XL: Make allocations simpler avoid redundant allocs. (#1961)

- Reduce 10MiB buffers for loopy calls to use 128KiB.
- start using 128KiB buffer where needed.

erasure-readfile.go

@@ -17,6 +17,7 @@
 package main
 
 import (
+	"bytes"
 	"encoding/hex"
 	"errors"
 	"io"
@@ -25,6 +26,59 @@ import (
 	"github.com/klauspost/reedsolomon"
 )
 
+// isSuccessDecodeBlocks - do we have all the blocks to be successfully decoded?.
+// input disks here are expected to be ordered i.e parityBlocks
+// are preceded by dataBlocks. For for information look at getOrderedDisks().
+func isSuccessDecodeBlocks(disks []StorageAPI, dataBlocks int) bool {
+	// Count number of data and parity blocks that were read.
+	var successDataBlocksCount = 0
+	var successParityBlocksCount = 0
+	for index, disk := range disks {
+		if disk == nil {
+			continue
+		}
+		if index < dataBlocks {
+			successDataBlocksCount++
+			continue
+		}
+		successParityBlocksCount++
+	}
+	// Returns true if we have atleast dataBlocks + 1 parity.
+	return successDataBlocksCount+successParityBlocksCount >= dataBlocks+1
+}
+
+// isSuccessDataBlocks - do we have all the data blocks?
+// input disks here are expected to be ordered i.e parityBlocks
+// are preceded by dataBlocks. For for information look at getOrderedDisks().
+func isSuccessDataBlocks(disks []StorageAPI, dataBlocks int) bool {
+	// Count number of data blocks that were read.
+	var successDataBlocksCount = 0
+	for index, disk := range disks[:dataBlocks] {
+		if disk == nil {
+			continue
+		}
+		if index < dataBlocks {
+			successDataBlocksCount++
+		}
+	}
+	// Returns true if we have all the dataBlocks.
+	return successDataBlocksCount >= dataBlocks
+}
+
+// getOrderedDisks - get ordered disks from erasure distribution.
+// returns ordered slice of disks from their actual distribution.
+func getOrderedDisks(distribution []int, disks []StorageAPI, blockCheckSums []checkSumInfo) (orderedDisks []StorageAPI, orderedBlockCheckSums []checkSumInfo) {
+	orderedDisks = make([]StorageAPI, len(disks))
+	orderedBlockCheckSums = make([]checkSumInfo, len(disks))
+	// From disks gets ordered disks.
+	for index := range disks {
+		blockIndex := distribution[index]
+		orderedDisks[blockIndex-1] = disks[index]
+		orderedBlockCheckSums[blockIndex-1] = blockCheckSums[index]
+	}
+	return orderedDisks, orderedBlockCheckSums
+}
+
 // erasureReadFile - read bytes from erasure coded files and writes to given writer.
 // Erasure coded files are read block by block as per given erasureInfo and data chunks
 // are decoded into a data block. Data block is trimmed for given offset and length,
@@ -36,26 +90,24 @@ func erasureReadFile(writer io.Writer, disks []StorageAPI, volume string, path s
 
 	// Gather previously calculated block checksums.
 	blockCheckSums := metaPartBlockChecksums(disks, eInfos, partName)
-	orderedBlockCheckSums := make([]checkSumInfo, len(disks))
 
-	// []orderedDisks will have first eInfo.DataBlocks disks as data disks and rest will be parity.
-	orderedDisks := make([]StorageAPI, len(disks))
-	for index := range disks {
-		blockIndex := eInfo.Distribution[index]
-		orderedDisks[blockIndex-1] = disks[index]
-		orderedBlockCheckSums[blockIndex-1] = blockCheckSums[index]
-	}
+	// []orderedDisks will have first eInfo.DataBlocks disks as data
+	// disks and rest will be parity.
+	orderedDisks, orderedBlockCheckSums := getOrderedDisks(eInfo.Distribution, disks, blockCheckSums)
 
-	// bitrotVerify verifies if the file on a particular disk does not have bitrot by verifying the hash of
-	// the contents of the file.
+	// bitrotVerify verifies if the file on a particular disk doesn't have bitrot
+	// by verifying the hash of the contents of the file.
 	bitrotVerify := func() func(diskIndex int) bool {
 		verified := make([]bool, len(orderedDisks))
-		// Return closure so that we have reference to []verified and not recalculate the hash on it
-		// everytime the function is called for the same disk.
+		// Return closure so that we have reference to []verified and
+		// not recalculate the hash on it everytime the function is
+		// called for the same disk.
 		return func(diskIndex int) bool {
 			if verified[diskIndex] {
+				// Already validated.
 				return true
 			}
+			// Is this a valid block?
 			isValid := isValidBlock(orderedDisks[diskIndex], volume, path, orderedBlockCheckSums[diskIndex])
 			verified[diskIndex] = isValid
 			return isValid
@@ -65,128 +117,166 @@ func erasureReadFile(writer io.Writer, disks []StorageAPI, volume string, path s
 	// Total bytes written to writer
 	bytesWritten := int64(0)
 
+	// Each element of enBlocks holds curChunkSize'd amount of data read from its corresponding disk.
+	enBlocks := make([][]byte, len(orderedDisks))
+
 	// chunkSize is roughly BlockSize/DataBlocks.
 	// chunkSize is calculated such that chunkSize*DataBlocks accommodates BlockSize bytes.
 	// So chunkSize*DataBlocks can be slightly larger than BlockSize if BlockSize is not divisible by
 	// DataBlocks. The extra space will have 0-padding.
 	chunkSize := getEncodedBlockLen(eInfo.BlockSize, eInfo.DataBlocks)
 
+	// Get start and end block, also bytes to be skipped based on the input offset.
 	startBlock, endBlock, bytesToSkip := getBlockInfo(offset, totalLength, eInfo.BlockSize)
 
 	// For each block, read chunk from each disk. If we are able to read all the data disks then we don't
 	// need to read parity disks. If one of the data disk is missing we need to read DataBlocks+1 number
 	// of disks. Once read, we Reconstruct() missing data if needed and write it to the given writer.
 	for block := startBlock; bytesWritten < length; block++ {
-		// curChunkSize will be chunkSize except for the last block because the size of the last block
-		// can be less than BlockSize.
+		// curChunkSize is chunkSize until end block.
 		curChunkSize := chunkSize
 		if block == endBlock && (totalLength%eInfo.BlockSize != 0) {
 			// If this is the last block and size of the block is < BlockSize.
 			curChunkSize = getEncodedBlockLen(totalLength%eInfo.BlockSize, eInfo.DataBlocks)
 		}
 
-		// Each element of enBlocks holds curChunkSize'd amount of data read from its corresponding disk.
-		enBlocks := make([][]byte, len(disks))
+		// Block offset.
+		// NOTE: That for the offset calculation we have to use chunkSize and
+		// not curChunkSize. If we use curChunkSize for offset calculation
+		// then it can result in wrong offset for the last block.
+		blockOffset := block * chunkSize
 
 		// Figure out the number of disks that are needed for the read.
 		// We will need DataBlocks number of disks if all the data disks are up.
 		// We will need DataBlocks+1 number of disks even if one of the data disks is down.
-		diskCount := 0
+		readableDiskCount := 0
+
 		// Count the number of data disks that are up.
 		for _, disk := range orderedDisks[:eInfo.DataBlocks] {
 			if disk == nil {
 				continue
 			}
-			diskCount++
+			readableDiskCount++
 		}
 
-		if diskCount < eInfo.DataBlocks {
-			// Not enough data disks up, so we need DataBlocks+1 number of disks for reed-solomon Reconstruct()
-			diskCount = eInfo.DataBlocks + 1
+		// Readable disks..
+		if readableDiskCount < eInfo.DataBlocks {
+			// Not enough data disks up, so we need DataBlocks+1 number
+			// of disks for reed-solomon Reconstruct()
+			readableDiskCount = eInfo.DataBlocks + 1
 		}
 
-		wg := &sync.WaitGroup{}
+		// Initialize wait group.
+		var wg = &sync.WaitGroup{}
 
-		// current disk index from which to read, this will be used later in case one of the parallel reads fails.
+		// Current disk index from which to read, this will be used later
+		// in case one of the parallel reads fails.
 		index := 0
+
 		// Read from the disks in parallel.
 		for _, disk := range orderedDisks {
 			if disk == nil {
 				index++
 				continue
 			}
+
+			// Increment wait group.
 			wg.Add(1)
+
+			// Start reading from disk in a go-routine.
 			go func(index int, disk StorageAPI) {
 				defer wg.Done()
-				ok := bitrotVerify(index)
-				if !ok {
+
+				// Verify bit rot for this disk slice.
+				if !bitrotVerify(index) {
 					// So that we don't read from this disk for the next block.
 					orderedDisks[index] = nil
 					return
 				}
-				buf := make([]byte, curChunkSize)
-				// Note that for the offset calculation we have to use chunkSize and not
-				// curChunkSize. If we use curChunkSize for offset calculation then it
-				// can result in wrong offset for the last block.
-				n, err := disk.ReadFile(volume, path, block*chunkSize, buf)
+
+				// Chunk writer.
+				chunkWriter := bytes.NewBuffer(make([]byte, 0, curChunkSize))
+
+				// CopyN copies until current chunk size.
+				err := copyN(chunkWriter, disk, volume, path, blockOffset, curChunkSize)
 				if err != nil {
 					// So that we don't read from this disk for the next block.
 					orderedDisks[index] = nil
 					return
 				}
-				enBlocks[index] = buf[:n]
+
+				// Copy the read blocks.
+				enBlocks[index] = chunkWriter.Bytes()
+
+				// Reset the buffer.
+				chunkWriter.Reset()
+
+				// Successfully read.
 			}(index, disk)
+
 			index++
-			diskCount--
-			if diskCount == 0 {
+			readableDiskCount--
+			// We have read all the readable disks.
+			if readableDiskCount == 0 {
 				break
 			}
 		}
+
+		// Wait for all the reads to finish.
 		wg.Wait()
 
-		// Count number of data and parity blocks that were read.
-		var successDataBlocksCount = 0
-		var successParityBlocksCount = 0
-		for bufidx, buf := range enBlocks {
-			if buf == nil {
-				continue
-			}
-			if bufidx < eInfo.DataBlocks {
-				successDataBlocksCount++
-				continue
-			}
-			successParityBlocksCount++
-		}
+		// FIXME: make this parallel.
 
-		if successDataBlocksCount < eInfo.DataBlocks {
-			// If we don't have DataBlocks number of data blocks we will have to read enough
-			// parity blocks such that we have DataBlocks+1 number for blocks for reedsolomon.Reconstruct()
+		// If we have all the data blocks no need to decode.
+		if !isSuccessDataBlocks(orderedDisks, eInfo.DataBlocks) {
+			// If we don't have DataBlocks number of data blocks we
+			// will have to read enough parity blocks such that we
+			// have DataBlocks+1 number for blocks for rs.Reconstruct().
+			// index is either dataBlocks or dataBlocks + 1.
 			for ; index < len(orderedDisks); index++ {
-				if (successDataBlocksCount + successParityBlocksCount) == (eInfo.DataBlocks + 1) {
-					// We have DataBlocks+1 blocks, enough for reedsolomon.Reconstruct()
+				// We have enough blocks to decode, break out.
+				if isSuccessDecodeBlocks(orderedDisks, eInfo.DataBlocks) {
+					// We have DataBlocks+1 blocks, enough for rs.Reconstruct()
 					break
 				}
-				ok := bitrotVerify(index)
-				if !ok {
+
+				// This disk was previously set to nil and ignored, do not read again.
+				if orderedDisks[index] == nil {
+					continue
+				}
+
+				// Verify bit-rot for this index.
+				if !bitrotVerify(index) {
 					// Mark nil so that we don't read from this disk for the next block.
 					orderedDisks[index] = nil
 					continue
 				}
-				buf := make([]byte, curChunkSize)
-				n, err := orderedDisks[index].ReadFile(volume, path, block*chunkSize, buf)
+
+				// Chunk writer.
+				chunkWriter := bytes.NewBuffer(make([]byte, 0, curChunkSize))
+
+				// CopyN copies until current chunk size.
+				err := copyN(chunkWriter, orderedDisks[index], volume, path, blockOffset, curChunkSize)
 				if err != nil {
-					// Mark nil so that we don't read from this disk for the next block.
+					// ERROR: Mark nil so that we don't read from
+					// this disk for the next block.
 					orderedDisks[index] = nil
 					continue
 				}
-				successParityBlocksCount++
-				enBlocks[index] = buf[:n]
+
+				// Copy the read blocks.
+				chunkWriter.Read(enBlocks[index])
+
+				// Reset the buffer.
+				chunkWriter.Reset()
 			}
+
 			// Reconstruct the missing data blocks.
 			err := decodeData(enBlocks, eInfo.DataBlocks, eInfo.ParityBlocks)
 			if err != nil {
 				return bytesWritten, err
 			}
+			// Success.
 		}
 
 		var outSize, outOffset int64
@@ -209,14 +299,18 @@ func erasureReadFile(writer io.Writer, disks []StorageAPI, volume string, path s
 			// We should not send more data than what was requested.
 			outSize = length - bytesWritten
 		}
+
 		// Write data blocks.
 		n, err := writeDataBlocks(writer, enBlocks, eInfo.DataBlocks, outOffset, outSize)
 		if err != nil {
 			return bytesWritten, err
 		}
+
+		// Update total bytes written.
 		bytesWritten += n
 	}
 
+	// Success.
 	return bytesWritten, nil
 }
 
@@ -273,14 +367,18 @@ func isValidBlock(disk StorageAPI, volume, path string, blockCheckSum checkSumIn
 
 // decodeData - decode encoded blocks.
 func decodeData(enBlocks [][]byte, dataBlocks, parityBlocks int) error {
+	// Initialized reedsolomon.
 	rs, err := reedsolomon.New(dataBlocks, parityBlocks)
 	if err != nil {
 		return err
 	}
+
+	// Reconstruct encoded blocks.
 	err = rs.Reconstruct(enBlocks)
 	if err != nil {
 		return err
 	}
+
 	// Verify reconstructed blocks (parity).
 	ok, err := rs.Verify(enBlocks)
 	if err != nil {
@@ -291,5 +389,7 @@ func decodeData(enBlocks [][]byte, dataBlocks, parityBlocks int) error {
 		err = errors.New("Verification failed after reconstruction, data likely corrupted.")
 		return err
 	}
+
+	// Success.
 	return nil
 }

erasure-utils.go

@@ -18,6 +18,7 @@ package main
 
 import (
 	"bytes"
+	"errors"
 	"hash"
 	"io"
 
@@ -46,21 +47,17 @@ func newHash(algo string) hash.Hash {
 	}
 }
 
+// hashSum calculates the hash of the entire path and returns.
 func hashSum(disk StorageAPI, volume, path string, writer hash.Hash) ([]byte, error) {
-	startOffset := int64(0)
-	// Read until io.EOF.
-	for {
-		buf := make([]byte, blockSizeV1)
-		n, err := disk.ReadFile(volume, path, startOffset, buf)
-		if err == io.EOF {
-			break
-		}
-		if err != nil {
-			return nil, err
-		}
-		writer.Write(buf[:n])
-		startOffset += n
+	// Allocate staging buffer of 128KiB for copyBuffer.
+	buf := make([]byte, 128*1024)
+
+	// Copy entire buffer to writer.
+	if err := copyBuffer(writer, disk, volume, path, buf); err != nil {
+		return nil, err
 	}
+
+	// Return the final hash sum.
 	return writer.Sum(nil), nil
 }
 
@@ -149,3 +146,86 @@ func getEncodedBlockLen(inputLen int64, dataBlocks int) (curEncBlockSize int64)
 	curEncBlockSize = (inputLen + int64(dataBlocks) - 1) / int64(dataBlocks)
 	return curEncBlockSize
 }
+
+// copyN - copies from disk, volume, path to input writer until length
+// is reached at volume, path or an error occurs. A success copyN returns
+// err == nil, not err == EOF. Additionally offset can be provided to start
+// the read at. copyN returns io.EOF if there aren't enough data to be read.
+func copyN(writer io.Writer, disk StorageAPI, volume string, path string, offset int64, length int64) (err error) {
+	// Use 128KiB staging buffer to read upto length.
+	buf := make([]byte, 128*1024)
+
+	// Read into writer until length.
+	for length > 0 {
+		nr, er := disk.ReadFile(volume, path, offset, buf)
+		if nr > 0 {
+			nw, ew := writer.Write(buf[0:nr])
+			if nw > 0 {
+				// Decrement the length.
+				length -= int64(nw)
+
+				// Progress the offset.
+				offset += int64(nw)
+			}
+			if ew != nil {
+				err = ew
+				break
+			}
+			if nr != int64(nw) {
+				err = io.ErrShortWrite
+				break
+			}
+		}
+		if er == io.EOF || er == io.ErrUnexpectedEOF {
+			break
+		}
+		if er != nil {
+			err = er
+		}
+	}
+
+	// Success.
+	return err
+}
+
+// copyBuffer - copies from disk, volume, path to input writer until either EOF
+// is reached at volume, path or an error occurs. A success copyBuffer returns
+// err == nil, not err == EOF. Because copyBuffer is defined to read from path
+// until EOF. It does not treat an EOF from ReadFile an error to be reported.
+// Additionally copyBuffer stages through the provided buffer; otherwise if it
+// has zero length, returns error.
+func copyBuffer(writer io.Writer, disk StorageAPI, volume string, path string, buf []byte) error {
+	// Error condition of zero length buffer.
+	if buf != nil && len(buf) == 0 {
+		return errors.New("empty buffer in readBuffer")
+	}
+
+	// Starting offset for Reading the file.
+	startOffset := int64(0)
+
+	// Read until io.EOF.
+	for {
+		n, err := disk.ReadFile(volume, path, startOffset, buf)
+		if n > 0 {
+			var m int
+			m, err = writer.Write(buf[:n])
+			if err != nil {
+				return err
+			}
+			if int64(m) != n {
+				return io.ErrShortWrite
+			}
+		}
+		if err != nil {
+			if err == io.EOF || err == io.ErrUnexpectedEOF {
+				break
+			}
+			return err
+		}
+		// Progress the offset.
+		startOffset += n
+	}
+
+	// Success.
+	return nil
+}

format-config-v1.go

@@ -17,6 +17,7 @@
 package main
 
 import (
+	"bytes"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -346,9 +347,10 @@ func reorderDisks(bootstrapDisks []StorageAPI, formatConfigs []*formatConfigV1)
 
 // loadFormat - loads format.json from disk.
 func loadFormat(disk StorageAPI) (format *formatConfigV1, err error) {
-	var buffer []byte
-	buffer, err = readAll(disk, minioMetaBucket, formatConfigFile)
-	if err != nil {
+	// Allocate staging buffer of 32KiB for copyBuffer.
+	buf := make([]byte, 32*1024)
+	var buffer = new(bytes.Buffer)
+	if err = copyBuffer(buffer, disk, minioMetaBucket, formatConfigFile, buf); err != nil {
 		// 'file not found' and 'volume not found' as
 		// same. 'volume not found' usually means its a fresh disk.
 		if err == errFileNotFound || err == errVolumeNotFound {
@@ -366,11 +368,15 @@ func loadFormat(disk StorageAPI) (format *formatConfigV1, err error) {
 		}
 		return nil, err
 	}
+
+	// Try to decode format json into formatConfigV1 struct.
 	format = &formatConfigV1{}
-	err = json.Unmarshal(buffer, format)
-	if err != nil {
+	d := json.NewDecoder(buffer)
+	if err = d.Decode(format); err != nil {
 		return nil, err
 	}
+
+	// Success.
 	return format, nil
 }
 

fs-v1-metadata.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"bytes"
 	"encoding/json"
 	"path"
 	"sort"
@@ -57,16 +58,23 @@ func (m *fsMetaV1) AddObjectPart(partNumber int, partName string, partETag strin
 }
 
 // readFSMetadata - returns the object metadata `fs.json` content.
-func (fs fsObjects) readFSMetadata(bucket, object string) (fsMeta fsMetaV1, err error) {
-	var buffer []byte
-	buffer, err = readAll(fs.storage, bucket, path.Join(object, fsMetaJSONFile))
-	if err != nil {
+func readFSMetadata(disk StorageAPI, bucket, object string) (fsMeta fsMetaV1, err error) {
+	// 32KiB staging buffer for copying `fs.json`.
+	var buf = make([]byte, 32*1024)
+
+	// `fs.json` writer.
+	var buffer = new(bytes.Buffer)
+	if err = copyBuffer(buffer, disk, bucket, path.Join(object, fsMetaJSONFile), buf); err != nil {
 		return fsMetaV1{}, err
 	}
-	err = json.Unmarshal(buffer, &fsMeta)
-	if err != nil {
+
+	//  Decode `fs.json` into fsMeta structure.
+	d := json.NewDecoder(buffer)
+	if err = d.Decode(&fsMeta); err != nil {
 		return fsMetaV1{}, err
 	}
+
+	// Success.
 	return fsMeta, nil
 }
 

fs-v1-multipart.go

@@ -299,7 +299,8 @@ func (fs fsObjects) PutObjectPart(bucket, object, uploadID string, partID int, s
 	// Initialize md5 writer.
 	md5Writer := md5.New()
 
-	var buf = make([]byte, blockSizeV1)
+	// Allocate 32KiB buffer for staging buffer.
+	var buf = make([]byte, 128*1024)
 	for {
 		n, err := io.ReadFull(data, buf)
 		if err == io.EOF {
@@ -331,7 +332,7 @@ func (fs fsObjects) PutObjectPart(bucket, object, uploadID string, partID int, s
 		return "", InvalidUploadID{UploadID: uploadID}
 	}
 
-	fsMeta, err := fs.readFSMetadata(minioMetaBucket, uploadIDPath)
+	fsMeta, err := readFSMetadata(fs.storage, minioMetaBucket, uploadIDPath)
 	if err != nil {
 		return "", toObjectErr(err, minioMetaBucket, uploadIDPath)
 	}
@@ -367,7 +368,7 @@ func (fs fsObjects) listObjectParts(bucket, object, uploadID string, partNumberM
 	result := ListPartsInfo{}
 
 	uploadIDPath := path.Join(mpartMetaPrefix, bucket, object, uploadID)
-	fsMeta, err := fs.readFSMetadata(minioMetaBucket, uploadIDPath)
+	fsMeta, err := readFSMetadata(fs.storage, minioMetaBucket, uploadIDPath)
 	if err != nil {
 		return ListPartsInfo{}, toObjectErr(err, minioMetaBucket, uploadIDPath)
 	}
@@ -475,7 +476,7 @@ func (fs fsObjects) CompleteMultipartUpload(bucket string, object string, upload
 	}
 
 	// Read saved fs metadata for ongoing multipart.
-	fsMeta, err := fs.readFSMetadata(minioMetaBucket, uploadIDPath)
+	fsMeta, err := readFSMetadata(fs.storage, minioMetaBucket, uploadIDPath)
 	if err != nil {
 		return "", toObjectErr(err, minioMetaBucket, uploadIDPath)
 	}
@@ -487,7 +488,9 @@ func (fs fsObjects) CompleteMultipartUpload(bucket string, object string, upload
 	}
 
 	tempObj := path.Join(tmpMetaPrefix, uploadID, "object1")
-	var buffer = make([]byte, blockSizeV1)
+
+	// Allocate 32KiB buffer for staging buffer.
+	var buf = make([]byte, 128*1024)
 
 	// Loop through all parts, validate them and then commit to disk.
 	for i, part := range parts {
@@ -509,16 +512,21 @@ func (fs fsObjects) CompleteMultipartUpload(bucket string, object string, upload
 		totalLeft := fsMeta.Parts[partIdx].Size
 		for totalLeft > 0 {
 			var n int64
-			n, err = fs.storage.ReadFile(minioMetaBucket, multipartPartFile, offset, buffer)
+			n, err = fs.storage.ReadFile(minioMetaBucket, multipartPartFile, offset, buf)
+			if n > 0 {
+				if err = fs.storage.AppendFile(minioMetaBucket, tempObj, buf[:n]); err != nil {
+					return "", toObjectErr(err, minioMetaBucket, tempObj)
+				}
+			}
 			if err != nil {
+				if err == io.EOF || err == io.ErrUnexpectedEOF {
+					break
+				}
 				if err == errFileNotFound {
 					return "", InvalidPart{}
 				}
 				return "", toObjectErr(err, minioMetaBucket, multipartPartFile)
 			}
-			if err = fs.storage.AppendFile(minioMetaBucket, tempObj, buffer[:n]); err != nil {
-				return "", toObjectErr(err, minioMetaBucket, tempObj)
-			}
 			offset += n
 			totalLeft -= n
 		}

fs-v1.go

@@ -17,8 +17,10 @@
 package main
 
 import (
+	"bytes"
 	"crypto/md5"
 	"encoding/hex"
+	"encoding/json"
 	"io"
 	"os"
 	"path"
@@ -45,8 +47,26 @@ func initFormatFS(storageDisk StorageAPI) error {
 }
 
 // loads format.json from minioMetaBucket if it exists.
-func loadFormatFS(storageDisk StorageAPI) ([]byte, error) {
-	return readAll(storageDisk, minioMetaBucket, fsFormatJSONFile)
+func loadFormatFS(storageDisk StorageAPI) (format formatConfigV1, err error) {
+	// Allocate 32k buffer, this is sufficient for the most of `format.json`.
+	buf := make([]byte, 32*1024)
+
+	// Allocate a new `format.json` buffer writer.
+	var buffer = new(bytes.Buffer)
+
+	// Reads entire `format.json`.
+	if err = copyBuffer(buffer, storageDisk, minioMetaBucket, fsFormatJSONFile, buf); err != nil {
+		return formatConfigV1{}, err
+	}
+
+	// Unmarshal format config.
+	d := json.NewDecoder(buffer)
+	if err = d.Decode(&format); err != nil {
+		return formatConfigV1{}, err
+	}
+
+	// Return structured `format.json`.
+	return format, nil
 }
 
 // Should be called when process shuts down.
@@ -74,6 +94,7 @@ func newFSObjects(disk string) (ObjectLayer, error) {
 
 	// Runs house keeping code, like creating minioMetaBucket, cleaning up tmp files etc.
 	fsHouseKeeping(storage)
+
 	// loading format.json from minioMetaBucket.
 	// Note: The format.json content is ignored, reserved for future use.
 	_, err = loadFormatFS(storage)
@@ -88,10 +109,12 @@ func newFSObjects(disk string) (ObjectLayer, error) {
 			return nil, err
 		}
 	}
+
 	// Register the callback that should be called when the process shuts down.
 	registerShutdown(func() {
 		shutdownFS(storage)
 	})
+
 	// Return successfully initialized object layer.
 	return fsObjects{
 		storage:            storage,
@@ -178,7 +201,7 @@ func (fs fsObjects) DeleteBucket(bucket string) error {
 /// Object Operations
 
 // GetObject - get an object.
-func (fs fsObjects) GetObject(bucket, object string, startOffset int64, length int64, writer io.Writer) error {
+func (fs fsObjects) GetObject(bucket, object string, offset int64, length int64, writer io.Writer) error {
 	// Verify if bucket is valid.
 	if !IsValidBucketName(bucket) {
 		return BucketNameInvalid{Bucket: bucket}
@@ -188,26 +211,28 @@ func (fs fsObjects) GetObject(bucket, object string, startOffset int64, length i
 		return ObjectNameInvalid{Bucket: bucket, Object: object}
 	}
 	var totalLeft = length
+	buf := make([]byte, 32*1024) // Allocate a 32KiB staging buffer.
 	for totalLeft > 0 {
-		// Figure out the right blockSize as it was encoded before.
-		var curBlockSize int64
+		// Figure out the right size for the buffer.
+		var curSize int64
 		if blockSizeV1 < totalLeft {
-			curBlockSize = blockSizeV1
+			curSize = blockSizeV1
 		} else {
-			curBlockSize = totalLeft
+			curSize = totalLeft
 		}
-		buf := make([]byte, curBlockSize)
-		n, err := fs.storage.ReadFile(bucket, object, startOffset, buf)
+		// Reads the file at offset.
+		n, err := fs.storage.ReadFile(bucket, object, offset, buf[:curSize])
 		if err != nil {
 			return toObjectErr(err, bucket, object)
 		}
-		_, err = writer.Write(buf[:n])
+		// Write to response writer.
+		m, err := writer.Write(buf[:n])
 		if err != nil {
 			return toObjectErr(err, bucket, object)
 		}
-		totalLeft -= n
-		startOffset += n
-	}
+		totalLeft -= int64(m)
+		offset += int64(m)
+	} // Success.
 	return nil
 }
 
@@ -276,7 +301,7 @@ func (fs fsObjects) PutObject(bucket string, object string, size int64, data io.
 		}
 	} else {
 		// Allocate a buffer to Read() the object upload stream.
-		buf := make([]byte, blockSizeV1)
+		buf := make([]byte, 32*1024)
 		// Read the buffer till io.EOF and append the read data to
 		// the temporary file.
 		for {

posix.go

@@ -418,14 +418,9 @@ func (s *posix) ReadFile(volume string, path string, offset int64, buf []byte) (
 	// Close the reader.
 	defer file.Close()
 
-	// Read file.
+	// Read full until buffer.
 	m, err := io.ReadFull(file, buf)
 
-	// Error unexpected is valid, set this back to nil.
-	if err == io.ErrUnexpectedEOF {
-		err = nil
-	}
-
 	// Success.
 	return int64(m), err
 }

xl-v1-healing.go

@@ -16,11 +16,7 @@
 
 package main
 
-import (
-	"encoding/json"
-	"path"
-	"sync"
-)
+import "sync"
 
 // Get the highest integer from a given integer slice.
 func highestInt(intSlice []int64, highestInt int64) (highestInteger int64) {
@@ -54,28 +50,23 @@ func listObjectVersions(partsMetadata []xlMetaV1, errs []error) (versions []int6
 func (xl xlObjects) readAllXLMetadata(bucket, object string) ([]xlMetaV1, []error) {
 	errs := make([]error, len(xl.storageDisks))
 	metadataArray := make([]xlMetaV1, len(xl.storageDisks))
-	xlMetaPath := path.Join(object, xlMetaJSONFile)
 	var wg = &sync.WaitGroup{}
+	// Read `xl.json` parallelly across disks.
 	for index, disk := range xl.storageDisks {
 		if disk == nil {
 			errs[index] = errDiskNotFound
 			continue
 		}
 		wg.Add(1)
+		// Read `xl.json` in routine.
 		go func(index int, disk StorageAPI) {
 			defer wg.Done()
-			buffer, err := readAll(disk, bucket, xlMetaPath)
+			var err error
+			metadataArray[index], err = readXLMeta(disk, bucket, object)
 			if err != nil {
 				errs[index] = err
 				return
 			}
-			err = json.Unmarshal(buffer, &metadataArray[index])
-			if err != nil {
-				// Unable to parse xl.json, set error.
-				errs[index] = err
-				return
-			}
-			errs[index] = nil
 		}(index, disk)
 	}
 

xl-v1-metadata.go

@@ -201,8 +201,7 @@ func (xl xlObjects) readXLMetadata(bucket, object string) (xlMeta xlMetaV1, err
 		if disk == nil {
 			continue
 		}
-		var buf []byte
-		buf, err = readAll(disk, bucket, path.Join(object, xlMetaJSONFile))
+		xlMeta, err = readXLMeta(disk, bucket, object)
 		if err != nil {
 			// For any reason disk is not available continue and read from other disks.
 			if err == errDiskNotFound || err == errFaultyDisk {
@@ -210,10 +209,6 @@ func (xl xlObjects) readXLMetadata(bucket, object string) (xlMeta xlMetaV1, err
 			}
 			return xlMetaV1{}, err
 		}
-		err = json.Unmarshal(buf, &xlMeta)
-		if err != nil {
-			return xlMetaV1{}, err
-		}
 		break
 	}
 	return xlMeta, nil

xl-v1-multipart-common.go

@@ -17,6 +17,7 @@
 package main
 
 import (
+	"bytes"
 	"encoding/json"
 	"path"
 	"sort"
@@ -69,16 +70,25 @@ func (u uploadsV1) Index(uploadID string) int {
 
 // readUploadsJSON - get all the saved uploads JSON.
 func readUploadsJSON(bucket, object string, disk StorageAPI) (uploadIDs uploadsV1, err error) {
+	// Staging buffer of 128KiB kept for reading `uploads.json`.
+	var buf = make([]byte, 128*1024)
+
+	// Writer holding `uploads.json` content.
+	var buffer = new(bytes.Buffer)
+
 	uploadJSONPath := path.Join(mpartMetaPrefix, bucket, object, uploadsJSONFile)
-	// Read all of 'uploads.json'
-	buffer, rErr := readAll(disk, minioMetaBucket, uploadJSONPath)
-	if rErr != nil {
-		return uploadsV1{}, rErr
+	// Reads entire `uploads.json`.
+	if err = copyBuffer(buffer, disk, minioMetaBucket, uploadJSONPath, buf); err != nil {
+		return uploadsV1{}, err
 	}
-	rErr = json.Unmarshal(buffer, &uploadIDs)
-	if rErr != nil {
-		return uploadsV1{}, rErr
+
+	// Decode `uploads.json`.
+	d := json.NewDecoder(buffer)
+	if err = d.Decode(&uploadIDs); err != nil {
+		return uploadsV1{}, err
 	}
+
+	// Success.
 	return uploadIDs, nil
 }
 

xl-v1-utils.go

@@ -18,7 +18,7 @@ package main
 
 import (
 	"bytes"
-	"io"
+	"encoding/json"
 	"math/rand"
 	"path"
 	"time"
@@ -64,48 +64,25 @@ func randInts(count int) []int {
 	return ints
 }
 
-// readAll - returns contents from volume/path as byte array.
-func readAll(disk StorageAPI, volume string, path string) ([]byte, error) {
-	var writer = new(bytes.Buffer)
-	startOffset := int64(0)
+// readXLMeta reads `xl.json` returns contents as byte array.
+func readXLMeta(disk StorageAPI, bucket string, object string) (xlMeta xlMetaV1, err error) {
+	// Allocate 32k buffer, this is sufficient for the most of `xl.json`.
+	buf := make([]byte, 128*1024)
 
-	// Allocate 10MiB buffer.
-	buf := make([]byte, blockSizeV1)
+	// Allocate a new `xl.json` buffer writer.
+	var buffer = new(bytes.Buffer)
 
-	// Read until io.EOF.
-	for {
-		n, err := disk.ReadFile(volume, path, startOffset, buf)
-		if err == io.EOF {
-			break
-		}
-		if err != nil && err != io.EOF {
-			return nil, err
-		}
-		writer.Write(buf[:n])
-		startOffset += n
+	// Reads entire `xl.json`.
+	if err = copyBuffer(buffer, disk, bucket, path.Join(object, xlMetaJSONFile), buf); err != nil {
+		return xlMetaV1{}, err
 	}
-	return writer.Bytes(), nil
-}
-
-// readXLMeta reads `xl.json` returns contents as byte array.
-func readXLMeta(disk StorageAPI, bucket string, object string) ([]byte, error) {
-	var writer = new(bytes.Buffer)
-	startOffset := int64(0)
-
-	// Allocate 2MiB buffer, this is sufficient for the most of `xl.json`.
-	buf := make([]byte, 2*1024*1024)
 
-	// Read until io.EOF.
-	for {
-		n, err := disk.ReadFile(bucket, path.Join(object, xlMetaJSONFile), startOffset, buf)
-		if err == io.EOF {
-			break
-		}
-		if err != nil && err != io.EOF {
-			return nil, err
-		}
-		writer.Write(buf[:n])
-		startOffset += n
+	// Unmarshal xl metadata.
+	d := json.NewDecoder(buffer)
+	if err = d.Decode(&xlMeta); err != nil {
+		return xlMetaV1{}, err
 	}
-	return writer.Bytes(), nil
+
+	// Return structured `xl.json`.
+	return xlMeta, nil
 }