Reduce snaphots memory usage. Pass mount options to snapshots.

main.go

@@ -383,7 +383,13 @@ func (d *ofsDriver) Mount(r *volume.MountRequest) (*volume.MountResponse, error)
 												dest := filepath.Join(snapshotsPath, i)
 												if err := os.Mkdir(dest, os.ModePerm); err == nil || os.IsExist(err) {
 													// Note: There is a missing "mount" argument so the mount continues running in a background process
-													if err := applyEnv(exec.Command("/sbin/mount.objectivefs", name, dest), v.Env).Run(); err != nil {
+													var ssCmd *exec.Cmd
+													if len(v.Opts) == 0 {
+														ssCmd = exec.Command("/sbin/mount.objectivefs", name, dest)
+													} else {
+														ssCmd = exec.Command("/sbin/mount.objectivefs", "-o"+v.Opts, name, dest)
+													}
+													if err := applyEnv(ssCmd, makeSnapshotEnv(v.Env)).Run(); err != nil {
 														log.WithFields(log.Fields{"name": r.Name, "snapshot": i}).Warn("Failed to mount a new snapshot.")
 													} else {
 														log.WithFields(log.Fields{"name": r.Name, "snapshot": i}).Debug("Snapshot mounted.")
@@ -598,6 +604,28 @@ func applyEnv(cmd *exec.Cmd, env []string) *exec.Cmd {
 	return cmd
 }
 
+func makeSnapshotEnv(env []string) []string {
+	// We must conserve memory as there are hundreds of snaphots
+	// Note: This is a minimum based on documentation
+	const cacheSizeValue = "CACHESIZE=64MiB"
+
+	result := make([]string, len(env))
+	copy(result, env)
+
+	hasCacheSize := false
+	for i, j := range result {
+		if strings.HasPrefix(j, "CACHESIZE=") {
+			result[i] = cacheSizeValue
+			hasCacheSize = true
+		}
+	}
+	if !hasCacheSize {
+		result = append(result, cacheSizeValue)
+	}
+
+	return result
+}
+
 func generateSnapshotsFromRulesForNow(rules string) (map[string]bool, error) {
 	if timesB, err := exec.Command("/sbin/mount.objectivefs", "snapshot", "-vs", rules).Output(); err == nil {
 		var result = make(map[string]bool)