overlay: create a common function for deleting all overlay data (optionally excluding sysupgrade.tgz)

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

2 files changed, 41 insertions, 0 deletions

diff --git a/libfstools/libfstools.h b/libfstools/libfstools.h
index a9f8576..1d41eea 100644
--- a/libfstools/libfstools.h
+++ b/libfstools/libfstools.h
@@ -48,4 +48,6 @@ extern int jffs2_switch(struct volume *v);
 extern int handle_whiteout(const char *dir);
 extern void foreachdir(const char *dir, int (*cb)(const char*));
 
+extern void overlay_delete(const char *dir, bool keep_sysupgrade);
+
 #endif
diff --git a/libfstools/overlay.c b/libfstools/overlay.c
index 21012ba..c535693 100644
--- a/libfstools/overlay.c
+++ b/libfstools/overlay.c
@@ -32,6 +32,38 @@
 
 #define SWITCH_JFFS2 "/tmp/.switch_jffs2"
 
+static bool keep_sysupgrade;
+
+static int
+handle_rmdir(const char *dir)
+{
+	struct dirent *dt;
+	struct stat st;
+	DIR *d;
+	int fd;
+
+	d = opendir(dir);
+	if (!d)
+		return -1;
+
+	fd = dirfd(d);
+
+	while ((dt = readdir(d)) != NULL) {
+		if (fstatat(fd, dt->d_name, &st, AT_SYMLINK_NOFOLLOW) || S_ISDIR(st.st_mode))
+			continue;
+
+		if (keep_sysupgrade && !strcmp(dt->d_name, "sysupgrade.tgz"))
+			continue;
+
+		unlinkat(fd, dt->d_name, 0);
+	}
+
+	closedir(d);
+	rmdir(dir);
+
+	return 0;
+}
+
 void
 foreachdir(const char *dir, int (*cb)(const char*))
 {
@@ -51,6 +83,13 @@ foreachdir(const char *dir, int (*cb)(const char*))
 	cb(dir);
 }
 
+void
+overlay_delete(const char *dir, bool _keep_sysupgrade)
+{
+	keep_sysupgrade = _keep_sysupgrade;
+	foreachdir(dir, handle_rmdir);
+}
+
 static int
 overlay_mount(struct volume *v, char *fs)
 {