api: Introduce metadata update APIs to update only metadata (#11962)

Current implementation heavily relies on readAllFileInfo
but with the advent of xl.meta inlined with data, we cannot
easily avoid reading data when we are only interested is
updating metadata, this leads to invariably write
amplification during metadata updates, repeatedly reading
data when we are only interested in updating metadata.

This PR ensures that we implement a metadata only update
API at storage layer, that handles updates to metadata alone
for any given version - given the version is valid and
present.

This helps reduce the chattiness for following calls..

- PutObjectTags
- DeleteObjectTags
- PutObjectLegalHold
- PutObjectRetention
- ReplicateObject (updates metadata on replication status)

cmd/bucket-replication.go

@@ -571,11 +571,6 @@ func getReplicationAction(oi1 ObjectInfo, oi2 minio.ObjectInfo) replicationActio
 // replicateObject replicates the specified version of the object to destination bucket
 // The source object is then updated to reflect the replication status.
 func replicateObject(ctx context.Context, objInfo ObjectInfo, objectAPI ObjectLayer) {
-	z, ok := objectAPI.(*erasureServerPools)
-	if !ok {
-		return
-	}
-
 	bucket := objInfo.Bucket
 	object := objInfo.Name
 
@@ -734,17 +729,27 @@ func replicateObject(ctx context.Context, objInfo ObjectInfo, objectAPI ObjectLa
 		eventName = event.ObjectReplicationFailed
 	}
 
+	z, ok := objectAPI.(*erasureServerPools)
+	if !ok {
+		return
+	}
+
 	// This lower level implementation is necessary to avoid write locks from CopyObject.
 	poolIdx, err := z.getPoolIdx(ctx, bucket, object, objInfo.Size)
 	if err != nil {
 		logger.LogIf(ctx, fmt.Errorf("Unable to update replication metadata for %s/%s(%s): %w", bucket, objInfo.Name, objInfo.VersionID, err))
 	} else {
-		if err = z.serverPools[poolIdx].getHashedSet(object).updateObjectMeta(ctx, bucket, object, objInfo.UserDefined, ObjectOptions{
-			VersionID: objInfo.VersionID,
-		}); err != nil {
+		fi := FileInfo{}
+		fi.VersionID = objInfo.VersionID
+		fi.Metadata = make(map[string]string, len(objInfo.UserDefined))
+		for k, v := range objInfo.UserDefined {
+			fi.Metadata[k] = v
+		}
+		if err = z.serverPools[poolIdx].getHashedSet(object).updateObjectMeta(ctx, bucket, object, fi); err != nil {
 			logger.LogIf(ctx, fmt.Errorf("Unable to update replication metadata for %s/%s(%s): %w", bucket, objInfo.Name, objInfo.VersionID, err))
 		}
 	}
+
 	opType := replication.MetadataReplicationType
 	if rtype == replicateAll {
 		opType = replication.ObjectReplicationType