partIDLock := er.NewNSLock(bucket, pathJoin(object, uploadID, strconv.Itoa(partID)))
	plkctx, err := partIDLock.GetLock(ctx, globalOperationTimeout)
	if err != nil {
		return PartInfo{}, err
	}

	ctx = plkctx.Context()
	defer partIDLock.Unlock(plkctx)

	// Read lock for upload id, only held while reading the upload metadata.
	uploadIDRLock := er.NewNSLock(bucket, pathJoin(object, uploadID))

	}

	// This call shouldn't be used for anything other than metadata updates or adding self referential versions.
	if !srcInfo.metadataOnly {
		return oi, NotImplemented{}
	}

	if !dstOpts.NoLock {
		lk := er.NewNSLock(dstBucket, dstObject)
		lkctx, err := lk.GetLock(ctx, globalOperationTimeout)
		if err != nil {
			return oi, err
		}
		ctx = lkctx.Context()
		defer lk.Unlock(lkctx)
	}

	o.EvalRetentionBypassFn = f
}

// ObjectLayer implements primitives for object API layer.
type ObjectLayer interface {
	// Locking operations on object.
	NewNSLock(bucket string, objects ...string) RWLocker

	// Storage operations.
	Shutdown(context.Context) error
	NSScanner(ctx context.Context, updates chan<- DataUsageInfo, wantCycle uint32, scanMode madmin.HealScanMode) error

		writeErrorResponse(ctx, w, errorCodes.ToAPIErr(ErrEmptyRequestBody), r.URL)
		return
	}

	// Take read lock on object, here so subsequent lower-level
	// calls do not need to.
	lock := objectAPI.NewNSLock(bucket, object)
	lkctx, err := lock.GetRLock(ctx, globalOperationTimeout)
	if err != nil {
		writeErrorResponse(ctx, w, toAPIError(ctx, err), r.URL)
		return
	}
	ctx = lkctx.Context()