From e9c111c8d0620ae18929586ce554d598ff8f8f28 Mon Sep 17 00:00:00 2001
From: Harshavardhana <harsha@minio.io>
Date: Tue, 4 Feb 2020 10:04:37 +0530
Subject: [PATCH] Avoid unnecessary statPart() calls in PutObjectPart (#8905)

Assume `xl.json` as the source of truth for all operations.
---
 cmd/xl-v1-metadata.go  |  2 +-
 cmd/xl-v1-multipart.go | 45 +++---------------------------------------
 2 files changed, 4 insertions(+), 43 deletions(-)

diff --git a/cmd/xl-v1-metadata.go b/cmd/xl-v1-metadata.go
index 2cefe5cd0..3b4ab2477 100644
--- a/cmd/xl-v1-metadata.go
+++ b/cmd/xl-v1-metadata.go
@@ -40,7 +40,7 @@ const erasureAlgorithmKlauspost = "klauspost/reedsolomon/vandermonde"
 type ObjectPartInfo struct {
 	Number     int    `json:"number"`
 	Name       string `json:"name"`
-	ETag       string `json:"etag"`
+	ETag       string `json:"etag,omitempty"`
 	Size       int64  `json:"size"`
 	ActualSize int64  `json:"actualSize"`
 }
diff --git a/cmd/xl-v1-multipart.go b/cmd/xl-v1-multipart.go
index 0db7e3567..bfd76563a 100644
--- a/cmd/xl-v1-multipart.go
+++ b/cmd/xl-v1-multipart.go
@@ -76,34 +76,6 @@ func (xl xlObjects) removeObjectPart(bucket, object, uploadID, partName string)
 	g.Wait()
 }
 
-// statPart - returns fileInfo structure for a successful stat on part file.
-func (xl xlObjects) statPart(ctx context.Context, bucket, object, uploadID, partName string) (fileInfo FileInfo, err error) {
-	var ignoredErrs []error
-	partNamePath := path.Join(xl.getUploadIDDir(bucket, object, uploadID), partName)
-	for _, disk := range xl.getLoadBalancedDisks() {
-		if disk == nil {
-			ignoredErrs = append(ignoredErrs, errDiskNotFound)
-			continue
-		}
-		fileInfo, err = disk.StatFile(minioMetaMultipartBucket, partNamePath)
-		if err == nil {
-			return fileInfo, nil
-		}
-		// For any reason disk was deleted or goes offline we continue to next disk.
-		if IsErrIgnored(err, objMetadataOpIgnoredErrs...) {
-			ignoredErrs = append(ignoredErrs, err)
-			continue
-		}
-		// Error is not ignored, return right here.
-		logger.LogIf(ctx, err)
-		return FileInfo{}, err
-	}
-	// If all errors were ignored, reduce to maximal occurrence
-	// based on the read quorum.
-	readQuorum := len(xl.getDisks()) / 2
-	return FileInfo{}, reduceReadQuorumErrs(ctx, ignoredErrs, nil, readQuorum)
-}
-
 // commitXLMetadata - commit `xl.json` from source prefix to destination prefix in the given slice of disks.
 func commitXLMetadata(ctx context.Context, disks []StorageAPI, srcBucket, srcPrefix, dstBucket, dstPrefix string, quorum int) ([]StorageAPI, error) {
 	srcJSONFile := path.Join(srcPrefix, xlMetaJSONFile)
@@ -446,17 +418,12 @@ func (xl xlObjects) PutObjectPart(ctx context.Context, bucket, object, uploadID
 		return pi, toObjectErr(err, minioMetaMultipartBucket, uploadIDPath)
 	}
 
-	fi, err := xl.statPart(ctx, bucket, object, uploadID, partSuffix)
-	if err != nil {
-		return pi, toObjectErr(err, minioMetaMultipartBucket, partSuffix)
-	}
-
 	// Return success.
 	return PartInfo{
 		PartNumber:   partID,
-		LastModified: fi.ModTime,
+		LastModified: xlMeta.Stat.ModTime,
 		ETag:         md5hex,
-		Size:         fi.Size,
+		Size:         xlMeta.Stat.Size,
 		ActualSize:   data.ActualSize(),
 	}, nil
 }
@@ -531,15 +498,10 @@ func (xl xlObjects) ListObjectParts(ctx context.Context, bucket, object, uploadI
 	}
 	count := maxParts
 	for _, part := range parts {
-		var fi FileInfo
-		fi, err = xl.statPart(ctx, bucket, object, uploadID, part.Name)
-		if err != nil {
-			return result, toObjectErr(err, minioMetaBucket, path.Join(uploadID, part.Name))
-		}
 		result.Parts = append(result.Parts, PartInfo{
 			PartNumber:   part.Number,
 			ETag:         part.ETag,
-			LastModified: fi.ModTime,
+			LastModified: xlValidMeta.Stat.ModTime,
 			Size:         part.Size,
 		})
 		count--
@@ -667,7 +629,6 @@ func (xl xlObjects) CompleteMultipartUpload(ctx context.Context, bucket string,
 		// Add incoming parts.
 		xlMeta.Parts[i] = ObjectPartInfo{
 			Number:     part.PartNumber,
-			ETag:       part.ETag,
 			Size:       currentXLMeta.Parts[partIdx].Size,
 			Name:       fmt.Sprintf("part.%d", part.PartNumber),
 			ActualSize: currentXLMeta.Parts[partIdx].ActualSize,