xl: Rename getOrderedDisks as shuffleDisks appropriately. (#3796)

This PR is for readability cleanup

- getOrderedDisks as shuffleDisks
- getOrderedPartsMetadata as shufflePartsMetadata

Distribution is now a second argument instead being the
primary input argument for brevity.

Also change the usage of type casted int64(0), instead
rely on direct type reference as `var variable int64` everywhere.

cmd/erasure-readfile.go

@@ -192,7 +192,7 @@ func erasureReadFile(writer io.Writer, disks []StorageAPI, volume string, path s
 	}()
 
 	// Total bytes written to writer
-	bytesWritten := int64(0)
+	var bytesWritten int64
 
 	startBlock := offset / blockSize
 	endBlock := (offset + length) / blockSize
@@ -263,7 +263,7 @@ func erasureReadFile(writer io.Writer, disks []StorageAPI, volume string, path s
 		}
 
 		// Offset in enBlocks from where data should be read from.
-		enBlocksOffset := int64(0)
+		var enBlocksOffset int64
 
 		// Total data to be read from enBlocks.
 		enBlocksLength := curBlockSize

cmd/erasure-readfile_test.go

@@ -121,35 +121,6 @@ func testGetReadDisks(t *testing.T, xl *xlObjects) {
 	}
 }
 
-// Test getOrderedDisks which returns ordered slice of disks from their
-// actual distribution.
-func testGetOrderedDisks(t *testing.T, xl *xlObjects) {
-	disks := xl.storageDisks
-	distribution := []int{16, 14, 12, 10, 8, 6, 4, 2, 1, 3, 5, 7, 9, 11, 13, 15}
-	orderedDisks := getOrderedDisks(distribution, disks)
-	// From the "distribution" above you can notice that:
-	// 1st data block is in the 9th disk (i.e distribution index 8)
-	// 2nd data block is in the 8th disk (i.e distribution index 7) and so on.
-	if orderedDisks[0] != disks[8] ||
-		orderedDisks[1] != disks[7] ||
-		orderedDisks[2] != disks[9] ||
-		orderedDisks[3] != disks[6] ||
-		orderedDisks[4] != disks[10] ||
-		orderedDisks[5] != disks[5] ||
-		orderedDisks[6] != disks[11] ||
-		orderedDisks[7] != disks[4] ||
-		orderedDisks[8] != disks[12] ||
-		orderedDisks[9] != disks[3] ||
-		orderedDisks[10] != disks[13] ||
-		orderedDisks[11] != disks[2] ||
-		orderedDisks[12] != disks[14] ||
-		orderedDisks[13] != disks[1] ||
-		orderedDisks[14] != disks[15] ||
-		orderedDisks[15] != disks[0] {
-		t.Errorf("getOrderedDisks returned incorrect order.")
-	}
-}
-
 // Test for isSuccessDataBlocks and isSuccessDecodeBlocks.
 func TestIsSuccessBlocks(t *testing.T) {
 	dataBlocks := 8
@@ -217,7 +188,7 @@ func TestIsSuccessBlocks(t *testing.T) {
 	}
 }
 
-// Wrapper function for testGetReadDisks, testGetOrderedDisks.
+// Wrapper function for testGetReadDisks, testShuffleDisks.
 func TestErasureReadUtils(t *testing.T) {
 	nDisks := 16
 	disks, err := getRandomDisks(nDisks)
@@ -236,7 +207,6 @@ func TestErasureReadUtils(t *testing.T) {
 	defer removeRoots(disks)
 	xl := objLayer.(*xlObjects)
 	testGetReadDisks(t, xl)
-	testGetOrderedDisks(t, xl)
 }
 
 // Simulates a faulty disk for ReadFile()

cmd/erasure-utils.go

@@ -116,7 +116,7 @@ func writeDataBlocks(dst io.Writer, enBlocks [][]byte, dataBlocks int, offset in
 	write := length
 
 	// Counter to increment total written.
-	totalWritten := int64(0)
+	var totalWritten int64
 
 	// Write all data blocks to dst.
 	for _, block := range enBlocks[:dataBlocks] {
@@ -180,7 +180,7 @@ func copyBuffer(writer io.Writer, disk StorageAPI, volume string, path string, b
 	}
 
 	// Starting offset for Reading the file.
-	startOffset := int64(0)
+	var startOffset int64
 
 	// Read until io.EOF.
 	for {

cmd/fs-v1-background-append.go

@@ -210,7 +210,7 @@ func (fs fsObjects) appendParts(bucket, object, uploadID string, info bgAppendPa
 func (fs fsObjects) appendPart(bucket, object, uploadID string, part objectPartInfo, buf []byte) error {
 	partPath := pathJoin(fs.fsPath, minioMetaMultipartBucket, bucket, object, uploadID, part.Name)
 
-	offset := int64(0)
+	var offset int64
 	// Read each file part to start writing to the temporary concatenated object.
 	file, size, err := fsOpenFile(partPath, offset)
 	if err != nil {

cmd/fs-v1-multipart.go

@@ -463,7 +463,7 @@ func (fs fsObjects) CopyObjectPart(srcBucket, srcObject, dstBucket, dstObject, u
 	pipeReader, pipeWriter := io.Pipe()
 
 	go func() {
-		startOffset := int64(0) // Read the whole file.
+		var startOffset int64 // Read the whole file.
 		if gerr := fs.GetObject(srcBucket, srcObject, startOffset, length, pipeWriter); gerr != nil {
 			errorIf(gerr, "Unable to read %s/%s.", srcBucket, srcObject)
 			pipeWriter.CloseWithError(gerr)
@@ -864,7 +864,7 @@ func (fs fsObjects) CompleteMultipartUpload(bucket string, object string, upload
 			multipartPartFile := pathJoin(fs.fsPath, minioMetaMultipartBucket, uploadIDPath, partSuffix)
 
 			var reader io.ReadCloser
-			offset := int64(0)
+			var offset int64
 			reader, _, err = fsOpenFile(multipartPartFile, offset)
 			if err != nil {
 				fs.rwPool.Close(fsMetaPathMultipart)

cmd/fs-v1.go

@@ -395,7 +395,7 @@ func (fs fsObjects) CopyObject(srcBucket, srcObject, dstBucket, dstObject string
 	pipeReader, pipeWriter := io.Pipe()
 
 	go func() {
-		startOffset := int64(0) // Read the whole file.
+		var startOffset int64 // Read the whole file.
 		if gerr := fs.GetObject(srcBucket, srcObject, startOffset, length, pipeWriter); gerr != nil {
 			errorIf(gerr, "Unable to read %s/%s.", srcBucket, srcObject)
 			pipeWriter.CloseWithError(gerr)

cmd/lock-instrument_test.go

@@ -653,14 +653,14 @@ func TestNsLockMapDeleteLockInfoEntryForOps(t *testing.T) {
 	} else {
 		t.Fatalf("Entry for <volume> %s, <path> %s should have existed. ", param.volume, param.path)
 	}
-	if globalNSMutex.counters.granted != int64(0) {
-		t.Errorf("Expected the count of total running locks to be %v, but got %v", int64(0), globalNSMutex.counters.granted)
+	if globalNSMutex.counters.granted != 0 {
+		t.Errorf("Expected the count of total running locks to be %v, but got %v", 0, globalNSMutex.counters.granted)
 	}
-	if globalNSMutex.counters.blocked != int64(0) {
-		t.Errorf("Expected the count of total blocked locks to be %v, but got %v", int64(0), globalNSMutex.counters.blocked)
+	if globalNSMutex.counters.blocked != 0 {
+		t.Errorf("Expected the count of total blocked locks to be %v, but got %v", 0, globalNSMutex.counters.blocked)
 	}
-	if globalNSMutex.counters.total != int64(0) {
-		t.Errorf("Expected the count of all locks to be %v, but got %v", int64(0), globalNSMutex.counters.total)
+	if globalNSMutex.counters.total != 0 {
+		t.Errorf("Expected the count of all locks to be %v, but got %v", 0, globalNSMutex.counters.total)
 	}
 }
 
@@ -723,13 +723,13 @@ func TestNsLockMapDeleteLockInfoEntryForVolumePath(t *testing.T) {
 		t.Fatalf("Entry for <volume> %s, <path> %s should have been deleted. ", param.volume, param.path)
 	}
 	// The lock count values should be 0.
-	if globalNSMutex.counters.granted != int64(0) {
-		t.Errorf("Expected the count of total running locks to be %v, but got %v", int64(0), globalNSMutex.counters.granted)
+	if globalNSMutex.counters.granted != 0 {
+		t.Errorf("Expected the count of total running locks to be %v, but got %v", 0, globalNSMutex.counters.granted)
 	}
-	if globalNSMutex.counters.blocked != int64(0) {
-		t.Errorf("Expected the count of total blocked locks to be %v, but got %v", int64(0), globalNSMutex.counters.blocked)
+	if globalNSMutex.counters.blocked != 0 {
+		t.Errorf("Expected the count of total blocked locks to be %v, but got %v", 0, globalNSMutex.counters.blocked)
 	}
-	if globalNSMutex.counters.total != int64(0) {
-		t.Errorf("Expected the count of all locks to be %v, but got %v", int64(0), globalNSMutex.counters.total)
+	if globalNSMutex.counters.total != 0 {
+		t.Errorf("Expected the count of all locks to be %v, but got %v", 0, globalNSMutex.counters.total)
 	}
 }

cmd/object-api-putobject_test.go

@@ -146,7 +146,7 @@ func testObjectAPIPutObject(obj ObjectLayer, instanceType string, t TestErrHandl
 		// data with size different from the actual number of bytes available in the reader
 		{bucket, object, data, nil, "", int64(len(data) - 1), getMD5Hash(data[:len(data)-1]), nil},
 		{bucket, object, nilBytes, nil, "", int64(len(nilBytes) + 1), getMD5Hash(nilBytes), IncompleteBody{}},
-		{bucket, object, fiveMBBytes, nil, "", int64(0), getMD5Hash(fiveMBBytes), nil},
+		{bucket, object, fiveMBBytes, nil, "", 0, getMD5Hash(fiveMBBytes), nil},
 
 		// Test case 30
 		// valid data with X-Amz-Meta- meta

cmd/object-handlers.go

@@ -133,7 +133,7 @@ func (api objectAPIHandlers) GetObjectHandler(w http.ResponseWriter, r *http.Req
 	}
 
 	// Get the object.
-	startOffset := int64(0)
+	var startOffset int64
 	length := objInfo.Size
 	if hrange != nil {
 		startOffset = hrange.offsetBegin
@@ -620,7 +620,7 @@ func (api objectAPIHandlers) CopyObjectPartHandler(w http.ResponseWriter, r *htt
 	}
 
 	// Get the object.
-	startOffset := int64(0)
+	var startOffset int64
 	length := objInfo.Size
 	if hrange != nil {
 		startOffset = hrange.offsetBegin

cmd/server_utils_test.go

@@ -91,7 +91,7 @@ func calculateStreamContentLength(dataLen, chunkSize int64) int64 {
 	}
 	chunksCount := int64(dataLen / chunkSize)
 	remainingBytes := int64(dataLen % chunkSize)
-	streamLen := int64(0)
+	var streamLen int64
 	streamLen += chunksCount * calculateSignedChunkLength(chunkSize)
 	if remainingBytes > 0 {
 		streamLen += calculateSignedChunkLength(remainingBytes)

cmd/xl-v1-healing.go

@@ -371,9 +371,9 @@ func healObject(storageDisks []StorageAPI, bucket string, object string, quorum
 	}
 
 	// Reorder so that we have data disks first and parity disks next.
-	latestDisks = getOrderedDisks(latestMeta.Erasure.Distribution, latestDisks)
-	outDatedDisks = getOrderedDisks(latestMeta.Erasure.Distribution, outDatedDisks)
-	partsMetadata = getOrderedPartsMetadata(latestMeta.Erasure.Distribution, partsMetadata)
+	latestDisks = shuffleDisks(latestDisks, latestMeta.Erasure.Distribution)
+	outDatedDisks = shuffleDisks(outDatedDisks, latestMeta.Erasure.Distribution)
+	partsMetadata = shufflePartsMetadata(partsMetadata, latestMeta.Erasure.Distribution)
 
 	// We write at temporary location and then rename to fianal location.
 	tmpID := mustGetUUID()

cmd/xl-v1-multipart.go

@@ -544,7 +544,7 @@ func (xl xlObjects) CopyObjectPart(srcBucket, srcObject, dstBucket, dstObject, u
 	pipeReader, pipeWriter := io.Pipe()
 
 	go func() {
-		startOffset := int64(0) // Read the whole file.
+		var startOffset int64 // Read the whole file.
 		if gerr := xl.GetObject(srcBucket, srcObject, startOffset, length, pipeWriter); gerr != nil {
 			errorIf(gerr, "Unable to read %s of the object `%s/%s`.", srcBucket, srcObject)
 			pipeWriter.CloseWithError(toObjectErr(gerr, srcBucket, srcObject))
@@ -607,8 +607,7 @@ func (xl xlObjects) PutObjectPart(bucket, object, uploadID string, partID int, s
 		return PartInfo{}, err
 	}
 
-	onlineDisks = getOrderedDisks(xlMeta.Erasure.Distribution, onlineDisks)
-	_ = getOrderedPartsMetadata(xlMeta.Erasure.Distribution, partsMetadata)
+	onlineDisks = shuffleDisks(onlineDisks, xlMeta.Erasure.Distribution)
 
 	// Need a unique name for the part being written in minioMetaBucket to
 	// accommodate concurrent PutObjectPart requests
@@ -919,10 +918,10 @@ func (xl xlObjects) CompleteMultipartUpload(bucket string, object string, upload
 	}
 
 	// Order online disks in accordance with distribution order.
-	onlineDisks = getOrderedDisks(xlMeta.Erasure.Distribution, onlineDisks)
+	onlineDisks = shuffleDisks(onlineDisks, xlMeta.Erasure.Distribution)
 
 	// Order parts metadata in accordance with distribution order.
-	partsMetadata = getOrderedPartsMetadata(xlMeta.Erasure.Distribution, partsMetadata)
+	partsMetadata = shufflePartsMetadata(partsMetadata, xlMeta.Erasure.Distribution)
 
 	// Save current xl meta for validation.
 	var currentXLMeta = xlMeta

cmd/xl-v1-object.go

@@ -58,7 +58,7 @@ func (xl xlObjects) CopyObject(srcBucket, srcObject, dstBucket, dstObject string
 	}
 
 	// Reorder online disks based on erasure distribution order.
-	onlineDisks = getOrderedDisks(xlMeta.Erasure.Distribution, onlineDisks)
+	onlineDisks = shuffleDisks(onlineDisks, xlMeta.Erasure.Distribution)
 
 	// Length of the file to read.
 	length := xlMeta.Stat.Size
@@ -106,7 +106,7 @@ func (xl xlObjects) CopyObject(srcBucket, srcObject, dstBucket, dstObject string
 	pipeReader, pipeWriter := io.Pipe()
 
 	go func() {
-		startOffset := int64(0) // Read the whole file.
+		var startOffset int64 // Read the whole file.
 		if gerr := xl.GetObject(srcBucket, srcObject, startOffset, length, pipeWriter); gerr != nil {
 			errorIf(gerr, "Unable to read %s of the object `%s/%s`.", srcBucket, srcObject)
 			pipeWriter.CloseWithError(toObjectErr(gerr, srcBucket, srcObject))
@@ -163,10 +163,10 @@ func (xl xlObjects) GetObject(bucket, object string, startOffset int64, length i
 	}
 
 	// Reorder online disks based on erasure distribution order.
-	onlineDisks = getOrderedDisks(xlMeta.Erasure.Distribution, onlineDisks)
+	onlineDisks = shuffleDisks(onlineDisks, xlMeta.Erasure.Distribution)
 
 	// Reorder parts metadata based on erasure distribution order.
-	metaArr = getOrderedPartsMetadata(xlMeta.Erasure.Distribution, metaArr)
+	metaArr = shufflePartsMetadata(metaArr, xlMeta.Erasure.Distribution)
 
 	// For negative length read everything.
 	if length < 0 {
@@ -242,7 +242,7 @@ func (xl xlObjects) GetObject(bucket, object string, startOffset int64, length i
 		}
 	}
 
-	totalBytesRead := int64(0)
+	var totalBytesRead int64
 
 	chunkSize := getChunkSize(xlMeta.Erasure.BlockSize, xlMeta.Erasure.DataBlocks)
 	pool := bpool.NewBytePool(chunkSize, len(onlineDisks))
@@ -525,7 +525,7 @@ func (xl xlObjects) PutObject(bucket string, object string, size int64, data io.
 	}
 
 	// Order disks according to erasure distribution
-	onlineDisks := getOrderedDisks(partsMetadata[0].Erasure.Distribution, xl.storageDisks)
+	onlineDisks := shuffleDisks(xl.storageDisks, partsMetadata[0].Erasure.Distribution)
 
 	// Delete temporary object in the event of failure.
 	// If PutObject succeeded there would be no temporary
@@ -533,7 +533,7 @@ func (xl xlObjects) PutObject(bucket string, object string, size int64, data io.
 	defer xl.deleteObject(minioMetaTmpBucket, tempObj)
 
 	// Total size of the written object
-	sizeWritten := int64(0)
+	var sizeWritten int64
 
 	// Read data and split into parts - similar to multipart mechanism
 	for partIdx := 1; ; partIdx++ {
@@ -550,9 +550,10 @@ func (xl xlObjects) PutObject(bucket string, object string, size int64, data io.
 			return ObjectInfo{}, toObjectErr(err, bucket, object)
 		}
 
-		// Prepare file for eventual optimization in the disk
+		// Hint the filesystem to pre-allocate one continuous large block.
+		// This is only an optimization.
 		if curPartSize > 0 {
-			// Calculate the real size of the part in the disk and prepare it for eventual optimization
+			// Calculate the real size of the part in the disk.
 			actualSize := xl.sizeOnDisk(curPartSize, xlMeta.Erasure.BlockSize, xlMeta.Erasure.DataBlocks)
 			for _, disk := range onlineDisks {
 				if disk != nil {

cmd/xl-v1-utils.go

@@ -306,26 +306,34 @@ func readAllXLMetadata(disks []StorageAPI, bucket, object string) ([]xlMetaV1, [
 	return metadataArray, errs
 }
 
-// Return ordered partsMetadata depending on distribution.
-func getOrderedPartsMetadata(distribution []int, partsMetadata []xlMetaV1) (orderedPartsMetadata []xlMetaV1) {
-	orderedPartsMetadata = make([]xlMetaV1, len(partsMetadata))
+// Return shuffled partsMetadata depending on distribution.
+func shufflePartsMetadata(partsMetadata []xlMetaV1, distribution []int) (shuffledPartsMetadata []xlMetaV1) {
+	if distribution == nil {
+		return partsMetadata
+	}
+	shuffledPartsMetadata = make([]xlMetaV1, len(partsMetadata))
+	// Shuffle slice xl metadata for expected distribution.
 	for index := range partsMetadata {
 		blockIndex := distribution[index]
-		orderedPartsMetadata[blockIndex-1] = partsMetadata[index]
+		shuffledPartsMetadata[blockIndex-1] = partsMetadata[index]
 	}
-	return orderedPartsMetadata
+	return shuffledPartsMetadata
 }
 
-// getOrderedDisks - get ordered disks from erasure distribution.
-// returns ordered slice of disks from their actual distribution.
-func getOrderedDisks(distribution []int, disks []StorageAPI) (orderedDisks []StorageAPI) {
-	orderedDisks = make([]StorageAPI, len(disks))
-	// From disks gets ordered disks.
+// shuffleDisks - shuffle input disks slice depending on the
+// erasure distribution. return shuffled slice of disks with
+// their expected distribution.
+func shuffleDisks(disks []StorageAPI, distribution []int) (shuffledDisks []StorageAPI) {
+	if distribution == nil {
+		return disks
+	}
+	shuffledDisks = make([]StorageAPI, len(disks))
+	// Shuffle disks for expected distribution.
 	for index := range disks {
 		blockIndex := distribution[index]
-		orderedDisks[blockIndex-1] = disks[index]
+		shuffledDisks[blockIndex-1] = disks[index]
 	}
-	return orderedDisks
+	return shuffledDisks
 }
 
 // Errors specifically generated by getPartSizeFromIdx function.

cmd/xl-v1-utils_test.go

@@ -383,3 +383,51 @@ func TestGetPartSizeFromIdx(t *testing.T) {
 		}
 	}
 }
+
+func TestShuffleDisks(t *testing.T) {
+	nDisks := 16
+	disks, err := getRandomDisks(nDisks)
+	if err != nil {
+		t.Fatal(err)
+	}
+	endpoints, err := parseStorageEndpoints(disks)
+	if err != nil {
+		t.Fatal(err)
+	}
+	objLayer, _, err := initObjectLayer(endpoints)
+	if err != nil {
+		removeRoots(disks)
+		t.Fatal(err)
+	}
+	defer removeRoots(disks)
+	xl := objLayer.(*xlObjects)
+	testShuffleDisks(t, xl)
+}
+
+// Test shuffleDisks which returns shuffled slice of disks for their actual distribution.
+func testShuffleDisks(t *testing.T, xl *xlObjects) {
+	disks := xl.storageDisks
+	distribution := []int{16, 14, 12, 10, 8, 6, 4, 2, 1, 3, 5, 7, 9, 11, 13, 15}
+	shuffledDisks := shuffleDisks(disks, distribution)
+	// From the "distribution" above you can notice that:
+	// 1st data block is in the 9th disk (i.e distribution index 8)
+	// 2nd data block is in the 8th disk (i.e distribution index 7) and so on.
+	if shuffledDisks[0] != disks[8] ||
+		shuffledDisks[1] != disks[7] ||
+		shuffledDisks[2] != disks[9] ||
+		shuffledDisks[3] != disks[6] ||
+		shuffledDisks[4] != disks[10] ||
+		shuffledDisks[5] != disks[5] ||
+		shuffledDisks[6] != disks[11] ||
+		shuffledDisks[7] != disks[4] ||
+		shuffledDisks[8] != disks[12] ||
+		shuffledDisks[9] != disks[3] ||
+		shuffledDisks[10] != disks[13] ||
+		shuffledDisks[11] != disks[2] ||
+		shuffledDisks[12] != disks[14] ||
+		shuffledDisks[13] != disks[1] ||
+		shuffledDisks[14] != disks[15] ||
+		shuffledDisks[15] != disks[0] {
+		t.Errorf("shuffleDisks returned incorrect order.")
+	}
+}