set -lockfile using CSILVM_LOCKFILE_PATH env var

README.md

@@ -186,8 +186,8 @@ It is expected that the CO will connect to the plugin through the unix socket an
 
 ### Locking
 
-If the `-lockfile` parameter is specified, an exclusive `flock()` is held on
-that file whenever any lvm2 command-line utility is invoked. This prevents
+If the `-lockfile` parameter is specified or the `CSILVM_LOCKFILE_PATH` environment variable is set,
+an exclusive `flock()` is held on that file whenever any lvm2 command-line utility is invoked. This prevents
 multiple CSILVM processes from performing concurrent lvm operations that can
 lead to deadlocks in the underlying lvm2 implementation. For example,
 https://jira.mesosphere.com/browse/DCOS_OSS-5434 and

cmd/csilvm/csilvm.go

@@ -78,6 +78,8 @@ func main() {
 	// - https://github.com/lvmteam/lvm2/issues/23
 	if *lockFilePathF != "" {
 		lvm.SetLockFilePath(*lockFilePathF)
+	} else if path := os.Getenv("CSILVM_LOCKFILE_PATH"); path != "" {
+		lvm.SetLockFilePath(path)
 	}
 	// Determine listen address.
 	if *socketFileF != "" && *socketFileEnvF != "" {