Nslock fixes (#1803)

* XL/Multipart: Support parallel upload of parts by doing NS locking appropriately.

* XL/Multipart: hold lock on the multipart upload while aborting.

xl-v1-multipart.go

@@ -112,30 +112,35 @@ func (xl xlObjects) putObjectPartCommon(bucket string, object string, uploadID s
 	if !IsValidObjectName(object) {
 		return "", ObjectNameInvalid{Bucket: bucket, Object: object}
 	}
-	// Hold write lock on the uploadID so that no one aborts it.
+	uploadIDLocked := false
+	defer func() {
+		if uploadIDLocked {
+			nsMutex.Unlock(minioMetaBucket, pathJoin(mpartMetaPrefix, bucket, object, uploadID))
+		}
+	}()
+	// Figure out the erasure distribution first.
 	nsMutex.Lock(minioMetaBucket, pathJoin(mpartMetaPrefix, bucket, object, uploadID))
-	defer nsMutex.Unlock(minioMetaBucket, pathJoin(mpartMetaPrefix, bucket, object, uploadID))
+	uploadIDLocked = true
 
 	if !xl.isUploadIDExists(bucket, object, uploadID) {
 		return "", InvalidUploadID{UploadID: uploadID}
 	}
 
 	uploadIDPath := path.Join(mpartMetaPrefix, bucket, object, uploadID)
+	xlMeta, err := xl.readXLMetadata(minioMetaBucket, uploadIDPath)
+	if err != nil {
+		return "", toObjectErr(err, minioMetaBucket, uploadIDPath)
+	}
+
 	// List all online disks.
 	onlineDisks, higherVersion, err := xl.listOnlineDisks(minioMetaBucket, pathJoin(mpartMetaPrefix, bucket, object, uploadID))
 	if err != nil {
 		return "", toObjectErr(err, bucket, object)
 	}
 
-	// Increment version only if we have online disks less than configured storage disks.
-	if diskCount(onlineDisks) < len(xl.storageDisks) {
-		higherVersion++
-	}
-
-	xlMeta, err := xl.readXLMetadata(minioMetaBucket, uploadIDPath)
-	if err != nil {
-		return "", toObjectErr(err, minioMetaBucket, uploadIDPath)
-	}
+	// Unlock the uploadID so that parallel uploads of parts can happen.
+	nsMutex.Unlock(minioMetaBucket, pathJoin(mpartMetaPrefix, bucket, object, uploadID))
+	uploadIDLocked = false
 
 	// Initialize a new erasure with online disks and new distribution.
 	erasure := newErasure(onlineDisks, xlMeta.Erasure.Distribution)
@@ -179,6 +184,29 @@ func (xl xlObjects) putObjectPartCommon(bucket string, object string, uploadID s
 		}
 	}
 
+	// Hold lock as we are updating UPLODID/xl.json and renaming the part file from tmp location.
+	nsMutex.Lock(minioMetaBucket, pathJoin(mpartMetaPrefix, bucket, object, uploadID))
+	uploadIDLocked = true
+
+	if !xl.isUploadIDExists(bucket, object, uploadID) {
+		return "", InvalidUploadID{UploadID: uploadID}
+	}
+
+	// List all online disks.
+	onlineDisks, higherVersion, err = xl.listOnlineDisks(minioMetaBucket, pathJoin(mpartMetaPrefix, bucket, object, uploadID))
+	if err != nil {
+		return "", toObjectErr(err, bucket, object)
+	}
+
+	// Increment version only if we have online disks less than configured storage disks.
+	if diskCount(onlineDisks) < len(xl.storageDisks) {
+		higherVersion++
+	}
+
+	xlMeta, err = xl.readXLMetadata(minioMetaBucket, uploadIDPath)
+	if err != nil {
+		return "", toObjectErr(err, minioMetaBucket, uploadIDPath)
+	}
 	// Rename temporary part file to its final location.
 	partPath := path.Join(mpartMetaPrefix, bucket, object, uploadID, partSuffix)
 	err = xl.renameObject(minioMetaBucket, tmpPartPath, minioMetaBucket, partPath)
@@ -190,7 +218,6 @@ func (xl xlObjects) putObjectPartCommon(bucket string, object string, uploadID s
 	xlMeta.Stat.Version = higherVersion
 	xlMeta.AddObjectPart(partID, partSuffix, newMD5Hex, size)
 
-	uploadIDPath = path.Join(mpartMetaPrefix, bucket, object, uploadID)
 	tempUploadIDPath := path.Join(tmpMetaPrefix, uploadID)
 	if err = xl.writeXLMetadata(minioMetaBucket, tempUploadIDPath, xlMeta); err != nil {
 		return "", toObjectErr(err, minioMetaBucket, tempUploadIDPath)
@@ -475,6 +502,8 @@ func (xl xlObjects) abortMultipartUploadCommon(bucket, object, uploadID string)
 		return toObjectErr(err, bucket, object)
 	}
 
+	nsMutex.Lock(minioMetaBucket, pathJoin(mpartMetaPrefix, bucket, object))
+	defer nsMutex.Unlock(minioMetaBucket, pathJoin(mpartMetaPrefix, bucket, object))
 	// Validate if there are other incomplete upload-id's present for
 	// the object, if yes do not attempt to delete 'uploads.json'.
 	uploadsJSON, err := readUploadsJSON(bucket, object, xl.storageDisks...)