From 9212e11b90c30296c75654958617982de814aa22 Mon Sep 17 00:00:00 2001
From: Harshavardhana <harsha@minio.io>
Date: Sun, 24 Jul 2016 22:49:27 -0700
Subject: [PATCH] XL/GetObject: When disk is not available, checksum should be
 empty. (#2276)

---
 xl-v1-metadata.go |  2 +-
 xl-v1-object.go   | 21 ++++++++++++---------
 2 files changed, 13 insertions(+), 10 deletions(-)

diff --git a/xl-v1-metadata.go b/xl-v1-metadata.go
index 49a16f2b4..7e71d1788 100644
--- a/xl-v1-metadata.go
+++ b/xl-v1-metadata.go
@@ -156,7 +156,7 @@ func (m *xlMetaV1) AddCheckSum(partName, algorithm, checkSum string) {
 }
 
 // GetCheckSum - get checksum of a part.
-func (m *xlMetaV1) GetCheckSum(partName string) (checkSum, algorithm string, err error) {
+func (m xlMetaV1) GetCheckSum(partName string) (checkSum, algorithm string, err error) {
 	for _, sum := range m.Erasure.Checksum {
 		if sum.Name == partName {
 			return sum.Hash, sum.Algorithm, nil
diff --git a/xl-v1-object.go b/xl-v1-object.go
index 3554cde93..dd440adb0 100644
--- a/xl-v1-object.go
+++ b/xl-v1-object.go
@@ -79,14 +79,12 @@ func (xl xlObjects) GetObject(bucket, object string, startOffset int64, length i
 	onlineDisks, modTime := listOnlineDisks(xl.storageDisks, metaArr, errs)
 
 	// Pick latest valid metadata.
-	var xlMeta xlMetaV1
-	for _, meta := range metaArr {
-		if meta.IsValid() && meta.Stat.ModTime == modTime {
-			xlMeta = meta
-			break
-		}
-	}
+	xlMeta := pickValidXLMeta(metaArr, modTime)
+
+	// Reorder online disks based on erasure distribution order.
 	onlineDisks = getOrderedDisks(xlMeta.Erasure.Distribution, onlineDisks)
+
+	// Reorder parts metadata based on erasure distribution order.
 	metaArr = getOrderedPartsMetadata(xlMeta.Erasure.Distribution, metaArr)
 
 	// Reply back invalid range if the input offset and length fall out of range.
@@ -172,9 +170,14 @@ func (xl xlObjects) GetObject(bucket, object string, startOffset int64, length i
 
 		// Get the checksums of the current part.
 		checkSums := make([]string, len(onlineDisks))
-		for index := range onlineDisks {
+		for index, disk := range onlineDisks {
+			// Disk is not found skip the checksum.
+			if disk == nil {
+				checkSums[index] = ""
+				continue
+			}
 			checkSums[index], _, err = metaArr[index].GetCheckSum(partName)
-			if err != nil {
+			if err != nil { // FIXME - relook at returning error here.
 				return toObjectErr(err, bucket, object)
 			}
 		}