xl: Fix rare freeze after many disk/network errors (#4438)

xl.storageDisks is sometimes passed to some low-level XL functions. Some disks in
xl.storageDisks are set to nil when they encounter some errors. This means all
elements in xl.storageDisks will be nil after some time which lead to an unusable XL.

cmd/erasure-createfile.go

@@ -29,7 +29,7 @@ import (
 // all the disks, writes also calculate individual block's checksum
 // for future bit-rot protection.
 func erasureCreateFile(disks []StorageAPI, volume, path string, reader io.Reader, allowEmpty bool, blockSize int64,
-	dataBlocks, parityBlocks int, algo HashAlgo, writeQuorum int) (bytesWritten int64, checkSums []string, err error) {
+	dataBlocks, parityBlocks int, algo HashAlgo, writeQuorum int) (newDisks []StorageAPI, bytesWritten int64, checkSums []string, err error) {
 
 	// Allocated blockSized buffer for reading from incoming stream.
 	buf := make([]byte, blockSize)
@@ -43,7 +43,7 @@ func erasureCreateFile(disks []StorageAPI, volume, path string, reader io.Reader
 		// FIXME: this is a bug in Golang, n == 0 and err ==
 		// io.ErrUnexpectedEOF for io.ReadFull function.
 		if n == 0 && rErr == io.ErrUnexpectedEOF {
-			return 0, nil, traceError(rErr)
+			return nil, 0, nil, traceError(rErr)
 		}
 		if rErr == io.EOF {
 			// We have reached EOF on the first byte read, io.Reader
@@ -51,28 +51,28 @@ func erasureCreateFile(disks []StorageAPI, volume, path string, reader io.Reader
 			// data. Will create a 0byte file instead.
 			if bytesWritten == 0 && allowEmpty {
 				blocks = make([][]byte, len(disks))
-				rErr = appendFile(disks, volume, path, blocks, hashWriters, writeQuorum)
+				newDisks, rErr = appendFile(disks, volume, path, blocks, hashWriters, writeQuorum)
 				if rErr != nil {
-					return 0, nil, rErr
+					return nil, 0, nil, rErr
 				}
 			} // else we have reached EOF after few reads, no need to
 			// add an additional 0bytes at the end.
 			break
 		}
 		if rErr != nil && rErr != io.ErrUnexpectedEOF {
-			return 0, nil, traceError(rErr)
+			return nil, 0, nil, traceError(rErr)
 		}
 		if n > 0 {
 			// Returns encoded blocks.
 			var enErr error
 			blocks, enErr = encodeData(buf[0:n], dataBlocks, parityBlocks)
 			if enErr != nil {
-				return 0, nil, enErr
+				return nil, 0, nil, enErr
 			}
 
 			// Write to all disks.
-			if err = appendFile(disks, volume, path, blocks, hashWriters, writeQuorum); err != nil {
-				return 0, nil, err
+			if newDisks, err = appendFile(disks, volume, path, blocks, hashWriters, writeQuorum); err != nil {
+				return nil, 0, nil, err
 			}
 			bytesWritten += int64(n)
 		}
@@ -82,7 +82,7 @@ func erasureCreateFile(disks []StorageAPI, volume, path string, reader io.Reader
 	for i := range checkSums {
 		checkSums[i] = hex.EncodeToString(hashWriters[i].Sum(nil))
 	}
-	return bytesWritten, checkSums, nil
+	return newDisks, bytesWritten, checkSums, nil
 }
 
 // encodeData - encodes incoming data buffer into
@@ -110,7 +110,7 @@ func encodeData(dataBuffer []byte, dataBlocks, parityBlocks int) ([][]byte, erro
 }
 
 // appendFile - append data buffer at path.
-func appendFile(disks []StorageAPI, volume, path string, enBlocks [][]byte, hashWriters []hash.Hash, writeQuorum int) (err error) {
+func appendFile(disks []StorageAPI, volume, path string, enBlocks [][]byte, hashWriters []hash.Hash, writeQuorum int) ([]StorageAPI, error) {
 	var wg = &sync.WaitGroup{}
 	var wErrs = make([]error, len(disks))
 	// Write encoded data to quorum disks in parallel.
@@ -126,8 +126,6 @@ func appendFile(disks []StorageAPI, volume, path string, enBlocks [][]byte, hash
 			wErr := disk.AppendFile(volume, path, enBlocks[index])
 			if wErr != nil {
 				wErrs[index] = traceError(wErr)
-				// Ignore disk which returned an error.
-				disks[index] = nil
 				return
 			}
 
@@ -142,5 +140,5 @@ func appendFile(disks []StorageAPI, volume, path string, enBlocks [][]byte, hash
 	// Wait for all the appends to finish.
 	wg.Wait()
 
-	return reduceWriteQuorumErrs(wErrs, objectOpIgnoredErrs, writeQuorum)
+	return evalDisks(disks, wErrs), reduceWriteQuorumErrs(wErrs, objectOpIgnoredErrs, writeQuorum)
 }

cmd/erasure-createfile_test.go

@@ -56,7 +56,7 @@ func TestErasureCreateFile(t *testing.T) {
 		t.Fatal(err)
 	}
 	// Test when all disks are up.
-	size, _, err := erasureCreateFile(disks, "testbucket", "testobject1", bytes.NewReader(data), true, blockSize, dataBlocks, parityBlocks, bitRotAlgo, dataBlocks+1)
+	_, size, _, err := erasureCreateFile(disks, "testbucket", "testobject1", bytes.NewReader(data), true, blockSize, dataBlocks, parityBlocks, bitRotAlgo, dataBlocks+1)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -69,7 +69,7 @@ func TestErasureCreateFile(t *testing.T) {
 	disks[5] = AppendDiskDown{disks[5].(*posix)}
 
 	// Test when two disks are down.
-	size, _, err = erasureCreateFile(disks, "testbucket", "testobject2", bytes.NewReader(data), true, blockSize, dataBlocks, parityBlocks, bitRotAlgo, dataBlocks+1)
+	_, size, _, err = erasureCreateFile(disks, "testbucket", "testobject2", bytes.NewReader(data), true, blockSize, dataBlocks, parityBlocks, bitRotAlgo, dataBlocks+1)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -83,7 +83,7 @@ func TestErasureCreateFile(t *testing.T) {
 	disks[8] = AppendDiskDown{disks[8].(*posix)}
 	disks[9] = AppendDiskDown{disks[9].(*posix)}
 
-	size, _, err = erasureCreateFile(disks, "testbucket", "testobject3", bytes.NewReader(data), true, blockSize, dataBlocks, parityBlocks, bitRotAlgo, dataBlocks+1)
+	_, size, _, err = erasureCreateFile(disks, "testbucket", "testobject3", bytes.NewReader(data), true, blockSize, dataBlocks, parityBlocks, bitRotAlgo, dataBlocks+1)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -93,7 +93,7 @@ func TestErasureCreateFile(t *testing.T) {
 
 	// 1 more disk down. 7 disk down in total. Should return quorum error.
 	disks[10] = AppendDiskDown{disks[10].(*posix)}
-	_, _, err = erasureCreateFile(disks, "testbucket", "testobject4", bytes.NewReader(data), true, blockSize, dataBlocks, parityBlocks, bitRotAlgo, dataBlocks+1)
+	_, _, _, err = erasureCreateFile(disks, "testbucket", "testobject4", bytes.NewReader(data), true, blockSize, dataBlocks, parityBlocks, bitRotAlgo, dataBlocks+1)
 	if errorCause(err) != errXLWriteQuorum {
 		t.Errorf("erasureCreateFile return value: expected errXLWriteQuorum, got %s", err)
 	}

cmd/erasure-healfile_test.go

@@ -48,7 +48,7 @@ func TestErasureHealFile(t *testing.T) {
 		t.Fatal(err)
 	}
 	// Create a test file.
-	size, checkSums, err := erasureCreateFile(disks, "testbucket", "testobject1", bytes.NewReader(data), true, blockSize, dataBlocks, parityBlocks, bitRotAlgo, dataBlocks+1)
+	_, size, checkSums, err := erasureCreateFile(disks, "testbucket", "testobject1", bytes.NewReader(data), true, blockSize, dataBlocks, parityBlocks, bitRotAlgo, dataBlocks+1)
 	if err != nil {
 		t.Fatal(err)
 	}

cmd/erasure-readfile_test.go

@@ -242,7 +242,7 @@ func TestErasureReadFileDiskFail(t *testing.T) {
 	}
 
 	// Create a test file to read from.
-	size, checkSums, err := erasureCreateFile(disks, "testbucket", "testobject", bytes.NewReader(data), true, blockSize, dataBlocks, parityBlocks, bitRotAlgo, dataBlocks+1)
+	_, size, checkSums, err := erasureCreateFile(disks, "testbucket", "testobject", bytes.NewReader(data), true, blockSize, dataBlocks, parityBlocks, bitRotAlgo, dataBlocks+1)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -325,7 +325,7 @@ func TestErasureReadFileOffsetLength(t *testing.T) {
 	}
 
 	// Create a test file to read from.
-	size, checkSums, err := erasureCreateFile(disks, "testbucket", "testobject", bytes.NewReader(data), true, blockSize, dataBlocks, parityBlocks, bitRotAlgo, dataBlocks+1)
+	_, size, checkSums, err := erasureCreateFile(disks, "testbucket", "testobject", bytes.NewReader(data), true, blockSize, dataBlocks, parityBlocks, bitRotAlgo, dataBlocks+1)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -404,7 +404,7 @@ func TestErasureReadFileRandomOffsetLength(t *testing.T) {
 	iterations := 10000
 
 	// Create a test file to read from.
-	size, checkSums, err := erasureCreateFile(disks, "testbucket", "testobject", bytes.NewReader(data), true, blockSize, dataBlocks, parityBlocks, bitRotAlgo, dataBlocks+1)
+	_, size, checkSums, err := erasureCreateFile(disks, "testbucket", "testobject", bytes.NewReader(data), true, blockSize, dataBlocks, parityBlocks, bitRotAlgo, dataBlocks+1)
 	if err != nil {
 		t.Fatal(err)
 	}

cmd/xl-v1-healing.go

@@ -468,7 +468,7 @@ func healObject(storageDisks []StorageAPI, bucket string, object string, quorum
 	}
 
 	// Generate and write `xl.json` generated from other disks.
-	aErr = writeUniqueXLMetadata(outDatedDisks, minioMetaTmpBucket, tmpID, partsMetadata, diskCount(outDatedDisks))
+	outDatedDisks, aErr = writeUniqueXLMetadata(outDatedDisks, minioMetaTmpBucket, tmpID, partsMetadata, diskCount(outDatedDisks))
 	if aErr != nil {
 		return 0, 0, toObjectErr(aErr, bucket, object)
 	}

cmd/xl-v1-metadata.go

@@ -389,7 +389,7 @@ func deleteAllXLMetadata(disks []StorageAPI, bucket, prefix string, errs []error
 }
 
 // Rename `xl.json` content to destination location for each disk in order.
-func renameXLMetadata(disks []StorageAPI, srcBucket, srcEntry, dstBucket, dstEntry string, quorum int) error {
+func renameXLMetadata(disks []StorageAPI, srcBucket, srcEntry, dstBucket, dstEntry string, quorum int) ([]StorageAPI, error) {
 	isDir := false
 	srcXLJSON := path.Join(srcEntry, xlMetaJSONFile)
 	dstXLJSON := path.Join(dstEntry, xlMetaJSONFile)
@@ -397,7 +397,7 @@ func renameXLMetadata(disks []StorageAPI, srcBucket, srcEntry, dstBucket, dstEnt
 }
 
 // writeUniqueXLMetadata - writes unique `xl.json` content for each disk in order.
-func writeUniqueXLMetadata(disks []StorageAPI, bucket, prefix string, xlMetas []xlMetaV1, quorum int) error {
+func writeUniqueXLMetadata(disks []StorageAPI, bucket, prefix string, xlMetas []xlMetaV1, quorum int) ([]StorageAPI, error) {
 	var wg = &sync.WaitGroup{}
 	var mErrs = make([]error, len(disks))
 
@@ -419,8 +419,6 @@ func writeUniqueXLMetadata(disks []StorageAPI, bucket, prefix string, xlMetas []
 			err := writeXLMetadata(disk, bucket, prefix, xlMetas[index])
 			if err != nil {
 				mErrs[index] = err
-				// Ignore disk which returned an error.
-				disks[index] = nil
 			}
 		}(index, disk)
 	}
@@ -433,11 +431,11 @@ func writeUniqueXLMetadata(disks []StorageAPI, bucket, prefix string, xlMetas []
 		// Delete all `xl.json` successfully renamed.
 		deleteAllXLMetadata(disks, bucket, prefix, mErrs)
 	}
-	return err
+	return evalDisks(disks, mErrs), err
 }
 
 // writeSameXLMetadata - write `xl.json` on all disks in order.
-func writeSameXLMetadata(disks []StorageAPI, bucket, prefix string, xlMeta xlMetaV1, writeQuorum, readQuorum int) error {
+func writeSameXLMetadata(disks []StorageAPI, bucket, prefix string, xlMeta xlMetaV1, writeQuorum, readQuorum int) ([]StorageAPI, error) {
 	var wg = &sync.WaitGroup{}
 	var mErrs = make([]error, len(disks))
 
@@ -459,8 +457,6 @@ func writeSameXLMetadata(disks []StorageAPI, bucket, prefix string, xlMeta xlMet
 			err := writeXLMetadata(disk, bucket, prefix, metadata)
 			if err != nil {
 				mErrs[index] = err
-				// Ignore disk which returned an error.
-				disks[index] = nil
 			}
 		}(index, disk, xlMeta)
 	}
@@ -473,5 +469,5 @@ func writeSameXLMetadata(disks []StorageAPI, bucket, prefix string, xlMeta xlMet
 		// Delete all `xl.json` successfully renamed.
 		deleteAllXLMetadata(disks, bucket, prefix, mErrs)
 	}
-	return err
+	return evalDisks(disks, mErrs), err
 }

cmd/xl-v1-multipart.go

@@ -233,7 +233,7 @@ func (xl xlObjects) statPart(bucket, object, uploadID, partName string) (fileInf
 }
 
 // commitXLMetadata - commit `xl.json` from source prefix to destination prefix in the given slice of disks.
-func commitXLMetadata(disks []StorageAPI, srcBucket, srcPrefix, dstBucket, dstPrefix string, quorum int) error {
+func commitXLMetadata(disks []StorageAPI, srcBucket, srcPrefix, dstBucket, dstPrefix string, quorum int) ([]StorageAPI, error) {
 	var wg = &sync.WaitGroup{}
 	var mErrs = make([]error, len(disks))
 
@@ -257,8 +257,6 @@ func commitXLMetadata(disks []StorageAPI, srcBucket, srcPrefix, dstBucket, dstPr
 			rErr := disk.RenameFile(srcBucket, srcJSONFile, dstBucket, dstJSONFile)
 			if rErr != nil {
 				mErrs[index] = traceError(rErr)
-				// Ignore disk which returned an error.
-				disks[index] = nil
 				return
 			}
 			mErrs[index] = nil
@@ -272,7 +270,7 @@ func commitXLMetadata(disks []StorageAPI, srcBucket, srcPrefix, dstBucket, dstPr
 		// Delete all `xl.json` successfully renamed.
 		deleteAllXLMetadata(disks, dstBucket, dstPrefix, mErrs)
 	}
-	return err
+	return evalDisks(disks, mErrs), err
 }
 
 // listMultipartUploads - lists all multipart uploads.
@@ -491,7 +489,7 @@ func (xl xlObjects) newMultipartUpload(bucket string, object string, meta map[st
 	uploadIDPath := path.Join(bucket, object, uploadID)
 	tempUploadIDPath := uploadID
 	// Write updated `xl.json` to all disks.
-	err := writeSameXLMetadata(xl.storageDisks, minioMetaTmpBucket, tempUploadIDPath, xlMeta, xl.writeQuorum, xl.readQuorum)
+	disks, err := writeSameXLMetadata(xl.storageDisks, minioMetaTmpBucket, tempUploadIDPath, xlMeta, xl.writeQuorum, xl.readQuorum)
 	if err != nil {
 		return "", toObjectErr(err, minioMetaTmpBucket, tempUploadIDPath)
 	}
@@ -501,7 +499,7 @@ func (xl xlObjects) newMultipartUpload(bucket string, object string, meta map[st
 	defer xl.deleteObject(minioMetaTmpBucket, tempUploadIDPath)
 
 	// Attempt to rename temp upload object to actual upload path object
-	rErr := renameObject(xl.storageDisks, minioMetaTmpBucket, tempUploadIDPath, minioMetaMultipartBucket, uploadIDPath, xl.writeQuorum)
+	_, rErr := renameObject(disks, minioMetaTmpBucket, tempUploadIDPath, minioMetaMultipartBucket, uploadIDPath, xl.writeQuorum)
 	if rErr != nil {
 		return "", toObjectErr(rErr, minioMetaMultipartBucket, uploadIDPath)
 	}
@@ -657,7 +655,7 @@ func (xl xlObjects) PutObjectPart(bucket, object, uploadID string, partID int, s
 	allowEmpty := true
 
 	// Erasure code data and write across all disks.
-	sizeWritten, checkSums, err := erasureCreateFile(onlineDisks, minioMetaTmpBucket, tmpPartPath, teeReader, allowEmpty, xlMeta.Erasure.BlockSize, xl.dataBlocks, xl.parityBlocks, bitRotAlgo, xl.writeQuorum)
+	onlineDisks, sizeWritten, checkSums, err := erasureCreateFile(onlineDisks, minioMetaTmpBucket, tmpPartPath, teeReader, allowEmpty, xlMeta.Erasure.BlockSize, xl.dataBlocks, xl.parityBlocks, bitRotAlgo, xl.writeQuorum)
 	if err != nil {
 		return PartInfo{}, toObjectErr(err, bucket, object)
 	}
@@ -702,7 +700,7 @@ func (xl xlObjects) PutObjectPart(bucket, object, uploadID string, partID int, s
 
 	// Rename temporary part file to its final location.
 	partPath := path.Join(uploadIDPath, partSuffix)
-	err = renamePart(onlineDisks, minioMetaTmpBucket, tmpPartPath, minioMetaMultipartBucket, partPath, xl.writeQuorum)
+	onlineDisks, err = renamePart(onlineDisks, minioMetaTmpBucket, tmpPartPath, minioMetaMultipartBucket, partPath, xl.writeQuorum)
 	if err != nil {
 		return PartInfo{}, toObjectErr(err, minioMetaMultipartBucket, partPath)
 	}
@@ -746,10 +744,11 @@ func (xl xlObjects) PutObjectPart(bucket, object, uploadID string, partID int, s
 	tempXLMetaPath := newUUID
 
 	// Writes a unique `xl.json` each disk carrying new checksum related information.
-	if err = writeUniqueXLMetadata(onlineDisks, minioMetaTmpBucket, tempXLMetaPath, partsMetadata, xl.writeQuorum); err != nil {
+	if onlineDisks, err = writeUniqueXLMetadata(onlineDisks, minioMetaTmpBucket, tempXLMetaPath, partsMetadata, xl.writeQuorum); err != nil {
 		return PartInfo{}, toObjectErr(err, minioMetaTmpBucket, tempXLMetaPath)
 	}
-	rErr := commitXLMetadata(onlineDisks, minioMetaTmpBucket, tempXLMetaPath, minioMetaMultipartBucket, uploadIDPath, xl.writeQuorum)
+	var rErr error
+	onlineDisks, rErr = commitXLMetadata(onlineDisks, minioMetaTmpBucket, tempXLMetaPath, minioMetaMultipartBucket, uploadIDPath, xl.writeQuorum)
 	if rErr != nil {
 		return PartInfo{}, toObjectErr(rErr, minioMetaMultipartBucket, uploadIDPath)
 	}
@@ -986,11 +985,12 @@ func (xl xlObjects) CompleteMultipartUpload(bucket string, object string, upload
 	}
 
 	// Write unique `xl.json` for each disk.
-	if err = writeUniqueXLMetadata(onlineDisks, minioMetaTmpBucket, tempUploadIDPath, partsMetadata, xl.writeQuorum); err != nil {
+	if onlineDisks, err = writeUniqueXLMetadata(onlineDisks, minioMetaTmpBucket, tempUploadIDPath, partsMetadata, xl.writeQuorum); err != nil {
 		return ObjectInfo{}, toObjectErr(err, minioMetaTmpBucket, tempUploadIDPath)
 	}
 
-	rErr := commitXLMetadata(onlineDisks, minioMetaTmpBucket, tempUploadIDPath, minioMetaMultipartBucket, uploadIDPath, xl.writeQuorum)
+	var rErr error
+	onlineDisks, rErr = commitXLMetadata(onlineDisks, minioMetaTmpBucket, tempUploadIDPath, minioMetaMultipartBucket, uploadIDPath, xl.writeQuorum)
 	if rErr != nil {
 		return ObjectInfo{}, toObjectErr(rErr, minioMetaMultipartBucket, uploadIDPath)
 	}
@@ -1018,7 +1018,7 @@ func (xl xlObjects) CompleteMultipartUpload(bucket string, object string, upload
 		// NOTE: Do not use online disks slice here.
 		// The reason is that existing object should be purged
 		// regardless of `xl.json` status and rolled back in case of errors.
-		err = renameObject(xl.storageDisks, bucket, object, minioMetaTmpBucket, newUniqueID, xl.writeQuorum)
+		_, err = renameObject(xl.storageDisks, bucket, object, minioMetaTmpBucket, newUniqueID, xl.writeQuorum)
 		if err != nil {
 			return ObjectInfo{}, toObjectErr(err, bucket, object)
 		}
@@ -1038,7 +1038,7 @@ func (xl xlObjects) CompleteMultipartUpload(bucket string, object string, upload
 	}
 
 	// Rename the multipart object to final location.
-	if err = renameObject(onlineDisks, minioMetaMultipartBucket, uploadIDPath, bucket, object, xl.writeQuorum); err != nil {
+	if onlineDisks, err = renameObject(onlineDisks, minioMetaMultipartBucket, uploadIDPath, bucket, object, xl.writeQuorum); err != nil {
 		return ObjectInfo{}, toObjectErr(err, bucket, object)
 	}
 

cmd/xl-v1-object.go

@@ -94,11 +94,11 @@ func (xl xlObjects) CopyObject(srcBucket, srcObject, dstBucket, dstObject string
 		tempObj := mustGetUUID()
 
 		// Write unique `xl.json` for each disk.
-		if err = writeUniqueXLMetadata(onlineDisks, minioMetaTmpBucket, tempObj, partsMetadata, xl.writeQuorum); err != nil {
+		if onlineDisks, err = writeUniqueXLMetadata(onlineDisks, minioMetaTmpBucket, tempObj, partsMetadata, xl.writeQuorum); err != nil {
 			return ObjectInfo{}, toObjectErr(err, srcBucket, srcObject)
 		}
 		// Rename atomically `xl.json` from tmp location to destination for each disk.
-		if err = renameXLMetadata(onlineDisks, minioMetaTmpBucket, tempObj, srcBucket, srcObject, xl.writeQuorum); err != nil {
+		if onlineDisks, err = renameXLMetadata(onlineDisks, minioMetaTmpBucket, tempObj, srcBucket, srcObject, xl.writeQuorum); err != nil {
 			return ObjectInfo{}, toObjectErr(err, srcBucket, srcObject)
 		}
 		return xlMeta.ToObjectInfo(srcBucket, srcObject), nil
@@ -374,7 +374,7 @@ func undoRename(disks []StorageAPI, srcBucket, srcEntry, dstBucket, dstEntry str
 
 // rename - common function that renamePart and renameObject use to rename
 // the respective underlying storage layer representations.
-func rename(disks []StorageAPI, srcBucket, srcEntry, dstBucket, dstEntry string, isDir bool, quorum int) error {
+func rename(disks []StorageAPI, srcBucket, srcEntry, dstBucket, dstEntry string, isDir bool, quorum int) ([]StorageAPI, error) {
 	// Initialize sync waitgroup.
 	var wg = &sync.WaitGroup{}
 
@@ -398,8 +398,6 @@ func rename(disks []StorageAPI, srcBucket, srcEntry, dstBucket, dstEntry string,
 			err := disk.RenameFile(srcBucket, srcEntry, dstBucket, dstEntry)
 			if err != nil && err != errFileNotFound {
 				errs[index] = traceError(err)
-				// Ignore disk which returned an error.
-				disks[index] = nil
 			}
 		}(index, disk)
 	}
@@ -414,14 +412,14 @@ func rename(disks []StorageAPI, srcBucket, srcEntry, dstBucket, dstEntry string,
 		// Undo all the partial rename operations.
 		undoRename(disks, srcBucket, srcEntry, dstBucket, dstEntry, isDir, errs)
 	}
-	return err
+	return evalDisks(disks, errs), err
 }
 
 // renamePart - renames a part of the source object to the destination
 // across all disks in parallel. Additionally if we have errors and do
 // not have a readQuorum partially renamed files are renamed back to
 // its proper location.
-func renamePart(disks []StorageAPI, srcBucket, srcPart, dstBucket, dstPart string, quorum int) error {
+func renamePart(disks []StorageAPI, srcBucket, srcPart, dstBucket, dstPart string, quorum int) ([]StorageAPI, error) {
 	isDir := false
 	return rename(disks, srcBucket, srcPart, dstBucket, dstPart, isDir, quorum)
 }
@@ -430,7 +428,7 @@ func renamePart(disks []StorageAPI, srcBucket, srcPart, dstBucket, dstPart strin
 // across all disks in parallel. Additionally if we have errors and do
 // not have a readQuorum partially renamed files are renamed back to
 // its proper location.
-func renameObject(disks []StorageAPI, srcBucket, srcObject, dstBucket, dstObject string, quorum int) error {
+func renameObject(disks []StorageAPI, srcBucket, srcObject, dstBucket, dstObject string, quorum int) ([]StorageAPI, error) {
 	isDir := true
 	return rename(disks, srcBucket, srcObject, dstBucket, dstObject, isDir, quorum)
 }
@@ -573,8 +571,12 @@ func (xl xlObjects) PutObject(bucket string, object string, size int64, data io.
 		// when size == -1 because in this case, we are not able to predict how many parts we will have.
 		allowEmptyPart := partIdx == 1
 
+		var partSizeWritten int64
+		var checkSums []string
+		var erasureErr error
+
 		// Erasure code data and write across all disks.
-		partSizeWritten, checkSums, erasureErr := erasureCreateFile(onlineDisks, minioMetaTmpBucket, tempErasureObj, partReader, allowEmptyPart, partsMetadata[0].Erasure.BlockSize, partsMetadata[0].Erasure.DataBlocks, partsMetadata[0].Erasure.ParityBlocks, bitRotAlgo, xl.writeQuorum)
+		onlineDisks, partSizeWritten, checkSums, erasureErr = erasureCreateFile(onlineDisks, minioMetaTmpBucket, tempErasureObj, partReader, allowEmptyPart, partsMetadata[0].Erasure.BlockSize, partsMetadata[0].Erasure.DataBlocks, partsMetadata[0].Erasure.ParityBlocks, bitRotAlgo, xl.writeQuorum)
 		if erasureErr != nil {
 			return ObjectInfo{}, toObjectErr(erasureErr, minioMetaTmpBucket, tempErasureObj)
 		}
@@ -674,7 +676,7 @@ func (xl xlObjects) PutObject(bucket string, object string, size int64, data io.
 		// NOTE: Do not use online disks slice here.
 		// The reason is that existing object should be purged
 		// regardless of `xl.json` status and rolled back in case of errors.
-		err = renameObject(xl.storageDisks, bucket, object, minioMetaTmpBucket, newUniqueID, xl.writeQuorum)
+		_, err = renameObject(xl.storageDisks, bucket, object, minioMetaTmpBucket, newUniqueID, xl.writeQuorum)
 		if err != nil {
 			return ObjectInfo{}, toObjectErr(err, bucket, object)
 		}
@@ -689,12 +691,12 @@ func (xl xlObjects) PutObject(bucket string, object string, size int64, data io.
 	}
 
 	// Write unique `xl.json` for each disk.
-	if err = writeUniqueXLMetadata(onlineDisks, minioMetaTmpBucket, tempObj, partsMetadata, xl.writeQuorum); err != nil {
+	if onlineDisks, err = writeUniqueXLMetadata(onlineDisks, minioMetaTmpBucket, tempObj, partsMetadata, xl.writeQuorum); err != nil {
 		return ObjectInfo{}, toObjectErr(err, bucket, object)
 	}
 
 	// Rename the successfully written temporary object to final location.
-	err = renameObject(onlineDisks, minioMetaTmpBucket, tempObj, bucket, object, xl.writeQuorum)
+	onlineDisks, err = renameObject(onlineDisks, minioMetaTmpBucket, tempObj, bucket, object, xl.writeQuorum)
 	if err != nil {
 		return ObjectInfo{}, toObjectErr(err, bucket, object)
 	}

cmd/xl-v1-utils.go

@@ -357,6 +357,24 @@ func shuffleDisks(disks []StorageAPI, distribution []int) (shuffledDisks []Stora
 	return shuffledDisks
 }
 
+// evalDisks - returns a new slice of disks where nil is set if
+// the correspond error in errs slice is not nil
+func evalDisks(disks []StorageAPI, errs []error) []StorageAPI {
+	if len(errs) != len(disks) {
+		errorIf(errors.New("unexpected disks/errors slice length"), "unable to evaluate internal disks")
+		return nil
+	}
+	newDisks := make([]StorageAPI, len(disks))
+	for index := range errs {
+		if errs[index] == nil {
+			newDisks[index] = disks[index]
+		} else {
+			newDisks[index] = nil
+		}
+	}
+	return newDisks
+}
+
 // Errors specifically generated by getPartSizeFromIdx function.
 var (
 	errPartSizeZero  = errors.New("Part size cannot be zero")

cmd/xl-v1-utils_test.go

@@ -18,6 +18,7 @@ package cmd
 
 import (
 	"encoding/json"
+	"errors"
 	"reflect"
 	"strconv"
 	"testing"
@@ -429,3 +430,61 @@ func testShuffleDisks(t *testing.T, xl *xlObjects) {
 		t.Errorf("shuffleDisks returned incorrect order.")
 	}
 }
+
+// TestEvalDisks tests the behavior of evalDisks
+func TestEvalDisks(t *testing.T) {
+	nDisks := 16
+	disks, err := getRandomDisks(nDisks)
+	if err != nil {
+		t.Fatal(err)
+	}
+	objLayer, _, err := initObjectLayer(mustGetNewEndpointList(disks...))
+	if err != nil {
+		removeRoots(disks)
+		t.Fatal(err)
+	}
+	defer removeRoots(disks)
+	xl := objLayer.(*xlObjects)
+	testShuffleDisks(t, xl)
+}
+
+func testEvalDisks(t *testing.T, xl *xlObjects) {
+	disks := xl.storageDisks
+
+	diskErr := errors.New("some disk error")
+	errs := []error{
+		diskErr, nil, nil, nil,
+		nil, diskErr, nil, nil,
+		diskErr, nil, nil, nil,
+		nil, nil, nil, diskErr,
+	}
+
+	// Test normal setup with some disks
+	// returning errors
+	newDisks := evalDisks(disks, errs)
+	if newDisks[0] != nil ||
+		newDisks[1] != disks[1] ||
+		newDisks[2] != disks[2] ||
+		newDisks[3] != disks[3] ||
+		newDisks[4] != disks[4] ||
+		newDisks[5] != nil ||
+		newDisks[6] != disks[6] ||
+		newDisks[7] != disks[7] ||
+		newDisks[8] != nil ||
+		newDisks[9] != disks[9] ||
+		newDisks[10] != disks[10] ||
+		newDisks[11] != disks[11] ||
+		newDisks[12] != disks[12] ||
+		newDisks[13] != disks[13] ||
+		newDisks[14] != disks[14] ||
+		newDisks[15] != nil {
+		t.Errorf("evalDisks returned incorrect new disk set.")
+	}
+
+	// Test when number of errs doesn't match with number of disks
+	errs = []error{nil, nil, nil, nil}
+	newDisks = evalDisks(disks, errs)
+	if newDisks != nil {
+		t.Errorf("evalDisks returned no nil slice")
+	}
+}