fs: PutObject create 0byte objects properly. (#3387)

Current code always appends to a file only if 1byte or
more was sent on the wire was affecting both PutObject
and PutObjectPart uploads.

This patch fixes such a situation and resolves #3385

cmd/fs-createfile.go

@@ -27,11 +27,9 @@ func fsCreateFile(disk StorageAPI, reader io.Reader, buf []byte, tmpBucket, temp
 			return 0, traceError(rErr)
 		}
 		bytesWritten += int64(n)
-		if n > 0 {
-			wErr := disk.AppendFile(tmpBucket, tempObj, buf[0:n])
-			if wErr != nil {
-				return 0, traceError(wErr)
-			}
+		wErr := disk.AppendFile(tmpBucket, tempObj, buf[0:n])
+		if wErr != nil {
+			return 0, traceError(wErr)
 		}
 		if rErr == io.EOF {
 			break

cmd/fs-v1-multipart.go

@@ -301,6 +301,7 @@ func (fs fsObjects) PutObjectPart(bucket, object, uploadID string, partID int, s
 		fs.storage.DeleteFile(minioMetaTmpBucket, tmpPartPath)
 		return "", toObjectErr(cErr, minioMetaTmpBucket, tmpPartPath)
 	}
+
 	// Should return IncompleteBody{} error when reader has fewer
 	// bytes than specified in request header.
 	if bytesWritten < size {

cmd/fs-v1-multipart_test.go

@@ -59,6 +59,12 @@ func TestNewMultipartUploadFaultyDisk(t *testing.T) {
 
 // TestPutObjectPartFaultyDisk - test PutObjectPart with faulty disks
 func TestPutObjectPartFaultyDisk(t *testing.T) {
+	root, err := newTestConfig("us-east-1")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer removeAll(root)
+
 	// Prepare for tests
 	disk := filepath.Join(os.TempDir(), "minio-"+nextSuffix())
 	defer removeAll(disk)
@@ -69,7 +75,7 @@ func TestPutObjectPartFaultyDisk(t *testing.T) {
 	data := []byte("12345")
 	dataLen := int64(len(data))
 
-	if err := obj.MakeBucket(bucketName); err != nil {
+	if err = obj.MakeBucket(bucketName); err != nil {
 		t.Fatal("Cannot create bucket, err: ", err)
 	}
 
@@ -97,7 +103,7 @@ func TestPutObjectPartFaultyDisk(t *testing.T) {
 					t.Fatal("Unexpected error ", err)
 				}
 			case 3:
-			case 2, 4, 5:
+			case 2, 4, 5, 6:
 				if !isSameType(errorCause(err), InvalidUploadID{}) {
 					t.Fatal("Unexpected error ", err)
 				}

cmd/fs-v1.go

@@ -392,45 +392,37 @@ func (fs fsObjects) PutObject(bucket string, object string, size int64, data io.
 		limitDataReader = data
 	}
 
-	if size == 0 {
-		// For size 0 we write a 0byte file.
-		err = fs.storage.AppendFile(minioMetaTmpBucket, tempObj, []byte(""))
+	// Prepare file to avoid disk fragmentation
+	if size > 0 {
+		err = fs.storage.PrepareFile(minioMetaTmpBucket, tempObj, size)
 		if err != nil {
-			fs.storage.DeleteFile(minioMetaTmpBucket, tempObj)
-			return ObjectInfo{}, toObjectErr(traceError(err), bucket, object)
+			return ObjectInfo{}, toObjectErr(err, bucket, object)
 		}
-	} else {
+	}
 
-		// Prepare file to avoid disk fragmentation
-		if size > 0 {
-			err = fs.storage.PrepareFile(minioMetaTmpBucket, tempObj, size)
-			if err != nil {
-				return ObjectInfo{}, toObjectErr(err, bucket, object)
-			}
-		}
+	// Allocate a buffer to Read() from request body
+	bufSize := int64(readSizeV1)
+	if size > 0 && bufSize > size {
+		bufSize = size
+	}
 
-		// Allocate a buffer to Read() from request body
-		bufSize := int64(readSizeV1)
-		if size > 0 && bufSize > size {
-			bufSize = size
-		}
-		buf := make([]byte, int(bufSize))
-		teeReader := io.TeeReader(limitDataReader, multiWriter)
-		var bytesWritten int64
-		bytesWritten, err = fsCreateFile(fs.storage, teeReader, buf, minioMetaTmpBucket, tempObj)
-		if err != nil {
-			fs.storage.DeleteFile(minioMetaTmpBucket, tempObj)
-			errorIf(err, "Failed to create object %s/%s", bucket, object)
-			return ObjectInfo{}, toObjectErr(err, bucket, object)
-		}
+	buf := make([]byte, int(bufSize))
+	teeReader := io.TeeReader(limitDataReader, multiWriter)
+	var bytesWritten int64
+	bytesWritten, err = fsCreateFile(fs.storage, teeReader, buf, minioMetaTmpBucket, tempObj)
+	if err != nil {
+		fs.storage.DeleteFile(minioMetaTmpBucket, tempObj)
+		errorIf(err, "Failed to create object %s/%s", bucket, object)
+		return ObjectInfo{}, toObjectErr(err, bucket, object)
+	}
 
-		// Should return IncompleteBody{} error when reader has fewer
-		// bytes than specified in request header.
-		if bytesWritten < size {
-			fs.storage.DeleteFile(minioMetaTmpBucket, tempObj)
-			return ObjectInfo{}, traceError(IncompleteBody{})
-		}
+	// Should return IncompleteBody{} error when reader has fewer
+	// bytes than specified in request header.
+	if bytesWritten < size {
+		fs.storage.DeleteFile(minioMetaTmpBucket, tempObj)
+		return ObjectInfo{}, traceError(IncompleteBody{})
 	}
+
 	// Delete the temporary object in the case of a
 	// failure. If PutObject succeeds, then there would be
 	// nothing to delete.