busybox/util-linux/swaponoff.c
Denys Vlasenko f417ffd88f Make swapon and swapoff individually selectable.
For example, without swapoff, code shrinks by 277 bytes.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2016-11-14 17:30:50 +01:00

333 lines
8.8 KiB
C

/* vi: set sw=4 ts=4: */
/*
* Mini swapon/swapoff implementation for busybox
*
* Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
*
* Licensed under GPLv2, see file LICENSE in this source tree.
*/
//config:config SWAPON
//config: bool "swapon"
//config: default y
//config: select PLATFORM_LINUX
//config: help
//config: This option enables the 'swapon' utility.
//config: Once you have created some swap space using 'mkswap', you also need
//config: to enable your swap space with the 'swapon' utility. The 'swapoff'
//config: utility is used, typically at system shutdown, to disable any swap
//config: space. If you are not using any swap space, you can leave this
//config: option disabled.
//config:
//config:config FEATURE_SWAPON_DISCARD
//config: bool "Support discard option -d"
//config: default y
//config: depends on SWAPON
//config: help
//config: Enable support for discarding swap area blocks at swapon and/or as
//config: the kernel frees them. This option enables both the -d option on
//config: 'swapon' and the 'discard' option for swap entries in /etc/fstab.
//config:
//config:config FEATURE_SWAPON_PRI
//config: bool "Support priority option -p"
//config: default y
//config: depends on SWAPON
//config: help
//config: Enable support for setting swap device priority in swapon.
//config:
//config:config SWAPOFF
//config: bool "swapoff"
//config: default y
//config: select PLATFORM_LINUX
//config: help
//config: This option enables the 'swapoff' utility.
//applet:IF_SWAPON(APPLET_ODDNAME(swapon, swap_on_off, BB_DIR_SBIN, BB_SUID_DROP, swapon))
//applet:IF_SWAPOFF(APPLET_ODDNAME(swapoff, swap_on_off, BB_DIR_SBIN, BB_SUID_DROP, swapoff))
//kbuild:lib-$(CONFIG_SWAPON) += swaponoff.o
//kbuild:lib-$(CONFIG_SWAPOFF) += swaponoff.o
//usage:#define swapon_trivial_usage
//usage: "[-a] [-e]" IF_FEATURE_SWAPON_DISCARD(" [-d[POL]]") IF_FEATURE_SWAPON_PRI(" [-p PRI]") " [DEVICE]"
//usage:#define swapon_full_usage "\n\n"
//usage: "Start swapping on DEVICE\n"
//usage: "\n -a Start swapping on all swap devices"
//usage: IF_FEATURE_SWAPON_DISCARD(
//usage: "\n -d[POL] Discard blocks at swapon (POL=once),"
//usage: "\n as freed (POL=pages), or both (POL omitted)"
//usage: )
//usage: "\n -e Silently skip devices that do not exist"
//usage: IF_FEATURE_SWAPON_PRI(
//usage: "\n -p PRI Set swap device priority"
//usage: )
//usage:
//usage:#define swapoff_trivial_usage
//usage: "[-a] [DEVICE]"
//usage:#define swapoff_full_usage "\n\n"
//usage: "Stop swapping on DEVICE\n"
//usage: "\n -a Stop swapping on all swap devices"
#include "libbb.h"
#include "common_bufsiz.h"
#include <mntent.h>
#ifndef __BIONIC__
# include <sys/swap.h>
#endif
#if ENABLE_FEATURE_MOUNT_LABEL
# include "volume_id.h"
#else
# define resolve_mount_spec(fsname) ((void)0)
#endif
#ifndef MNTTYPE_SWAP
# define MNTTYPE_SWAP "swap"
#endif
#if ENABLE_FEATURE_SWAPON_DISCARD
#ifndef SWAP_FLAG_DISCARD
#define SWAP_FLAG_DISCARD 0x10000
#endif
#ifndef SWAP_FLAG_DISCARD_ONCE
#define SWAP_FLAG_DISCARD_ONCE 0x20000
#endif
#ifndef SWAP_FLAG_DISCARD_PAGES
#define SWAP_FLAG_DISCARD_PAGES 0x40000
#endif
#define SWAP_FLAG_DISCARD_MASK \
(SWAP_FLAG_DISCARD | SWAP_FLAG_DISCARD_ONCE | SWAP_FLAG_DISCARD_PAGES)
#endif
#if ENABLE_FEATURE_SWAPON_DISCARD || ENABLE_FEATURE_SWAPON_PRI
struct globals {
int flags;
} FIX_ALIASING;
#define G (*(struct globals*)bb_common_bufsiz1)
#define g_flags (G.flags)
#define save_g_flags() int save_g_flags = g_flags
#define restore_g_flags() g_flags = save_g_flags
#else
#define g_flags 0
#define save_g_flags() ((void)0)
#define restore_g_flags() ((void)0)
#endif
#define INIT_G() do { setup_common_bufsiz(); } while (0)
#if ENABLE_SWAPOFF
# if ENABLE_SWAPON
# define do_swapoff (applet_name[5] == 'f')
# else
# define do_swapoff 1
# endif
#else
# define do_swapoff 0
#endif
/* Command line options */
enum {
OPTBIT_a, /* -a all */
OPTBIT_e, /* -e ifexists */
IF_FEATURE_SWAPON_DISCARD( OPTBIT_d ,) /* -d discard */
IF_FEATURE_SWAPON_PRI ( OPTBIT_p ,) /* -p priority */
OPT_a = 1 << OPTBIT_a,
OPT_e = 1 << OPTBIT_e,
OPT_d = IF_FEATURE_SWAPON_DISCARD((1 << OPTBIT_d)) + 0,
OPT_p = IF_FEATURE_SWAPON_PRI ((1 << OPTBIT_p)) + 0,
};
#define OPT_ALL (option_mask32 & OPT_a)
#define OPT_DISCARD (option_mask32 & OPT_d)
#define OPT_IFEXISTS (option_mask32 & OPT_e)
#define OPT_PRIO (option_mask32 & OPT_p)
static int swap_enable_disable(char *device)
{
int err = 0;
int quiet = 0;
resolve_mount_spec(&device);
if (do_swapoff) {
err = swapoff(device);
/* Don't complain on OPT_ALL if not a swap device or if it doesn't exist */
quiet = (OPT_ALL && (errno == EINVAL || errno == ENOENT));
} else {
/* swapon */
struct stat st;
err = stat(device, &st);
if (!err) {
if (ENABLE_DESKTOP && S_ISREG(st.st_mode)) {
if (st.st_blocks * (off_t)512 < st.st_size) {
bb_error_msg("%s: file has holes", device);
return 1;
}
}
err = swapon(device, g_flags);
/* Don't complain on swapon -a if device is already in use */
quiet = (OPT_ALL && errno == EBUSY);
}
/* Don't complain if file does not exist with -e option */
if (err && OPT_IFEXISTS && errno == ENOENT)
err = 0;
}
if (err && !quiet) {
bb_simple_perror_msg(device);
return 1;
}
return 0;
}
#if ENABLE_FEATURE_SWAPON_DISCARD
static void set_discard_flag(char *s)
{
/* Unset the flag first to allow fstab options to override */
/* options set on the command line */
g_flags = (g_flags & ~SWAP_FLAG_DISCARD_MASK) | SWAP_FLAG_DISCARD;
if (!s) /* No optional policy value on the commandline */
return;
/* Skip prepended '=' */
if (*s == '=')
s++;
/* For fstab parsing: remove other appended options */
*strchrnul(s, ',') = '\0';
if (strcmp(s, "once") == 0)
g_flags |= SWAP_FLAG_DISCARD_ONCE;
if (strcmp(s, "pages") == 0)
g_flags |= SWAP_FLAG_DISCARD_PAGES;
}
#else
#define set_discard_flag(s) ((void)0)
#endif
#if ENABLE_FEATURE_SWAPON_PRI
static void set_priority_flag(char *s)
{
unsigned prio;
/* For fstab parsing: remove other appended options */
*strchrnul(s, ',') = '\0';
/* Max allowed 32767 (== SWAP_FLAG_PRIO_MASK) */
prio = bb_strtou(s, NULL, 10);
if (!errno) {
/* Unset the flag first to allow fstab options to override */
/* options set on the command line */
g_flags = (g_flags & ~SWAP_FLAG_PRIO_MASK) | SWAP_FLAG_PREFER |
MIN(prio, SWAP_FLAG_PRIO_MASK);
}
}
#else
#define set_priority_flag(s) ((void)0)
#endif
static int do_em_all_in_fstab(void)
{
struct mntent *m;
int err = 0;
FILE *f = xfopen_for_read("/etc/fstab");
while ((m = getmntent(f)) != NULL) {
if (strcmp(m->mnt_type, MNTTYPE_SWAP) == 0) {
/* swapon -a should ignore entries with noauto,
* but swapoff -a should process them
*/
if (do_swapoff || hasmntopt(m, MNTOPT_NOAUTO) == NULL) {
/* each swap space might have different flags */
/* save global flags for the next round */
save_g_flags();
if (ENABLE_FEATURE_SWAPON_DISCARD) {
char *p = hasmntopt(m, "discard");
if (p) {
/* move to '=' or to end of string */
p += 7;
set_discard_flag(p);
}
}
if (ENABLE_FEATURE_SWAPON_PRI) {
char *p = hasmntopt(m, "pri");
if (p) {
set_priority_flag(p + 4);
}
}
err |= swap_enable_disable(m->mnt_fsname);
restore_g_flags();
}
}
}
if (ENABLE_FEATURE_CLEAN_UP)
endmntent(f);
return err;
}
static int do_all_in_proc_swaps(void)
{
char *line;
int err = 0;
FILE *f = fopen_for_read("/proc/swaps");
/* Don't complain if missing */
if (f) {
while ((line = xmalloc_fgetline(f)) != NULL) {
if (line[0] == '/') {
*strchrnul(line, ' ') = '\0';
err |= swap_enable_disable(line);
}
free(line);
}
if (ENABLE_FEATURE_CLEAN_UP)
fclose(f);
}
return err;
}
#define OPTSTR_SWAPON "ae" \
IF_FEATURE_SWAPON_DISCARD("d::") \
IF_FEATURE_SWAPON_PRI("p:")
int swap_on_off_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int swap_on_off_main(int argc UNUSED_PARAM, char **argv)
{
IF_FEATURE_SWAPON_PRI(char *prio;)
IF_FEATURE_SWAPON_DISCARD(char *discard = NULL;)
int ret = 0;
INIT_G();
getopt32(argv, do_swapoff ? "ae" : OPTSTR_SWAPON
IF_FEATURE_SWAPON_DISCARD(, &discard)
IF_FEATURE_SWAPON_PRI(, &prio)
);
argv += optind;
if (OPT_DISCARD) {
set_discard_flag(discard);
}
if (OPT_PRIO) {
set_priority_flag(prio);
}
if (OPT_ALL) {
/* swapoff -a does also /proc/swaps */
if (do_swapoff)
ret = do_all_in_proc_swaps();
ret |= do_em_all_in_fstab();
} else if (!*argv) {
/* if not -a we need at least one arg */
bb_show_usage();
}
/* Unset -a now to allow for more messages in swap_enable_disable */
option_mask32 = option_mask32 & ~OPT_a;
/* Now process devices on the commandline if any */
while (*argv) {
ret |= swap_enable_disable(*argv++);
}
return ret;
}