update cache logic to calculate chunk size based on toatl cache

Author: Sneha-at

Diff for: pkg/gce-pd-csi-driver/cache.go

@@ -175,10 +175,18 @@ func setupCaching(devicePath string, req *csi.NodeStageVolumeRequest, nodeId str
 		klog.V(4).Infof("Assuming valid data cache size and mode, resizing cache is not supported")
 	} else {
 		cacheSize := req.GetPublishContext()[common.ContextDataCacheSize]
-		chunkSize, err := fetchChunkSizeKiB(cacheSize)
+		maxChunkSizeStr := strconv.FormatFloat(maxChunkSize, 'g', -1, 64)
+		var chunkSize string
+		cachePvSize, err := fetchPvSize(raidedLocalSsdPath)
 		if err != nil {
-			klog.Errorf("Errored to fetch cache size, verify the data-cache-size is valid: got %v, error: %q", cacheSize, err)
-			return mainDevicePath, err
+			klog.Errorf("Errored while fetching PV size, got %v, falling back to default chunkSize of %v", err, maxChunkSize)
+			chunkSize = maxChunkSizeStr
+		} else {
+			chunkSize, err = fetchChunkSizeKiB(cachePvSize)
+			if err != nil {
+				klog.Errorf("Errored to fetch cache size, verify the data-cache-size is valid: got %v, error: %q", chunkSize, err)
+				chunkSize = maxChunkSizeStr
+			}
 		}
 		// Check if LV exists
 		info, err = common.RunCommand("" /* pipedCmd */, nil /* pipedCmdArg */, "lvs", args...)
@@ -674,3 +682,39 @@ func addRaidedLSSDToVg(vgName, lssdPath string) error {
 	}
 	return nil
 }
+
+func fetchPvSize(pvName string) (string, error) {
+	var pvSize string
+	args := []string{
+		"--select",
+		"pv_name=" + pvName,
+		"-o",
+		"--noheadings",
+		"pv_size",
+		"--units=b",
+	}
+	info, err := common.RunCommand("" /* pipedCmd */, nil /* pipedCmdArg */, "pvs", args...)
+	if err != nil {
+		return "", fmt.Errorf("errored while fetching PV size %v: %s", err, info)
+	}
+	infoString := strings.TrimSpace(string(info))
+	infoSlice := strings.Fields(infoString)
+	re, err := regexp.Compile("^[0-9]+B$")
+	if err != nil {
+		return "", fmt.Errorf("Errored while compiling regex for PV size")
+	}
+	for _, i := range infoSlice {
+		if re.MatchString(i) {
+			pvSize = strings.TrimSuffix(i, "B")
+			break
+		}
+	}
+	if pvSize != "" {
+		pvSizeInt, err := strconv.ParseFloat(pvSize, 64)
+		if err != nil {
+			return "", fmt.Errorf("Error while fetching PV size for cache")
+		}
+		return strconv.FormatInt(int64(pvSizeInt/KiB), 10) + "KiB", nil
+	}
+	return "", fmt.Errorf("Error fetching PV size for cache")
+}