Overlay reformats on reboot with fstools_overlay_name bootparam

I tested the latest fstools boot parameter option (fstools_overlay_name) introduced in #9, but it has an issue: the overlay partition gets reformatted on every boot, causing all changes on the device to be lost.

It appears that during the mount_root done phase, mount_root does not pick up the overlay name from the fstools_overlay_name boot parameter, so it fails to locate the correct partition. As a result, the .fs_state file is not created.

From fad83e23386ae9101c3a5785be2bd9c5131c6ce5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?B=C3=A1lint=20Husz=C3=A1r?= <balint.huszar@intelliport.hu>
Date: Thu, 9 Apr 2026 17:11:13 +0200
Subject: [PATCH] Fix volume_find dataname param to use bootargs

---
 mount_root.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/mount_root.c b/mount_root.c
index 392e912..37c5650 100644
--- a/mount_root.c
+++ b/mount_root.c
@@ -115,7 +115,13 @@ stop(int argc, char *argv[1])
 static int
 done(int argc, char *argv[1])
 {
-	struct volume *v = volume_find("rootfs_data");
+	char dataparam[BUFLEN];
+	char *dataname = "rootfs_data";
+
+	if (get_var_from_file("/proc/cmdline", "fstools_overlay_name", dataparam, sizeof(dataparam)))
+		dataname = dataparam;
+	
+	struct volume *v = volume_find(dataname);
 
 	if (!v)
 		return -1;
-- 
2.39.5

Start in mount_root.c, especially the done() phase and its volume_find("rootfs_data") lookup; compare this path with the fstools_overlay_name value in /proc/cmdline. Reproduce a reboot with that boot parameter and verify that the overlay partition is found, .fs_state is created, and existing device changes are preserved.