From 247e835d7bb01d3592765946e8296b494a0aa846 Mon Sep 17 00:00:00 2001
From: Krishna Srinivas <krishna@minio.io>
Date: Fri, 6 May 2016 01:21:56 +0530
Subject: [PATCH] object: move go-routine listing from posix to objectLayer.
 (#1491)

---
 fs-objects-multipart.go                       |   5 +-
 fs-objects.go                                 |  83 ++++-
 object-api-listobjects_test.go                |  13 +-
 object-common-multipart.go                    | 289 +++++++++---------
 posix-dir-common.go                           | 228 --------------
 posix-dir-nix.go => posix-list-dir-nix.go     |  89 +++---
 ...-dir-others.go => posix-list-dir-others.go |  48 ++-
 posix.go                                      | 208 ++-----------
 rpc-client.go                                 |  51 ++--
 rpc-server-datatypes.go                       |  21 +-
 rpc-server.go                                 |  32 +-
 storage-api-interface.go                      |   2 +-
 tree-walk.go                                  | 284 +++++++++++++++++
 xl-erasure-v1.go                              | 260 ++--------------
 xl-objects-multipart.go                       |   2 +-
 xl-objects.go                                 | 141 ++++++---
 16 files changed, 758 insertions(+), 998 deletions(-)
 delete mode 100644 posix-dir-common.go
 rename posix-dir-nix.go => posix-list-dir-nix.go (60%)
 rename posix-dir-others.go => posix-list-dir-others.go (55%)
 create mode 100644 tree-walk.go

diff --git a/fs-objects-multipart.go b/fs-objects-multipart.go
index 2c714b8fd..f5387a948 100644
--- a/fs-objects-multipart.go
+++ b/fs-objects-multipart.go
@@ -24,7 +24,7 @@ import (
 
 // ListMultipartUploads - list multipart uploads.
 func (fs fsObjects) ListMultipartUploads(bucket, prefix, keyMarker, uploadIDMarker, delimiter string, maxUploads int) (ListMultipartsInfo, error) {
-	return listMultipartUploadsCommon(fs.storage, bucket, prefix, keyMarker, uploadIDMarker, delimiter, maxUploads)
+	return listMultipartUploadsCommon(fs, bucket, prefix, keyMarker, uploadIDMarker, delimiter, maxUploads)
 }
 
 // NewMultipartUpload - initialize a new multipart upload, returns a unique id.
@@ -100,8 +100,7 @@ func (fs fsObjects) CompleteMultipartUpload(bucket string, object string, upload
 	}
 
 	// Cleanup all the parts.
-	recursive := false
-	if err = cleanupUploadedParts(fs.storage, mpartMetaPrefix, bucket, object, uploadID, recursive); err != nil {
+	if err = cleanupUploadedParts(fs.storage, mpartMetaPrefix, bucket, object, uploadID); err != nil {
 		return "", err
 	}
 
diff --git a/fs-objects.go b/fs-objects.go
index f10641e96..77369d170 100644
--- a/fs-objects.go
+++ b/fs-objects.go
@@ -20,15 +20,20 @@ import (
 	"io"
 	"path/filepath"
 	"strings"
+	"sync"
 
+	"github.com/Sirupsen/logrus"
 	"github.com/minio/minio/pkg/mimedb"
 )
 
 // fsObjects - Implements fs object layer.
 type fsObjects struct {
-	storage StorageAPI
+	storage            StorageAPI
+	listObjectMap      map[listParams][]*treeWalker
+	listObjectMapMutex *sync.Mutex
 }
 
+// FIXME: constructor should return a pointer.
 // newFSObjects - initialize new fs object layer.
 func newFSObjects(exportPath string) (ObjectLayer, error) {
 	var storage StorageAPI
@@ -51,7 +56,11 @@ func newFSObjects(exportPath string) (ObjectLayer, error) {
 	cleanupAllTmpEntries(storage)
 
 	// Return successfully initialized object layer.
-	return fsObjects{storage}, nil
+	return fsObjects{
+		storage:            storage,
+		listObjectMap:      make(map[listParams][]*treeWalker),
+		listObjectMapMutex: &sync.Mutex{},
+	}, nil
 }
 
 /// Bucket operations
@@ -151,6 +160,12 @@ func (fs fsObjects) ListObjects(bucket, prefix, marker, delimiter string, maxKey
 	if !IsValidBucketName(bucket) {
 		return ListObjectsInfo{}, BucketNameInvalid{Bucket: bucket}
 	}
+	// Verify whether the bucket exists.
+	if isExist, err := isBucketExist(fs.storage, bucket); err != nil {
+		return ListObjectsInfo{}, err
+	} else if !isExist {
+		return ListObjectsInfo{}, BucketNotFound{Bucket: bucket}
+	}
 	if !IsValidObjectPrefix(prefix) {
 		return ListObjectsInfo{}, ObjectNameInvalid{Bucket: bucket, Object: prefix}
 	}
@@ -170,17 +185,71 @@ func (fs fsObjects) ListObjects(bucket, prefix, marker, delimiter string, maxKey
 		}
 	}
 
+	if maxKeys == 0 {
+		return ListObjectsInfo{}, nil
+	}
+
+	// Over flowing count - reset to maxObjectList.
+	if maxKeys < 0 || maxKeys > maxObjectList {
+		maxKeys = maxObjectList
+	}
+
 	// Default is recursive, if delimiter is set then list non recursive.
 	recursive := true
 	if delimiter == slashSeparator {
 		recursive = false
 	}
-	fileInfos, eof, err := fs.storage.ListFiles(bucket, prefix, marker, recursive, maxKeys)
-	if err != nil {
-		return ListObjectsInfo{}, toObjectErr(err, bucket)
+
+	walker := lookupTreeWalk(fs, listParams{bucket, recursive, marker, prefix})
+	if walker == nil {
+		walker = startTreeWalk(fs, bucket, prefix, marker, recursive)
 	}
-	if maxKeys == 0 {
-		return ListObjectsInfo{}, nil
+	var fileInfos []FileInfo
+	var eof bool
+	var nextMarker string
+	log.Debugf("Reading from the tree walk channel has begun.")
+	for i := 0; i < maxKeys; {
+		walkResult, ok := <-walker.ch
+		if !ok {
+			// Closed channel.
+			eof = true
+			break
+		}
+		// For any walk error return right away.
+		if walkResult.err != nil {
+			log.WithFields(logrus.Fields{
+				"bucket":    bucket,
+				"prefix":    prefix,
+				"marker":    marker,
+				"recursive": recursive,
+			}).Debugf("Walk resulted in an error %s", walkResult.err)
+			// File not found is a valid case.
+			if walkResult.err == errFileNotFound {
+				return ListObjectsInfo{}, nil
+			}
+			return ListObjectsInfo{}, toObjectErr(walkResult.err, bucket, prefix)
+		}
+		fileInfo := walkResult.fileInfo
+		nextMarker = fileInfo.Name
+		fileInfos = append(fileInfos, fileInfo)
+		if walkResult.end {
+			eof = true
+			break
+		}
+		i++
+	}
+	if len(fileInfos) == 0 {
+		eof = true
+	}
+	params := listParams{bucket, recursive, nextMarker, prefix}
+	log.WithFields(logrus.Fields{
+		"bucket":    params.bucket,
+		"recursive": params.recursive,
+		"marker":    params.marker,
+		"prefix":    params.prefix,
+	}).Debugf("Save the tree walk into map for subsequent requests.")
+	if !eof {
+		saveTreeWalk(fs, params, walker)
 	}
 
 	result := ListObjectsInfo{IsTruncated: !eof}
diff --git a/object-api-listobjects_test.go b/object-api-listobjects_test.go
index 90310f467..04836bf6b 100644
--- a/object-api-listobjects_test.go
+++ b/object-api-listobjects_test.go
@@ -535,6 +535,7 @@ func TestListObjects(t *testing.T) {
 			t.Errorf("Test %d: Expected to pass, but failed with: <ERROR> %s", i+1, err.Error())
 		}
 		if err == nil && !testCase.shouldPass {
+			t.Log(result)
 			t.Errorf("Test %d: Expected to fail with <ERROR> \"%s\", but passed instead", i+1, testCase.err.Error())
 		}
 		// Failed as expected, but does it fail for the expected reason.
@@ -543,11 +544,15 @@ func TestListObjects(t *testing.T) {
 				t.Errorf("Test %d: Expected to fail with error \"%s\", but instead failed with error \"%s\" instead", i+1, testCase.err.Error(), err.Error())
 			}
 		}
-		// Since there are cases for which ListObjects fails, this is necessary.
-		// Test passes as expected, but the output values are verified for correctness here.
+		// Since there are cases for which ListObjects fails, this is
+		// necessary. Test passes as expected, but the output values
+		// are verified for correctness here.
 		if err == nil && testCase.shouldPass {
-			// The length of the expected ListObjectsResult.Objects should match in both expected result from test cases and in the output.
-			// On failure calling t.Fatalf, otherwise it may lead to index out of range error in assertion following this.
+			// The length of the expected ListObjectsResult.Objects
+			// should match in both expected result from test cases
+			// and in the output. On failure calling t.Fatalf,
+			// otherwise it may lead to index out of range error in
+			// assertion following this.
 			if len(testCase.result.Objects) != len(result.Objects) {
 				t.Fatalf("Test %d: Expected number of object in the result to be '%d', but found '%d' objects instead", i+1, len(testCase.result.Objects), len(result.Objects))
 			}
diff --git a/object-common-multipart.go b/object-common-multipart.go
index 00912b3f8..ba9ab0a4e 100644
--- a/object-common-multipart.go
+++ b/object-common-multipart.go
@@ -23,9 +23,9 @@ import (
 	"io"
 	"io/ioutil"
 	"path"
+	"sort"
 	"strconv"
 	"strings"
-	"sync"
 
 	"github.com/Sirupsen/logrus"
 	"github.com/skyrings/skyring-common/tools/uuid"
@@ -164,37 +164,24 @@ func putObjectPartCommon(storage StorageAPI, bucket string, object string, uploa
 
 // Cleanup all temp entries inside tmpMetaPrefix directory, upon server initialization.
 func cleanupAllTmpEntries(storage StorageAPI) error {
-	recursive := true // Recursively delete all files inside 'tmp' directory.
-	return cleanupUploadedParts(storage, tmpMetaPrefix, "", "", "", recursive)
+	return cleanupUploadedParts(storage, tmpMetaPrefix, "", "", "")
 }
 
 // Wrapper to which removes all the uploaded parts after a successful
 // complete multipart upload.
-func cleanupUploadedParts(storage StorageAPI, prefix, bucket, object, uploadID string, recursive bool) error {
-	markerPath := ""
-	var wg = &sync.WaitGroup{}
-	for {
-		uploadIDPath := path.Join(prefix, bucket, object, uploadID)
-		fileInfos, eof, err := storage.ListFiles(minioMetaBucket, uploadIDPath, markerPath, recursive, 1000)
-		if err != nil {
-			return toObjectErr(err, bucket, object)
-		}
-		// Loop through all files and delete each in go-routine, while
-		// adding each operation to a wait group.
-		for _, fileInfo := range fileInfos {
-			wg.Add(1)
-			go func(fi FileInfo) {
-				defer wg.Done()
-				storage.DeleteFile(minioMetaBucket, fi.Name)
-			}(fileInfo)
-		}
-		if eof {
-			break
+func cleanupUploadedParts(storage StorageAPI, prefix, bucket, object, uploadID string) error {
+	multipartDir := path.Join(prefix, bucket, object)
+	entries, err := storage.ListDir(minioMetaBucket, multipartDir)
+	if err != nil {
+		return err
+	}
+	for _, entry := range entries {
+		if strings.HasPrefix(entry, uploadID) {
+			if err = storage.DeleteFile(minioMetaBucket, path.Join(multipartDir, entry)); err != nil {
+				return err
+			}
 		}
-		markerPath = fileInfos[len(fileInfos)-1].Name
 	}
-	// Wait for all the routines.
-	wg.Wait()
 	return nil
 }
 
@@ -213,47 +200,40 @@ func abortMultipartUploadCommon(storage StorageAPI, bucket, object, uploadID str
 	} else if !status {
 		return InvalidUploadID{UploadID: uploadID}
 	}
-	recursive := false // Cleanup all the top level files and folders matching uploadID.
-	return cleanupUploadedParts(storage, mpartMetaPrefix, bucket, object, uploadID, recursive)
+	return cleanupUploadedParts(storage, mpartMetaPrefix, bucket, object, uploadID)
 }
 
 // listLeafEntries - lists all entries if a given prefixPath is a leaf
 // directory, returns error if any - returns empty list if prefixPath
 // is not a leaf directory.
-func listLeafEntries(storage StorageAPI, prefixPath string) (entries []FileInfo, e error) {
-	var markerPath string
-	for {
-		fileInfos, eof, err := storage.ListFiles(minioMetaBucket, prefixPath, markerPath, false, 1000)
-		if err != nil {
-			log.WithFields(logrus.Fields{
-				"prefixPath": prefixPath,
-				"markerPath": markerPath,
-			}).Errorf("%s", err)
-			return nil, err
-		}
-		for _, fileInfo := range fileInfos {
-			// Set marker for next batch of ListFiles.
-			markerPath = fileInfo.Name
-			if fileInfo.Mode.IsDir() {
-				// If a directory is found, doesn't return anything.
-				return nil, nil
-			}
-			fileName := path.Base(fileInfo.Name)
-			if !strings.Contains(fileName, ".") {
-				// Skip the entry if it is of the pattern bucket/object/uploadID.partNum.md5sum
-				// and retain entries of the pattern bucket/object/uploadID
-				entries = append(entries, fileInfo)
-			}
-		}
-		if eof {
-			break
+func listLeafEntries(storage StorageAPI, prefixPath string) (entries []string, err error) {
+	entries, err = storage.ListDir(minioMetaBucket, prefixPath)
+	if err != nil {
+		return nil, err
+	}
+	for _, entry := range entries {
+		if strings.HasSuffix(entry, slashSeparator) {
+			return nil, nil
 		}
 	}
 	return entries, nil
 }
 
 // listMetaBucketMultipartFiles - list all files at a given prefix inside minioMetaBucket.
-func listMetaBucketMultipartFiles(storage StorageAPI, prefixPath string, markerPath string, recursive bool, maxKeys int) (allFileInfos []FileInfo, eof bool, err error) {
+func listMetaBucketMultipartFiles(layer ObjectLayer, prefixPath string, markerPath string, recursive bool, maxKeys int) (fileInfos []FileInfo, eof bool, err error) {
+	var storage StorageAPI
+	switch l := layer.(type) {
+	case fsObjects:
+		storage = l.storage
+	case xlObjects:
+		storage = l.storage
+	}
+
+	walker := lookupTreeWalk(layer, listParams{minioMetaBucket, recursive, markerPath, prefixPath})
+	if walker == nil {
+		walker = startTreeWalk(layer, minioMetaBucket, prefixPath, markerPath, recursive)
+	}
+
 	// newMaxKeys tracks the size of entries which are going to be
 	// returned back.
 	var newMaxKeys int
@@ -261,64 +241,53 @@ func listMetaBucketMultipartFiles(storage StorageAPI, prefixPath string, markerP
 	// Following loop gathers and filters out special files inside
 	// minio meta volume.
 	for {
-		var fileInfos []FileInfo
-		// List files up to maxKeys-newMaxKeys, since we are skipping
-		// entries for special files.
-		fileInfos, eof, err = storage.ListFiles(minioMetaBucket, prefixPath, markerPath, recursive, maxKeys-newMaxKeys)
-		if err != nil {
+		walkResult, ok := <-walker.ch
+		if !ok {
+			// Closed channel.
+			eof = true
+			break
+		}
+		// For any walk error return right away.
+		if walkResult.err != nil {
 			log.WithFields(logrus.Fields{
-				"prefixPath": prefixPath,
-				"markerPath": markerPath,
-				"recursive":  recursive,
-				"maxKeys":    maxKeys,
-			}).Errorf("%s", err)
-			return nil, true, err
+				"bucket":    minioMetaBucket,
+				"prefix":    prefixPath,
+				"marker":    markerPath,
+				"recursive": recursive,
+			}).Debugf("Walk resulted in an error %s", walkResult.err)
+			// File not found is a valid case.
+			if walkResult.err == errFileNotFound {
+				return nil, true, nil
+			}
+			return nil, false, toObjectErr(walkResult.err, minioMetaBucket, prefixPath)
 		}
-		// Loop through and validate individual file.
-		for _, fi := range fileInfos {
-			var entries []FileInfo
-			if fi.Mode.IsDir() {
-				// List all the entries if fi.Name is a leaf directory, if
-				// fi.Name is not a leaf directory then the resulting
-				// entries are empty.
-				entries, err = listLeafEntries(storage, fi.Name)
-				if err != nil {
-					log.WithFields(logrus.Fields{
-						"prefixPath": fi.Name,
-					}).Errorf("%s", err)
-					return nil, false, err
-				}
+		fi := walkResult.fileInfo
+		var entries []string
+		if fi.Mode.IsDir() {
+			// List all the entries if fi.Name is a leaf directory, if
+			// fi.Name is not a leaf directory then the resulting
+			// entries are empty.
+			entries, err = listLeafEntries(storage, fi.Name)
+			if err != nil {
+				log.WithFields(logrus.Fields{
+					"prefixPath": fi.Name,
+				}).Errorf("%s", err)
+				return nil, false, err
 			}
-			// Set markerPath for next batch of listing.
-			markerPath = fi.Name
-			if len(entries) > 0 {
-				// We reach here for non-recursive case and a leaf entry.
-				for _, entry := range entries {
-					allFileInfos = append(allFileInfos, entry)
-					newMaxKeys++
-					// If we have reached the maxKeys, it means we have listed
-					// everything that was requested. Return right here.
-					if newMaxKeys == maxKeys {
-						// Return values:
-						// allFileInfos : "maxKeys" number of entries.
-						// eof : eof returned by fs.storage.ListFiles()
-						// error : nil
-						return
-					}
+		}
+		if len(entries) > 0 {
+			// We reach here for non-recursive case and a leaf entry.
+			sort.Strings(entries)
+			for _, entry := range entries {
+				if strings.ContainsRune(entry, '.') {
+					continue
 				}
-			} else {
-				// We reach here for a non-recursive case non-leaf entry
-				// OR recursive case with fi.Name matching pattern bucket/object/uploadID[.partNum.md5sum]
-				if !fi.Mode.IsDir() { // Do not skip non-recursive case directory entries.
-					// Skip files matching pattern bucket/object/uploadID.partNum.md5sum
-					// and retain files matching pattern bucket/object/uploadID
-					specialFile := path.Base(fi.Name)
-					if strings.Contains(specialFile, ".") {
-						// Contains partnumber and md5sum info, skip this.
-						continue
-					}
+				var fileInfo FileInfo
+				fileInfo, err = storage.StatFile(minioMetaBucket, path.Join(fi.Name, entry))
+				if err != nil {
+					return nil, false, err
 				}
-				allFileInfos = append(allFileInfos, fi)
+				fileInfos = append(fileInfos, fileInfo)
 				newMaxKeys++
 				// If we have reached the maxKeys, it means we have listed
 				// everything that was requested. Return right here.
@@ -330,20 +299,39 @@ func listMetaBucketMultipartFiles(storage StorageAPI, prefixPath string, markerP
 					return
 				}
 			}
-		}
-		// If we have reached eof then we break out.
-		if eof {
-			break
+		} else {
+			// We reach here for a non-recursive case non-leaf entry
+			// OR recursive case with fi.Name matching pattern bucket/object/uploadID[.partNum.md5sum]
+			if !fi.Mode.IsDir() { // Do not skip non-recursive case directory entries.
+				// Skip files matching pattern bucket/object/uploadID.partNum.md5sum
+				// and retain files matching pattern bucket/object/uploadID
+				specialFile := path.Base(fi.Name)
+				if strings.Contains(specialFile, ".") {
+					// Contains partnumber and md5sum info, skip this.
+					continue
+				}
+			}
+			fileInfos = append(fileInfos, fi)
+			newMaxKeys++
+			// If we have reached the maxKeys, it means we have listed
+			// everything that was requested. Return right here.
+			if newMaxKeys == maxKeys {
+				// Return values:
+				// allFileInfos : "maxKeys" number of entries.
+				// eof : eof returned by fs.storage.ListFiles()
+				// error : nil
+				return
+			}
 		}
 	}
 
 	// Return entries here.
-	return allFileInfos, eof, nil
+	return fileInfos, eof, nil
 }
 
 // listMultipartUploadsCommon - lists all multipart uploads, common
 // function for both object layers.
-func listMultipartUploadsCommon(storage StorageAPI, bucket, prefix, keyMarker, uploadIDMarker, delimiter string, maxUploads int) (ListMultipartsInfo, error) {
+func listMultipartUploadsCommon(layer ObjectLayer, bucket, prefix, keyMarker, uploadIDMarker, delimiter string, maxUploads int) (ListMultipartsInfo, error) {
 	result := ListMultipartsInfo{}
 	// Verify if bucket is valid.
 	if !IsValidBucketName(bucket) {
@@ -401,7 +389,7 @@ func listMultipartUploadsCommon(storage StorageAPI, bucket, prefix, keyMarker, u
 	}
 
 	// List all the multipart files at prefixPath, starting with marker keyMarkerPath.
-	fileInfos, eof, err := listMetaBucketMultipartFiles(storage, multipartPrefixPath, multipartMarkerPath, recursive, maxUploads)
+	fileInfos, eof, err := listMetaBucketMultipartFiles(layer, multipartPrefixPath, multipartMarkerPath, recursive, maxUploads)
 	if err != nil {
 		log.WithFields(logrus.Fields{
 			"prefixPath": multipartPrefixPath,
@@ -446,61 +434,60 @@ func listMultipartUploadsCommon(storage StorageAPI, bucket, prefix, keyMarker, u
 func listObjectPartsCommon(storage StorageAPI, bucket, object, uploadID string, partNumberMarker, maxParts int) (ListPartsInfo, error) {
 	// Verify if bucket is valid.
 	if !IsValidBucketName(bucket) {
-		return ListPartsInfo{}, BucketNameInvalid{Bucket: bucket}
+		return ListPartsInfo{}, (BucketNameInvalid{Bucket: bucket})
 	}
 	if !IsValidObjectName(object) {
-		return ListPartsInfo{}, ObjectNameInvalid{Bucket: bucket, Object: object}
+		return ListPartsInfo{}, (ObjectNameInvalid{Bucket: bucket, Object: object})
 	}
 	if status, err := isUploadIDExists(storage, bucket, object, uploadID); err != nil {
 		return ListPartsInfo{}, err
 	} else if !status {
-		return ListPartsInfo{}, InvalidUploadID{UploadID: uploadID}
+		return ListPartsInfo{}, (InvalidUploadID{UploadID: uploadID})
 	}
 	result := ListPartsInfo{}
-	var markerPath string
-	nextPartNumberMarker := 0
-	uploadIDPath := path.Join(mpartMetaPrefix, bucket, object, uploadID)
-	// Figure out the marker for the next subsequent calls, if the
-	// partNumberMarker is already set.
-	if partNumberMarker > 0 {
-		partNumberMarkerPath := uploadIDPath + "." + fmt.Sprintf("%.5d", partNumberMarker) + "."
-		fileInfos, _, err := storage.ListFiles(minioMetaBucket, partNumberMarkerPath, "", false, 1)
-		if err != nil {
-			return result, toObjectErr(err, minioMetaBucket, partNumberMarkerPath)
-		}
-		if len(fileInfos) == 0 {
-			return result, InvalidPart{}
-		}
-		markerPath = fileInfos[0].Name
-	}
-	uploadIDPrefix := uploadIDPath + "."
-	fileInfos, eof, err := storage.ListFiles(minioMetaBucket, uploadIDPrefix, markerPath, false, maxParts)
+	entries, err := storage.ListDir(minioMetaBucket, path.Join(mpartMetaPrefix, bucket, object))
 	if err != nil {
-		return result, InvalidPart{}
+		return result, err
 	}
-	for _, fileInfo := range fileInfos {
-		fileName := path.Base(fileInfo.Name)
-		splitResult := strings.Split(fileName, ".")
-		partNum, err := strconv.Atoi(splitResult[1])
+	sort.Strings(entries)
+	var newEntries []string
+	for _, entry := range entries {
+		if !strings.Contains(entry, ".") {
+			continue
+		}
+		if !strings.HasPrefix(entry, uploadID) {
+			continue
+		}
+		newEntries = append(newEntries, entry)
+	}
+	idx := sort.SearchStrings(newEntries, fmt.Sprintf("%s.%.5d.", uploadID, partNumberMarker+1))
+	newEntries = newEntries[idx:]
+	count := maxParts
+	for _, entry := range newEntries {
+		fi, err := storage.StatFile(minioMetaBucket, path.Join(mpartMetaPrefix, bucket, object, entry))
+		splitEntry := strings.Split(entry, ".")
+		partNum, err := strconv.Atoi(splitEntry[1])
 		if err != nil {
-			return result, err
+			return ListPartsInfo{}, err
 		}
-		md5sum := splitResult[2]
 		result.Parts = append(result.Parts, partInfo{
 			PartNumber:   partNum,
-			LastModified: fileInfo.ModTime,
-			ETag:         md5sum,
-			Size:         fileInfo.Size,
+			LastModified: fi.ModTime,
+			ETag:         splitEntry[2],
+			Size:         fi.Size,
 		})
-		nextPartNumberMarker = partNum
+		count--
+		if count == 0 {
+			break
+		}
+	}
+	if len(newEntries) > len(result.Parts) {
+		result.IsTruncated = true
 	}
 	result.Bucket = bucket
 	result.Object = object
 	result.UploadID = uploadID
-	result.PartNumberMarker = partNumberMarker
-	result.NextPartNumberMarker = nextPartNumberMarker
 	result.MaxParts = maxParts
-	result.IsTruncated = !eof
 	return result, nil
 }
 
diff --git a/posix-dir-common.go b/posix-dir-common.go
deleted file mode 100644
index 933399ac5..000000000
--- a/posix-dir-common.go
+++ /dev/null
@@ -1,228 +0,0 @@
-/*
- * Minio Cloud Storage, (C) 2016 Minio, Inc.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package main
-
-import (
-	"os"
-	"path"
-	"sort"
-	"strings"
-	"time"
-)
-
-// fsDirent carries directory entries.
-type fsDirent struct {
-	name    string
-	modTime time.Time // On Solaris and older unix distros this is empty.
-	size    int64     // On Solaris and older unix distros this is empty.
-	mode    os.FileMode
-}
-
-// IsDir - returns true if fsDirent is a directory
-func (ent fsDirent) IsDir() bool {
-	return ent.mode.IsDir()
-}
-
-// IsSymlink - returns true if fsDirent is a symbolic link
-func (ent fsDirent) IsSymlink() bool {
-	return ent.mode&os.ModeSymlink == os.ModeSymlink
-}
-
-// IsRegular - returns true if fsDirent is a regular file
-func (ent fsDirent) IsRegular() bool {
-	return ent.mode.IsRegular()
-}
-
-// byDirentName is a collection satisfying sort.Interface.
-type byDirentName []fsDirent
-
-func (d byDirentName) Len() int           { return len(d) }
-func (d byDirentName) Swap(i, j int)      { d[i], d[j] = d[j], d[i] }
-func (d byDirentName) Less(i, j int) bool { return d[i].name < d[j].name }
-
-// Using sort.Search() internally to jump to the file entry containing
-// the prefix.
-func searchDirents(dirents []fsDirent, x string) int {
-	processFunc := func(i int) bool {
-		return dirents[i].name >= x
-	}
-	return sort.Search(len(dirents), processFunc)
-}
-
-// Tree walk result carries results of tree walking.
-type treeWalkResult struct {
-	fileInfo FileInfo
-	err      error
-	end      bool
-}
-
-// Tree walk notify carries a channel which notifies tree walk
-// results, additionally it also carries information if treeWalk
-// should be timedOut.
-type treeWalker struct {
-	ch       <-chan treeWalkResult
-	timedOut bool
-}
-
-// treeWalk walks FS directory tree recursively pushing fileInfo into the channel as and when it encounters files.
-func treeWalk(bucketDir, prefixDir, entryPrefixMatch, marker string, recursive bool, send func(treeWalkResult) bool, count *int) bool {
-	// Example:
-	// if prefixDir="one/two/three/" and marker="four/five.txt" treeWalk is recursively
-	// called with prefixDir="one/two/three/four/" and marker="five.txt"
-
-	// Convert dirent to FileInfo
-	direntToFileInfo := func(dirent fsDirent) (FileInfo, error) {
-		fileInfo := FileInfo{}
-		// Convert to full object name.
-		fileInfo.Name = path.Join(prefixDir, dirent.name)
-		if dirent.modTime.IsZero() && dirent.size == 0 {
-			// ModifiedTime and Size are zero, Stat() and figure out
-			// the actual values that need to be set.
-			fi, err := os.Stat(path.Join(bucketDir, prefixDir, dirent.name))
-			if err != nil {
-				return FileInfo{}, err
-			}
-			// Fill size and modtime.
-			fileInfo.ModTime = fi.ModTime()
-			fileInfo.Size = fi.Size()
-			fileInfo.Mode = fi.Mode()
-		} else {
-			// If ModTime or Size are set then use them
-			// without attempting another Stat operation.
-			fileInfo.ModTime = dirent.modTime
-			fileInfo.Size = dirent.size
-			fileInfo.Mode = dirent.mode
-		}
-		if fileInfo.Mode.IsDir() {
-			// Add "/" suffix again for directories as
-			fileInfo.Size = 0
-			fileInfo.Name += "/"
-		}
-		return fileInfo, nil
-	}
-
-	var markerBase, markerDir string
-	if marker != "" {
-		// Ex: if marker="four/five.txt", markerDir="four/" markerBase="five.txt"
-		markerSplit := strings.SplitN(marker, slashSeparator, 2)
-		markerDir = markerSplit[0]
-		if len(markerSplit) == 2 {
-			markerDir += slashSeparator
-			markerBase = markerSplit[1]
-		}
-	}
-
-	// Entry prefix match function.
-	prefixMatchFn := func(dirent fsDirent) bool {
-		if dirent.IsDir() || dirent.IsRegular() {
-			// Does dirent name has reserved prefixes or suffixes.
-			hasReserved := hasReservedPrefix(dirent.name) || hasReservedSuffix(dirent.name)
-			// All dirents which match prefix and do not have reserved
-			// keywords in them are valid entries.
-			return strings.HasPrefix(dirent.name, entryPrefixMatch) && !hasReserved && isValidPath(dirent.name)
-		}
-		return false
-	}
-
-	// scandir returns entries that begins with entryPrefixMatch
-	dirents, err := scandir(path.Join(bucketDir, prefixDir), prefixMatchFn, true)
-	if err != nil {
-		send(treeWalkResult{err: err})
-		return false
-	}
-
-	// example:
-	// If markerDir="four/" searchDirents() returns the index of "four/" in the sorted
-	// dirents list. We skip all the dirent entries till "four/"
-	dirents = dirents[searchDirents(dirents, markerDir):]
-	*count += len(dirents)
-	for i, dirent := range dirents {
-		if i == 0 && markerDir == dirent.name && !dirent.IsDir() {
-			// If the first entry is not a directory
-			// we need to skip this entry.
-			*count--
-			continue
-		}
-		if dirent.IsDir() && recursive {
-			// If the entry is a directory, we will need recurse into it.
-			markerArg := ""
-			if dirent.name == markerDir {
-				// We need to pass "five.txt" as marker only if we are
-				// recursing into "four/"
-				markerArg = markerBase
-			}
-			*count--
-			if !treeWalk(bucketDir, path.Join(prefixDir, dirent.name), "", markerArg, recursive, send, count) {
-				return false
-			}
-			continue
-		}
-		fileInfo, err := direntToFileInfo(dirent)
-		if err != nil {
-			send(treeWalkResult{err: err})
-			return false
-		}
-		*count--
-		if !send(treeWalkResult{fileInfo: fileInfo}) {
-			return false
-		}
-	}
-	return true
-}
-
-// Initiate a new treeWalk in a goroutine.
-func startTreeWalk(fsPath, bucket, prefix, marker string, recursive bool) *treeWalker {
-	// Example 1
-	// If prefix is "one/two/three/" and marker is "one/two/three/four/five.txt"
-	// treeWalk is called with prefixDir="one/two/three/" and marker="four/five.txt"
-	// and entryPrefixMatch=""
-
-	// Example 2
-	// if prefix is "one/two/th" and marker is "one/two/three/four/five.txt"
-	// treeWalk is called with prefixDir="one/two/" and marker="three/four/five.txt"
-	// and entryPrefixMatch="th"
-	ch := make(chan treeWalkResult, fsListLimit)
-	walkNotify := treeWalker{ch: ch}
-	entryPrefixMatch := prefix
-	prefixDir := ""
-	lastIndex := strings.LastIndex(prefix, slashSeparator)
-	if lastIndex != -1 {
-		entryPrefixMatch = prefix[lastIndex+1:]
-		prefixDir = prefix[:lastIndex+1]
-	}
-	count := 0
-	marker = strings.TrimPrefix(marker, prefixDir)
-	go func() {
-		defer close(ch)
-		send := func(walkResult treeWalkResult) bool {
-			if count == 0 {
-				walkResult.end = true
-			}
-			timer := time.After(time.Second * 60)
-			select {
-			case ch <- walkResult:
-				return true
-			case <-timer:
-				walkNotify.timedOut = true
-				return false
-			}
-		}
-		bucketDir := path.Join(fsPath, bucket)
-		treeWalk(bucketDir, prefixDir, entryPrefixMatch, marker, recursive, send, &count)
-	}()
-	return &walkNotify
-}
diff --git a/posix-dir-nix.go b/posix-list-dir-nix.go
similarity index 60%
rename from posix-dir-nix.go
rename to posix-list-dir-nix.go
index 17c748b75..1991428e4 100644
--- a/posix-dir-nix.go
+++ b/posix-list-dir-nix.go
@@ -22,9 +22,11 @@ import (
 	"os"
 	"path"
 	"runtime"
-	"sort"
+	"strings"
 	"syscall"
 	"unsafe"
+
+	"github.com/Sirupsen/logrus"
 )
 
 const (
@@ -47,9 +49,8 @@ func clen(n []byte) int {
 
 // parseDirents - inspired from
 // https://golang.org/src/syscall/syscall_<os>.go
-func parseDirents(dirPath string, buf []byte) []fsDirent {
+func parseDirents(dirPath string, buf []byte) (entries []string, err error) {
 	bufidx := 0
-	dirents := []fsDirent{}
 	for bufidx < len(buf) {
 		dirent := (*syscall.Dirent)(unsafe.Pointer(&buf[bufidx]))
 		// On non-Linux operating systems for rec length of zero means
@@ -58,7 +59,7 @@ func parseDirents(dirPath string, buf []byte) []fsDirent {
 			break
 		}
 		bufidx += int(dirent.Reclen)
-		// Skip dirents if they are absent in directory.
+		// Skip if they are absent in directory.
 		if isEmptyDirent(dirent) {
 			continue
 		}
@@ -69,56 +70,57 @@ func parseDirents(dirPath string, buf []byte) []fsDirent {
 			continue
 		}
 
-		var mode os.FileMode
 		switch dirent.Type {
-		case syscall.DT_BLK, syscall.DT_WHT:
-			mode = os.ModeDevice
-		case syscall.DT_CHR:
-			mode = os.ModeDevice | os.ModeCharDevice
 		case syscall.DT_DIR:
-			mode = os.ModeDir
-		case syscall.DT_FIFO:
-			mode = os.ModeNamedPipe
-		case syscall.DT_LNK:
-			mode = os.ModeSymlink
+			entries = append(entries, name+slashSeparator)
 		case syscall.DT_REG:
-			mode = 0
-		case syscall.DT_SOCK:
-			mode = os.ModeSocket
+			entries = append(entries, name)
 		case syscall.DT_UNKNOWN:
 			// On Linux XFS does not implement d_type for on disk
 			// format << v5. Fall back to Stat().
-			if fi, err := os.Stat(path.Join(dirPath, name)); err == nil {
-				mode = fi.Mode()
+			var fi os.FileInfo
+			if fi, err = os.Stat(path.Join(dirPath, name)); err == nil {
+				if fi.IsDir() {
+					entries = append(entries, fi.Name()+slashSeparator)
+				} else if fi.Mode().IsRegular() {
+					entries = append(entries, fi.Name())
+				}
 			} else {
-				// Caller listing would fail, if Stat failed but we
-				// won't crash the server.
-				mode = 0xffffffff
+				// This is unexpected.
+				return
 			}
+		default:
+			// Skip entries which are not file or directory.
+			// FIXME: should we handle symlinks?
+			continue
 		}
-
-		dirents = append(dirents, fsDirent{
-			name: name,
-			mode: mode,
-		})
 	}
-	return dirents
+	return
 }
 
-// scans the directory dirPath, calling filter() on each directory
-// entry.  Entries for which filter() returns true are stored, lexically
-// sorted using sort.Sort(). If filter is NULL, all entries are selected.
-// If namesOnly is true, dirPath is not appended into entry name.
-func scandir(dirPath string, filter func(fsDirent) bool, namesOnly bool) ([]fsDirent, error) {
+// Return all the entries at the directory dirPath.
+func readDir(dirPath string) (entries []string, err error) {
 	buf := make([]byte, readDirentBufSize)
 	d, err := os.Open(dirPath)
 	if err != nil {
+		log.WithFields(logrus.Fields{
+			"dirPath": dirPath,
+		}).Debugf("Open failed with %s", err)
+
+		// File is really not found.
+		if os.IsNotExist(err) {
+			return nil, errFileNotFound
+		}
+
+		// File path cannot be verified since one of the parents is a file.
+		if strings.Contains(err.Error(), "not a directory") {
+			return nil, errFileNotFound
+		}
 		return nil, err
 	}
 	defer d.Close()
 
 	fd := int(d.Fd())
-	dirents := []fsDirent{}
 	for {
 		nbuf, err := syscall.ReadDirent(fd, buf)
 		if err != nil {
@@ -127,20 +129,11 @@ func scandir(dirPath string, filter func(fsDirent) bool, namesOnly bool) ([]fsDi
 		if nbuf <= 0 {
 			break
 		}
-		for _, dirent := range parseDirents(dirPath, buf[:nbuf]) {
-			if !namesOnly {
-				dirent.name = path.Join(dirPath, dirent.name)
-			}
-			if dirent.IsDir() {
-				dirent.name += "/"
-				dirent.size = 0
-			}
-			if filter == nil || filter(dirent) {
-				dirents = append(dirents, dirent)
-			}
+		var tmpEntries []string
+		if tmpEntries, err = parseDirents(dirPath, buf[:nbuf]); err != nil {
+			return nil, err
 		}
+		entries = append(entries, tmpEntries...)
 	}
-
-	sort.Sort(byDirentName(dirents))
-	return dirents, nil
+	return
 }
diff --git a/posix-dir-others.go b/posix-list-dir-others.go
similarity index 55%
rename from posix-dir-others.go
rename to posix-list-dir-others.go
index f8b34b466..25d74a714 100644
--- a/posix-dir-others.go
+++ b/posix-list-dir-others.go
@@ -21,22 +21,32 @@ package main
 import (
 	"io"
 	"os"
-	"path"
-	"sort"
+	"strings"
+
+	"github.com/Sirupsen/logrus"
 )
 
-// scans the directory dirPath, calling filter() on each directory
-// entry.  Entries for which filter() returns true are stored, lexically
-// sorted using sort.Sort(). If filter is NULL, all entries are selected.
-// If namesOnly is true, dirPath is not appended into entry name.
-func scandir(dirPath string, filter func(fsDirent) bool, namesOnly bool) ([]fsDirent, error) {
+// Return all the entries at the directory dirPath.
+func readDir(dirPath string) (entries []string, err error) {
 	d, err := os.Open(dirPath)
 	if err != nil {
+		log.WithFields(logrus.Fields{
+			"dirPath": dirPath,
+		}).Debugf("Open failed with %s", err)
+
+		// File is really not found.
+		if os.IsNotExist(err) {
+			return nil, errFileNotFound
+		}
+
+		// File path cannot be verified since one of the parents is a file.
+		if strings.Contains(err.Error(), "not a directory") {
+			return nil, errFileNotFound
+		}
 		return nil, err
 	}
 	defer d.Close()
 
-	var dirents []fsDirent
 	for {
 		fis, err := d.Readdir(1000)
 		if err != nil {
@@ -46,25 +56,13 @@ func scandir(dirPath string, filter func(fsDirent) bool, namesOnly bool) ([]fsDi
 			return nil, err
 		}
 		for _, fi := range fis {
-			dirent := fsDirent{
-				name:    fi.Name(),
-				modTime: fi.ModTime(),
-				size:    fi.Size(),
-				mode:    fi.Mode(),
-			}
-			if !namesOnly {
-				dirent.name = path.Join(dirPath, dirent.name)
-			}
-			if dirent.IsDir() {
+			if fi.Mode().IsDir() {
 				// append "/" instead of "\" so that sorting is done as expected.
-				dirent.name += slashSeparator
-			}
-			if filter == nil || filter(dirent) {
-				dirents = append(dirents, dirent)
+				entries = append(entries, fi.Name()+slashSeparator)
+			} else if fi.Mode().IsRegular() {
+				entries = append(entries, fi.Name())
 			}
 		}
 	}
-
-	sort.Sort(byDirentName(dirents))
-	return dirents, nil
+	return
 }
diff --git a/posix.go b/posix.go
index d177e3c29..f1f2c4ddb 100644
--- a/posix.go
+++ b/posix.go
@@ -19,38 +19,24 @@ package main
 import (
 	"io"
 	"os"
-	slashpath "path"
+	"path"
 	"path/filepath"
 	"strings"
-	"sync"
 	"syscall"
 
-	"path"
-
 	"github.com/Sirupsen/logrus"
 	"github.com/minio/minio/pkg/disk"
 	"github.com/minio/minio/pkg/safe"
 )
 
 const (
-	fsListLimit       = 1000
 	fsMinSpacePercent = 5
 )
 
-// listParams - list object params used for list object map
-type listParams struct {
-	bucket    string
-	recursive bool
-	marker    string
-	prefix    string
-}
-
 // fsStorage - implements StorageAPI interface.
 type fsStorage struct {
-	diskPath           string
-	minFreeDisk        int64
-	listObjectMap      map[listParams][]*treeWalker
-	listObjectMapMutex *sync.Mutex
+	diskPath    string
+	minFreeDisk int64
 }
 
 // isDirEmpty - returns whether given directory is empty or not.
@@ -98,10 +84,8 @@ func newPosix(diskPath string) (StorageAPI, error) {
 		return nil, syscall.ENOTDIR
 	}
 	fs := fsStorage{
-		diskPath:           diskPath,
-		minFreeDisk:        fsMinSpacePercent, // Minimum 5% disk should be free.
-		listObjectMap:      make(map[listParams][]*treeWalker),
-		listObjectMapMutex: &sync.Mutex{},
+		diskPath:    diskPath,
+		minFreeDisk: fsMinSpacePercent, // Minimum 5% disk should be free.
 	}
 	log.WithFields(logrus.Fields{
 		"diskPath":    diskPath,
@@ -158,25 +142,23 @@ func removeDuplicateVols(volsInfo []VolInfo) []VolInfo {
 
 // gets all the unique directories from diskPath.
 func getAllUniqueVols(dirPath string) ([]VolInfo, error) {
-	volumeFn := func(dirent fsDirent) bool {
-		// Return all directories.
-		return dirent.IsDir() && isValidVolname(path.Clean(dirent.name))
-	}
-	namesOnly := true // Returned are only names.
-	dirents, err := scandir(dirPath, volumeFn, namesOnly)
+	entries, err := readDir(dirPath)
 	if err != nil {
 		log.WithFields(logrus.Fields{
-			"dirPath":   dirPath,
-			"namesOnly": true,
-		}).Debugf("Scandir failed with error %s", err)
+			"dirPath": dirPath,
+		}).Debugf("readDir failed with error %s", err)
 		return nil, err
 	}
 	var volsInfo []VolInfo
-	for _, dirent := range dirents {
-		fi, err := os.Stat(pathJoin(dirPath, dirent.name))
+	for _, entry := range entries {
+		if !strings.HasSuffix(entry, slashSeparator) || !isValidVolname(filepath.Clean(entry)) {
+			// Skip if entry is neither a directory not a valid volume name.
+			continue
+		}
+		fi, err := os.Stat(pathJoin(dirPath, entry))
 		if err != nil {
 			log.WithFields(logrus.Fields{
-				"path": pathJoin(dirPath, dirent.name),
+				"path": pathJoin(dirPath, entry),
 			}).Debugf("Stat failed with error %s", err)
 			return nil, err
 		}
@@ -372,62 +354,9 @@ func (s fsStorage) DeleteVol(volume string) error {
 	return nil
 }
 
-// Save the goroutine reference in the map
-func (s *fsStorage) saveTreeWalk(params listParams, walker *treeWalker) {
-	s.listObjectMapMutex.Lock()
-	defer s.listObjectMapMutex.Unlock()
-
-	log.WithFields(logrus.Fields{
-		"bucket":    params.bucket,
-		"recursive": params.recursive,
-		"marker":    params.marker,
-		"prefix":    params.prefix,
-	}).Debugf("saveTreeWalk has been invoked.")
-
-	walkers, _ := s.listObjectMap[params]
-	walkers = append(walkers, walker)
-
-	s.listObjectMap[params] = walkers
-	log.Debugf("Successfully saved in listObjectMap.")
-}
-
-// Lookup the goroutine reference from map
-func (s *fsStorage) lookupTreeWalk(params listParams) *treeWalker {
-	s.listObjectMapMutex.Lock()
-	defer s.listObjectMapMutex.Unlock()
-
-	log.WithFields(logrus.Fields{
-		"bucket":    params.bucket,
-		"recursive": params.recursive,
-		"marker":    params.marker,
-		"prefix":    params.prefix,
-	}).Debugf("lookupTreeWalk has been invoked.")
-	if walkChs, ok := s.listObjectMap[params]; ok {
-		for i, walkCh := range walkChs {
-			if !walkCh.timedOut {
-				newWalkChs := walkChs[i+1:]
-				if len(newWalkChs) > 0 {
-					s.listObjectMap[params] = newWalkChs
-				} else {
-					delete(s.listObjectMap, params)
-				}
-				log.WithFields(logrus.Fields{
-					"bucket":    params.bucket,
-					"recursive": params.recursive,
-					"marker":    params.marker,
-					"prefix":    params.prefix,
-				}).Debugf("Found the previous saved listsObjects params.")
-				return walkCh
-			}
-		}
-		// As all channels are timed out, delete the map entry
-		delete(s.listObjectMap, params)
-	}
-	return nil
-}
-
-// List operation.
-func (s fsStorage) ListFiles(volume, prefix, marker string, recursive bool, count int) ([]FileInfo, bool, error) {
+// ListDir - return all the entries at the given directory path.
+// If an entry is a directory it will be returned with a trailing "/".
+func (s fsStorage) ListDir(volume, dirPath string) ([]string, error) {
 	// Verify if volume is valid and it exists.
 	volumeDir, err := s.getVolumeDir(volume)
 	if err != nil {
@@ -435,100 +364,21 @@ func (s fsStorage) ListFiles(volume, prefix, marker string, recursive bool, coun
 			"diskPath": s.diskPath,
 			"volume":   volume,
 		}).Debugf("getVolumeDir failed with %s", err)
-		return nil, true, err
-	}
-	var fileInfos []FileInfo
-
-	if marker != "" {
-		// Verify if marker has prefix.
-		if marker != "" && !strings.HasPrefix(marker, prefix) {
-			log.WithFields(logrus.Fields{
-				"diskPath": s.diskPath,
-				"marker":   marker,
-				"prefix":   prefix,
-			}).Debugf("Marker doesn't have prefix in common.")
-			return nil, true, errInvalidArgument
-		}
-	}
-
-	// Return empty response for a valid request when count is 0.
-	if count == 0 {
-		return nil, true, nil
-	}
-
-	// Over flowing count - reset to fsListLimit.
-	if count < 0 || count > fsListLimit {
-		count = fsListLimit
+		return nil, err
 	}
-
-	// Verify if prefix exists.
-	prefixDir := slashpath.Dir(prefix)
-	prefixRootDir := slashpath.Join(volumeDir, prefixDir)
-	if status, err := isDirExist(prefixRootDir); !status {
-		if err == nil {
-			// Prefix does not exist, not an error just respond empty list response.
-			return nil, true, nil
-		} else if err.Error() == syscall.ENOTDIR.Error() {
-			// Prefix exists as a file.
-			return nil, true, nil
-		}
-
+	// Stat a volume entry.
+	_, err = os.Stat(volumeDir)
+	if err != nil {
 		log.WithFields(logrus.Fields{
-			"volumeDir":     volumeDir,
-			"prefixRootDir": prefixRootDir,
-		}).Debugf("isDirExist returned an unhandled error %s", err)
-
-		// Rest errors should be treated as failure.
-		return nil, true, err
-	}
-
-	// Maximum 1000 files returned in a single call.
-	// Further calls will set right marker value to continue reading the rest of the files.
-	// popTreeWalker returns nil if the call to ListFiles is done for the first time.
-	// On further calls to ListFiles to retrive more files within the timeout period,
-	// popTreeWalker returns the channel from which rest of the objects can be retrieved.
-	walker := s.lookupTreeWalk(listParams{volume, recursive, marker, prefix})
-	if walker == nil {
-		walker = startTreeWalk(filepath.ToSlash(s.diskPath), volume, prefix, marker, recursive)
-	}
-	nextMarker := ""
-	log.Debugf("Reading from the tree walk channel has begun.")
-	for i := 0; i < count; {
-		walkResult, ok := <-walker.ch
-		if !ok {
-			// Closed channel.
-			return fileInfos, true, nil
-		}
-		// For any walk error return right away.
-		if walkResult.err != nil {
-			log.WithFields(logrus.Fields{
-				"diskPath":  s.diskPath,
-				"volume":    volume,
-				"prefix":    prefix,
-				"marker":    marker,
-				"recursive": recursive,
-			}).Debugf("Walk resulted in an error %s", walkResult.err)
-			return nil, true, walkResult.err
-		}
-		fileInfo := walkResult.fileInfo
-		fileInfo.Name = filepath.ToSlash(fileInfo.Name)
-		fileInfos = append(fileInfos, fileInfo)
-		// We have listed everything return.
-		if walkResult.end {
-			return fileInfos, true, nil
+			"diskPath": s.diskPath,
+			"volume":   volume,
+		}).Debugf("Stat on the volume failed with %s", err)
+		if os.IsNotExist(err) {
+			return nil, errVolumeNotFound
 		}
-		nextMarker = fileInfo.Name
-		i++
+		return nil, err
 	}
-	params := listParams{volume, recursive, nextMarker, prefix}
-	log.WithFields(logrus.Fields{
-		"bucket":    params.bucket,
-		"recursive": params.recursive,
-		"marker":    params.marker,
-		"prefix":    params.prefix,
-	}).Debugf("Save the tree walk into map for subsequent requests.")
-	s.saveTreeWalk(params, walker)
-	return fileInfos, false, nil
+	return readDir(pathJoin(volumeDir, dirPath))
 }
 
 // ReadFile - read a file at a given offset.
diff --git a/rpc-client.go b/rpc-client.go
index 32068bf6b..513656646 100644
--- a/rpc-client.go
+++ b/rpc-client.go
@@ -31,7 +31,7 @@ import (
 	"github.com/Sirupsen/logrus"
 )
 
-type networkFS struct {
+type networkStorage struct {
 	netScheme  string
 	netAddr    string
 	netPath    string
@@ -109,7 +109,7 @@ func newRPCClient(networkPath string) (StorageAPI, error) {
 	}
 
 	// Initialize network storage.
-	ndisk := &networkFS{
+	ndisk := &networkStorage{
 		netScheme:  "http", // TODO: fix for ssl rpc support.
 		netAddr:    netAddr,
 		netPath:    netPath,
@@ -122,7 +122,7 @@ func newRPCClient(networkPath string) (StorageAPI, error) {
 }
 
 // MakeVol - make a volume.
-func (n networkFS) MakeVol(volume string) error {
+func (n networkStorage) MakeVol(volume string) error {
 	reply := GenericReply{}
 	if err := n.rpcClient.Call("Storage.MakeVolHandler", volume, &reply); err != nil {
 		log.WithFields(logrus.Fields{
@@ -134,7 +134,7 @@ func (n networkFS) MakeVol(volume string) error {
 }
 
 // ListVols - List all volumes.
-func (n networkFS) ListVols() (vols []VolInfo, err error) {
+func (n networkStorage) ListVols() (vols []VolInfo, err error) {
 	ListVols := ListVolsReply{}
 	err = n.rpcClient.Call("Storage.ListVolsHandler", "", &ListVols)
 	if err != nil {
@@ -145,7 +145,7 @@ func (n networkFS) ListVols() (vols []VolInfo, err error) {
 }
 
 // StatVol - get current Stat volume info.
-func (n networkFS) StatVol(volume string) (volInfo VolInfo, err error) {
+func (n networkStorage) StatVol(volume string) (volInfo VolInfo, err error) {
 	if err = n.rpcClient.Call("Storage.StatVolHandler", volume, &volInfo); err != nil {
 		log.WithFields(logrus.Fields{
 			"volume": volume,
@@ -156,7 +156,7 @@ func (n networkFS) StatVol(volume string) (volInfo VolInfo, err error) {
 }
 
 // DeleteVol - Delete a volume.
-func (n networkFS) DeleteVol(volume string) error {
+func (n networkStorage) DeleteVol(volume string) error {
 	reply := GenericReply{}
 	if err := n.rpcClient.Call("Storage.DeleteVolHandler", volume, &reply); err != nil {
 		log.WithFields(logrus.Fields{
@@ -170,7 +170,7 @@ func (n networkFS) DeleteVol(volume string) error {
 // File operations.
 
 // CreateFile - create file.
-func (n networkFS) CreateFile(volume, path string) (writeCloser io.WriteCloser, err error) {
+func (n networkStorage) CreateFile(volume, path string) (writeCloser io.WriteCloser, err error) {
 	writeURL := new(url.URL)
 	writeURL.Scheme = n.netScheme
 	writeURL.Host = n.netAddr
@@ -205,7 +205,7 @@ func (n networkFS) CreateFile(volume, path string) (writeCloser io.WriteCloser,
 }
 
 // StatFile - get latest Stat information for a file at path.
-func (n networkFS) StatFile(volume, path string) (fileInfo FileInfo, err error) {
+func (n networkStorage) StatFile(volume, path string) (fileInfo FileInfo, err error) {
 	if err = n.rpcClient.Call("Storage.StatFileHandler", StatFileArgs{
 		Vol:  volume,
 		Path: path,
@@ -220,7 +220,7 @@ func (n networkFS) StatFile(volume, path string) (fileInfo FileInfo, err error)
 }
 
 // ReadFile - reads a file.
-func (n networkFS) ReadFile(volume string, path string, offset int64) (reader io.ReadCloser, err error) {
+func (n networkStorage) ReadFile(volume string, path string, offset int64) (reader io.ReadCloser, err error) {
 	readURL := new(url.URL)
 	readURL.Scheme = n.netScheme
 	readURL.Host = n.netAddr
@@ -247,31 +247,24 @@ func (n networkFS) ReadFile(volume string, path string, offset int64) (reader io
 	return resp.Body, nil
 }
 
-// ListFiles - List all files in a volume.
-func (n networkFS) ListFiles(volume, prefix, marker string, recursive bool, count int) (files []FileInfo, eof bool, err error) {
-	listFilesReply := ListFilesReply{}
-	if err = n.rpcClient.Call("Storage.ListFilesHandler", ListFilesArgs{
-		Vol:       volume,
-		Prefix:    prefix,
-		Marker:    marker,
-		Recursive: recursive,
-		Count:     count,
-	}, &listFilesReply); err != nil {
+// ListDir - list all entries at prefix.
+func (n networkStorage) ListDir(volume, path string) (entries []string, err error) {
+	if err = n.rpcClient.Call("Storage.ListDirHandler", ListDirArgs{
+		Vol:  volume,
+		Path: path,
+	}, &entries); err != nil {
 		log.WithFields(logrus.Fields{
-			"volume":    volume,
-			"prefix":    prefix,
-			"marker":    marker,
-			"recursive": recursive,
-			"count":     count,
-		}).Debugf("Storage.ListFilesHandlers failed with %s", err)
-		return nil, true, toStorageErr(err)
+			"volume": volume,
+			"path":   path,
+		}).Debugf("Storage.ListDirHandlers failed with %s", err)
+		return nil, toStorageErr(err)
 	}
 	// Return successfully unmarshalled results.
-	return listFilesReply.Files, listFilesReply.EOF, nil
+	return entries, nil
 }
 
 // DeleteFile - Delete a file at path.
-func (n networkFS) DeleteFile(volume, path string) (err error) {
+func (n networkStorage) DeleteFile(volume, path string) (err error) {
 	reply := GenericReply{}
 	if err = n.rpcClient.Call("Storage.DeleteFileHandler", DeleteFileArgs{
 		Vol:  volume,
@@ -287,7 +280,7 @@ func (n networkFS) DeleteFile(volume, path string) (err error) {
 }
 
 // RenameFile - Rename file.
-func (n networkFS) RenameFile(srcVolume, srcPath, dstVolume, dstPath string) (err error) {
+func (n networkStorage) RenameFile(srcVolume, srcPath, dstVolume, dstPath string) (err error) {
 	reply := GenericReply{}
 	if err = n.rpcClient.Call("Storage.RenameFileHandler", RenameFileArgs{
 		SrcVol:  srcVolume,
diff --git a/rpc-server-datatypes.go b/rpc-server-datatypes.go
index 60159b19a..7202e9668 100644
--- a/rpc-server-datatypes.go
+++ b/rpc-server-datatypes.go
@@ -27,21 +27,6 @@ type ListVolsReply struct {
 	Vols []VolInfo
 }
 
-// ListFilesArgs list file args.
-type ListFilesArgs struct {
-	Vol       string
-	Prefix    string
-	Marker    string
-	Recursive bool
-	Count     int
-}
-
-// ListFilesReply list file reply.
-type ListFilesReply struct {
-	Files []FileInfo
-	EOF   bool
-}
-
 // StatFileArgs stat file args.
 type StatFileArgs struct {
 	Vol  string
@@ -54,6 +39,12 @@ type DeleteFileArgs struct {
 	Path string
 }
 
+// ListDirArgs list dir args.
+type ListDirArgs struct {
+	Vol  string
+	Path string
+}
+
 // RenameFileArgs rename file args.
 type RenameFileArgs struct {
 	SrcVol  string
diff --git a/rpc-server.go b/rpc-server.go
index 92f6749af..c65190993 100644
--- a/rpc-server.go
+++ b/rpc-server.go
@@ -69,39 +69,31 @@ func (s *storageServer) DeleteVolHandler(arg *string, reply *GenericReply) error
 
 /// File operations
 
-// ListFilesHandler - list files handler.
-func (s *storageServer) ListFilesHandler(arg *ListFilesArgs, reply *ListFilesReply) error {
-	files, eof, err := s.storage.ListFiles(arg.Vol, arg.Prefix, arg.Marker, arg.Recursive, arg.Count)
+// StatFileHandler - stat file handler is rpc wrapper to stat file.
+func (s *storageServer) StatFileHandler(arg *StatFileArgs, reply *FileInfo) error {
+	fileInfo, err := s.storage.StatFile(arg.Vol, arg.Path)
 	if err != nil {
 		log.WithFields(logrus.Fields{
-			"volume":    arg.Vol,
-			"prefix":    arg.Prefix,
-			"marker":    arg.Marker,
-			"recursive": arg.Recursive,
-			"count":     arg.Count,
-		}).Debugf("ListFiles failed with error %s", err)
+			"volume": arg.Vol,
+			"path":   arg.Path,
+		}).Debugf("StatFile failed with error %s", err)
 		return err
 	}
-
-	// Fill reply structure.
-	reply.Files = files
-	reply.EOF = eof
-
-	// Return success.
+	*reply = fileInfo
 	return nil
 }
 
-// StatFileHandler - stat file handler is rpc wrapper to stat file.
-func (s *storageServer) StatFileHandler(arg *StatFileArgs, reply *FileInfo) error {
-	fileInfo, err := s.storage.StatFile(arg.Vol, arg.Path)
+// ListDirHandler - list directory handler is rpc wrapper to list dir.
+func (s *storageServer) ListDirHandler(arg *ListDirArgs, reply *[]string) error {
+	entries, err := s.storage.ListDir(arg.Vol, arg.Path)
 	if err != nil {
 		log.WithFields(logrus.Fields{
 			"volume": arg.Vol,
 			"path":   arg.Path,
-		}).Debugf("StatFile failed with error %s", err)
+		}).Debugf("ListDir failed with error %s", err)
 		return err
 	}
-	*reply = fileInfo
+	*reply = entries
 	return nil
 }
 
diff --git a/storage-api-interface.go b/storage-api-interface.go
index dff3865e7..c27c798c4 100644
--- a/storage-api-interface.go
+++ b/storage-api-interface.go
@@ -27,7 +27,7 @@ type StorageAPI interface {
 	DeleteVol(volume string) (err error)
 
 	// File operations.
-	ListFiles(volume, prefix, marker string, recursive bool, count int) (files []FileInfo, eof bool, err error)
+	ListDir(volume, dirPath string) ([]string, error)
 	ReadFile(volume string, path string, offset int64) (readCloser io.ReadCloser, err error)
 	CreateFile(volume string, path string) (writeCloser io.WriteCloser, err error)
 	StatFile(volume string, path string) (file FileInfo, err error)
diff --git a/tree-walk.go b/tree-walk.go
new file mode 100644
index 000000000..3aaae2279
--- /dev/null
+++ b/tree-walk.go
@@ -0,0 +1,284 @@
+/*
+ * Minio Cloud Storage, (C) 2016 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package main
+
+import (
+	"os"
+	"path"
+	"sort"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/Sirupsen/logrus"
+)
+
+// listParams - list object params used for list object map
+type listParams struct {
+	bucket    string
+	recursive bool
+	marker    string
+	prefix    string
+}
+
+// Tree walk result carries results of tree walking.
+type treeWalkResult struct {
+	fileInfo FileInfo
+	err      error
+	end      bool
+}
+
+// Tree walk notify carries a channel which notifies tree walk
+// results, additionally it also carries information if treeWalk
+// should be timedOut.
+type treeWalker struct {
+	ch       <-chan treeWalkResult
+	timedOut bool
+}
+
+// treeWalk walks FS directory tree recursively pushing fileInfo into the channel as and when it encounters files.
+func treeWalk(disk StorageAPI, bucket, prefixDir, entryPrefixMatch, marker string, recursive bool, send func(treeWalkResult) bool, count *int) bool {
+	// Example:
+	// if prefixDir="one/two/three/" and marker="four/five.txt" treeWalk is recursively
+	// called with prefixDir="one/two/three/four/" and marker="five.txt"
+
+	// Convert entry to FileInfo
+	entryToFileInfo := func(entry string) (fileInfo FileInfo, err error) {
+		if strings.HasSuffix(entry, slashSeparator) {
+			// Object name needs to be full path.
+			fileInfo.Name = path.Join(prefixDir, entry)
+			fileInfo.Name += slashSeparator
+			fileInfo.Mode = os.ModeDir
+			return
+		}
+		if fileInfo, err = disk.StatFile(bucket, path.Join(prefixDir, entry)); err != nil {
+			return
+		}
+		// Object name needs to be full path.
+		fileInfo.Name = path.Join(prefixDir, entry)
+		return
+	}
+
+	var markerBase, markerDir string
+	if marker != "" {
+		// Ex: if marker="four/five.txt", markerDir="four/" markerBase="five.txt"
+		markerSplit := strings.SplitN(marker, slashSeparator, 2)
+		markerDir = markerSplit[0]
+		if len(markerSplit) == 2 {
+			markerDir += slashSeparator
+			markerBase = markerSplit[1]
+		}
+	}
+	entries, err := disk.ListDir(bucket, prefixDir)
+	if err != nil {
+		send(treeWalkResult{err: err})
+		return false
+	}
+	if entryPrefixMatch != "" {
+		for i, entry := range entries {
+			if !strings.HasPrefix(entry, entryPrefixMatch) {
+				entries[i] = ""
+			}
+			if hasReservedPrefix(entry) || hasReservedSuffix(entry) {
+				entries[i] = ""
+			}
+		}
+	}
+	sort.StringSlice(entries).Sort()
+	// Skip the empty strings
+	for len(entries) > 0 && entries[0] == "" {
+		entries = entries[1:]
+	}
+	if len(entries) == 0 {
+		return true
+	}
+	// example:
+	// If markerDir="four/" Search() returns the index of "four/" in the sorted
+	// entries list so we skip all the entries till "four/"
+	idx := sort.StringSlice(entries).Search(markerDir)
+	entries = entries[idx:]
+	*count += len(entries)
+	for i, entry := range entries {
+		if i == 0 && markerDir == entry {
+			if !recursive {
+				// Skip as the marker would already be listed in the previous listing.
+				*count--
+				continue
+			}
+			if recursive && !strings.HasSuffix(entry, slashSeparator) {
+				// We should not skip for recursive listing and if markerDir is a directory
+				// for ex. if marker is "four/five.txt" markerDir will be "four/" which
+				// should not be skipped, instead it will need to be treeWalk()'ed into.
+
+				// Skip if it is a file though as it would be listed in previous listing.
+				*count--
+				continue
+			}
+		}
+
+		if recursive && strings.HasSuffix(entry, slashSeparator) {
+			// If the entry is a directory, we will need recurse into it.
+			markerArg := ""
+			if entry == markerDir {
+				// We need to pass "five.txt" as marker only if we are
+				// recursing into "four/"
+				markerArg = markerBase
+			}
+			*count--
+			prefixMatch := "" // Valid only for first level treeWalk and empty for subdirectories.
+			if !treeWalk(disk, bucket, path.Join(prefixDir, entry), prefixMatch, markerArg, recursive, send, count) {
+				return false
+			}
+			continue
+		}
+		*count--
+		fileInfo, err := entryToFileInfo(entry)
+		if err != nil {
+			// The file got deleted in the interim between ListDir() and StatFile()
+			// Ignore error and continue.
+			continue
+		}
+		if !send(treeWalkResult{fileInfo: fileInfo}) {
+			return false
+		}
+	}
+	return true
+}
+
+// Initiate a new treeWalk in a goroutine.
+func startTreeWalk(layer ObjectLayer, bucket, prefix, marker string, recursive bool) *treeWalker {
+	// Example 1
+	// If prefix is "one/two/three/" and marker is "one/two/three/four/five.txt"
+	// treeWalk is called with prefixDir="one/two/three/" and marker="four/five.txt"
+	// and entryPrefixMatch=""
+
+	// Example 2
+	// if prefix is "one/two/th" and marker is "one/two/three/four/five.txt"
+	// treeWalk is called with prefixDir="one/two/" and marker="three/four/five.txt"
+	// and entryPrefixMatch="th"
+	var disk StorageAPI
+	switch l := layer.(type) {
+	case xlObjects:
+		disk = l.storage
+	case fsObjects:
+		disk = l.storage
+	}
+
+	ch := make(chan treeWalkResult, maxObjectList)
+	walkNotify := treeWalker{ch: ch}
+	entryPrefixMatch := prefix
+	prefixDir := ""
+	lastIndex := strings.LastIndex(prefix, slashSeparator)
+	if lastIndex != -1 {
+		entryPrefixMatch = prefix[lastIndex+1:]
+		prefixDir = prefix[:lastIndex+1]
+	}
+	count := 0
+	marker = strings.TrimPrefix(marker, prefixDir)
+	go func() {
+		defer close(ch)
+		send := func(walkResult treeWalkResult) bool {
+			if count == 0 {
+				walkResult.end = true
+			}
+			timer := time.After(time.Second * 60)
+			select {
+			case ch <- walkResult:
+				return true
+			case <-timer:
+				walkNotify.timedOut = true
+				return false
+			}
+		}
+		treeWalk(disk, bucket, prefixDir, entryPrefixMatch, marker, recursive, send, &count)
+	}()
+	return &walkNotify
+}
+
+// Save the goroutine reference in the map
+func saveTreeWalk(layer ObjectLayer, params listParams, walker *treeWalker) {
+	var listObjectMap map[listParams][]*treeWalker
+	var listObjectMapMutex *sync.Mutex
+	switch l := layer.(type) {
+	case xlObjects:
+		listObjectMap = l.listObjectMap
+		listObjectMapMutex = l.listObjectMapMutex
+	case fsObjects:
+		listObjectMap = l.listObjectMap
+		listObjectMapMutex = l.listObjectMapMutex
+	}
+	listObjectMapMutex.Lock()
+	defer listObjectMapMutex.Unlock()
+
+	log.WithFields(logrus.Fields{
+		"bucket":    params.bucket,
+		"recursive": params.recursive,
+		"marker":    params.marker,
+		"prefix":    params.prefix,
+	}).Debugf("saveTreeWalk has been invoked.")
+
+	walkers, _ := listObjectMap[params]
+	walkers = append(walkers, walker)
+
+	listObjectMap[params] = walkers
+	log.Debugf("Successfully saved in listObjectMap.")
+}
+
+// Lookup the goroutine reference from map
+func lookupTreeWalk(layer ObjectLayer, params listParams) *treeWalker {
+	var listObjectMap map[listParams][]*treeWalker
+	var listObjectMapMutex *sync.Mutex
+	switch l := layer.(type) {
+	case xlObjects:
+		listObjectMap = l.listObjectMap
+		listObjectMapMutex = l.listObjectMapMutex
+	case fsObjects:
+		listObjectMap = l.listObjectMap
+		listObjectMapMutex = l.listObjectMapMutex
+	}
+	listObjectMapMutex.Lock()
+	defer listObjectMapMutex.Unlock()
+
+	log.WithFields(logrus.Fields{
+		"bucket":    params.bucket,
+		"recursive": params.recursive,
+		"marker":    params.marker,
+		"prefix":    params.prefix,
+	}).Debugf("lookupTreeWalk has been invoked.")
+	if walkChs, ok := listObjectMap[params]; ok {
+		for i, walkCh := range walkChs {
+			if !walkCh.timedOut {
+				newWalkChs := walkChs[i+1:]
+				if len(newWalkChs) > 0 {
+					listObjectMap[params] = newWalkChs
+				} else {
+					delete(listObjectMap, params)
+				}
+				log.WithFields(logrus.Fields{
+					"bucket":    params.bucket,
+					"recursive": params.recursive,
+					"marker":    params.marker,
+					"prefix":    params.prefix,
+				}).Debugf("Found the previous saved listsObjects params.")
+				return walkCh
+			}
+		}
+		// As all channels are timed out, delete the map entry
+		delete(listObjectMap, params)
+	}
+	return nil
+}
diff --git a/xl-erasure-v1.go b/xl-erasure-v1.go
index f52383992..83020af37 100644
--- a/xl-erasure-v1.go
+++ b/xl-erasure-v1.go
@@ -21,9 +21,10 @@ import (
 	"io"
 	"os"
 	slashpath "path"
-	"sort"
 	"strings"
 
+	"path"
+
 	"github.com/Sirupsen/logrus"
 	"github.com/klauspost/reedsolomon"
 )
@@ -377,254 +378,35 @@ func (xl XL) StatVol(volume string) (volInfo VolInfo, err error) {
 	return volInfo, nil
 }
 
-// isLeafDirectory - check if a given path is leaf directory. i.e
-// there are no more directories inside it. Erasure code backend
-// format it means that the parent directory is the actual object name.
-func isLeafDirectory(disk StorageAPI, volume, leafPath string) (isLeaf bool) {
-	var markerPath string
-	var xlListCount = 1000 // Count page.
-	for {
-		fileInfos, eof, err := disk.ListFiles(volume, leafPath, markerPath, false, xlListCount)
-		if err != nil {
-			log.WithFields(logrus.Fields{
-				"volume":     volume,
-				"leafPath":   leafPath,
-				"markerPath": markerPath,
-				"recursive":  false,
-				"count":      xlListCount,
-			}).Errorf("ListFiles failed with %s", err)
-			break
-		}
-		for _, fileInfo := range fileInfos {
-			if fileInfo.Mode.IsDir() {
-				// Directory found, not a leaf directory, return right here.
-				return false
-			}
-		}
-		if eof {
-			break
-		}
-		// MarkerPath to get the next set of files.
-		markerPath = fileInfos[len(fileInfos)-1].Name
-	}
-	// Exhausted all the entries, no directories found must be leaf
-	// return right here.
-	return true
-}
-
-// extractMetadata - extract xl metadata.
-func extractMetadata(disk StorageAPI, volume, path string) (xlMetaV1, error) {
-	xlMetaV1FilePath := slashpath.Join(path, xlMetaV1File)
-	// We are not going to read partial data from metadata file,
-	// read the whole file always.
-	offset := int64(0)
-	metadataReader, err := disk.ReadFile(volume, xlMetaV1FilePath, offset)
-	if err != nil {
-		log.WithFields(logrus.Fields{
-			"volume": volume,
-			"path":   xlMetaV1FilePath,
-			"offset": offset,
-		}).Errorf("ReadFile failed with %s", err)
-		return xlMetaV1{}, err
-	}
-	// Close metadata reader.
-	defer metadataReader.Close()
-
-	metadata, err := xlMetaV1Decode(metadataReader)
-	if err != nil {
-		log.WithFields(logrus.Fields{
-			"volume": volume,
-			"path":   xlMetaV1FilePath,
-			"offset": offset,
-		}).Errorf("xlMetaV1Decode failed with %s", err)
-		return xlMetaV1{}, err
-	}
-	return metadata, nil
-}
-
-// Extract file info from paths.
-func extractFileInfo(disk StorageAPI, volume, path string) (FileInfo, error) {
-	fileInfo := FileInfo{}
-	fileInfo.Volume = volume
-	fileInfo.Name = path
-
-	metadata, err := extractMetadata(disk, volume, path)
-	if err != nil {
-		log.WithFields(logrus.Fields{
-			"volume": volume,
-			"path":   path,
-		}).Errorf("extractMetadata failed with %s", err)
-		return FileInfo{}, err
-	}
-	fileInfo.Size = metadata.Stat.Size
-	fileInfo.ModTime = metadata.Stat.ModTime
-	fileInfo.Mode = os.FileMode(0644) // This is a file already.
-	return fileInfo, nil
+// isLeafDirectoryXL - check if a given path is leaf directory. i.e
+// if it contains file xlMetaV1File
+func isLeafDirectoryXL(disk StorageAPI, volume, leafPath string) (isLeaf bool) {
+	_, err := disk.StatFile(volume, path.Join(leafPath, xlMetaV1File))
+	return err == nil
 }
 
-// byFileInfoName is a collection satisfying sort.Interface.
-type byFileInfoName []FileInfo
-
-func (d byFileInfoName) Len() int           { return len(d) }
-func (d byFileInfoName) Swap(i, j int)      { d[i], d[j] = d[j], d[i] }
-func (d byFileInfoName) Less(i, j int) bool { return d[i].Name < d[j].Name }
-
-// ListFiles files at prefix.
-func (xl XL) ListFiles(volume, prefix, marker string, recursive bool, count int) (filesInfo []FileInfo, eof bool, err error) {
+// ListDir - return all the entries at the given directory path.
+// If an entry is a directory it will be returned with a trailing "/".
+func (xl XL) ListDir(volume, dirPath string) (entries []string, err error) {
 	if !isValidVolname(volume) {
-		return nil, true, errInvalidArgument
+		return nil, errInvalidArgument
 	}
-
-	// TODO: Fix: If readQuorum is met, its assumed that disks are in consistent file list.
-	// exclude disks those are not in consistent file list and check count of remaining disks
-	// are met readQuorum.
-
-	// Treat empty file list specially
-	emptyCount := 0
-	errCount := 0
-	successCount := 0
-
-	var firstFilesInfo []FileInfo
-	var firstEOF bool
-	var firstErr error
+	// FIXME: need someway to figure out which disk has the latest namespace
+	// so that Listing can be done there. One option is always do Listing from
+	// the "local" disk - if it is down user has to list using another XL server.
+	// This way user knows from which disk he is listing from.
 
 	for _, disk := range xl.storageDisks {
-		if filesInfo, eof, err = listFiles(disk, volume, prefix, marker, recursive, count); err == nil {
-			// we need to return first successful result
-			if firstFilesInfo == nil {
-				firstFilesInfo = filesInfo
-				firstEOF = eof
-			}
-
-			if len(filesInfo) == 0 {
-				emptyCount++
-			} else {
-				successCount++
-			}
-		} else {
-			if firstErr == nil {
-				firstErr = err
-			}
-
-			errCount++
-		}
-	}
-
-	if errCount >= xl.readQuorum {
-		return nil, false, firstErr
-	} else if successCount >= xl.readQuorum {
-		return firstFilesInfo, firstEOF, nil
-	} else if emptyCount >= xl.readQuorum {
-		return []FileInfo{}, true, nil
-	}
-
-	return nil, false, errReadQuorum
-}
-
-func listFiles(disk StorageAPI, volume, prefix, marker string, recursive bool, count int) (filesInfo []FileInfo, eof bool, err error) {
-	var fsFilesInfo []FileInfo
-	var markerPath = marker
-	if marker != "" {
-		isLeaf := isLeafDirectory(disk, volume, retainSlash(marker))
-		if isLeaf {
-			// For leaf for now we just point to the first block, make it
-			// dynamic in future based on the availability of storage disks.
-			markerPath = slashpath.Join(marker, xlMetaV1File)
-		}
-	}
-
-	// Loop and capture the proper fileInfos, requires extraction and
-	// separation of XL related metadata information.
-	for {
-		fsFilesInfo, eof, err = disk.ListFiles(volume, prefix, markerPath, recursive, count)
-		if err != nil {
-			log.WithFields(logrus.Fields{
-				"volume":    volume,
-				"prefix":    prefix,
-				"marker":    markerPath,
-				"recursive": recursive,
-				"count":     count,
-			}).Errorf("ListFiles failed with %s", err)
-			return nil, true, err
-		}
-		for _, fsFileInfo := range fsFilesInfo {
-			// Skip metadata files.
-			if strings.HasSuffix(fsFileInfo.Name, xlMetaV1File) {
-				continue
-			}
-			var fileInfo FileInfo
-			var isLeaf bool
-			if fsFileInfo.Mode.IsDir() {
-				isLeaf = isLeafDirectory(disk, volume, fsFileInfo.Name)
-			}
-			if isLeaf || !fsFileInfo.Mode.IsDir() {
-				// Extract the parent of leaf directory or file to get the
-				// actual name.
-				path := slashpath.Dir(fsFileInfo.Name)
-				fileInfo, err = extractFileInfo(disk, volume, path)
-				if err != nil {
-					log.WithFields(logrus.Fields{
-						"volume": volume,
-						"path":   path,
-					}).Errorf("extractFileInfo failed with %s", err)
-					// For a leaf directory, if err is FileNotFound then
-					// perhaps has a missing metadata. Ignore it and let
-					// healing finish its job it will become available soon.
-					if err == errFileNotFound {
-						continue
-					}
-					// For any other errors return to the caller.
-					return nil, true, err
-				}
-			} else {
-				fileInfo = fsFileInfo
-			}
-			filesInfo = append(filesInfo, fileInfo)
-			count--
-			if count == 0 {
-				break
-			}
-		}
-		if len(fsFilesInfo) > 0 {
-			// markerPath for the next disk.ListFiles() iteration.
-			markerPath = fsFilesInfo[len(fsFilesInfo)-1].Name
+		if entries, err = disk.ListDir(volume, dirPath); err != nil {
+			continue
 		}
-		if count == 0 && recursive && !strings.HasSuffix(markerPath, xlMetaV1File) {
-			// If last entry is not file.json then loop once more to check if we have reached eof.
-			fsFilesInfo, eof, err = disk.ListFiles(volume, prefix, markerPath, recursive, 1)
-			if err != nil {
-				log.WithFields(logrus.Fields{
-					"volume":    volume,
-					"prefix":    prefix,
-					"marker":    markerPath,
-					"recursive": recursive,
-					"count":     1,
-				}).Errorf("ListFiles failed with %s", err)
-				return nil, true, err
-			}
-			if !eof {
-				// file.N and file.json are always in pairs and hence this
-				// entry has to be file.json. If not better to manually investigate
-				// and fix it.
-				// For the next ListFiles() call we can safely assume that the
-				// marker is "object/file.json"
-				if !strings.HasSuffix(fsFilesInfo[0].Name, xlMetaV1File) {
-					log.WithFields(logrus.Fields{
-						"volume":          volume,
-						"prefix":          prefix,
-						"fsFileInfo.Name": fsFilesInfo[0].Name,
-					}).Errorf("ListFiles failed with %s, expected %s to be a file.json file.", err, fsFilesInfo[0].Name)
-					return nil, true, errUnexpected
-				}
+		for i, entry := range entries {
+			if strings.HasSuffix(entry, slashSeparator) && isLeafDirectoryXL(disk, volume, path.Join(dirPath, entry)) {
+				entries[i] = strings.TrimSuffix(entry, slashSeparator)
 			}
 		}
-		if count == 0 || eof {
-			break
-		}
 	}
-	// Sort to make sure we sort entries back properly.
-	sort.Sort(byFileInfoName(filesInfo))
-	return filesInfo, eof, nil
+	return
 }
 
 // Object API.
diff --git a/xl-objects-multipart.go b/xl-objects-multipart.go
index 70db1492d..b4bd3c8ae 100644
--- a/xl-objects-multipart.go
+++ b/xl-objects-multipart.go
@@ -62,7 +62,7 @@ func partNumToPartFileName(partNum int) string {
 
 // ListMultipartUploads - list multipart uploads.
 func (xl xlObjects) ListMultipartUploads(bucket, prefix, keyMarker, uploadIDMarker, delimiter string, maxUploads int) (ListMultipartsInfo, error) {
-	return listMultipartUploadsCommon(xl.storage, bucket, prefix, keyMarker, uploadIDMarker, delimiter, maxUploads)
+	return listMultipartUploadsCommon(xl, bucket, prefix, keyMarker, uploadIDMarker, delimiter, maxUploads)
 }
 
 // NewMultipartUpload - initialize a new multipart upload, returns a unique id.
diff --git a/xl-objects.go b/xl-objects.go
index e6f147a31..f49fedd58 100644
--- a/xl-objects.go
+++ b/xl-objects.go
@@ -22,7 +22,9 @@ import (
 	"path"
 	"path/filepath"
 	"strings"
+	"sync"
 
+	"github.com/Sirupsen/logrus"
 	"github.com/minio/minio/pkg/mimedb"
 )
 
@@ -33,9 +35,17 @@ const (
 
 // xlObjects - Implements fs object layer.
 type xlObjects struct {
-	storage StorageAPI
+	storage            StorageAPI
+	listObjectMap      map[listParams][]*treeWalker
+	listObjectMapMutex *sync.Mutex
 }
 
+func isLeafDirectory(disk StorageAPI, volume, leafPath string) bool {
+	_, err := disk.StatFile(volume, pathJoin(leafPath, multipartMetaFile))
+	return err == nil
+}
+
+// FIXME: constructor should return a pointer.
 // newXLObjects - initialize new xl object layer.
 func newXLObjects(exportPaths ...string) (ObjectLayer, error) {
 	storage, err := newXL(exportPaths...)
@@ -47,7 +57,11 @@ func newXLObjects(exportPaths ...string) (ObjectLayer, error) {
 	cleanupAllTmpEntries(storage)
 
 	// Return successfully initialized object layer.
-	return xlObjects{storage}, nil
+	return xlObjects{
+		storage:            storage,
+		listObjectMap:      make(map[listParams][]*treeWalker),
+		listObjectMapMutex: &sync.Mutex{},
+	}, nil
 }
 
 /// Bucket operations
@@ -226,13 +240,17 @@ func (xl xlObjects) DeleteObject(bucket, object string) error {
 	return nil
 }
 
-// TODO - support non-recursive case, figure out file size for files uploaded using multipart.
-
 func (xl xlObjects) ListObjects(bucket, prefix, marker, delimiter string, maxKeys int) (ListObjectsInfo, error) {
 	// Verify if bucket is valid.
 	if !IsValidBucketName(bucket) {
 		return ListObjectsInfo{}, BucketNameInvalid{Bucket: bucket}
 	}
+	// Verify whether the bucket exists.
+	if isExist, err := isBucketExist(xl.storage, bucket); err != nil {
+		return ListObjectsInfo{}, err
+	} else if !isExist {
+		return ListObjectsInfo{}, BucketNotFound{Bucket: bucket}
+	}
 	if !IsValidObjectPrefix(prefix) {
 		return ListObjectsInfo{}, ObjectNameInvalid{Bucket: bucket, Object: prefix}
 	}
@@ -261,64 +279,91 @@ func (xl xlObjects) ListObjects(bucket, prefix, marker, delimiter string, maxKey
 	if delimiter == slashSeparator {
 		recursive = false
 	}
-	var allFileInfos, fileInfos []FileInfo
+
+	walker := lookupTreeWalk(xl, listParams{bucket, recursive, marker, prefix})
+	if walker == nil {
+		walker = startTreeWalk(xl, bucket, prefix, marker, recursive)
+	}
+	var fileInfos []FileInfo
 	var eof bool
 	var err error
-	for {
-		fileInfos, eof, err = xl.storage.ListFiles(bucket, prefix, marker, recursive, maxKeys)
-		if err != nil {
-			return ListObjectsInfo{}, toObjectErr(err, bucket)
+	var nextMarker string
+	log.Debugf("Reading from the tree walk channel has begun.")
+	for i := 0; i < maxKeys; {
+		walkResult, ok := <-walker.ch
+		if !ok {
+			// Closed channel.
+			eof = true
+			break
 		}
-		for _, fileInfo := range fileInfos {
-			// FIXME: use fileInfo.Mode.IsDir() instead after fixing the bug in
-			// XL listing which is not reseting the Mode to 0 for leaf dirs.
-			if strings.HasSuffix(fileInfo.Name, slashSeparator) && isLeafDirectory(xl.storage, bucket, fileInfo.Name) {
-				// Set the Mode to a "regular" file.
-				var info MultipartObjectInfo
-				info, err = getMultipartObjectInfo(xl.storage, bucket, fileInfo.Name)
-				if err == nil {
-					fileInfo.Mode = 0
+		// For any walk error return right away.
+		if walkResult.err != nil {
+			log.WithFields(logrus.Fields{
+				"bucket":    bucket,
+				"prefix":    prefix,
+				"marker":    marker,
+				"recursive": recursive,
+			}).Debugf("Walk resulted in an error %s", walkResult.err)
+			// File not found is a valid case.
+			if walkResult.err == errFileNotFound {
+				return ListObjectsInfo{}, nil
+			}
+			return ListObjectsInfo{}, toObjectErr(walkResult.err, bucket, prefix)
+		}
+		fileInfo := walkResult.fileInfo
+		if strings.HasSuffix(fileInfo.Name, slashSeparator) && isLeafDirectory(xl.storage, bucket, fileInfo.Name) {
+			// Code flow reaches here for non-recursive listing.
 
-					fileInfo.Name = strings.TrimSuffix(fileInfo.Name, slashSeparator)
-					fileInfo.Size = info.Size
-					fileInfo.ModTime = info.ModTime
-					fileInfo.MD5Sum = info.MD5Sum
-				} else if err != errFileNotFound {
-					return ListObjectsInfo{}, toObjectErr(err, bucket, fileInfo.Name)
-				}
-				allFileInfos = append(allFileInfos, fileInfo)
-				maxKeys--
-				continue
-			} else if strings.HasSuffix(fileInfo.Name, multipartMetaFile) {
-				fileInfo.Name = path.Dir(fileInfo.Name)
-				var info MultipartObjectInfo
-				info, err = getMultipartObjectInfo(xl.storage, bucket, fileInfo.Name)
-				if err != nil {
-					return ListObjectsInfo{}, toObjectErr(err, bucket, fileInfo.Name)
-				}
+			var info MultipartObjectInfo
+			info, err = getMultipartObjectInfo(xl.storage, bucket, fileInfo.Name)
+			if err == nil {
+				// Set the Mode to a "regular" file.
+				fileInfo.Mode = 0
+				fileInfo.Name = strings.TrimSuffix(fileInfo.Name, slashSeparator)
 				fileInfo.Size = info.Size
-				fileInfo.ModTime = info.ModTime
 				fileInfo.MD5Sum = info.MD5Sum
-				allFileInfos = append(allFileInfos, fileInfo)
-				maxKeys--
-				continue
-			} else if strings.HasSuffix(fileInfo.Name, multipartSuffix) {
-				continue
+				fileInfo.ModTime = info.ModTime
+			} else if err != errFileNotFound {
+				return ListObjectsInfo{}, toObjectErr(err, bucket, fileInfo.Name)
 			}
-			allFileInfos = append(allFileInfos, fileInfo)
-			maxKeys--
-		}
-		if maxKeys == 0 {
-			break
+		} else if strings.HasSuffix(fileInfo.Name, multipartMetaFile) {
+			// Code flow reaches here for recursive listing.
+
+			// for object/00000.minio.multipart, strip the base name
+			// and calculate get the object size.
+			fileInfo.Name = path.Dir(fileInfo.Name)
+			var info MultipartObjectInfo
+			info, err = getMultipartObjectInfo(xl.storage, bucket, fileInfo.Name)
+			if err != nil {
+				return ListObjectsInfo{}, toObjectErr(err, bucket, fileInfo.Name)
+			}
+			fileInfo.Size = info.Size
+		} else if strings.HasSuffix(fileInfo.Name, multipartSuffix) {
+			// Ignore the part files like object/00001.minio.multipart
+			continue
 		}
-		if eof {
+		nextMarker = fileInfo.Name
+		fileInfos = append(fileInfos, fileInfo)
+		if walkResult.end {
+			eof = true
 			break
 		}
+		i++
+	}
+	params := listParams{bucket, recursive, nextMarker, prefix}
+	log.WithFields(logrus.Fields{
+		"bucket":    params.bucket,
+		"recursive": params.recursive,
+		"marker":    params.marker,
+		"prefix":    params.prefix,
+	}).Debugf("Save the tree walk into map for subsequent requests.")
+	if !eof {
+		saveTreeWalk(xl, params, walker)
 	}
 
 	result := ListObjectsInfo{IsTruncated: !eof}
 
-	for _, fileInfo := range allFileInfos {
+	for _, fileInfo := range fileInfos {
 		// With delimiter set we fill in NextMarker and Prefixes.
 		if delimiter == slashSeparator {
 			result.NextMarker = fileInfo.Name