Support bucket versioning (#9377)

- Implement a new xl.json 2.0.0 format to support,
  this moves the entire marshaling logic to POSIX
  layer, top layer always consumes a common FileInfo
  construct which simplifies the metadata reads.
- Implement list object versions
- Migrate to siphash from crchash for new deployments
  for object placements.

Fixes #2111

cmd/erasure-lowlevel-heal.go

@@ -0,0 +1,48 @@
+/*
+ * MinIO Cloud Storage, (C) 2016-2020 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 cmd
+
+import (
+	"context"
+	"io"
+
+	"github.com/minio/minio/cmd/logger"
+)
+
+// Heal heals the shard files on non-nil writers. Note that the quorum passed is 1
+// as healing should continue even if it has been successful healing only one shard file.
+func (e Erasure) Heal(ctx context.Context, readers []io.ReaderAt, writers []io.Writer, size int64) error {
+	r, w := io.Pipe()
+	go func() {
+		if err := e.Decode(ctx, w, readers, 0, size, size, nil); err != nil {
+			w.CloseWithError(err)
+			return
+		}
+		w.Close()
+	}()
+	buf := make([]byte, e.blockSize)
+	// quorum is 1 because CreateFile should continue writing as long as we are writing to even 1 disk.
+	n, err := e.Encode(ctx, r, writers, buf, 1)
+	if err != nil {
+		return err
+	}
+	if n != size {
+		logger.LogIf(ctx, errLessData)
+		return errLessData
+	}
+	return nil
+}