[v6,1/2] OVL_MNT: add helpers to setup overlayfs mountpoint

diff --git a/include/safe_file_ops_fn.h b/include/safe_file_ops_fn.h
index 35ec4fb1f..052fb1b9a 100644
--- a/include/safe_file_ops_fn.h
+++ b/include/safe_file_ops_fn.h
@@ -76,4 +76,8 @@  void safe_touch(const char *file, const int lineno,
 		const char *pathname,
 		mode_t mode, const struct timespec times[2]);
 
+/* helper functions to setup overlayfs mountpoint */
+void create_overlay_dirs(void);
+int mount_overlay(const char *file, const int lineno, int skip);
+
 #endif /* SAFE_FILE_OPS_FN */
diff --git a/include/tst_fs.h b/include/tst_fs.h
index b2b19ada6..ebca065c6 100644
--- a/include/tst_fs.h
+++ b/include/tst_fs.h
@@ -50,6 +50,12 @@  enum {
 	TST_GB = 1073741824,
 };
 
+#define OVL_BASE_MNTPOINT        "mntpoint"
+#define OVL_LOWER	OVL_BASE_MNTPOINT"/lower"
+#define OVL_UPPER	OVL_BASE_MNTPOINT"/upper"
+#define OVL_WORK	OVL_BASE_MNTPOINT"/work"
+#define OVL_MNT		OVL_BASE_MNTPOINT"/ovl"
+
 /*
  * @path: path is the pathname of any file within the mounted file system
  * @mult: mult should be TST_KB, TST_MB or TST_GB
diff --git a/include/tst_safe_file_ops.h b/include/tst_safe_file_ops.h
index 5c3fea4e2..b62a7447f 100644
--- a/include/tst_safe_file_ops.h
+++ b/include/tst_safe_file_ops.h
@@ -59,4 +59,10 @@ 
 	safe_touch(__FILE__, __LINE__, NULL, \
 			(pathname), (mode), (times))
 
+#define SAFE_MOUNT_OVERLAY() \
+	((void) mount_overlay(__FILE__, __LINE__, 1))
+
+#define TST_MOUNT_OVERLAY() \
+	(mount_overlay(__FILE__, __LINE__, 0) == 0)
+
 #endif /* TST_SAFE_FILE_OPS */
diff --git a/include/tst_test.h b/include/tst_test.h
index e4b935c45..f3b8901a2 100644
--- a/include/tst_test.h
+++ b/include/tst_test.h
@@ -121,6 +121,7 @@  struct tst_test {
 	int needs_root:1;
 	int forks_child:1;
 	int needs_device:1;
+	int needs_overlay:1;
 	int needs_checkpoints:1;
 	int format_device:1;
 	int mount_device:1;
diff --git a/lib/tst_fs_setup.c b/lib/tst_fs_setup.c
new file mode 100644
index 000000000..32a6218e3
--- /dev/null
+++ b/lib/tst_fs_setup.c
@@ -0,0 +1,49 @@ 
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <dirent.h>
+#include <errno.h>
+#include <sys/mount.h>
+
+#define TST_NO_DEFAULT_MAIN
+#include "tst_test.h"
+#include "tst_fs.h"
+
+#define TST_FS_SETUP_OVERLAYFS_MSG "overlayfs is not configured in this kernel"
+#define TST_FS_SETUP_OVERLAYFS_CONFIG "lowerdir="OVL_LOWER",upperdir="OVL_UPPER",workdir="OVL_WORK
+
+void create_overlay_dirs(void)
+{
+	DIR *dir = opendir(OVL_LOWER);
+	if (dir == NULL) {
+		SAFE_MKDIR(OVL_LOWER, 0755);
+		SAFE_MKDIR(OVL_UPPER, 0755);
+		SAFE_MKDIR(OVL_WORK, 0755);
+		SAFE_MKDIR(OVL_MNT, 0755);
+		return;
+	}
+	closedir(dir);
+}
+
+int mount_overlay(const char *file, const int lineno, int skip)
+{
+	int ret = 0;
+
+	create_overlay_dirs();
+	ret = mount("overlay", OVL_MNT, "overlay", 0,
+				TST_FS_SETUP_OVERLAYFS_CONFIG);
+	if (ret == 0)
+		return 0;
+
+	if (errno == ENODEV) {
+		if (skip) {
+			tst_brk(TCONF, "%s:%d: " TST_FS_SETUP_OVERLAYFS_MSG,
+				file, lineno);
+		} else {
+			tst_res(TINFO, "%s:%d: " TST_FS_SETUP_OVERLAYFS_MSG,
+				file, lineno);
+		}
+	} else {
+		tst_brk(TBROK | TERRNO, "overlayfs mount failed");
+	}
+	return ret;
+}
diff --git a/lib/tst_test.c b/lib/tst_test.c
index 2d88adbd7..95f389d2e 100644
--- a/lib/tst_test.c
+++ b/lib/tst_test.c
@@ -50,6 +50,7 @@  static int iterations = 1;
 static float duration = -1;
 static pid_t main_pid, lib_pid;
 static int mntpoint_mounted;
+static int ovl_mounted;
 static struct timespec tst_start_time; /* valid only for test pid */
 
 struct results {
@@ -871,6 +872,17 @@  static void do_setup(int argc, char *argv[])
 			prepare_device();
 	}
 
+	if (tst_test->needs_overlay && !tst_test->mount_device) {
+		tst_brk(TBROK, "tst_test->mount_device must be set");
+	}
+	if (tst_test->needs_overlay && !mntpoint_mounted) {
+		tst_brk(TBROK, "tst_test->mntpoint must be mounted");
+	}
+	if (tst_test->needs_overlay && !ovl_mounted) {
+		SAFE_MOUNT_OVERLAY();
+		ovl_mounted = 1;
+	}
+
 	if (tst_test->resource_files)
 		copy_resources();
 
@@ -891,6 +903,9 @@  static void do_test_setup(void)
 
 static void do_cleanup(void)
 {
+	if (ovl_mounted)
+		SAFE_UMOUNT(OVL_MNT);
+
 	if (mntpoint_mounted)
 		tst_umount(tst_test->mntpoint);