/*
 * ionice: set or get process io scheduling class and priority
 *
 * Copyright (C) 2005 Jens Axboe <jens@axboe.dk>
 *
 * Released under the terms of the GNU General Public License version 2
 *
 */
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <getopt.h>
#include <unistd.h>
#include <sys/syscall.h>
#include <ctype.h>

#include "nls.h"
#include "strutils.h"
#include "c.h"
#include "closestream.h"

static int tolerant;

static inline int ioprio_set(int which, int who, int ioprio)
{
	return syscall(SYS_ioprio_set, which, who, ioprio);
}

static inline int ioprio_get(int which, int who)
{
	return syscall(SYS_ioprio_get, which, who);
}

enum {
	IOPRIO_CLASS_NONE,
	IOPRIO_CLASS_RT,
	IOPRIO_CLASS_BE,
	IOPRIO_CLASS_IDLE,
};

enum {
	IOPRIO_WHO_PROCESS = 1,
	IOPRIO_WHO_PGRP,
	IOPRIO_WHO_USER,
};

#define IOPRIO_CLASS_SHIFT	(13)
#define IOPRIO_PRIO_MASK	((1UL << IOPRIO_CLASS_SHIFT) - 1)

#define IOPRIO_PRIO_CLASS(mask)	((mask) >> IOPRIO_CLASS_SHIFT)
#define IOPRIO_PRIO_DATA(mask)	((mask) & IOPRIO_PRIO_MASK)
#define IOPRIO_PRIO_VALUE(class, data)	(((class) << IOPRIO_CLASS_SHIFT) | data)

const char *to_prio[] = {
	[IOPRIO_CLASS_NONE] = "none",
	[IOPRIO_CLASS_RT]   = "realtime",
	[IOPRIO_CLASS_BE]   = "best-effort",
	[IOPRIO_CLASS_IDLE] = "idle"
};

static int parse_ioclass(const char *str)
{
	size_t i;

	for (i = 0; i < ARRAY_SIZE(to_prio); i++)
		if (!strcasecmp(str, to_prio[i]))
			return i;
	return -1;
}

static void ioprio_print(int pid)
{
	int ioprio = ioprio_get(IOPRIO_WHO_PROCESS, pid);

	if (ioprio == -1)
		err(EXIT_FAILURE, _("ioprio_get failed"));
	else {
		int ioclass = IOPRIO_PRIO_CLASS(ioprio);
		const char *name = _("unknown");

		if (ioclass > 0 && (size_t) ioclass < ARRAY_SIZE(to_prio))
			name = to_prio[ioclass];

		if (ioclass != IOPRIO_CLASS_IDLE)
			printf("%s: prio %lu\n", name,
					IOPRIO_PRIO_DATA(ioprio));
		else
			printf("%s\n", name);
	}
}

static void ioprio_setpid(pid_t pid, int ioclass, int data)
{
	int rc = ioprio_set(IOPRIO_WHO_PROCESS, pid,
			    IOPRIO_PRIO_VALUE(ioclass, data));

	if (rc == -1 && !tolerant)
		err(EXIT_FAILURE, _("ioprio_set failed"));
}

static void __attribute__ ((__noreturn__)) usage(FILE * out)
{
	fprintf(out,
	       _("\n"
		 "%1$s - sets or gets process io scheduling class and priority.\n"
		 "\n"
		 "Usage:\n"
		 "  %1$s [OPTION] -p PID [PID...]\n"
		 "  %1$s [OPTION] COMMAND\n"
		 "\n"
		 "Options:\n"
		 "  -c, --class <class>   scheduling class name or number\n"
		 "                           0: none, 1: realtime, 2: best-effort, 3: idle\n"
		 "  -n, --classdata <num> scheduling class data\n"
		 "                           0-7 for realtime and best-effort classes\n"
		 "  -p, --pid=PID         view or modify already running process\n"
		 "  -t, --ignore          ignore failures\n"
		 "  -V, --version         output version information and exit\n"
		 "  -h, --help            display this help and exit\n\n"),
		program_invocation_short_name);

	exit(out == stderr ? EXIT_FAILURE : EXIT_SUCCESS);
}

int main(int argc, char **argv)
{
	int data = 4, set = 0, ioclass = IOPRIO_CLASS_BE, c;
	pid_t pid = 0;

	static const struct option longopts[] = {
		{ "classdata", required_argument, NULL, 'n' },
		{ "class",     required_argument, NULL, 'c' },
		{ "help",      no_argument,       NULL, 'h' },
		{ "ignore",    no_argument,       NULL, 't' },
		{ "pid",       required_argument, NULL, 'p' },
		{ "version",   no_argument,       NULL, 'V' },
		{ NULL, 0, NULL, 0 }
	};

	setlocale(LC_ALL, "");
	bindtextdomain(PACKAGE, LOCALEDIR);
	textdomain(PACKAGE);
	atexit(close_stdout);

	while ((c = getopt_long(argc, argv, "+n:c:p:tVh", longopts, NULL)) != EOF)
		switch (c) {
		case 'n':
			data = strtos32_or_err(optarg, _("invalid class data argument"));
			set |= 1;
			break;
		case 'c':
			if (isdigit(*optarg))
				ioclass = strtos32_or_err(optarg,
						_("invalid class argument"));
			else {
				ioclass = parse_ioclass(optarg);
				if (ioclass < 0)
					errx(EXIT_FAILURE,
						_("unknown scheduling class: '%s'"),
						optarg);
			}
			set |= 2;
			break;
		case 'p':
			pid = strtos32_or_err(optarg, _("invalid PID argument"));
			break;
		case 't':
			tolerant = 1;
			break;
		case 'V':
			printf(_("%s from %s\n"),
				program_invocation_short_name, PACKAGE_STRING);
			return EXIT_SUCCESS;
		case 'h':
			usage(stdout);
		default:
			usage(stderr);
		}

	switch (ioclass) {
		case IOPRIO_CLASS_NONE:
			if ((set & 1) && !tolerant)
				warnx(_("ignoring given class data for none class"));
			data = 0;
			break;
		case IOPRIO_CLASS_RT:
		case IOPRIO_CLASS_BE:
			break;
		case IOPRIO_CLASS_IDLE:
			if ((set & 1) && !tolerant)
				warnx(_("ignoring given class data for idle class"));
			data = 7;
			break;
		default:
			if (!tolerant)
				warnx(_("unknown prio class %d"), ioclass);
			break;
	}

	if (!set && !pid && optind == argc)
		/*
		 * ionice without options, print the current ioprio
		 */
		ioprio_print(0);

	else if (!set && pid) {
		/*
		 * ionice -p PID [PID ...]
		 */
		ioprio_print(pid);

		for(; argv[optind]; ++optind) {
			pid = strtos32_or_err(argv[optind], _("invalid PID argument"));
			ioprio_print(pid);
		}
	} else if (set && pid) {
		/*
		 * ionice -c CLASS -p PID [PID ...]
		 */
		ioprio_setpid(pid, ioclass, data);

		for(; argv[optind]; ++optind) {
			pid = strtos32_or_err(argv[optind], _("invalid PID argument"));
			ioprio_setpid(pid, ioclass, data);
		}
	} else if (argv[optind]) {
		/*
		 * ionice [-c CLASS] COMMAND
		 */
		ioprio_setpid(0, ioclass, data);
		execvp(argv[optind], &argv[optind]);
		err(EXIT_FAILURE, _("executing %s failed"), argv[optind]);
	} else
		usage(stderr);


	return EXIT_SUCCESS;
}