support decommissioning of tiered objects (#16751)

cmd/erasure-object.go

@@ -2089,3 +2089,46 @@ func (er erasureObjects) restoreTransitionedObject(ctx context.Context, bucket s
 	})
 	return setRestoreHeaderFn(oi, err)
 }
+
+// DecomTieredObject - moves tiered object to another pool during decommissioning.
+func (er erasureObjects) DecomTieredObject(ctx context.Context, bucket, object string, fi FileInfo, opts ObjectOptions) error {
+	if opts.UserDefined == nil {
+		opts.UserDefined = make(map[string]string)
+	}
+	// overlay Erasure info for this set of disks
+	storageDisks := er.getDisks()
+	// Get parity and data drive count based on storage class metadata
+	parityDrives := globalStorageClass.GetParityForSC(opts.UserDefined[xhttp.AmzStorageClass])
+	if parityDrives < 0 {
+		parityDrives = er.defaultParityCount
+	}
+	dataDrives := len(storageDisks) - parityDrives
+
+	// we now know the number of blocks this object needs for data and parity.
+	// writeQuorum is dataBlocks + 1
+	writeQuorum := dataDrives
+	if dataDrives == parityDrives {
+		writeQuorum++
+	}
+
+	// Initialize parts metadata
+	partsMetadata := make([]FileInfo, len(storageDisks))
+
+	fi2 := newFileInfo(pathJoin(bucket, object), dataDrives, parityDrives)
+	fi.Erasure = fi2.Erasure
+	// Initialize erasure metadata.
+	for index := range partsMetadata {
+		partsMetadata[index] = fi
+		partsMetadata[index].Erasure.Index = index + 1
+	}
+
+	// Order disks according to erasure distribution
+	var onlineDisks []StorageAPI
+	onlineDisks, partsMetadata = shuffleDisksAndPartsMetadata(storageDisks, partsMetadata, fi)
+
+	if _, err := writeUniqueFileInfo(ctx, onlineDisks, bucket, object, partsMetadata, writeQuorum); err != nil {
+		return toObjectErr(err, bucket, object)
+	}
+
+	return nil
+}