From c49a80db412027ae49637f2e3696175f90a9360d Mon Sep 17 00:00:00 2001
From: Krishna Srinivas <634494+krishnasrinivas@users.noreply.github.com>
Date: Mon, 26 Oct 2020 16:19:42 -0700
Subject: [PATCH] fix: use meta.Erasure.Index for GetObject() to reconstruct
 object (#10764)

---
 cmd/erasure-metadata-utils.go | 24 ++++++++++++++++++++++++
 cmd/erasure-metadata.go       |  3 ++-
 cmd/erasure-metadata_test.go  |  3 +++
 cmd/erasure-object.go         |  5 +++--
 4 files changed, 32 insertions(+), 3 deletions(-)

diff --git a/cmd/erasure-metadata-utils.go b/cmd/erasure-metadata-utils.go
index dca0212bc..e3c0ab295 100644
--- a/cmd/erasure-metadata-utils.go
+++ b/cmd/erasure-metadata-utils.go
@@ -153,6 +153,30 @@ func readVersionFromDisks(ctx context.Context, disks []StorageAPI, bucket, objec
 	return metadataArray, g.Wait()
 }
 
+// Return disks ordered by the meta.Erasure.Index information.
+func shuffleDisksByIndex(disks []StorageAPI, metaArr []FileInfo) (shuffledDisks []StorageAPI) {
+	shuffledDisks = make([]StorageAPI, len(disks))
+	for i, meta := range metaArr {
+		if disks[i] == nil {
+			continue
+		}
+		shuffledDisks[meta.Erasure.Index-1] = disks[i]
+	}
+	return shuffledDisks
+}
+
+// Return FileInfo slice ordered by the meta.Erasure.Index information.
+func shufflePartsMetadataByIndex(disks []StorageAPI, metaArr []FileInfo) []FileInfo {
+	newMetaArr := make([]FileInfo, len(disks))
+	for i, meta := range metaArr {
+		if disks[i] == nil {
+			continue
+		}
+		newMetaArr[meta.Erasure.Index-1] = metaArr[i]
+	}
+	return newMetaArr
+}
+
 // Return shuffled partsMetadata depending on distribution.
 func shufflePartsMetadata(partsMetadata []FileInfo, distribution []int) (shuffledPartsMetadata []FileInfo) {
 	if distribution == nil {
diff --git a/cmd/erasure-metadata.go b/cmd/erasure-metadata.go
index abd538558..5d8fc6def 100644
--- a/cmd/erasure-metadata.go
+++ b/cmd/erasure-metadata.go
@@ -91,7 +91,8 @@ func (fi FileInfo) IsValid() bool {
 	dataBlocks := fi.Erasure.DataBlocks
 	parityBlocks := fi.Erasure.ParityBlocks
 	return ((dataBlocks >= parityBlocks) &&
-		(dataBlocks != 0) && (parityBlocks != 0))
+		(dataBlocks != 0) && (parityBlocks != 0) &&
+		(fi.Erasure.Index > 0 && fi.Erasure.Distribution != nil))
 }
 
 // ToObjectInfo - Converts metadata to object info.
diff --git a/cmd/erasure-metadata_test.go b/cmd/erasure-metadata_test.go
index 438955e7e..f8da2931e 100644
--- a/cmd/erasure-metadata_test.go
+++ b/cmd/erasure-metadata_test.go
@@ -47,6 +47,7 @@ func TestAddObjectPart(t *testing.T) {
 
 	// Setup.
 	fi := newFileInfo("test-object", 8, 8)
+	fi.Erasure.Index = 1
 	if !fi.IsValid() {
 		t.Fatalf("unable to get xl meta")
 	}
@@ -80,6 +81,7 @@ func TestObjectPartIndex(t *testing.T) {
 
 	// Setup.
 	fi := newFileInfo("test-object", 8, 8)
+	fi.Erasure.Index = 1
 	if !fi.IsValid() {
 		t.Fatalf("unable to get xl meta")
 	}
@@ -108,6 +110,7 @@ func TestObjectPartIndex(t *testing.T) {
 func TestObjectToPartOffset(t *testing.T) {
 	// Setup.
 	fi := newFileInfo("test-object", 8, 8)
+	fi.Erasure.Index = 1
 	if !fi.IsValid() {
 		t.Fatalf("unable to get xl meta")
 	}
diff --git a/cmd/erasure-object.go b/cmd/erasure-object.go
index fe71dd134..f6a9bc4a8 100644
--- a/cmd/erasure-object.go
+++ b/cmd/erasure-object.go
@@ -215,11 +215,12 @@ func (er erasureObjects) GetObject(ctx context.Context, bucket, object string, s
 }
 
 func (er erasureObjects) getObjectWithFileInfo(ctx context.Context, bucket, object string, startOffset int64, length int64, writer io.Writer, etag string, opts ObjectOptions, fi FileInfo, metaArr []FileInfo, onlineDisks []StorageAPI) error {
+	tmpDisks := onlineDisks
 	// Reorder online disks based on erasure distribution order.
-	onlineDisks = shuffleDisks(onlineDisks, fi.Erasure.Distribution)
+	onlineDisks = shuffleDisksByIndex(tmpDisks, metaArr)
 
 	// Reorder parts metadata based on erasure distribution order.
-	metaArr = shufflePartsMetadata(metaArr, fi.Erasure.Distribution)
+	metaArr = shufflePartsMetadataByIndex(tmpDisks, metaArr)
 
 	// For negative length read everything.
 	if length < 0 {