From 39331b6b4e6ee99c7f21ca3996cf73cb9d03bd15 Mon Sep 17 00:00:00 2001
From: Harshavardhana <harsha@minio.io>
Date: Tue, 18 Oct 2016 11:13:25 -0700
Subject: [PATCH] xl: GetCheckSumInfo() shouldn't fail if hash not available.
 (#2984)

In a multipart upload scenario disks going down and coming backup
can lead to certain parts missing on the disk/server which was
going down. This is a valid case since these blocks can be
missing and should be healed through heal operation. But we are
not supposed to fail prematurely since we have enough data on
the other disks as well within read-quorum.

This fix relaxes previous assumption, fixes a major corruption
issue reproduced by @vadmeste.

Fixes #2976
---
 cmd/xl-v1-healing.go    | 5 +----
 cmd/xl-v1-metadata.go   | 8 ++++----
 cmd/xl-v1-multipart.go  | 8 +++++---
 cmd/xl-v1-object.go     | 5 +----
 cmd/xl-v1-utils_test.go | 2 +-
 5 files changed, 12 insertions(+), 16 deletions(-)

diff --git a/cmd/xl-v1-healing.go b/cmd/xl-v1-healing.go
index 2e6c9c1af..a3da4d10b 100644
--- a/cmd/xl-v1-healing.go
+++ b/cmd/xl-v1-healing.go
@@ -171,10 +171,7 @@ func (xl xlObjects) HealObject(bucket, object string) error {
 		partName := latestMeta.Parts[partIndex].Name
 		partSize := latestMeta.Parts[partIndex].Size
 		erasure := latestMeta.Erasure
-		sumInfo, err := latestMeta.Erasure.GetCheckSumInfo(partName)
-		if err != nil {
-			return err
-		}
+		sumInfo := latestMeta.Erasure.GetCheckSumInfo(partName)
 		// Heal the part file.
 		checkSums, err := erasureHealFile(latestDisks, outDatedDisks,
 			bucket, pathJoin(object, partName),
diff --git a/cmd/xl-v1-metadata.go b/cmd/xl-v1-metadata.go
index 0208a91ff..56638d520 100644
--- a/cmd/xl-v1-metadata.go
+++ b/cmd/xl-v1-metadata.go
@@ -81,14 +81,14 @@ func (e *erasureInfo) AddCheckSumInfo(ckSumInfo checkSumInfo) {
 }
 
 // GetCheckSumInfo - get checksum of a part.
-func (e erasureInfo) GetCheckSumInfo(partName string) (ckSum checkSumInfo, err error) {
+func (e erasureInfo) GetCheckSumInfo(partName string) (ckSum checkSumInfo) {
 	// Return the checksum.
 	for _, sum := range e.Checksum {
 		if sum.Name == partName {
-			return sum, nil
+			return sum
 		}
 	}
-	return checkSumInfo{}, traceError(errUnexpected)
+	return checkSumInfo{Algorithm: bitRotAlgo}
 }
 
 // statInfo - carries stat information of the object.
@@ -197,7 +197,7 @@ func (m xlMetaV1) ObjectToPartOffset(offset int64) (partIndex int, partOffset in
 func pickValidXLMeta(metaArr []xlMetaV1, modTime time.Time) xlMetaV1 {
 	// Pick latest valid metadata.
 	for _, meta := range metaArr {
-		if meta.IsValid() && meta.Stat.ModTime == modTime {
+		if meta.IsValid() && meta.Stat.ModTime.Equal(modTime) {
 			return meta
 		}
 	}
diff --git a/cmd/xl-v1-multipart.go b/cmd/xl-v1-multipart.go
index b50758c8c..d645d56f2 100644
--- a/cmd/xl-v1-multipart.go
+++ b/cmd/xl-v1-multipart.go
@@ -386,8 +386,6 @@ func (xl xlObjects) PutObjectPart(bucket, object, uploadID string, partID int, s
 	tmpSuffix := getUUID()
 	tmpPartPath := path.Join(tmpMetaPrefix, tmpSuffix)
 
-	lreader := data
-
 	// Initialize md5 writer.
 	md5Writer := md5.New()
 
@@ -401,12 +399,16 @@ func (xl xlObjects) PutObjectPart(bucket, object, uploadID string, partID int, s
 
 	mw := io.MultiWriter(writers...)
 
+	var lreader io.Reader
 	// Limit the reader to its provided size > 0.
 	if size > 0 {
 		// This is done so that we can avoid erroneous clients sending
 		// more data than the set content size.
 		lreader = io.LimitReader(data, size)
-	} // else we read till EOF.
+	} else {
+		// else we read till EOF.
+		lreader = data
+	}
 
 	// Construct a tee reader for md5sum.
 	teeReader := io.TeeReader(lreader, mw)
diff --git a/cmd/xl-v1-object.go b/cmd/xl-v1-object.go
index d67a515fc..130a28d1f 100644
--- a/cmd/xl-v1-object.go
+++ b/cmd/xl-v1-object.go
@@ -187,10 +187,7 @@ func (xl xlObjects) GetObject(bucket, object string, startOffset int64, length i
 				checkSums[index] = ""
 				continue
 			}
-			ckSumInfo, err := metaArr[index].Erasure.GetCheckSumInfo(partName)
-			if err != nil { // FIXME - relook at returning error here.
-				return toObjectErr(err, bucket, object)
-			}
+			ckSumInfo := metaArr[index].Erasure.GetCheckSumInfo(partName)
 			checkSums[index] = ckSumInfo.Hash
 			// Set checksum algo only once, while it is possible to have
 			// different algos per block because of our `xl.json`.
diff --git a/cmd/xl-v1-utils_test.go b/cmd/xl-v1-utils_test.go
index 05d329489..34563c564 100644
--- a/cmd/xl-v1-utils_test.go
+++ b/cmd/xl-v1-utils_test.go
@@ -209,7 +209,7 @@ func compareXLMetaV1(t *testing.T, unMarshalXLMeta, gjsonXLMeta xlMetaV1) {
 	if unMarshalXLMeta.Stat.Size != gjsonXLMeta.Stat.Size {
 		t.Errorf("Expected the stat size to be %v, but got %v.", unMarshalXLMeta.Stat.Size, gjsonXLMeta.Stat.Size)
 	}
-	if unMarshalXLMeta.Stat.ModTime != gjsonXLMeta.Stat.ModTime {
+	if !unMarshalXLMeta.Stat.ModTime.Equal(gjsonXLMeta.Stat.ModTime) {
 		t.Errorf("Expected the modTime to be \"%v\", but got \"%v\".", unMarshalXLMeta.Stat.ModTime, gjsonXLMeta.Stat.ModTime)
 	}
 	if unMarshalXLMeta.Erasure.Algorithm != gjsonXLMeta.Erasure.Algorithm {