/*
 * Copyright (C) 2025 Mateusz Guzik
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#define _GNU_SOURCE

#include <sys/types.h>
#include <sys/stat.h>

#include <assert.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

/*
 * Invoke a bunch of VFS syscalls.
 *
 * Inspired by "vfsmix" testcase by Ingo Molnar:
 * https://lkml.org/lkml/2015/5/19/1009
 *
 * Note: mmap/munmap are deliberately omitted to avoid going into the VM
 * layer. This does ignore some of the VFS code.
 *
 * The idea is to let interested developers check where the time is
 * wast^Wspent while issuing typical syscalls.
 */

char *testcase_description = "vfstour1";

void testcase(unsigned long long *iterations, unsigned long nr)
{
	struct stat sb;
	char buf[128];
	char tmppath[] = "/tmp/willitscale.XXXXXX";
	char *tmpdir;
	char *tmpfile;
	int fd, ret;
	uid_t uid;
	gid_t gid;

	tmpdir = mkdtemp(tmppath);
	if (tmpdir == NULL) {
		perror("mkdtemp");
		exit(1);
	}
	rmdir(tmpdir);

	uid = getuid();
	gid = getgid();

	ret = asprintf(&tmpfile, "%s/file", tmppath);
	assert(ret != -1);

	while (1) {
		ret = mkdir(tmppath, 0700);
		assert(ret == 0);

		fd = open(tmpfile, O_RDWR | O_CREAT, 0600);
		assert(fd >= 0);

		ret = lstat(tmpfile, &sb);
		assert(ret == 0);

		ret = truncate(tmpfile, sizeof(buf) * 2);
		assert(ret == 0);

		ret = write(fd, buf, sizeof(buf));
		assert(ret == sizeof(buf));

		ret = fstat(fd, &sb);
		assert(ret == 0);

		ret = lseek(fd, 0, SEEK_SET);
		assert(ret == 0);

		ret = access(tmpfile, 0);
		assert(ret == 0);

		ret = read(fd, buf, sizeof(buf));
		assert(ret == sizeof(buf));

		ret = ftruncate(fd, sizeof(buf));
		assert(ret == 0);

		ret = chmod(tmpfile, 0400);
		assert(ret == 0);

		ret = close(fd);
		assert(ret == 0);

		ret = chown(tmpfile, uid, gid);
		assert(ret == 0);

		ret = unlink(tmpfile);
		assert(ret == 0);

		ret = rmdir(tmppath);
		assert(ret == 0);

		(*iterations)++;
	}
}