minio/cmd/erasure-object.go

// Copyright (c) 2015-2021 MinIO, Inc.
//
// This file is part of MinIO Object Storage stack
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

package cmd

import (
	"bytes"
	"context"
	"errors"
	"fmt"
	"io"
	"net/http"
	"path"
	"strings"
	"sync"

	"github.com/minio/madmin-go"
	"github.com/minio/minio-go/v7/pkg/tags"
	xhttp "github.com/minio/minio/cmd/http"
	"github.com/minio/minio/cmd/logger"
	"github.com/minio/minio/pkg/bucket/lifecycle"
	"github.com/minio/minio/pkg/bucket/replication"
	"github.com/minio/minio/pkg/event"
	"github.com/minio/minio/pkg/hash"
	"github.com/minio/minio/pkg/mimedb"
	"github.com/minio/minio/pkg/sync/errgroup"
)

// list all errors which can be ignored in object operations.
var objectOpIgnoredErrs = append(baseIgnoredErrs, errDiskAccessDenied, errUnformattedDisk)

/// Object Operations

func countOnlineDisks(onlineDisks []StorageAPI) (online int) {
	for _, onlineDisk := range onlineDisks {
		if onlineDisk != nil && onlineDisk.IsOnline() {
			online++
		}
	}
	return online
}

// CopyObject - copy object source object to destination object.
// if source object and destination object are same we only
// update metadata.
func (er erasureObjects) CopyObject(ctx context.Context, srcBucket, srcObject, dstBucket, dstObject string, srcInfo ObjectInfo, srcOpts, dstOpts ObjectOptions) (oi ObjectInfo, err error) {
	// This call shouldn't be used for anything other than metadata updates or adding self referential versions.
	if !srcInfo.metadataOnly {
		return oi, NotImplemented{}
	}

	defer ObjectPathUpdated(pathJoin(dstBucket, dstObject))
	if !dstOpts.NoLock {
		lk := er.NewNSLock(dstBucket, dstObject)
		lkctx, err := lk.GetLock(ctx, globalOperationTimeout)
		if err != nil {
			return oi, err
		}
		ctx = lkctx.Context()
		defer lk.Unlock(lkctx.Cancel)
	}
	// Read metadata associated with the object from all disks.
	storageDisks := er.getDisks()
	metaArr, errs := readAllFileInfo(ctx, storageDisks, srcBucket, srcObject, srcOpts.VersionID, true)

	// get Quorum for this object
	readQuorum, writeQuorum, err := objectQuorumFromMeta(ctx, metaArr, errs, er.defaultParityCount)
	if err != nil {
		return oi, toObjectErr(err, srcBucket, srcObject)
	}

	// List all online disks.
	onlineDisks, modTime, dataDir := listOnlineDisks(storageDisks, metaArr, errs)

	// Pick latest valid metadata.
	fi, err := pickValidFileInfo(ctx, metaArr, modTime, dataDir, readQuorum)
	if err != nil {
		return oi, toObjectErr(err, srcBucket, srcObject)
	}
	if fi.Deleted {
		if srcOpts.VersionID == "" {
			return oi, toObjectErr(errFileNotFound, srcBucket, srcObject)
		}
		return fi.ToObjectInfo(srcBucket, srcObject), toObjectErr(errMethodNotAllowed, srcBucket, srcObject)
	}

	versionID := srcInfo.VersionID
	if srcInfo.versionOnly {
		versionID = dstOpts.VersionID
		// preserve destination versionId if specified.
		if versionID == "" {
			versionID = mustGetUUID()
		}
		modTime = UTCNow()
	}
	fi.VersionID = versionID // set any new versionID we might have created
	fi.ModTime = modTime     // set modTime for the new versionID
	if !dstOpts.MTime.IsZero() {
		modTime = dstOpts.MTime
		fi.ModTime = dstOpts.MTime
	}
	fi.Metadata = srcInfo.UserDefined
	srcInfo.UserDefined["etag"] = srcInfo.ETag

	// Update `xl.meta` content on each disks.
	for index := range metaArr {
		if metaArr[index].IsValid() {
			metaArr[index].ModTime = modTime
			metaArr[index].VersionID = versionID
			metaArr[index].Metadata = srcInfo.UserDefined
		}
	}

	// Write unique `xl.meta` for each disk.
	if _, err = writeUniqueFileInfo(ctx, onlineDisks, srcBucket, srcObject, metaArr, writeQuorum); err != nil {
		return oi, toObjectErr(err, srcBucket, srcObject)
	}

	return fi.ToObjectInfo(srcBucket, srcObject), nil
}

// GetObjectNInfo - returns object info and an object
// Read(Closer). When err != nil, the returned reader is always nil.
func (er erasureObjects) GetObjectNInfo(ctx context.Context, bucket, object string, rs *HTTPRangeSpec, h http.Header, lockType LockType, opts ObjectOptions) (gr *GetObjectReader, err error) {
	var unlockOnDefer bool
	var nsUnlocker = func() {}
	defer func() {
		if unlockOnDefer {
			nsUnlocker()
		}
	}()

	// Acquire lock
	if lockType != noLock {
		lock := er.NewNSLock(bucket, object)
		switch lockType {
		case writeLock:
			lkctx, err := lock.GetLock(ctx, globalOperationTimeout)
			if err != nil {
				return nil, err
			}
			ctx = lkctx.Context()
			nsUnlocker = func() { lock.Unlock(lkctx.Cancel) }
		case readLock:
			lkctx, err := lock.GetRLock(ctx, globalOperationTimeout)
			if err != nil {
				return nil, err
			}
			ctx = lkctx.Context()
			nsUnlocker = func() { lock.RUnlock(lkctx.Cancel) }
		}
		unlockOnDefer = true
	}

	fi, metaArr, onlineDisks, err := er.getObjectFileInfo(ctx, bucket, object, opts, true)
	if err != nil {
		return nil, toObjectErr(err, bucket, object)
	}

	objInfo := fi.ToObjectInfo(bucket, object)
	if objInfo.DeleteMarker {
		if opts.VersionID == "" {
			return &GetObjectReader{
				ObjInfo: objInfo,
			}, toObjectErr(errFileNotFound, bucket, object)
		}
		// Make sure to return object info to provide extra information.
		return &GetObjectReader{
			ObjInfo: objInfo,
		}, toObjectErr(errMethodNotAllowed, bucket, object)
	}
	if objInfo.IsRemote() {
		gr, err := getTransitionedObjectReader(ctx, bucket, object, rs, h, objInfo, opts)
		if err != nil {
			return nil, err
		}
		unlockOnDefer = false
		return gr.WithCleanupFuncs(nsUnlocker), nil
	}

	fn, off, length, err := NewGetObjectReader(rs, objInfo, opts)
	if err != nil {
		return nil, err
	}
	unlockOnDefer = false
	pr, pw := io.Pipe()
	go func() {
		pw.CloseWithError(er.getObjectWithFileInfo(ctx, bucket, object, off, length, pw, fi, metaArr, onlineDisks))
	}()

	// Cleanup function to cause the go routine above to exit, in
	// case of incomplete read.
	pipeCloser := func() { pr.Close() }

	return fn(pr, h, opts.CheckPrecondFn, pipeCloser, nsUnlocker)
}

// GetObject - reads an object erasured coded across multiple
// disks. Supports additional parameters like offset and length
// which are synonymous with HTTP Range requests.
//
// startOffset indicates the starting read location of the object.
// length indicates the total length of the object.
func (er erasureObjects) GetObject(ctx context.Context, bucket, object string, startOffset int64, length int64, writer io.Writer, etag string, opts ObjectOptions) (err error) {
	// Lock the object before reading.
	lk := er.NewNSLock(bucket, object)
	lkctx, err := lk.GetRLock(ctx, globalOperationTimeout)
	if err != nil {
		return err
	}
	ctx = lkctx.Context()
	defer lk.RUnlock(lkctx.Cancel)

	// Start offset cannot be negative.
	if startOffset < 0 {
		logger.LogIf(ctx, errUnexpected, logger.Application)
		return errUnexpected
	}

	// Writer cannot be nil.
	if writer == nil {
		logger.LogIf(ctx, errUnexpected)
		return errUnexpected
	}

	return er.getObject(ctx, bucket, object, startOffset, length, writer, opts)
}

func (er erasureObjects) getObjectWithFileInfo(ctx context.Context, bucket, object string, startOffset int64, length int64, writer io.Writer, fi FileInfo, metaArr []FileInfo, onlineDisks []StorageAPI) error {
	// Reorder online disks based on erasure distribution order.
	// Reorder parts metadata based on erasure distribution order.
	onlineDisks, metaArr = shuffleDisksAndPartsMetadataByIndex(onlineDisks, metaArr, fi)

	// For negative length read everything.
	if length < 0 {
		length = fi.Size - startOffset
	}

	// Reply back invalid range if the input offset and length fall out of range.
	if startOffset > fi.Size || startOffset+length > fi.Size {
		logger.LogIf(ctx, InvalidRange{startOffset, length, fi.Size}, logger.Application)
		return InvalidRange{startOffset, length, fi.Size}
	}

	// Get start part index and offset.
	partIndex, partOffset, err := fi.ObjectToPartOffset(ctx, startOffset)
	if err != nil {
		return InvalidRange{startOffset, length, fi.Size}
	}

	// Calculate endOffset according to length
	endOffset := startOffset
	if length > 0 {
		endOffset += length - 1
	}

	// Get last part index to read given length.
	lastPartIndex, _, err := fi.ObjectToPartOffset(ctx, endOffset)
	if err != nil {
		return InvalidRange{startOffset, length, fi.Size}
	}

	var totalBytesRead int64
	erasure, err := NewErasure(ctx, fi.Erasure.DataBlocks, fi.Erasure.ParityBlocks, fi.Erasure.BlockSize)
	if err != nil {
		return toObjectErr(err, bucket, object)
	}
	var healOnce sync.Once

	for ; partIndex <= lastPartIndex; partIndex++ {
		if length == totalBytesRead {
			break
		}

		partNumber := fi.Parts[partIndex].Number

		// Save the current part name and size.
		partSize := fi.Parts[partIndex].Size

		partLength := partSize - partOffset
		// partLength should be adjusted so that we don't write more data than what was requested.
		if partLength > (length - totalBytesRead) {
			partLength = length - totalBytesRead
		}

		tillOffset := erasure.ShardFileOffset(partOffset, partLength, partSize)
		// Get the checksums of the current part.
		readers := make([]io.ReaderAt, len(onlineDisks))
		prefer := make([]bool, len(onlineDisks))
		for index, disk := range onlineDisks {
			if disk == OfflineDisk {
				continue
			}
			if !metaArr[index].IsValid() {
				continue
			}
			checksumInfo := metaArr[index].Erasure.GetChecksumInfo(partNumber)
			partPath := pathJoin(object, metaArr[index].DataDir, fmt.Sprintf("part.%d", partNumber))
			data := metaArr[index].Data
			readers[index] = newBitrotReader(disk, data, bucket, partPath, tillOffset,
				checksumInfo.Algorithm, checksumInfo.Hash, erasure.ShardSize())

			// Prefer local disks
			prefer[index] = disk.Hostname() == ""
		}

		written, err := erasure.Decode(ctx, writer, readers, partOffset, partLength, partSize, prefer)
		// Note: we should not be defer'ing the following closeBitrotReaders() call as
		// we are inside a for loop i.e if we use defer, we would accumulate a lot of open files by the time
		// we return from this function.
		closeBitrotReaders(readers)
		if err != nil {
			// If we have successfully written all the content that was asked
			// by the client, but we still see an error - this would mean
			// that we have some parts or data blocks missing or corrupted
			// - attempt a heal to successfully heal them for future calls.
			if written == partLength {
				var scan madmin.HealScanMode
				if errors.Is(err, errFileNotFound) {
					scan = madmin.HealNormalScan
				} else if errors.Is(err, errFileCorrupt) {
					scan = madmin.HealDeepScan
				}
				if scan != madmin.HealUnknownScan {
					healOnce.Do(func() {
						if _, healing := er.getOnlineDisksWithHealing(); !healing {
							go healObject(bucket, object, fi.VersionID, scan)
						}
					})
				}
			}
			if err != nil {
				return toObjectErr(err, bucket, object)
			}
		}
		for i, r := range readers {
			if r == nil {
				onlineDisks[i] = OfflineDisk
			}
		}
		// Track total bytes read from disk and written to the client.
		totalBytesRead += partLength
		// partOffset will be valid only for the first part, hence reset it to 0 for
		// the remaining parts.
		partOffset = 0
	} // End of read all parts loop.
	// Return success.
	return nil
}

// getObject wrapper for erasure GetObject
func (er erasureObjects) getObject(ctx context.Context, bucket, object string, startOffset, length int64, writer io.Writer, opts ObjectOptions) error {
	fi, metaArr, onlineDisks, err := er.getObjectFileInfo(ctx, bucket, object, opts, true)
	if err != nil {
		return toObjectErr(err, bucket, object)
	}
	if fi.Deleted {
		if opts.VersionID == "" {
			return toObjectErr(errFileNotFound, bucket, object)
		}
		// Make sure to return object info to provide extra information.
		return toObjectErr(errMethodNotAllowed, bucket, object)
	}

	return er.getObjectWithFileInfo(ctx, bucket, object, startOffset, length, writer, fi, metaArr, onlineDisks)
}

// GetObjectInfo - reads object metadata and replies back ObjectInfo.
func (er erasureObjects) GetObjectInfo(ctx context.Context, bucket, object string, opts ObjectOptions) (info ObjectInfo, err error) {
	if !opts.NoLock {
		// Lock the object before reading.
		lk := er.NewNSLock(bucket, object)
		lkctx, err := lk.GetRLock(ctx, globalOperationTimeout)
		if err != nil {
			return ObjectInfo{}, err
		}
		ctx = lkctx.Context()
		defer lk.RUnlock(lkctx.Cancel)
	}

	return er.getObjectInfo(ctx, bucket, object, opts)
}

func (er erasureObjects) getObjectFileInfo(ctx context.Context, bucket, object string, opts ObjectOptions, readData bool) (fi FileInfo, metaArr []FileInfo, onlineDisks []StorageAPI, err error) {
	disks := er.getDisks()

	// Read metadata associated with the object from all disks.
	metaArr, errs := readAllFileInfo(ctx, disks, bucket, object, opts.VersionID, readData)

	readQuorum, _, err := objectQuorumFromMeta(ctx, metaArr, errs, er.defaultParityCount)
	if err != nil {
		return fi, nil, nil, err
	}

	if reducedErr := reduceReadQuorumErrs(ctx, errs, objectOpIgnoredErrs, readQuorum); reducedErr != nil {
		if reducedErr == errErasureReadQuorum && bucket != minioMetaBucket {
			if _, ok := isObjectDangling(metaArr, errs, nil); ok {
				reducedErr = errFileNotFound
				if opts.VersionID != "" {
					reducedErr = errFileVersionNotFound
				}
				// Remove the dangling object only when:
				//  - This is a non versioned bucket
				//  - This is a versioned bucket and the version ID is passed, the reason
				//    is that we cannot fetch the ID of the latest version when we don't trust xl.meta
				if !opts.Versioned || opts.VersionID != "" {
					er.deleteObjectVersion(ctx, bucket, object, 1, FileInfo{
						Name:      object,
						VersionID: opts.VersionID,
					}, false)
				}
			}
		}
		return fi, nil, nil, toObjectErr(reducedErr, bucket, object)
	}

	// List all online disks.
	onlineDisks, modTime, dataDir := listOnlineDisks(disks, metaArr, errs)

	// Pick latest valid metadata.
	fi, err = pickValidFileInfo(ctx, metaArr, modTime, dataDir, readQuorum)
	if err != nil {
		return fi, nil, nil, err
	}

	// if one of the disk is offline, return right here no need
	// to attempt a heal on the object.
	if countErrs(errs, errDiskNotFound) > 0 {
		return fi, metaArr, onlineDisks, nil
	}

	var missingBlocks int
	for i, err := range errs {
		if err != nil && errors.Is(err, errFileNotFound) {
			missingBlocks++
			continue
		}
		if metaArr[i].IsValid() && metaArr[i].ModTime.Equal(fi.ModTime) && metaArr[i].DataDir == fi.DataDir {
			continue
		}
		missingBlocks++
	}

	// if missing metadata can be reconstructed, attempt to reconstruct.
	if missingBlocks > 0 && missingBlocks < readQuorum {
		if _, healing := er.getOnlineDisksWithHealing(); !healing {
			go healObject(bucket, object, fi.VersionID, madmin.HealNormalScan)
		}
	}

	return fi, metaArr, onlineDisks, nil
}

// getObjectInfo - wrapper for reading object metadata and constructs ObjectInfo.
func (er erasureObjects) getObjectInfo(ctx context.Context, bucket, object string, opts ObjectOptions) (objInfo ObjectInfo, err error) {
	fi, _, _, err := er.getObjectFileInfo(ctx, bucket, object, opts, false)
	if err != nil {
		return objInfo, toObjectErr(err, bucket, object)

	}
	objInfo = fi.ToObjectInfo(bucket, object)
	if !fi.VersionPurgeStatus.Empty() {
		// Make sure to return object info to provide extra information.
		return objInfo, toObjectErr(errMethodNotAllowed, bucket, object)
	}

	if fi.Deleted {
		if opts.VersionID == "" || opts.DeleteMarker {
			return objInfo, toObjectErr(errFileNotFound, bucket, object)
		}
		// Make sure to return object info to provide extra information.
		return objInfo, toObjectErr(errMethodNotAllowed, bucket, object)
	}

	return objInfo, nil
}

func undoRename(disks []StorageAPI, srcBucket, srcEntry, dstBucket, dstEntry string, isDir bool, errs []error) {
	// Undo rename object on disks where RenameFile succeeded.

	// If srcEntry/dstEntry are objects then add a trailing slash to copy
	// over all the parts inside the object directory
	if isDir {
		srcEntry = retainSlash(srcEntry)
		dstEntry = retainSlash(dstEntry)
	}
	g := errgroup.WithNErrs(len(disks))
	for index, disk := range disks {
		if disk == nil {
			continue
		}
		index := index
		g.Go(func() error {
			if errs[index] == nil {
				_ = disks[index].RenameFile(context.TODO(), dstBucket, dstEntry, srcBucket, srcEntry)
			}
			return nil
		}, index)
	}
	g.Wait()
}

// Similar to rename but renames data from srcEntry to dstEntry at dataDir
func renameData(ctx context.Context, disks []StorageAPI, srcBucket, srcEntry string, metadata []FileInfo, dstBucket, dstEntry string, writeQuorum int) ([]StorageAPI, error) {
	defer ObjectPathUpdated(pathJoin(srcBucket, srcEntry))
	defer ObjectPathUpdated(pathJoin(dstBucket, dstEntry))

	g := errgroup.WithNErrs(len(disks))

	// Rename file on all underlying storage disks.
	for index := range disks {
		index := index
		g.Go(func() error {
			if disks[index] == nil {
				return errDiskNotFound
			}
			// Pick one FileInfo for a disk at index.
			fi := metadata[index]
			// Assign index when index is initialized
			if fi.Erasure.Index == 0 {
				fi.Erasure.Index = index + 1
			}
			if fi.IsValid() {
				return disks[index].RenameData(ctx, srcBucket, srcEntry, fi, dstBucket, dstEntry)
			}
			return errFileCorrupt
		}, index)
	}

	// Wait for all renames to finish.
	errs := g.Wait()

	// We can safely allow RenameFile errors up to len(er.getDisks()) - writeQuorum
	// otherwise return failure. Cleanup successful renames.
	err := reduceWriteQuorumErrs(ctx, errs, objectOpIgnoredErrs, writeQuorum)
	return evalDisks(disks, errs), err
}

// rename - common function that renamePart and renameObject use to rename
// the respective underlying storage layer representations.
func rename(ctx context.Context, disks []StorageAPI, srcBucket, srcEntry, dstBucket, dstEntry string, isDir bool, writeQuorum int, ignoredErr []error) ([]StorageAPI, error) {
	if isDir {
		dstEntry = retainSlash(dstEntry)
		srcEntry = retainSlash(srcEntry)
	}
	defer ObjectPathUpdated(pathJoin(srcBucket, srcEntry))
	defer ObjectPathUpdated(pathJoin(dstBucket, dstEntry))

	g := errgroup.WithNErrs(len(disks))

	// Rename file on all underlying storage disks.
	for index := range disks {
		index := index
		g.Go(func() error {
			if disks[index] == nil {
				return errDiskNotFound
			}
			if err := disks[index].RenameFile(ctx, srcBucket, srcEntry, dstBucket, dstEntry); err != nil {
				if !IsErrIgnored(err, ignoredErr...) {
					return err
				}
			}
			return nil
		}, index)
	}

	// Wait for all renames to finish.
	errs := g.Wait()

	// We can safely allow RenameFile errors up to len(er.getDisks()) - writeQuorum
	// otherwise return failure. Cleanup successful renames.
	err := reduceWriteQuorumErrs(ctx, errs, objectOpIgnoredErrs, writeQuorum)
	if err == errErasureWriteQuorum {
		// Undo all the partial rename operations.
		undoRename(disks, srcBucket, srcEntry, dstBucket, dstEntry, isDir, errs)
	}
	return evalDisks(disks, errs), err
}

// PutObject - creates an object upon reading from the input stream
// until EOF, erasure codes the data across all disk and additionally
// writes `xl.meta` which carries the necessary metadata for future
// object operations.
func (er erasureObjects) PutObject(ctx context.Context, bucket string, object string, data *PutObjReader, opts ObjectOptions) (objInfo ObjectInfo, err error) {
	return er.putObject(ctx, bucket, object, data, opts)
}

// putObject wrapper for erasureObjects PutObject
func (er erasureObjects) putObject(ctx context.Context, bucket string, object string, r *PutObjReader, opts ObjectOptions) (objInfo ObjectInfo, err error) {
	defer func() {
		ObjectPathUpdated(pathJoin(bucket, object))
	}()

	data := r.Reader

	uniqueID := mustGetUUID()
	tempObj := uniqueID
	// No metadata is set, allocate a new one.
	if opts.UserDefined == nil {
		opts.UserDefined = make(map[string]string)
	}

	storageDisks := er.getDisks()

	parityDrives := len(storageDisks) / 2
	if !opts.MaxParity {
		// Get parity and data drive count based on storage class metadata
		parityDrives = globalStorageClass.GetParityForSC(opts.UserDefined[xhttp.AmzStorageClass])
		if parityDrives <= 0 {
			parityDrives = er.defaultParityCount
		}
	}
	dataDrives := len(storageDisks) - parityDrives

	// we now know the number of blocks this object needs for data and parity.
	// writeQuorum is dataBlocks + 1
	writeQuorum := dataDrives
	if dataDrives == parityDrives {
		writeQuorum++
	}

	// Validate input data size and it can never be less than zero.
	if data.Size() < -1 {
		logger.LogIf(ctx, errInvalidArgument, logger.Application)
		return ObjectInfo{}, toObjectErr(errInvalidArgument)
	}

	// Check if an object is present as one of the parent dir.
	// -- FIXME. (needs a new kind of lock).
	// -- FIXME (this also causes performance issue when disks are down).
	if opts.ParentIsObject != nil && opts.ParentIsObject(ctx, bucket, path.Dir(object)) {
		return ObjectInfo{}, toObjectErr(errFileParentIsFile, bucket, object)
	}

	// Initialize parts metadata
	partsMetadata := make([]FileInfo, len(storageDisks))

	fi := newFileInfo(pathJoin(bucket, object), dataDrives, parityDrives)
	fi.VersionID = opts.VersionID
	if opts.Versioned && fi.VersionID == "" {
		fi.VersionID = mustGetUUID()
	}
	fi.DataDir = mustGetUUID()

	// Initialize erasure metadata.
	for index := range partsMetadata {
		partsMetadata[index] = fi
	}

	// Order disks according to erasure distribution
	var onlineDisks []StorageAPI
	onlineDisks, partsMetadata = shuffleDisksAndPartsMetadata(storageDisks, partsMetadata, fi)

	erasure, err := NewErasure(ctx, fi.Erasure.DataBlocks, fi.Erasure.ParityBlocks, fi.Erasure.BlockSize)
	if err != nil {
		return ObjectInfo{}, toObjectErr(err, bucket, object)
	}

	// Fetch buffer for I/O, returns from the pool if not allocates a new one and returns.
	var buffer []byte
	switch size := data.Size(); {
	case size == 0:
		buffer = make([]byte, 1) // Allocate atleast a byte to reach EOF
	case size == -1:
		if size := data.ActualSize(); size > 0 && size < fi.Erasure.BlockSize {
			buffer = make([]byte, data.ActualSize()+256, data.ActualSize()*2+512)
		} else {
			buffer = er.bp.Get()
			defer er.bp.Put(buffer)
		}
	case size >= fi.Erasure.BlockSize:
		buffer = er.bp.Get()
		defer er.bp.Put(buffer)
	case size < fi.Erasure.BlockSize:
		// No need to allocate fully blockSizeV1 buffer if the incoming data is smaller.
		buffer = make([]byte, size, 2*size+int64(fi.Erasure.ParityBlocks+fi.Erasure.DataBlocks-1))
	}

	if len(buffer) > int(fi.Erasure.BlockSize) {
		buffer = buffer[:fi.Erasure.BlockSize]
	}

	partName := "part.1"
	tempErasureObj := pathJoin(uniqueID, fi.DataDir, partName)

	// Delete temporary object in the event of failure.
	// If PutObject succeeded there would be no temporary
	// object to delete.
	var online int
	defer func() {
		if online != len(onlineDisks) {
			er.deleteObject(context.Background(), minioMetaTmpBucket, tempObj, writeQuorum)
		}
	}()

	shardFileSize := erasure.ShardFileSize(data.Size())
	writers := make([]io.Writer, len(onlineDisks))
	var inlineBuffers []*bytes.Buffer
	if shardFileSize >= 0 {
		if !opts.Versioned && shardFileSize < smallFileThreshold {
			inlineBuffers = make([]*bytes.Buffer, len(onlineDisks))
		} else if shardFileSize < smallFileThreshold/8 {
			inlineBuffers = make([]*bytes.Buffer, len(onlineDisks))
		}
	}
	for i, disk := range onlineDisks {
		if disk == nil {
			continue
		}

		if len(inlineBuffers) > 0 {
			inlineBuffers[i] = bytes.NewBuffer(make([]byte, 0, shardFileSize))
			writers[i] = newStreamingBitrotWriterBuffer(inlineBuffers[i], DefaultBitrotAlgorithm, erasure.ShardSize())
			continue
		}
		writers[i] = newBitrotWriter(disk, minioMetaTmpBucket, tempErasureObj,
			shardFileSize, DefaultBitrotAlgorithm, erasure.ShardSize(), false)
	}

	n, erasureErr := erasure.Encode(ctx, data, writers, buffer, writeQuorum)
	closeBitrotWriters(writers)
	if erasureErr != nil {
		return ObjectInfo{}, toObjectErr(erasureErr, minioMetaTmpBucket, tempErasureObj)
	}

	// Should return IncompleteBody{} error when reader has fewer bytes
	// than specified in request header.
	if n < data.Size() {
		return ObjectInfo{}, IncompleteBody{Bucket: bucket, Object: object}
	}

	if !opts.NoLock {
		lk := er.NewNSLock(bucket, object)
		lkctx, err := lk.GetLock(ctx, globalOperationTimeout)
		if err != nil {
			return ObjectInfo{}, err
		}
		ctx = lkctx.Context()
		defer lk.Unlock(lkctx.Cancel)
	}

	for i, w := range writers {
		if w == nil {
			onlineDisks[i] = nil
			continue
		}
		if len(inlineBuffers) > 0 && inlineBuffers[i] != nil {
			partsMetadata[i].Data = inlineBuffers[i].Bytes()
		} else {
			partsMetadata[i].Data = nil
		}
		partsMetadata[i].AddObjectPart(1, "", n, data.ActualSize())
		partsMetadata[i].Erasure.AddChecksumInfo(ChecksumInfo{
			PartNumber: 1,
			Algorithm:  DefaultBitrotAlgorithm,
			Hash:       bitrotWriterSum(w),
		})
	}
	if opts.UserDefined["etag"] == "" {
		opts.UserDefined["etag"] = r.MD5CurrentHexString()
	}

	// Guess content-type from the extension if possible.
	if opts.UserDefined["content-type"] == "" {
		opts.UserDefined["content-type"] = mimedb.TypeByExtension(path.Ext(object))
	}

	modTime := opts.MTime
	if opts.MTime.IsZero() {
		modTime = UTCNow()
	}

	// Fill all the necessary metadata.
	// Update `xl.meta` content on each disks.
	for index := range partsMetadata {
		partsMetadata[index].Metadata = opts.UserDefined
		partsMetadata[index].Size = n
		partsMetadata[index].ModTime = modTime
	}

	// Rename the successfully written temporary object to final location.
	if onlineDisks, err = renameData(ctx, onlineDisks, minioMetaTmpBucket, tempObj, partsMetadata, bucket, object, writeQuorum); err != nil {
		logger.LogIf(ctx, err)
		return ObjectInfo{}, toObjectErr(err, bucket, object)
	}

	// Whether a disk was initially or becomes offline
	// during this upload, send it to the MRF list.
	for i := 0; i < len(onlineDisks); i++ {
		if onlineDisks[i] != nil && onlineDisks[i].IsOnline() {
			continue
		}
		er.addPartial(bucket, object, fi.VersionID)
		break
	}

	for i := 0; i < len(onlineDisks); i++ {
		if onlineDisks[i] != nil && onlineDisks[i].IsOnline() {
			// Object info is the same in all disks, so we can pick
			// the first meta from online disk
			fi = partsMetadata[i]
			break
		}
	}
	online = countOnlineDisks(onlineDisks)

	return fi.ToObjectInfo(bucket, object), nil
}

func (er erasureObjects) deleteObjectVersion(ctx context.Context, bucket, object string, writeQuorum int, fi FileInfo, forceDelMarker bool) error {
	defer ObjectPathUpdated(pathJoin(bucket, object))
	disks := er.getDisks()
	g := errgroup.WithNErrs(len(disks))
	for index := range disks {
		index := index
		g.Go(func() error {
			if disks[index] == nil {
				return errDiskNotFound
			}
			return disks[index].DeleteVersion(ctx, bucket, object, fi, forceDelMarker)
		}, index)
	}
	// return errors if any during deletion
	return reduceWriteQuorumErrs(ctx, g.Wait(), objectOpIgnoredErrs, writeQuorum)
}

// deleteEmptyDir knows only how to remove an empty directory (not the empty object with a
// trailing slash), this is called for the healing code to remove such directories.
func (er erasureObjects) deleteEmptyDir(ctx context.Context, bucket, object string) error {
	defer ObjectPathUpdated(pathJoin(bucket, object))

	if bucket == minioMetaTmpBucket {
		return nil
	}

	disks := er.getDisks()
	g := errgroup.WithNErrs(len(disks))
	for index := range disks {
		index := index
		g.Go(func() error {
			if disks[index] == nil {
				return errDiskNotFound
			}
			return disks[index].Delete(ctx, bucket, object, false)
		}, index)
	}

	// return errors if any during deletion
	return reduceWriteQuorumErrs(ctx, g.Wait(), objectOpIgnoredErrs, len(disks)/2+1)
}

// deleteObject - wrapper for delete object, deletes an object from
// all the disks in parallel, including `xl.meta` associated with the
// object.
func (er erasureObjects) deleteObject(ctx context.Context, bucket, object string, writeQuorum int) error {
	var err error
	defer ObjectPathUpdated(pathJoin(bucket, object))

	disks := er.getDisks()
	tmpObj := mustGetUUID()
	if bucket == minioMetaTmpBucket {
		tmpObj = object
	} else {
		// Rename the current object while requiring write quorum, but also consider
		// that a non found object in a given disk as a success since it already
		// confirms that the object doesn't have a part in that disk (already removed)
		disks, err = rename(ctx, disks, bucket, object, minioMetaTmpBucket, tmpObj, true, writeQuorum,
			[]error{errFileNotFound})
		if err != nil {
			return toObjectErr(err, bucket, object)
		}
	}

	g := errgroup.WithNErrs(len(disks))
	for index := range disks {
		index := index
		g.Go(func() error {
			if disks[index] == nil {
				return errDiskNotFound
			}
			return disks[index].Delete(ctx, minioMetaTmpBucket, tmpObj, true)
		}, index)
	}

	// return errors if any during deletion
	return reduceWriteQuorumErrs(ctx, g.Wait(), objectOpIgnoredErrs, writeQuorum)
}

// DeleteObjects deletes objects/versions in bulk, this function will still automatically split objects list
// into smaller bulks if some object names are found to be duplicated in the delete list, splitting
// into smaller bulks will avoid holding twice the write lock of the duplicated object names.
func (er erasureObjects) DeleteObjects(ctx context.Context, bucket string, objects []ObjectToDelete, opts ObjectOptions) ([]DeletedObject, []error) {
	errs := make([]error, len(objects))
	dobjects := make([]DeletedObject, len(objects))
	writeQuorums := make([]int, len(objects))

	storageDisks := er.getDisks()

	for i := range objects {
		// Assume (N/2 + 1) quorums for all objects
		// this is a theoretical assumption such that
		// for delete's we do not need to honor storage
		// class for objects which have reduced quorum
		// storage class only needs to be honored for
		// Read() requests alone which we already do.
		writeQuorums[i] = getWriteQuorum(len(storageDisks))
	}

	versions := make([]FileInfo, len(objects))
	for i := range objects {
		if objects[i].VersionID == "" {
			modTime := opts.MTime
			if opts.MTime.IsZero() {
				modTime = UTCNow()
			}
			uuid := opts.VersionID
			if uuid == "" {
				uuid = mustGetUUID()
			}
			if opts.Versioned || opts.VersionSuspended {
				versions[i] = FileInfo{
					Name:                          objects[i].ObjectName,
					ModTime:                       modTime,
					Deleted:                       true, // delete marker
					DeleteMarkerReplicationStatus: objects[i].DeleteMarkerReplicationStatus,
					VersionPurgeStatus:            objects[i].VersionPurgeStatus,
				}
				if opts.Versioned {
					versions[i].VersionID = uuid
				}
				continue
			}
		}
		versions[i] = FileInfo{
			Name:                          objects[i].ObjectName,
			VersionID:                     objects[i].VersionID,
			DeleteMarkerReplicationStatus: objects[i].DeleteMarkerReplicationStatus,
			VersionPurgeStatus:            objects[i].VersionPurgeStatus,
		}
	}

	// Initialize list of errors.
	var delObjErrs = make([][]error, len(storageDisks))

	var wg sync.WaitGroup
	// Remove versions in bulk for each disk
	for index, disk := range storageDisks {
		wg.Add(1)
		go func(index int, disk StorageAPI) {
			defer wg.Done()
			if disk == nil {
				delObjErrs[index] = make([]error, len(versions))
				for i := range versions {
					delObjErrs[index][i] = errDiskNotFound
				}
				return
			}
			delObjErrs[index] = disk.DeleteVersions(ctx, bucket, versions)
		}(index, disk)
	}

	wg.Wait()

	// Reduce errors for each object
	for objIndex := range objects {
		diskErrs := make([]error, len(storageDisks))
		// Iterate over disks to fetch the error
		// of deleting of the current object
		for i := range delObjErrs {
			// delObjErrs[i] is not nil when disks[i] is also not nil
			if delObjErrs[i] != nil {
				diskErrs[i] = delObjErrs[i][objIndex]
			}
		}
		err := reduceWriteQuorumErrs(ctx, diskErrs, objectOpIgnoredErrs, writeQuorums[objIndex])
		if objects[objIndex].VersionID != "" {
			errs[objIndex] = toObjectErr(err, bucket, objects[objIndex].ObjectName, objects[objIndex].VersionID)
		} else {
			errs[objIndex] = toObjectErr(err, bucket, objects[objIndex].ObjectName)
		}

		if errs[objIndex] == nil {
			ObjectPathUpdated(pathJoin(bucket, objects[objIndex].ObjectName))
		}

		if versions[objIndex].Deleted {
			dobjects[objIndex] = DeletedObject{
				DeleteMarker:                  versions[objIndex].Deleted,
				DeleteMarkerVersionID:         versions[objIndex].VersionID,
				DeleteMarkerMTime:             DeleteMarkerMTime{versions[objIndex].ModTime},
				DeleteMarkerReplicationStatus: versions[objIndex].DeleteMarkerReplicationStatus,
				ObjectName:                    versions[objIndex].Name,
				VersionPurgeStatus:            versions[objIndex].VersionPurgeStatus,
			}
		} else {
			dobjects[objIndex] = DeletedObject{
				ObjectName:                    versions[objIndex].Name,
				VersionID:                     versions[objIndex].VersionID,
				VersionPurgeStatus:            versions[objIndex].VersionPurgeStatus,
				DeleteMarkerReplicationStatus: versions[objIndex].DeleteMarkerReplicationStatus,
			}
		}
	}

	// Check failed deletes across multiple objects
	for _, version := range versions {
		// Check if there is any offline disk and add it to the MRF list
		for _, disk := range storageDisks {
			if disk != nil && disk.IsOnline() {
				// Skip attempted heal on online disks.
				continue
			}

			// all other direct versionId references we should
			// ensure no dangling file is left over.
			er.addPartial(bucket, version.Name, version.VersionID)
			break
		}
	}

	return dobjects, errs
}

// DeleteObject - deletes an object, this call doesn't necessary reply
// any error as it is not necessary for the handler to reply back a
// response to the client request.
func (er erasureObjects) DeleteObject(ctx context.Context, bucket, object string, opts ObjectOptions) (objInfo ObjectInfo, err error) {
	versionFound := true
	objInfo = ObjectInfo{VersionID: opts.VersionID} // version id needed in Delete API response.
	goi, gerr := er.GetObjectInfo(ctx, bucket, object, opts)
	if gerr != nil && goi.Name == "" {
		switch gerr.(type) {
		case InsufficientReadQuorum:
			return objInfo, InsufficientWriteQuorum{}
		}
		// For delete marker replication, versionID being replicated will not exist on disk
		if opts.DeleteMarker {
			versionFound = false
		} else {
			return objInfo, gerr
		}
	}
	// Acquire a write lock before deleting the object.
	lk := er.NewNSLock(bucket, object)
	lkctx, err := lk.GetLock(ctx, globalDeleteOperationTimeout)
	if err != nil {
		return ObjectInfo{}, err
	}
	ctx = lkctx.Context()
	defer lk.Unlock(lkctx.Cancel)

	storageDisks := er.getDisks()
	writeQuorum := len(storageDisks)/2 + 1
	var markDelete bool
	// Determine whether to mark object deleted for replication
	if goi.VersionID != "" {
		markDelete = true
	}

	// Default deleteMarker to true if object is under versioning
	deleteMarker := opts.Versioned

	if opts.VersionID != "" {
		// case where replica version needs to be deleted on target cluster
		if versionFound && opts.DeleteMarkerReplicationStatus == replication.Replica.String() {
			markDelete = false
		}
		if opts.VersionPurgeStatus.Empty() && opts.DeleteMarkerReplicationStatus == "" {
			markDelete = false
		}
		if opts.VersionPurgeStatus == Complete {
			markDelete = false
		}
		// determine if the version represents an object delete
		// deleteMarker = true
		if versionFound && !goi.DeleteMarker { // implies a versioned delete of object
			deleteMarker = false
		}
	}

	modTime := opts.MTime
	if opts.MTime.IsZero() {
		modTime = UTCNow()
	}

	if markDelete {
		if opts.Versioned || opts.VersionSuspended {
			fi := FileInfo{
				Name:                          object,
				Deleted:                       deleteMarker,
				MarkDeleted:                   markDelete,
				ModTime:                       modTime,
				DeleteMarkerReplicationStatus: opts.DeleteMarkerReplicationStatus,
				VersionPurgeStatus:            opts.VersionPurgeStatus,
				TransitionStatus:              opts.Transition.Status,
				ExpireRestored:                opts.Transition.ExpireRestored,
			}
			if opts.Versioned {
				fi.VersionID = mustGetUUID()
				if opts.VersionID != "" {
					fi.VersionID = opts.VersionID
				}
			}
			// versioning suspended means we add `null`
			// version as delete marker
			// Add delete marker, since we don't have any version specified explicitly.
			// Or if a particular version id needs to be replicated.
			if err = er.deleteObjectVersion(ctx, bucket, object, writeQuorum, fi, opts.DeleteMarker); err != nil {
				return objInfo, toObjectErr(err, bucket, object)
			}
			return fi.ToObjectInfo(bucket, object), nil
		}
	}

	// Delete the object version on all disks.
	if err = er.deleteObjectVersion(ctx, bucket, object, writeQuorum, FileInfo{
		Name:                          object,
		VersionID:                     opts.VersionID,
		MarkDeleted:                   markDelete,
		Deleted:                       deleteMarker,
		ModTime:                       modTime,
		DeleteMarkerReplicationStatus: opts.DeleteMarkerReplicationStatus,
		VersionPurgeStatus:            opts.VersionPurgeStatus,
		TransitionStatus:              opts.Transition.Status,
		ExpireRestored:                opts.Transition.ExpireRestored,
	}, opts.DeleteMarker); err != nil {
		return objInfo, toObjectErr(err, bucket, object)
	}

	for _, disk := range storageDisks {
		if disk != nil && disk.IsOnline() {
			continue
		}
		er.addPartial(bucket, object, opts.VersionID)
		break
	}

	return ObjectInfo{
		Bucket:             bucket,
		Name:               object,
		VersionID:          opts.VersionID,
		VersionPurgeStatus: opts.VersionPurgeStatus,
		ReplicationStatus:  replication.StatusType(opts.DeleteMarkerReplicationStatus),
	}, nil
}

// Send the successful but partial upload/delete, however ignore
// if the channel is blocked by other items.
func (er erasureObjects) addPartial(bucket, object, versionID string) {
	select {
	case er.mrfOpCh <- partialOperation{bucket: bucket, object: object, versionID: versionID}:
	default:
	}
}

func (er erasureObjects) PutObjectMetadata(ctx context.Context, bucket, object string, opts ObjectOptions) (ObjectInfo, error) {
	// Lock the object before updating tags.
	lk := er.NewNSLock(bucket, object)
	lkctx, err := lk.GetLock(ctx, globalOperationTimeout)
	if err != nil {
		return ObjectInfo{}, err
	}
	ctx = lkctx.Context()
	defer lk.Unlock(lkctx.Cancel)

	disks := er.getDisks()

	// Read metadata associated with the object from all disks.
	metaArr, errs := readAllFileInfo(ctx, disks, bucket, object, opts.VersionID, false)

	readQuorum, _, err := objectQuorumFromMeta(ctx, metaArr, errs, er.defaultParityCount)
	if err != nil {
		return ObjectInfo{}, toObjectErr(err, bucket, object)
	}

	// List all online disks.
	_, modTime, dataDir := listOnlineDisks(disks, metaArr, errs)

	// Pick latest valid metadata.
	fi, err := pickValidFileInfo(ctx, metaArr, modTime, dataDir, readQuorum)
	if err != nil {
		return ObjectInfo{}, toObjectErr(err, bucket, object)
	}
	if fi.Deleted {
		if opts.VersionID == "" {
			return ObjectInfo{}, toObjectErr(errFileNotFound, bucket, object)
		}
		return ObjectInfo{}, toObjectErr(errMethodNotAllowed, bucket, object)
	}

	for k, v := range opts.UserDefined {
		fi.Metadata[k] = v
	}
	fi.ModTime = opts.MTime
	fi.VersionID = opts.VersionID

	if err = er.updateObjectMeta(ctx, bucket, object, fi); err != nil {
		return ObjectInfo{}, toObjectErr(err, bucket, object)
	}

	objInfo := fi.ToObjectInfo(bucket, object)
	return objInfo, nil

}

// PutObjectTags - replace or add tags to an existing object
func (er erasureObjects) PutObjectTags(ctx context.Context, bucket, object string, tags string, opts ObjectOptions) (ObjectInfo, error) {
	// Lock the object before updating tags.
	lk := er.NewNSLock(bucket, object)
	lkctx, err := lk.GetLock(ctx, globalOperationTimeout)
	if err != nil {
		return ObjectInfo{}, err
	}
	ctx = lkctx.Context()
	defer lk.Unlock(lkctx.Cancel)

	disks := er.getDisks()

	// Read metadata associated with the object from all disks.
	metaArr, errs := readAllFileInfo(ctx, disks, bucket, object, opts.VersionID, false)

	readQuorum, _, err := objectQuorumFromMeta(ctx, metaArr, errs, er.defaultParityCount)
	if err != nil {
		return ObjectInfo{}, toObjectErr(err, bucket, object)
	}

	// List all online disks.
	_, modTime, dataDir := listOnlineDisks(disks, metaArr, errs)

	// Pick latest valid metadata.
	fi, err := pickValidFileInfo(ctx, metaArr, modTime, dataDir, readQuorum)
	if err != nil {
		return ObjectInfo{}, toObjectErr(err, bucket, object)
	}
	if fi.Deleted {
		if opts.VersionID == "" {
			return ObjectInfo{}, toObjectErr(errFileNotFound, bucket, object)
		}
		return ObjectInfo{}, toObjectErr(errMethodNotAllowed, bucket, object)
	}

	fi.Metadata[xhttp.AmzObjectTagging] = tags
	for k, v := range opts.UserDefined {
		fi.Metadata[k] = v
	}

	if err = er.updateObjectMeta(ctx, bucket, object, fi); err != nil {
		return ObjectInfo{}, toObjectErr(err, bucket, object)
	}

	return fi.ToObjectInfo(bucket, object), nil
}

// updateObjectMeta will update the metadata of a file.
func (er erasureObjects) updateObjectMeta(ctx context.Context, bucket, object string, fi FileInfo) error {
	if len(fi.Metadata) == 0 {
		return nil
	}

	disks := er.getDisks()

	g := errgroup.WithNErrs(len(disks))

	// Start writing `xl.meta` to all disks in parallel.
	for index := range disks {
		index := index
		g.Go(func() error {
			if disks[index] == nil {
				return errDiskNotFound
			}
			return disks[index].UpdateMetadata(ctx, bucket, object, fi)
		}, index)
	}

	// Wait for all the routines.
	mErrs := g.Wait()

	return reduceWriteQuorumErrs(ctx, mErrs, objectOpIgnoredErrs, getWriteQuorum(len(disks)))
}

// DeleteObjectTags - delete object tags from an existing object
func (er erasureObjects) DeleteObjectTags(ctx context.Context, bucket, object string, opts ObjectOptions) (ObjectInfo, error) {
	return er.PutObjectTags(ctx, bucket, object, "", opts)
}

// GetObjectTags - get object tags from an existing object
func (er erasureObjects) GetObjectTags(ctx context.Context, bucket, object string, opts ObjectOptions) (*tags.Tags, error) {
	// GetObjectInfo will return tag value as well
	oi, err := er.GetObjectInfo(ctx, bucket, object, opts)
	if err != nil {
		return nil, err
	}

	return tags.ParseObjectTags(oi.UserTags)
}

// TransitionObject - transition object content to target tier.
func (er erasureObjects) TransitionObject(ctx context.Context, bucket, object string, opts ObjectOptions) error {
	tgtClient, err := globalTierConfigMgr.getDriver(opts.Transition.Tier)
	if err != nil {
		return err
	}
	// Acquire write lock before starting to transition the object.
	lk := er.NewNSLock(bucket, object)
	lkctx, err := lk.GetLock(ctx, globalDeleteOperationTimeout)
	if err != nil {
		return err
	}
	ctx = lkctx.Context()
	defer lk.Unlock(lkctx.Cancel)

	fi, metaArr, onlineDisks, err := er.getObjectFileInfo(ctx, bucket, object, opts, true)
	if err != nil {
		return toObjectErr(err, bucket, object)
	}
	if fi.Deleted {
		if opts.VersionID == "" {
			return toObjectErr(errFileNotFound, bucket, object)
		}
		// Make sure to return object info to provide extra information.
		return toObjectErr(errMethodNotAllowed, bucket, object)
	}
	// verify that the object queued for transition is identical to that on disk.
	if !opts.MTime.Equal(fi.ModTime) || !strings.EqualFold(opts.Transition.ETag, extractETag(fi.Metadata)) {
		return toObjectErr(errFileNotFound, bucket, object)
	}
	// if object already transitioned, return
	if fi.TransitionStatus == lifecycle.TransitionComplete {
		return nil
	}
	if fi.XLV1 {
		if _, err = er.HealObject(ctx, bucket, object, "", madmin.HealOpts{NoLock: true}); err != nil {
			return err
		}
		// Fetch FileInfo again. HealObject migrates object the latest
		// format. Among other things this changes fi.DataDir and
		// possibly fi.Data (if data is inlined).
		fi, metaArr, onlineDisks, err = er.getObjectFileInfo(ctx, bucket, object, opts, true)
		if err != nil {
			return toObjectErr(err, bucket, object)
		}
	}
	destObj, err := genTransitionObjName()
	if err != nil {
		return err
	}

	pr, pw := io.Pipe()
	go func() {
		err := er.getObjectWithFileInfo(ctx, bucket, object, 0, fi.Size, pw, fi, metaArr, onlineDisks)
		pw.CloseWithError(err)
	}()
	if err = tgtClient.Put(ctx, destObj, pr, fi.Size); err != nil {
		pr.Close()
		logger.LogIf(ctx, fmt.Errorf("Unable to transition %s/%s(%s) to %s tier: %w", bucket, object, opts.VersionID, opts.Transition.Tier, err))
		return err
	}
	pr.Close()
	fi.TransitionStatus = lifecycle.TransitionComplete
	fi.TransitionedObjName = destObj
	fi.TransitionTier = opts.Transition.Tier
	eventName := event.ObjectTransitionComplete

	storageDisks := er.getDisks()
	writeQuorum := len(storageDisks)/2 + 1
	if err = er.deleteObjectVersion(ctx, bucket, object, writeQuorum, fi, false); err != nil {
		eventName = event.ObjectTransitionFailed
	}
	for _, disk := range storageDisks {
		if disk != nil && disk.IsOnline() {
			continue
		}
		er.addPartial(bucket, object, opts.VersionID)
		break
	}
	// Notify object deleted event.
	sendEvent(eventArgs{
		EventName:  eventName,
		BucketName: bucket,
		Object: ObjectInfo{
			Name:      object,
			VersionID: opts.VersionID,
		},
		Host: "Internal: [ILM-Transition]",
	})
	return err
}

// RestoreTransitionedObject - restore transitioned object content locally on this cluster.
// This is similar to PostObjectRestore from AWS GLACIER
// storage class. When PostObjectRestore API is called, a temporary copy of the object
// is restored locally to the bucket on source cluster until the restore expiry date.
// The copy that was transitioned continues to reside in the transitioned tier.
func (er erasureObjects) RestoreTransitionedObject(ctx context.Context, bucket, object string, opts ObjectOptions) error {
	return er.restoreTransitionedObject(ctx, bucket, object, opts)
}

// update restore status header in the metadata
func (er erasureObjects) updateRestoreMetadata(ctx context.Context, bucket, object string, objInfo ObjectInfo, opts ObjectOptions, rerr error) error {
	oi := objInfo.Clone()
	oi.metadataOnly = true // Perform only metadata updates.

	if rerr == nil {
		oi.UserDefined[xhttp.AmzRestore] = completedRestoreObj(opts.Transition.RestoreExpiry).String()
	} else { // allow retry in the case of failure to restore
		delete(oi.UserDefined, xhttp.AmzRestore)
	}
	if _, err := er.CopyObject(ctx, bucket, object, bucket, object, oi, ObjectOptions{
		VersionID: oi.VersionID,
	}, ObjectOptions{
		VersionID: oi.VersionID,
	}); err != nil {
		logger.LogIf(ctx, fmt.Errorf("Unable to update transition restore metadata for %s/%s(%s): %s", bucket, object, oi.VersionID, err))
		return err
	}
	return nil
}

// restoreTransitionedObject for multipart object chunks the file stream from remote tier into the same number of parts
// as in the xl.meta for this version and rehydrates the part.n into the fi.DataDir for this version as in the xl.meta
func (er erasureObjects) restoreTransitionedObject(ctx context.Context, bucket string, object string, opts ObjectOptions) error {
	defer func() {
		ObjectPathUpdated(pathJoin(bucket, object))
	}()
	setRestoreHeaderFn := func(oi ObjectInfo, rerr error) error {
		er.updateRestoreMetadata(ctx, bucket, object, oi, opts, rerr)
		return rerr
	}
	var oi ObjectInfo
	// get the file info on disk for transitioned object
	actualfi, _, _, err := er.getObjectFileInfo(ctx, bucket, object, opts, false)
	if err != nil {
		return setRestoreHeaderFn(oi, toObjectErr(err, bucket, object))
	}

	oi = actualfi.ToObjectInfo(bucket, object)
	ropts := putRestoreOpts(bucket, object, opts.Transition.RestoreRequest, oi)
	if len(oi.Parts) == 1 {
		var rs *HTTPRangeSpec
		gr, err := getTransitionedObjectReader(ctx, bucket, object, rs, http.Header{}, oi, opts)
		if err != nil {
			return setRestoreHeaderFn(oi, toObjectErr(err, bucket, object))
		}
		defer gr.Close()
		hashReader, err := hash.NewReader(gr, gr.ObjInfo.Size, "", "", gr.ObjInfo.Size)
		if err != nil {
			return setRestoreHeaderFn(oi, toObjectErr(err, bucket, object))
		}
		pReader := NewPutObjReader(hashReader)
		ropts.UserDefined[xhttp.AmzRestore] = completedRestoreObj(opts.Transition.RestoreExpiry).String()
		_, err = er.PutObject(ctx, bucket, object, pReader, ropts)
		return setRestoreHeaderFn(oi, toObjectErr(err, bucket, object))
	}

	uploadID, err := er.NewMultipartUpload(ctx, bucket, object, ropts)
	if err != nil {
		return setRestoreHeaderFn(oi, err)
	}

	var uploadedParts []CompletePart
	var rs *HTTPRangeSpec
	// get reader from the warm backend - note that even in the case of encrypted objects, this stream is still encrypted.
	gr, err := getTransitionedObjectReader(ctx, bucket, object, rs, http.Header{}, oi, opts)
	if err != nil {
		return setRestoreHeaderFn(oi, err)
	}
	defer gr.Close()

	// rehydrate the parts back on disk as per the original xl.meta prior to transition
	for _, partInfo := range oi.Parts {
		hr, err := hash.NewReader(gr, partInfo.Size, "", "", partInfo.Size)
		if err != nil {
			return setRestoreHeaderFn(oi, err)
		}
		pInfo, err := er.PutObjectPart(ctx, bucket, object, uploadID, partInfo.Number, NewPutObjReader(hr), ObjectOptions{})
		if err != nil {
			return setRestoreHeaderFn(oi, err)
		}
		if pInfo.Size != partInfo.Size {
			return setRestoreHeaderFn(oi, InvalidObjectState{Bucket: bucket, Object: object})
		}
		uploadedParts = append(uploadedParts, CompletePart{
			PartNumber: pInfo.PartNumber,
			ETag:       pInfo.ETag,
		})
	}
	_, err = er.CompleteMultipartUpload(ctx, bucket, object, uploadID, uploadedParts, ObjectOptions{
		MTime: oi.ModTime})
	return setRestoreHeaderFn(oi, err)
}