal)
-	defer signal.Stop(ch)
-	defer close(ch)
-
-	signal.Notify(ch, syscall.SIGINT, syscall.SIGTERM)
-	go func() {
-		for {
-			_, ok := <-ch
-			if !ok {
-				break
-			}
-			log.Println("Please wait server is being upgraded..")
-		}
-	}()
-
-	return migrateFSFormatV1ToV2(fsPath, fsUUID)
-}
-
-// List all buckets at meta bucket prefix in `.minio.sys/buckets/` path.
-// This is implemented to avoid a bug on windows with using readDir().
-func fsReaddirMetaBuckets(fsPath string) ([]string, error) {
-	f, err := os.Open(preparePath(pathJoin(fsPath, minioMetaBucket, bucketConfigPrefix)))
-	if err != nil {
-		if os.IsNotExist(err) {
-			return nil, errFileNotFound
-		} else if os.IsPermission(err) {
-			return nil, errFileAccessDenied
-		}
-		return nil, err
-	}
-	return f.Readdirnames(-1)
-}
-
-// List of all bucket metadata configs.
-var bucketMetadataConfigs = []string{
-	bucketNotificationConfig,
-	bucketListenerConfig,
-	bucketPolicyConfig,
-}
-
-// Migrates bucket metadata configs, ignores all other files.
-func migrateBucketMetadataConfigs(metaBucket, bucket, tmpBucket string) error {
-	for _, bucketMetaFile := range bucketMetadataConfigs {
-		fi, err := fsStat(pathJoin(metaBucket, tmpBucket, bucketMetaFile))
-		if err != nil {
-			// There are no such files or directories found,
-			// proceed to next bucket metadata config.
-			if os.IsNotExist(errorCause(err)) {
-				continue
-			}
-			return err
-		}
-
-		// Bucket metadata is a file, move it as an actual bucket config.
-		if fi.Mode().IsRegular() {
-			if err = fsRenameFile(pathJoin(metaBucket, tmpBucket, bucketMetaFile),
-				pathJoin(metaBucket, bucket, bucketMetaFile)); err != nil {
-				if errorCause(err) != errFileNotFound {
-					return err
-				}
-			}
-		}
-
-		// All other file types are ignored.
-	}
-
-	// Success.
-	return nil
-}
-
-// Attempts to migrate old object metadata files to newer format
-//
-// i.e
-//    -------------------------------------------------------
-//    .minio.sys/buckets/<bucket_name>/<object_path>/fs.json - V1
-//    -------------------------------------------------------
-//    .minio.sys/buckets/<bucket_name>/objects/<object_path>/fs.json - V2
-//    -------------------------------------------------------
-//
-func migrateFSFormatV1ToV2(fsPath, fsUUID string) (err error) {
-	metaBucket := pathJoin(fsPath, minioMetaBucket, bucketConfigPrefix)
-
-	var buckets []string
-	buckets, err = fsReaddirMetaBuckets(fsPath)
-	if err != nil && err != errFileNotFound {
-		return err
-	}
-
-	// Migrate all buckets present.
-	for _, bucket := range buckets {
-		// Temporary bucket of form .UUID-bucket.
-		tmpBucket := fmt.Sprintf(".%s-%s", fsUUID, bucket)
-
-		// Rename existing bucket as `.UUID-bucket`.
-		if err = fsRenameFile(pathJoin(metaBucket, bucket), pathJoin(metaBucket, tmpBucket)); err != nil {
-			return err
-		}
-
-		// Create a new bucket name with name as `bucket`.
-		if err = fsMkdir(pathJoin(metaBucket, bucket)); err != nil {
-			return err
-		}
-
-		// Migrate all the bucket metadata configs.
-		if err = migrateBucketMetadataConfigs(metaBucket, bucket, tmpBucket); err != nil {
-			return err
-		}
-
-		// Finally rename the temporary bucket to `bucket/objects` directory.
-		if err = fsRenameFile(pathJoin(metaBucket, tmpBucket),
-			pathJoin(metaBucket, bucket, objectMetaPrefix)); err != nil {
-			if errorCause(err) != errFileNotFound {
-				return err
-			}
-		}
-
-	}
-
-	log.Printf("Migrating bucket metadata format from \"%s\" to newer format \"%s\"... completed successfully.", fsFormatV1, fsFormatV2)
-
-	// If all goes well we return success.
-	return nil
-}
-
 // newFSObjectLayer - initialize new fs object layer.
 func newFSObjectLayer(fsPath string) (ObjectLayer, error) {
 	if fsPath == "" {
 		return nil, errInvalidArgument
 	}
 
+	var err error
 	// Disallow relative paths, figure out absolute paths.
-	fsPath, err := filepath.Abs(fsPath)
+	fsPath, err = filepath.Abs(fsPath)
 	if err != nil {
 		return nil, err
 	}
@@ -257,12 +127,6 @@ func newFSObjectLayer(fsPath string) (ObjectLayer, error) {
 		return nil, err
 	}
 
-	// Once initialized hold read lock for the entire operation
-	// of filesystem backend.
-	if _, err = fs.rwPool.Open(pathJoin(fsPath, minioMetaBucket, fsFormatJSONFile)); err != nil {
-		return nil, err
-	}
-
 	// Initialize and load bucket policies.
 	err = initBucketPolicies(fs)
 	if err != nil {
@@ -281,9 +145,6 @@ func newFSObjectLayer(fsPath string) (ObjectLayer, error) {
 
 // Should be called when process shuts down.
 func (fs fsObjects) Shutdown() error {
-	// Close the format.json read lock.
-	fs.rwPool.Close(pathJoin(fs.fsPath, minioMetaBucket, fsFormatJSONFile))
-
 	// Cleanup and delete tmp uuid.
 	return fsRemoveAll(pathJoin(fs.fsPath, minioMetaTmpBucket, fs.fsUUID))
 }
@@ -363,7 +224,7 @@ func (fs fsObjects) ListBuckets() ([]BucketInfo, error) {
 		return nil, traceError(err)
 	}
 	var bucketInfos []BucketInfo
-	entries, err := readDir(fs.fsPath)
+	entries, err := readDir(preparePath(fs.fsPath))
 	if err != nil {
 		return nil, toObjectErr(traceError(errDiskNotFound))
 	}
@@ -447,7 +308,7 @@ func (fs fsObjects) CopyObject(srcBucket, srcObject, dstBucket, dstObject string
 	// Check if this request is only metadata update.
 	cpMetadataOnly := isStringEqual(pathJoin(srcBucket, srcObject), pathJoin(dstBucket, dstObject))
 	if cpMetadataOnly {
-		fsMetaPath := pathJoin(fs.fsPath, minioMetaBucket, bucketMetaPrefix, srcBucket, objectMetaPrefix, srcObject, fsMetaJSONFile)
+		fsMetaPath := pathJoin(fs.fsPath, minioMetaBucket, bucketMetaPrefix, srcBucket, srcObject, fsMetaJSONFile)
 		var wlk *lock.LockedFile
 		wlk, err = fs.rwPool.Write(fsMetaPath)
 		if err != nil {
@@ -520,7 +381,7 @@ func (fs fsObjects) GetObject(bucket, object string, offset int64, length int64,
 	}
 
 	if bucket != minioMetaBucket {
-		fsMetaPath := pathJoin(fs.fsPath, minioMetaBucket, bucketMetaPrefix, bucket, objectMetaPrefix, object, fsMetaJSONFile)
+		fsMetaPath := pathJoin(fs.fsPath, minioMetaBucket, bucketMetaPrefix, bucket, object, fsMetaJSONFile)
 		_, err = fs.rwPool.Open(fsMetaPath)
 		if err != nil && err != errFileNotFound {
 			return toObjectErr(traceError(err), bucket, object)
@@ -562,7 +423,7 @@ func (fs fsObjects) GetObject(bucket, object string, offset int64, length int64,
 // getObjectInfo - wrapper for reading object metadata and constructs ObjectInfo.
 func (fs fsObjects) getObjectInfo(bucket, object string) (ObjectInfo, error) {
 	fsMeta := fsMetaV1{}
-	fsMetaPath := pathJoin(fs.fsPath, minioMetaBucket, bucketMetaPrefix, bucket, objectMetaPrefix, object, fsMetaJSONFile)
+	fsMetaPath := pathJoin(fs.fsPath, minioMetaBucket, bucketMetaPrefix, bucket, object, fsMetaJSONFile)
 
 	// Read `fs.json` to perhaps contend with
 	// parallel Put() operations.
@@ -669,7 +530,7 @@ func (fs fsObjects) PutObject(bucket string, object string, size int64, data io.
 	var wlk *lock.LockedFile
 	if bucket != minioMetaBucket {
 		bucketMetaDir := pathJoin(fs.fsPath, minioMetaBucket, bucketMetaPrefix)
-		fsMetaPath := pathJoin(bucketMetaDir, bucket, objectMetaPrefix, object, fsMetaJSONFile)
+		fsMetaPath := pathJoin(bucketMetaDir, bucket, object, fsMetaJSONFile)
 		wlk, err = fs.rwPool.Create(fsMetaPath)
 		if err != nil {
 			return ObjectInfo{}, toObjectErr(traceError(err), bucket, object)
@@ -796,7 +657,7 @@ func (fs fsObjects) DeleteObject(bucket, object string) error {
 	}
 
 	minioMetaBucketDir := pathJoin(fs.fsPath, minioMetaBucket)
-	fsMetaPath := pathJoin(minioMetaBucketDir, bucketMetaPrefix, bucket, objectMetaPrefix, object, fsMetaJSONFile)
+	fsMetaPath := pathJoin(minioMetaBucketDir, bucketMetaPrefix, bucket, object, fsMetaJSONFile)
 	if bucket != minioMetaBucket {
 		rwlk, lerr := fs.rwPool.Write(fsMetaPath)
 		if lerr == nil {
@@ -850,7 +711,7 @@ func (fs fsObjects) listDirFactory(isLeaf isLeafFunc) listDirFunc {
 // getObjectETag is a helper function, which returns only the md5sum
 // of the file on the disk.
 func (fs fsObjects) getObjectETag(bucket, entry string) (string, error) {
-	fsMetaPath := pathJoin(fs.fsPath, minioMetaBucket, bucketMetaPrefix, bucket, objectMetaPrefix, entry, fsMetaJSONFile)
+	fsMetaPath := pathJoin(fs.fsPath, minioMetaBucket, bucketMetaPrefix, bucket, entry, fsMetaJSONFile)
 
 	// Read `fs.json` to perhaps contend with
 	// parallel Put() operations.

cmd/fs-v1_test.go

@@ -21,10 +21,7 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
-	"strings"
 	"testing"
-
-	"github.com/minio/minio/pkg/lock"
 )
 
 // TestNewFS - tests initialization of all input disks
@@ -88,516 +85,6 @@ func TestFSShutdown(t *testing.T) {
 	}
 }
 
-// Tests migrating FS format without .minio.sys/buckets.
-func TestFSMigrateObjectWithoutObjects(t *testing.T) {
-	// Prepare for testing
-	disk := filepath.Join(globalTestTmpDir, "minio-"+nextSuffix())
-	defer 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, fsFormatJSONFile)
-	formatCfg := &formatConfigV1{
-		Version: "1",
-		Format:  "fs",
-		FS: &fsFormat{
-			Version: "1",
-		},
-	}
-
-	lk, err := lock.LockedOpenFile(preparePath(fsFormatPath), os.O_RDWR|os.O_CREATE, 0600)
-	if err != nil {
-		t.Fatal(err)
-	}
-	_, err = formatCfg.WriteTo(lk)
-	lk.Close()
-	if err != nil {
-		t.Fatal("Should not fail here", err)
-	}
-
-	if err = initFormatFS(disk, uuid); err != nil {
-		t.Fatal("Should not fail with unexpected", err)
-	}
-
-	formatCfg = &formatConfigV1{}
-	lk, err = lock.LockedOpenFile(preparePath(fsFormatPath), os.O_RDONLY, 0600)
-	if err != nil {
-		t.Fatal(err)
-	}
-	_, err = formatCfg.ReadFrom(lk)
-	lk.Close()
-	if err != nil {
-		t.Fatal("Should not fail here", err)
-	}
-	if formatCfg.FS.Version != fsFormatV2 {
-		t.Fatalf("Unexpected version detected expected \"%s\", got %s", fsFormatV2, formatCfg.FS.Version)
-	}
-}
-
-// Tests migrating FS format without .minio.sys/buckets.
-func TestFSMigrateObjectWithErr(t *testing.T) {
-	// Prepare for testing
-	disk := filepath.Join(globalTestTmpDir, "minio-"+nextSuffix())
-	defer 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, fsFormatJSONFile)
-	formatCfg := &formatConfigV1{
-		Version: "1",
-		Format:  "fs",
-		FS: &fsFormat{
-			Version: "10",
-		},
-	}
-
-	lk, err := lock.LockedOpenFile(preparePath(fsFormatPath), os.O_RDWR|os.O_CREATE, 0600)
-	if err != nil {
-		t.Fatal(err)
-	}
-	_, err = formatCfg.WriteTo(lk)
-	lk.Close()
-	if err != nil {
-		t.Fatal("Should not fail here", err)
-	}
-
-	if err = initFormatFS(disk, uuid); err != nil {
-		if !strings.Contains(errorCause(err).Error(), "Unable to validate 'format.json', corrupted backend format") {
-			t.Fatal("Should not fail with unexpected", err)
-		}
-	}
-
-	fsFormatPath = pathJoin(disk, minioMetaBucket, fsFormatJSONFile)
-	formatCfg = &formatConfigV1{
-		Version: "1",
-		Format:  "garbage",
-		FS: &fsFormat{
-			Version: "1",
-		},
-	}
-
-	lk, err = lock.LockedOpenFile(preparePath(fsFormatPath), os.O_RDWR|os.O_CREATE, 0600)
-	if err != nil {
-		t.Fatal(err)
-	}
-	_, err = formatCfg.WriteTo(lk)
-	lk.Close()
-	if err != nil {
-		t.Fatal("Should not fail here", err)
-	}
-
-	if err = initFormatFS(disk, uuid); err != nil {
-		if errorCause(err).Error() !=
-			"Unable to validate 'format.json', Unable to recognize backend format, Disk is not in FS format. garbage" {
-			t.Fatal("Should not fail with unexpected", err)
-		}
-	}
-
-}
-
-// Tests migrating FS format with .minio.sys/buckets filled with
-// objects such as policy.json/fs.json, notification.xml/fs.json
-// listener.json/fs.json.
-func TestFSMigrateObjectWithBucketConfigObjects(t *testing.T) {
-	// Prepare for testing
-	disk := filepath.Join(globalTestTmpDir, "minio-"+nextSuffix())
-	defer 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, fsFormatJSONFile)
-	formatCfg := &formatConfigV1{
-		Version: "1",
-		Format:  "fs",
-		FS: &fsFormat{
-			Version: "1",
-		},
-	}
-	lk, err := lock.LockedOpenFile(preparePath(fsFormatPath), os.O_RDWR|os.O_CREATE, 0600)
-	if err != nil {
-		t.Fatal(err)
-	}
-	_, err = formatCfg.WriteTo(lk)
-	lk.Close()
-	if err != nil {
-		t.Fatal("Should not fail here", err)
-	}
-
-	// Construct the full path of fs.json
-	fsPath1 := pathJoin(bucketMetaPrefix, "testvolume1", bucketPolicyConfig, fsMetaJSONFile)
-	fsPath1 = pathJoin(disk, minioMetaBucket, fsPath1)
-
-	fsMetaJSON := `{"version":"1.0.0","format":"fs","minio":{"release":"DEVELOPMENT.2017-03-27T02-26-33Z"},"meta":{"etag":"467886be95c8ecfd71a2900e3f461b4f"}`
-	if _, err = fsCreateFile(fsPath1, bytes.NewReader([]byte(fsMetaJSON)), nil, 0); err != nil {
-		t.Fatal(err)
-	}
-
-	// Construct the full path of fs.json
-	fsPath2 := pathJoin(bucketMetaPrefix, "testvolume2", bucketNotificationConfig, fsMetaJSONFile)
-	fsPath2 = pathJoin(disk, minioMetaBucket, fsPath2)
-
-	fsMetaJSON = `{"version":"1.0.0","format":"fs","minio":{"release":"DEVELOPMENT.2017-03-27T02-26-33Z"},"meta":{"etag":"467886be95c8ecfd71a2900eff461b4d"}`
-	if _, err = fsCreateFile(fsPath2, bytes.NewReader([]byte(fsMetaJSON)), nil, 0); err != nil {
-		t.Fatal(err)
-	}
-
-	// Construct the full path of fs.json
-	fsPath3 := pathJoin(bucketMetaPrefix, "testvolume3", bucketListenerConfig, fsMetaJSONFile)
-	fsPath3 = pathJoin(disk, minioMetaBucket, fsPath3)
-
-	fsMetaJSON = `{"version":"1.0.0","format":"fs","minio":{"release":"DEVELOPMENT.2017-03-27T02-26-33Z"},"meta":{"etag":"467886be95c8ecfd71a2900eff461b4d"}`
-	if _, err = fsCreateFile(fsPath3, bytes.NewReader([]byte(fsMetaJSON)), nil, 0); err != nil {
-		t.Fatal(err)
-	}
-
-	if err = initFormatFS(disk, mustGetUUID()); err != nil {
-		t.Fatal("Should not fail here", err)
-	}
-
-	fsPath1 = pathJoin(bucketMetaPrefix, "testvolume1", objectMetaPrefix, bucketPolicyConfig, fsMetaJSONFile)
-	fsPath1 = pathJoin(disk, minioMetaBucket, fsPath1)
-	fi, err := fsStatFile(fsPath1)
-	if err != nil {
-		t.Fatal("Path should exist and accessible after migration", err)
-	}
-	if fi.IsDir() {
-		t.Fatalf("Unexpected path %s should be a file", fsPath1)
-	}
-
-	fsPath2 = pathJoin(bucketMetaPrefix, "testvolume2", objectMetaPrefix, bucketNotificationConfig, fsMetaJSONFile)
-	fsPath2 = pathJoin(disk, minioMetaBucket, fsPath2)
-	fi, err = fsStatFile(fsPath2)
-	if err != nil {
-		t.Fatal("Path should exist and accessible after migration", err)
-	}
-	if fi.IsDir() {
-		t.Fatalf("Unexpected path %s should be a file", fsPath2)
-	}
-
-	fsPath3 = pathJoin(bucketMetaPrefix, "testvolume3", objectMetaPrefix, bucketListenerConfig, fsMetaJSONFile)
-	fsPath3 = pathJoin(disk, minioMetaBucket, fsPath3)
-	fi, err = fsStatFile(fsPath3)
-	if err != nil {
-		t.Fatal("Path should exist and accessible after migration", err)
-	}
-	if fi.IsDir() {
-		t.Fatalf("Unexpected path %s should be a file", fsPath3)
-	}
-
-	formatCfg = &formatConfigV1{}
-	lk, err = lock.LockedOpenFile(preparePath(fsFormatPath), os.O_RDONLY, 0600)
-	if err != nil {
-		t.Fatal(err)
-	}
-	_, err = formatCfg.ReadFrom(lk)
-	lk.Close()
-	if err != nil {
-		t.Fatal("Should not fail here", err)
-	}
-	if formatCfg.FS.Version != fsFormatV2 {
-		t.Fatalf("Unexpected version detected expected \"%s\", got %s", fsFormatV2, formatCfg.FS.Version)
-	}
-}
-
-// Tests migrating FS format with .minio.sys/buckets filled with
-// object metadata.
-func TestFSMigrateObjectWithObjects(t *testing.T) {
-	// Prepare for testing
-	disk := filepath.Join(globalTestTmpDir, "minio-"+nextSuffix())
-	defer 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, fsFormatJSONFile)
-	formatCfg := &formatConfigV1{
-		Version: "1",
-		Format:  "fs",
-		FS: &fsFormat{
-			Version: "1",
-		},
-	}
-	lk, err := lock.LockedOpenFile(preparePath(fsFormatPath), os.O_RDWR|os.O_CREATE, 0600)
-	if err != nil {
-		t.Fatal(err)
-	}
-	_, err = formatCfg.WriteTo(lk)
-	lk.Close()
-	if err != nil {
-		t.Fatal("Should not fail here", err)
-	}
-
-	// Construct the full path of fs.json
-	fsPath1 := pathJoin(bucketMetaPrefix, "testvolume1", "my-object1", fsMetaJSONFile)
-	fsPath1 = pathJoin(disk, minioMetaBucket, fsPath1)
-
-	fsMetaJSON := `{"version":"1.0.0","format":"fs","minio":{"release":"DEVELOPMENT.2017-03-27T02-26-33Z"},"meta":{"etag":"467886be95c8ecfd71a2900e3f461b4f"}`
-	if _, err = fsCreateFile(fsPath1, bytes.NewReader([]byte(fsMetaJSON)), nil, 0); err != nil {
-		t.Fatal(err)
-	}
-
-	// Construct the full path of fs.json
-	fsPath2 := pathJoin(bucketMetaPrefix, "testvolume2", "my-object2", fsMetaJSONFile)
-	fsPath2 = pathJoin(disk, minioMetaBucket, fsPath2)
-
-	fsMetaJSON = `{"version":"1.0.0","format":"fs","minio":{"release":"DEVELOPMENT.2017-03-27T02-26-33Z"},"meta":{"etag":"467886be95c8ecfd71a2900eff461b4d"}`
-	if _, err = fsCreateFile(fsPath2, bytes.NewReader([]byte(fsMetaJSON)), nil, 0); err != nil {
-		t.Fatal(err)
-	}
-
-	// Construct the full path of policy.json
-	ppath := pathJoin(bucketMetaPrefix, "testvolume2", bucketPolicyConfig)
-	ppath = pathJoin(disk, minioMetaBucket, ppath)
-
-	policyJSON := `{"Version":"2012-10-17","Statement":[{"Action":["s3:GetBucketLocation","s3:ListBucket"],"Effect":"Allow","Principal":{"AWS":["*"]},"Resource":["arn:aws:s3:::testbucket"],"Sid":""},{"Action":["s3:GetObject"],"Effect":"Allow","Principal":{"AWS":["*"]},"Resource":["arn:aws:s3:::testbucket/*"],"Sid":""}]}`
-	if _, err = fsCreateFile(ppath, bytes.NewReader([]byte(policyJSON)), nil, 0); err != nil {
-		t.Fatal(err)
-	}
-
-	if err = initFormatFS(disk, mustGetUUID()); err != nil {
-		t.Fatal("Should not fail here", err)
-	}
-
-	fsPath2 = pathJoin(bucketMetaPrefix, "testvolume2", objectMetaPrefix, "my-object2", fsMetaJSONFile)
-	fsPath2 = pathJoin(disk, minioMetaBucket, fsPath2)
-	fi, err := fsStatFile(fsPath2)
-	if err != nil {
-		t.Fatal("Path should exist and accessible after migration", err)
-	}
-	if fi.IsDir() {
-		t.Fatalf("Unexpected path %s should be a file", fsPath2)
-	}
-
-	formatCfg = &formatConfigV1{}
-	lk, err = lock.LockedOpenFile(preparePath(fsFormatPath), os.O_RDONLY, 0600)
-	if err != nil {
-		t.Fatal(err)
-	}
-	_, err = formatCfg.ReadFrom(lk)
-	lk.Close()
-	if err != nil {
-		t.Fatal("Should not fail here", err)
-	}
-	if formatCfg.FS.Version != fsFormatV2 {
-		t.Fatalf("Unexpected version detected expected \"%s\", got %s", fsFormatV2, formatCfg.FS.Version)
-	}
-
-	ppath = pathJoin(bucketMetaPrefix, "testvolume2", "acl.json")
-	ppath = pathJoin(disk, minioMetaBucket, ppath)
-
-	if _, err = fsCreateFile(ppath, bytes.NewReader([]byte("")), nil, 0); err != nil {
-		t.Fatal(err)
-	}
-
-	if err = initFormatFS(disk, mustGetUUID()); errorCause(err) != errCorruptedFormat {
-		t.Fatal("Should not fail here", err)
-	}
-}
-
-// TestFSCheckFormatFSErr - test loadFormatFS loading older format.
-func TestFSCheckFormatFSErr(t *testing.T) {
-	// Prepare for testing
-	disk := filepath.Join(globalTestTmpDir, "minio-"+nextSuffix())
-	defer 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, fsFormatJSONFile)
-	formatCfg := &formatConfigV1{
-		Version: "1",
-		Format:  "fs",
-		FS: &fsFormat{
-			Version: "1",
-		},
-	}
-
-	lk, err := lock.LockedOpenFile(preparePath(fsFormatPath), os.O_RDWR|os.O_CREATE, 0600)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	_, err = formatCfg.WriteTo(lk)
-	lk.Close()
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	formatCfg = &formatConfigV1{}
-	lk, err = lock.LockedOpenFile(preparePath(fsFormatPath), os.O_RDWR|os.O_CREATE, 0600)
-	if err != nil {
-		t.Fatal(err)
-	}
-	_, err = formatCfg.ReadFrom(lk)
-	lk.Close()
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	if err = checkFormatFS(formatCfg, fsFormatVersion); errorCause(err) != errFSFormatOld {
-		t.Fatal("Should not fail with unexpected", err)
-	}
-
-	formatCfg = &formatConfigV1{
-		Version: "1",
-		Format:  "fs",
-		FS: &fsFormat{
-			Version: "10",
-		},
-	}
-
-	lk, err = lock.LockedOpenFile(preparePath(fsFormatPath), os.O_RDWR|os.O_CREATE, 0600)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	_, err = formatCfg.WriteTo(lk)
-	lk.Close()
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	if err = checkFormatFS(formatCfg, fsFormatVersion); errorCause(err) != errCorruptedFormat {
-		t.Fatal("Should not fail with unexpected", err)
-	}
-
-	formatCfg = &formatConfigV1{
-		Version: "1",
-		Format:  "garbage",
-		FS: &fsFormat{
-			Version: "1",
-		},
-	}
-
-	lk, err = lock.LockedOpenFile(preparePath(fsFormatPath), os.O_RDWR|os.O_CREATE, 0600)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	_, err = formatCfg.WriteTo(lk)
-	lk.Close()
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	if err = checkFormatFS(formatCfg, fsFormatVersion); err != nil {
-		if errorCause(err).Error() != "Unable to recognize backend format, Disk is not in FS format. garbage" {
-			t.Fatal("Should not fail with unexpected", err)
-		}
-	}
-
-	if err = checkFormatFS(nil, fsFormatVersion); errorCause(err) != errUnexpected {
-		t.Fatal("Should fail with errUnexpected, but found", err)
-	}
-
-	formatCfg = &formatConfigV1{
-		Version: "1",
-		Format:  "fs",
-		FS: &fsFormat{
-			Version: "2",
-		},
-	}
-
-	lk, err = lock.LockedOpenFile(preparePath(fsFormatPath), os.O_RDWR|os.O_CREATE, 0600)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	_, err = formatCfg.WriteTo(lk)
-	lk.Close()
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	// Should not fail.
-	if err = checkFormatFS(formatCfg, fsFormatVersion); err != nil {
-		t.Fatal(err)
-	}
-}
-
-// TestFSCheckFormatFS - test loadFormatFS with healty and faulty disks
-func TestFSCheckFormatFS(t *testing.T) {
-	// Prepare for testing
-	disk := filepath.Join(globalTestTmpDir, "minio-"+nextSuffix())
-	defer 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, fsFormatJSONFile)
-	lk, err := lock.LockedOpenFile(preparePath(fsFormatPath), os.O_RDWR|os.O_CREATE, 0600)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	format := newFSFormatV2()
-	_, err = format.WriteTo(lk)
-	lk.Close()
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	// Loading corrupted format file
-	file, err := os.OpenFile(preparePath(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(preparePath(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.
-	removeAll(disk)
-	_, err = lock.LockedOpenFile(preparePath(fsFormatPath), os.O_RDONLY, 0600)
-	if err != nil && !os.IsNotExist(err) {
-		t.Fatal("Should return 'format.json' does not exist, but got", err)
-	}
-}
-
 // TestFSGetBucketInfo - test GetBucketInfo with healty and faulty disks
 func TestFSGetBucketInfo(t *testing.T) {
 	// Prepare for testing
@@ -633,7 +120,6 @@ func TestFSGetBucketInfo(t *testing.T) {
 	}
 }
 
-// Tests FS backend put object behavior.
 func TestFSPutObject(t *testing.T) {
 	// Prepare for tests
 	disk := filepath.Join(globalTestTmpDir, "minio-"+nextSuffix())

cmd/object-api-common.go

@@ -32,9 +32,6 @@ const (
 	// Buckets meta prefix.
 	bucketMetaPrefix = "buckets"
 
-	// Objects meta prefix.
-	objectMetaPrefix = "objects"
-
 	// ETag (hex encoded md5sum) of empty string.
 	emptyETag = "d41d8cd98f00b204e9800998ecf8427e"
 )

cmd/posix-list-dir-others.go

@@ -32,8 +32,6 @@ func readDir(dirPath string) (entries []string, err error) {
 		// File is really not found.
 		if os.IsNotExist(err) {
 			return nil, errFileNotFound
-		} else if os.IsPermission(err) {
-			return nil, errFileAccessDenied
 		}
 
 		// File path cannot be verified since one of the parents is a file.

cmd/posix.go

@@ -293,7 +293,7 @@ func (s *posix) ListVols() (volsInfo []VolInfo, err error) {
 		return nil, err
 	}
 
-	volsInfo, err = listVols(s.diskPath)
+	volsInfo, err = listVols(preparePath(s.diskPath))
 	if err != nil {
 		return nil, err
 	}

cmd/web-handlers_test.go

@@ -277,7 +277,7 @@ func testMakeBucketWebHandler(obj ObjectLayer, instanceType string, t TestErrHan
 		{".", false},
 		{"ab", false},
 		{"minio", false},
-		{".minio.sys", false},
+		{minioMetaBucket, false},
 		{bucketName, true},
 	}
 

cmd/xl-v1-healing.go

@@ -383,7 +383,7 @@ func healObject(storageDisks []StorageAPI, bucket string, object string, quorum
 	for index, disk := range outDatedDisks {
 		// Before healing outdated disks, we need to remove xl.json
 		// and part files from "bucket/object/" so that
-		// rename(".minio.sys", "tmp/tmpuuid/", "bucket", "object/") succeeds.
+		// rename(minioMetaBucket, "tmp/tmpuuid/", "bucket", "object/") succeeds.
 		if disk == nil {
 			// Not an outdated disk.
 			continue

cmd/xl-v1-healing_test.go

@@ -121,7 +121,7 @@ func TestHealFormatXL(t *testing.T) {
 	}
 	xl = obj.(*xlObjects)
 	for i := 0; i <= 15; i++ {
-		if err = xl.storageDisks[i].DeleteFile(".minio.sys", "format.json"); err != nil {
+		if err = xl.storageDisks[i].DeleteFile(minioMetaBucket, formatConfigFile); err != nil {
 			t.Fatal(err)
 		}
 	}
@@ -142,7 +142,7 @@ func TestHealFormatXL(t *testing.T) {
 	}
 	xl = obj.(*xlObjects)
 	for i := 0; i <= 15; i++ {
-		if err = xl.storageDisks[i].AppendFile(".minio.sys", "format.json", []byte("corrupted data")); err != nil {
+		if err = xl.storageDisks[i].AppendFile(minioMetaBucket, formatConfigFile, []byte("corrupted data")); err != nil {
 			t.Fatal(err)
 		}
 	}
@@ -163,7 +163,7 @@ func TestHealFormatXL(t *testing.T) {
 	}
 	xl = obj.(*xlObjects)
 	for i := 0; i <= 2; i++ {
-		if err = xl.storageDisks[i].DeleteFile(".minio.sys", "format.json"); err != nil {
+		if err = xl.storageDisks[i].DeleteFile(minioMetaBucket, formatConfigFile); err != nil {
 			t.Fatal(err)
 		}
 	}
@@ -184,7 +184,7 @@ func TestHealFormatXL(t *testing.T) {
 	}
 	xl = obj.(*xlObjects)
 	for i := 0; i <= 2; i++ {
-		if err = xl.storageDisks[i].DeleteFile(".minio.sys", "format.json"); err != nil {
+		if err = xl.storageDisks[i].DeleteFile(minioMetaBucket, formatConfigFile); err != nil {
 			t.Fatal(err)
 		}
 	}
@@ -216,7 +216,7 @@ func TestHealFormatXL(t *testing.T) {
 		t.Fatal(err)
 	}
 	for i := 0; i <= 2; i++ {
-		if err = xl.storageDisks[i].DeleteFile(".minio.sys", "format.json"); err != nil {
+		if err = xl.storageDisks[i].DeleteFile(minioMetaBucket, formatConfigFile); err != nil {
 			t.Fatal(err)
 		}
 	}

cmd/xl-v1.go

@@ -29,12 +29,6 @@ import (
 
 // XL constants.
 const (
-	// Format config file carries backend format specific details.
-	formatConfigFile = "format.json"
-
-	// Format config tmp file carries backend format.
-	formatConfigFileTmp = "format.json.tmp"
-
 	// XL metadata file carries per object metadata.
 	xlMetaJSONFile = "xl.json"
 

docs/shared-backend/DESIGN.md

@@ -81,7 +81,7 @@ An example here shows how the contention is handled with GetObject().
 GetObject() holds a read lock on `fs.json`.
 
 ```go
-	fsMetaPath := pathJoin(fs.fsPath, minioMetaBucket, bucketMetaPrefix, bucket, objectMetaPrefix, object, fsMetaJSONFile)
+	fsMetaPath := pathJoin(fs.fsPath, minioMetaBucket, bucketMetaPrefix, bucket, object, fsMetaJSONFile)
 	rlk, err := fs.rwPool.Open(fsMetaPath)
 	if err != nil {
 		return toObjectErr(traceError(err), bucket, object)
@@ -98,7 +98,7 @@ GetObject() holds a read lock on `fs.json`.
 A concurrent PutObject is requested on the same object, PutObject() attempts a write lock on `fs.json`.
 
 ```go
-	fsMetaPath := pathJoin(fs.fsPath, minioMetaBucket, bucketMetaPrefix, bucket, objectMetaPrefix, object, fsMetaJSONFile)
+	fsMetaPath := pathJoin(fs.fsPath, minioMetaBucket, bucketMetaPrefix, bucket, object, fsMetaJSONFile)
 	wlk, err := fs.rwPool.Create(fsMetaPath)
 	if err != nil {
 		return ObjectInfo{}, toObjectErr(err, bucket, object)

pkg/lock/lock.go

@@ -19,10 +19,16 @@
 package lock
 
 import (
+	"errors"
 	"os"
 	"sync"
 )
 
+var (
+	// ErrAlreadyLocked is returned if the underlying fd is already locked.
+	ErrAlreadyLocked = errors.New("file already locked")
+)
+
 // RLockedFile represents a read locked file, implements a special
 // closer which only closes the associated *os.File when the ref count.
 // has reached zero, i.e when all the readers have given up their locks.

pkg/lock/lock_nix.go

@@ -24,16 +24,12 @@ import (
 	"syscall"
 )
 
-// LockedOpenFile - initializes a new lock and protects
+// Internal function implements support for both
-// the file from concurrent access across mount points.
+// blocking and non blocking lock type.
-// This implementation doesn't support all the open
+func lockedOpenFile(path string, flag int, perm os.FileMode, lockType int) (*LockedFile, error) {
-// flags and shouldn't be considered as replacement
-// for os.OpenFile().
-func LockedOpenFile(path string, flag int, perm os.FileMode) (*LockedFile, error) {
-	var lockType int
 	switch flag {
 	case syscall.O_RDONLY:
-		lockType = syscall.LOCK_SH
+		lockType |= syscall.LOCK_SH
 	case syscall.O_WRONLY:
 		fallthrough
 	case syscall.O_RDWR:
@@ -41,7 +37,7 @@ func LockedOpenFile(path string, flag int, perm os.FileMode) (*LockedFile, error
 	case syscall.O_WRONLY | syscall.O_CREAT:
 		fallthrough
 	case syscall.O_RDWR | syscall.O_CREAT:
-		lockType = syscall.LOCK_EX
+		lockType |= syscall.LOCK_EX
 	default:
 		return nil, fmt.Errorf("Unsupported flag (%d)", flag)
 	}
@@ -53,6 +49,9 @@ func LockedOpenFile(path string, flag int, perm os.FileMode) (*LockedFile, error
 
 	if err = syscall.Flock(int(f.Fd()), lockType); err != nil {
 		f.Close()
+		if err == syscall.EWOULDBLOCK {
+			err = ErrAlreadyLocked
+		}
 		return nil, err
 	}
 
@@ -73,3 +72,21 @@ func LockedOpenFile(path string, flag int, perm os.FileMode) (*LockedFile, error
 
 	return &LockedFile{File: f}, nil
 }
+
+// TryLockedOpenFile - tries a new write lock, functionality
+// it is similar to LockedOpenFile with with syscall.LOCK_EX
+// mode but along with syscall.LOCK_NB such that the function
+// doesn't wait forever but instead returns if it cannot
+// acquire a write lock.
+func TryLockedOpenFile(path string, flag int, perm os.FileMode) (*LockedFile, error) {
+	return lockedOpenFile(path, flag, perm, syscall.LOCK_NB)
+}
+
+// LockedOpenFile - initializes a new lock and protects
+// the file from concurrent access across mount points.
+// This implementation doesn't support all the open
+// flags and shouldn't be considered as replacement
+// for os.OpenFile().
+func LockedOpenFile(path string, flag int, perm os.FileMode) (*LockedFile, error) {
+	return lockedOpenFile(path, flag, perm, 0)
+}

pkg/lock/lock_solaris.go

@@ -24,17 +24,8 @@ import (
 	"syscall"
 )
 
-// LockedOpenFile - initializes a new lock and protects
+// lockedOpenFile is an internal function.
-// the file from concurrent access across mount points.
+func lockedOpenFile(path string, flag int, perm os.FileMode, rlockType int) (*LockedFile, error) {
-// This implementation doesn't support all the open
-// flags and shouldn't be considered as replacement
-// for os.OpenFile().
-func LockedOpenFile(path string, flag int, perm os.FileMode) (*LockedFile, error) {
-	var lock syscall.Flock_t
-	lock.Start = 0
-	lock.Len = 0
-	lock.Pid = 0
-
 	var lockType int16
 	switch flag {
 	case syscall.O_RDONLY:
@@ -51,16 +42,24 @@ func LockedOpenFile(path string, flag int, perm os.FileMode) (*LockedFile, error
 		return nil, fmt.Errorf("Unsupported flag (%d)", flag)
 	}
 
-	lock.Type = lockType
+	var lock = syscall.Flock_t{
-	lock.Whence = 0
+		Start:  0,
+		Len:    0,
+		Pid:    0,
+		Type:   lockType,
+		Whence: 0,
+	}
 
 	f, err := os.OpenFile(path, flag, perm)
 	if err != nil {
 		return nil, err
 	}
 
-	if err = syscall.FcntlFlock(f.Fd(), syscall.F_SETLKW, &lock); err != nil {
+	if err = syscall.FcntlFlock(f.Fd(), rlockType, &lock); err != nil {
 		f.Close()
+		if err == syscall.EAGAIN {
+			err = ErrLocked
+		}
 		return nil, err
 	}
 
@@ -81,3 +80,21 @@ func LockedOpenFile(path string, flag int, perm os.FileMode) (*LockedFile, error
 
 	return &LockedFile{f}, nil
 }
+
+// TryLockedOpenFile - tries a new write lock, functionality
+// it is similar to LockedOpenFile with with syscall.LOCK_EX
+// mode but along with syscall.LOCK_NB such that the function
+// doesn't wait forever but instead returns if it cannot
+// acquire a write lock.
+func TryLockedOpenFile(path string, flag int, perm os.FileMode) (*LockedFile, error) {
+	return lockedOpenFile(path, flag, perm, syscall.F_SETLK)
+}
+
+// LockedOpenFile - initializes a new lock and protects
+// the file from concurrent access across mount points.
+// This implementation doesn't support all the open
+// flags and shouldn't be considered as replacement
+// for os.OpenFile().
+func LockedOpenFile(path string, flag int, perm os.FileMode) (*LockedFile, error) {
+	return lockedOpenFile(path, flag, perm, syscall.F_SETLKW)
+}

pkg/lock/lock_windows.go

@@ -19,7 +19,6 @@
 package lock
 
 import (
-	"errors"
 	"fmt"
 	"os"
 	"syscall"
@@ -31,24 +30,25 @@ import (
 var (
 	modkernel32    = syscall.NewLazyDLL("kernel32.dll")
 	procLockFileEx = modkernel32.NewProc("LockFileEx")
-
-	errLocked = errors.New("The process cannot access the file because another process has locked a portion of the file.")
 )
 
 const (
+	// https://msdn.microsoft.com/en-us/library/windows/desktop/aa365203(v=vs.85).aspx
+	lockFileExclusiveLock   = 2
+	lockFileFailImmediately = 1
+
 	// see https://msdn.microsoft.com/en-us/library/windows/desktop/ms681382(v=vs.85).aspx
 	errLockViolation syscall.Errno = 0x21
 )
 
-// LockedOpenFile - initializes a new lock and protects
+// lockedOpenFile is an internal function.
-// the file from concurrent access.
+func lockedOpenFile(path string, flag int, perm os.FileMode, lockType uint32) (*LockedFile, error) {
-func LockedOpenFile(path string, flag int, perm os.FileMode) (*LockedFile, error) {
 	f, err := open(path, flag, perm)
 	if err != nil {
 		return nil, err
 	}
 
-	if err = lockFile(syscall.Handle(f.Fd()), 0); err != nil {
+	if err = lockFile(syscall.Handle(f.Fd()), lockType); err != nil {
 		f.Close()
 		return nil, err
 	}
@@ -71,6 +71,21 @@ func LockedOpenFile(path string, flag int, perm os.FileMode) (*LockedFile, error
 	return &LockedFile{File: f}, nil
 }
 
+// TryLockedOpenFile - tries a new write lock, functionality
+// it is similar to LockedOpenFile with with syscall.LOCK_EX
+// mode but along with syscall.LOCK_NB such that the function
+// doesn't wait forever but instead returns if it cannot
+// acquire a write lock.
+func TryLockedOpenFile(path string, flag int, perm os.FileMode) (*LockedFile, error) {
+	return lockedOpenFile(path, flag, perm, lockFileFailImmediately)
+}
+
+// LockedOpenFile - initializes a new lock and protects
+// the file from concurrent access.
+func LockedOpenFile(path string, flag int, perm os.FileMode) (*LockedFile, error) {
+	return lockedOpenFile(path, flag, perm, 0)
+}
+
 // perm param is ignored, on windows file perms/NT acls
 // are not octet combinations. Providing access to NT
 // acls is out of scope here.
@@ -121,7 +136,7 @@ func open(path string, flag int, perm os.FileMode) (*os.File, error) {
 
 func lockFile(fd syscall.Handle, flags uint32) error {
 	// https://msdn.microsoft.com/en-us/library/windows/desktop/aa365203(v=vs.85).aspx
-	var flag uint32 = 2 // Lockfile exlusive.
+	var flag uint32 = lockFileExclusiveLock // Lockfile exlusive.
 	flag |= flags
 
 	if fd == syscall.InvalidHandle {
@@ -131,8 +146,8 @@ func lockFile(fd syscall.Handle, flags uint32) error {
 	err := lockFileEx(fd, flag, 1, 0, &syscall.Overlapped{})
 	if err == nil {
 		return nil
-	} else if err.Error() == errLocked.Error() {
+	} else if err.Error() == "The process cannot access the file because another process has locked a portion of the file." {
-		return errors.New("lock already acquired")
+		return ErrAlreadyLocked
 	} else if err != errLockViolation {
 		return err
 	}