/*
 * Copyright (C) 2013-2020 Canonical, Ltd.
 *
 * 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.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * This code is a complete clean re-write of the stress tool by
 * Colin Ian King <colin.king@canonical.com> and attempts to be
 * backwardly compatible with the stress tool by Amos Waterland
 * <apw@rossby.metr.ou.edu> but has more stress tests and more
 * functionality.
 *
 */
#include "stress-ng.h"

#define BUF_ALIGNMENT		(4096)
#define BUF_SIZE		(512)
#define MAX_OFFSETS		(16)

static const stress_help_t help[] = {
	{ NULL,	"readahead N",		"start N workers exercising file readahead" },
	{ NULL,	"readahead-bytes N",	"size of file to readahead on (default is 1GB)" },
	{ NULL,	"readahead-ops N",	"stop after N readahead bogo operations" },
	{ NULL,	NULL,			NULL }
};

static int stress_set_readahead_bytes(const char *opt)
{
	uint64_t readahead_bytes;

	readahead_bytes = stress_get_uint64_byte_filesystem(opt, 1);
	stress_check_range_bytes("readahead-bytes", readahead_bytes,
		MIN_HDD_BYTES, MAX_HDD_BYTES);
	return stress_set_setting("readahead-bytes", TYPE_ID_UINT64, &readahead_bytes);
}

static const stress_opt_set_func_t opt_set_funcs[] = {
	{ OPT_readahead_bytes,	stress_set_readahead_bytes },
	{ 0,			NULL }
};

#if defined(__linux__) && NEED_GLIBC(2,3,0)

static int do_readahead(
	const stress_args_t *args,
	const int fd,
	off_t *offsets,
	const uint64_t rounded_readahead_bytes)
{
	int i;

	for (i = 0; i < MAX_OFFSETS; i++) {
		offsets[i] = (stress_mwc64() % (rounded_readahead_bytes - BUF_SIZE)) & ~511;
		if (readahead(fd, offsets[i], BUF_SIZE) < 0) {
			pr_fail("%s: ftruncate failed, errno=%d (%s)\n",
				args->name, errno, strerror(errno));
			return -1;
		}
	}
	return 0;
}

/*
 *  stress_readahead
 *	stress file system cache via readahead calls
 */
static int stress_readahead(const stress_args_t *args)
{
	uint8_t *buf = NULL;
	uint64_t rounded_readahead_bytes, i;
	uint64_t readahead_bytes = DEFAULT_READAHEAD_BYTES;
	uint64_t misreads = 0;
	uint64_t baddata = 0;
	int ret, rc = EXIT_FAILURE;
	char filename[PATH_MAX];
	int flags = O_CREAT | O_RDWR | O_TRUNC;
	int fd;
	struct stat statbuf;

	if (!stress_get_setting("readahead-bytes", &readahead_bytes)) {
		if (g_opt_flags & OPT_FLAGS_MAXIMIZE)
			readahead_bytes = MAXIMIZED_FILE_SIZE;
		if (g_opt_flags & OPT_FLAGS_MINIMIZE)
			readahead_bytes = MIN_READAHEAD_BYTES;
	}
	readahead_bytes /= args->num_instances;
	if (readahead_bytes < MIN_READAHEAD_BYTES)
		readahead_bytes = MIN_READAHEAD_BYTES;

	ret = stress_temp_dir_mk_args(args);
	if (ret < 0)
		return exit_status(-rc);

	ret = posix_memalign((void **)&buf, BUF_ALIGNMENT, BUF_SIZE);
	if (ret || !buf) {
		rc = exit_status(errno);
		pr_err("%s: cannot allocate buffer\n", args->name);
		(void)stress_temp_dir_rm_args(args);
		return rc;
	}

	(void)stress_temp_filename_args(args,
		filename, sizeof(filename), stress_mwc32());

	if ((fd = open(filename, flags, S_IRUSR | S_IWUSR)) < 0) {
		rc = exit_status(errno);
		pr_fail("%s: open %s failed, errno=%d (%s)\n",
			args->name, filename, errno, strerror(errno));
		goto finish;
	}
	if (ftruncate(fd, (off_t)0) < 0) {
		rc = exit_status(errno);
		pr_fail("%s: ftruncate failed, errno=%d (%s)\n",
			args->name, errno, strerror(errno));
		goto close_finish;
	}
	(void)unlink(filename);

#if defined(HAVE_POSIX_FADVISE) && defined(POSIX_FADV_DONTNEED)
	if (posix_fadvise(fd, 0, readahead_bytes, POSIX_FADV_DONTNEED) < 0) {
		pr_fail("%s: posix_fadvise failed, errno=%d (%s)\n",
			args->name, errno, strerror(errno));
		goto close_finish;
	}
#endif

	/* Sequential Write */
	for (i = 0; i < readahead_bytes; i += BUF_SIZE) {
		ssize_t pret;
		size_t j;
		off_t o = i / BUF_SIZE;
seq_wr_retry:
		if (!keep_stressing_flag()) {
			pr_inf("%s: test expired during test setup "
				"(writing of data file)\n", args->name);
			rc = EXIT_SUCCESS;
			goto close_finish;
		}

		for (j = 0; j < BUF_SIZE; j++)
			buf[j] = (o + j) & 0xff;

		pret = pwrite(fd, buf, BUF_SIZE, i);
		if (pret <= 0) {
			if ((errno == EAGAIN) || (errno == EINTR))
				goto seq_wr_retry;
			if (errno == ENOSPC)
				break;
			if (errno) {
				pr_fail("%s: pwrite failed, errno=%d (%s)\n",
					args->name, errno, strerror(errno));
				goto close_finish;
			}
			continue;
		}
	}

	if (fstat(fd, &statbuf) < 0) {
		pr_fail("%s: fstat failed, errno=%d (%s)\n",
			args->name, errno, strerror(errno));
		goto close_finish;
	}

	/* Round to write size to get no partial reads */
	rounded_readahead_bytes = (uint64_t)statbuf.st_size -
		(statbuf.st_size % BUF_SIZE);

	do {
		off_t offsets[MAX_OFFSETS];

		if (do_readahead(args, fd, offsets, rounded_readahead_bytes) < 0)
			goto close_finish;

		for (i = 0; i < MAX_OFFSETS; i++) {
rnd_rd_retry:
			if (!keep_stressing())
				break;
			ret = pread(fd, buf, BUF_SIZE, offsets[i]);
			if (ret <= 0) {
				if ((errno == EAGAIN) || (errno == EINTR))
					goto rnd_rd_retry;
				if (errno) {
					pr_fail("%s: read failed, errno=%d (%s)\n",
						args->name, errno, strerror(errno));
					goto close_finish;
				}
				continue;
			}
			if (ret != BUF_SIZE)
				misreads++;

			if (g_opt_flags & OPT_FLAGS_VERIFY) {
				size_t j;
				off_t o = offsets[i] / BUF_SIZE;

				for (j = 0; j < BUF_SIZE; j++) {
					uint8_t v = (o + j) & 0xff;
					if (buf[j] != v)
						baddata++;
				}
				if (baddata) {
					pr_fail("%s: error in data between %ju and %ju\n",
						args->name,
						(intmax_t)offsets[i],
						(intmax_t)offsets[i] + BUF_SIZE - 1);
				}
			}
			inc_counter(args);
		}
	} while (keep_stressing());

	rc = EXIT_SUCCESS;
close_finish:
	(void)close(fd);
finish:
	free(buf);
	(void)stress_temp_dir_rm_args(args);

	if (misreads)
		pr_dbg("%s: %" PRIu64 " incomplete random reads\n",
			args->name, misreads);

	return rc;
}

stressor_info_t stress_readahead_info = {
	.stressor = stress_readahead,
	.class = CLASS_IO | CLASS_OS,
	.opt_set_funcs = opt_set_funcs,
	.help = help
};
#else
stressor_info_t stress_readahead_info = {
	.stressor = stress_not_implemented,
	.class = CLASS_IO | CLASS_OS,
	.opt_set_funcs = opt_set_funcs,
	.help = help
};
#endif