nsUnlocker := func() {}
	defer func() {
		if unlockOnDefer {
			nsUnlocker()
		}
	}()

	// Acquire lock
	if !opts.NoLock {
		lock := er.NewNSLock(bucket, object)
		lkctx, err := lock.GetRLock(ctx, globalOperationTimeout)
		if err != nil {
			return nil, err
		}
		ctx = lkctx.Context()

		// Release lock when the metadata is verified, and reader
		// is ready to be read.
		//

	defer partIDLock.Unlock(plkctx)

	// Read lock for upload id, only held while reading the upload metadata.
	uploadIDRLock := er.NewNSLock(bucket, pathJoin(object, uploadID))
	rlkctx, err := uploadIDRLock.GetRLock(ctx, globalOperationTimeout)
	if err != nil {
		return PartInfo{}, err
	}
	ctx = rlkctx.Context()
	defer uploadIDRLock.RUnlock(rlkctx)

		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()
	defer lock.RUnlock(lkctx)