diff --git a/cmd/fs-v1-metadata.go b/cmd/fs-v1-metadata.go
index ae0b3532a..f467991db 100644
--- a/cmd/fs-v1-metadata.go
+++ b/cmd/fs-v1-metadata.go
@@ -125,18 +125,18 @@ func (m *fsMetaV1) AddObjectPart(partNumber int, partName string, partETag strin
 	sort.Sort(byObjectPartNumber(m.Parts))
 }
 
-func (m *fsMetaV1) WriteTo(writer io.Writer) (n int64, err error) {
+func (m *fsMetaV1) WriteTo(lk *lock.LockedFile) (n int64, err error) {
 	var metadataBytes []byte
 	metadataBytes, err = json.Marshal(m)
 	if err != nil {
 		return 0, traceError(err)
 	}
 
-	if err = writer.(*lock.LockedFile).Truncate(0); err != nil {
+	if err = lk.Truncate(0); err != nil {
 		return 0, traceError(err)
 	}
 
-	if _, err = writer.Write(metadataBytes); err != nil {
+	if _, err = lk.Write(metadataBytes); err != nil {
 		return 0, traceError(err)
 	}
 
@@ -144,9 +144,14 @@ func (m *fsMetaV1) WriteTo(writer io.Writer) (n int64, err error) {
 	return int64(len(metadataBytes)), nil
 }
 
-func (m *fsMetaV1) ReadFrom(reader io.Reader) (n int64, err error) {
+func (m *fsMetaV1) ReadFrom(lk *lock.LockedFile) (n int64, err error) {
 	var metadataBytes []byte
-	metadataBytes, err = ioutil.ReadAll(reader)
+	fi, err := lk.Stat()
+	if err != nil {
+		return 0, traceError(err)
+	}
+
+	metadataBytes, err = ioutil.ReadAll(io.NewSectionReader(lk, 0, fi.Size()))
 	if err != nil {
 		return 0, traceError(err)
 	}
diff --git a/cmd/fs-v1-metadata_test.go b/cmd/fs-v1-metadata_test.go
index b1163d62f..c31008949 100644
--- a/cmd/fs-v1-metadata_test.go
+++ b/cmd/fs-v1-metadata_test.go
@@ -18,7 +18,6 @@ package cmd
 
 import (
 	"bytes"
-	"io"
 	"os"
 	"path/filepath"
 	"testing"
@@ -69,10 +68,9 @@ func TestReadFSMetadata(t *testing.T) {
 	}
 	defer rlk.Close()
 
-	sectionReader := io.NewSectionReader(rlk, 0, rlk.Size())
 	// Regular fs metadata reading, no errors expected
 	fsMeta := fsMetaV1{}
-	if _, err = fsMeta.ReadFrom(sectionReader); err != nil {
+	if _, err = fsMeta.ReadFrom(rlk.LockedFile); err != nil {
 		t.Fatal("Unexpected error ", err)
 	}
 
@@ -84,7 +82,7 @@ func TestReadFSMetadata(t *testing.T) {
 	file.Write([]byte{'a'})
 	file.Close()
 	fsMeta = fsMetaV1{}
-	if _, err := fsMeta.ReadFrom(sectionReader); err == nil {
+	if _, err := fsMeta.ReadFrom(rlk.LockedFile); err == nil {
 		t.Fatal("Should fail", err)
 	}
 }
@@ -119,10 +117,9 @@ func TestWriteFSMetadata(t *testing.T) {
 	}
 	defer rlk.Close()
 
-	sectionReader := io.NewSectionReader(rlk, 0, rlk.Size())
 	// FS metadata reading, no errors expected (healthy disk)
 	fsMeta := fsMetaV1{}
-	_, err = fsMeta.ReadFrom(sectionReader)
+	_, err = fsMeta.ReadFrom(rlk.LockedFile)
 	if err != nil {
 		t.Fatal("Unexpected error ", err)
 	}
diff --git a/cmd/fs-v1-multipart-common.go b/cmd/fs-v1-multipart-common.go
index 940b0645e..47b63690e 100644
--- a/cmd/fs-v1-multipart-common.go
+++ b/cmd/fs-v1-multipart-common.go
@@ -97,7 +97,7 @@ func (fs fsObjects) deleteUploadsJSON(bucket, object, uploadID string) error {
 // slice is empty then we remove/purge the file.
 func (fs fsObjects) removeUploadID(bucket, object, uploadID string, rwlk *lock.LockedFile) error {
 	uploadIDs := uploadsV1{}
-	_, err := uploadIDs.ReadFrom(io.NewSectionReader(rwlk, 0, rwlk.Size()))
+	_, err := uploadIDs.ReadFrom(rwlk)
 	if err != nil {
 		return err
 	}
@@ -121,7 +121,7 @@ func (fs fsObjects) removeUploadID(bucket, object, uploadID string, rwlk *lock.L
 func (fs fsObjects) addUploadID(bucket, object, uploadID string, initiated time.Time, rwlk *lock.LockedFile) error {
 	uploadIDs := uploadsV1{}
 
-	_, err := uploadIDs.ReadFrom(io.NewSectionReader(rwlk, 0, rwlk.Size()))
+	_, err := uploadIDs.ReadFrom(rwlk)
 	// For all unexpected errors, we return.
 	if err != nil && errorCause(err) != io.EOF {
 		return err
diff --git a/cmd/fs-v1-multipart.go b/cmd/fs-v1-multipart.go
index a1079f795..800cb2bb9 100644
--- a/cmd/fs-v1-multipart.go
+++ b/cmd/fs-v1-multipart.go
@@ -52,7 +52,7 @@ func (fs fsObjects) listMultipartUploadIDs(bucketName, objectName, uploadIDMarke
 
 	// Read `uploads.json`.
 	uploadIDs := uploadsV1{}
-	if _, err = uploadIDs.ReadFrom(io.NewSectionReader(rlk, 0, rlk.Size())); err != nil {
+	if _, err = uploadIDs.ReadFrom(rlk.LockedFile); err != nil {
 		return nil, false, err
 	}
 
@@ -378,7 +378,7 @@ func (fs fsObjects) PutObjectPart(bucket, object, uploadID string, partID int, s
 	defer rwlk.Close()
 
 	fsMeta := fsMetaV1{}
-	_, err = fsMeta.ReadFrom(io.NewSectionReader(rwlk, 0, rwlk.Size()))
+	_, err = fsMeta.ReadFrom(rwlk)
 	if err != nil {
 		return "", toObjectErr(err, minioMetaMultipartBucket, fsMetaPath)
 	}
@@ -499,7 +499,7 @@ func (fs fsObjects) listObjectParts(bucket, object, uploadID string, partNumberM
 	defer fs.rwPool.Close(fsMetaPath)
 
 	fsMeta := fsMetaV1{}
-	_, err = fsMeta.ReadFrom((io.NewSectionReader(metaFile, 0, metaFile.Size())))
+	_, err = fsMeta.ReadFrom(metaFile.LockedFile)
 	if err != nil {
 		return ListPartsInfo{}, toObjectErr(err, minioMetaBucket, fsMetaPath)
 	}
@@ -630,7 +630,7 @@ func (fs fsObjects) CompleteMultipartUpload(bucket string, object string, upload
 
 	fsMeta := fsMetaV1{}
 	// Read saved fs metadata for ongoing multipart.
-	_, err = fsMeta.ReadFrom(io.NewSectionReader(rlk, 0, rlk.Size()))
+	_, err = fsMeta.ReadFrom(rlk.LockedFile)
 	if err != nil {
 		fs.rwPool.Close(fsMetaPathMultipart)
 		return ObjectInfo{}, toObjectErr(err, minioMetaMultipartBucket, fsMetaPathMultipart)
diff --git a/cmd/fs-v1.go b/cmd/fs-v1.go
index 6db9c5635..85ced11f6 100644
--- a/cmd/fs-v1.go
+++ b/cmd/fs-v1.go
@@ -505,7 +505,7 @@ func (fs fsObjects) getObjectInfo(bucket, object string) (ObjectInfo, error) {
 	if err == nil {
 		// Read from fs metadata only if it exists.
 		defer fs.rwPool.Close(fsMetaPath)
-		if _, rerr := fsMeta.ReadFrom(io.NewSectionReader(rlk, 0, rlk.Size())); rerr != nil {
+		if _, rerr := fsMeta.ReadFrom(rlk.LockedFile); rerr != nil {
 			return ObjectInfo{}, toObjectErr(rerr, bucket, object)
 		}
 	}
diff --git a/cmd/object-api-multipart-common.go b/cmd/object-api-multipart-common.go
index b515d5b5e..448cca141 100644
--- a/cmd/object-api-multipart-common.go
+++ b/cmd/object-api-multipart-common.go
@@ -76,26 +76,30 @@ func (u *uploadsV1) IsEmpty() bool {
 	return len(u.Uploads) == 0
 }
 
-func (u *uploadsV1) WriteTo(writer io.Writer) (n int64, err error) {
+func (u *uploadsV1) WriteTo(lk *lock.LockedFile) (n int64, err error) {
 	// Serialize to prepare to write to disk.
 	var uplBytes []byte
 	uplBytes, err = json.Marshal(u)
 	if err != nil {
 		return 0, traceError(err)
 	}
-	if err = writer.(*lock.LockedFile).Truncate(0); err != nil {
+	if err = lk.Truncate(0); err != nil {
 		return 0, traceError(err)
 	}
-	_, err = writer.Write(uplBytes)
+	_, err = lk.Write(uplBytes)
 	if err != nil {
 		return 0, traceError(err)
 	}
 	return int64(len(uplBytes)), nil
 }
 
-func (u *uploadsV1) ReadFrom(reader io.Reader) (n int64, err error) {
+func (u *uploadsV1) ReadFrom(lk *lock.LockedFile) (n int64, err error) {
 	var uploadIDBytes []byte
-	uploadIDBytes, err = ioutil.ReadAll(reader)
+	fi, err := lk.Stat()
+	if err != nil {
+		return 0, traceError(err)
+	}
+	uploadIDBytes, err = ioutil.ReadAll(io.NewSectionReader(lk, 0, fi.Size()))
 	if err != nil {
 		return 0, traceError(err)
 	}
diff --git a/pkg/lock/lock.go b/pkg/lock/lock.go
index a72750fdc..f8632a667 100644
--- a/pkg/lock/lock.go
+++ b/pkg/lock/lock.go
@@ -89,14 +89,7 @@ func RLockedOpenFile(path string) (*RLockedFile, error) {
 
 }
 
-// LockedFile represents a locked file, implements a helper
-// method Size(), represents the size of the underlying object.
+// LockedFile represents a locked file
 type LockedFile struct {
 	*os.File
-	size int64
-}
-
-// Size - size of the underlying locked file.
-func (l *LockedFile) Size() int64 {
-	return l.size
 }
diff --git a/pkg/lock/lock_nix.go b/pkg/lock/lock_nix.go
index 14263335d..537255c01 100644
--- a/pkg/lock/lock_nix.go
+++ b/pkg/lock/lock_nix.go
@@ -71,5 +71,5 @@ func LockedOpenFile(path string, flag int, perm os.FileMode) (*LockedFile, error
 		}
 	}
 
-	return &LockedFile{File: f, size: st.Size()}, nil
+	return &LockedFile{File: f}, nil
 }
diff --git a/pkg/lock/lock_test.go b/pkg/lock/lock_test.go
index 4c3547417..abc8e71c3 100644
--- a/pkg/lock/lock_test.go
+++ b/pkg/lock/lock_test.go
@@ -80,9 +80,6 @@ func TestRWLockedFile(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	if rlk.Size() != 0 {
-		t.Fatal("File size should be zero", rlk.Size())
-	}
 	isClosed := rlk.IsClosed()
 	if isClosed {
 		t.Fatal("File ref count shouldn't be zero")
diff --git a/pkg/lock/lock_windows.go b/pkg/lock/lock_windows.go
index dcbb7ed33..04a00e093 100644
--- a/pkg/lock/lock_windows.go
+++ b/pkg/lock/lock_windows.go
@@ -65,7 +65,7 @@ func LockedOpenFile(path string, flag int, perm os.FileMode) (*LockedFile, error
 		}
 	}
 
-	return &LockedFile{File: f, size: st.Size()}, nil
+	return &LockedFile{File: f}, nil
 }
 
 func makeInheritSa() *syscall.SecurityAttributes {