util-linux/mkswap.c - codeaurora/busybox - Gitiles

 /* vi: set sw=4 ts=4: */
 /*
  * mkswap.c - set up a linux swap device
  *
  * (C) 1991 Linus Torvalds. This file may be redistributed as per
  * the Linux copyright.
  */

 /*
  * 20.12.91  -	time began. Got VM working yesterday by doing this by hand.
  *
  * Usage: mkswap [-c] [-vN] [-f] device [size-in-blocks]
  *
  *	-c   for readability checking. (Use it unless you are SURE!)
  *	-vN  for swap areas version N. (Only N=0,1 known today.)
  *      -f   for forcing swap creation even if it would smash partition table.
  *
  * The device may be a block device or an image of one, but this isn't
  * enforced (but it's not much fun on a character device :-).
  *
  * Patches from jaggy@purplet.demon.co.uk (Mike Jagdis) to make the
  * size-in-blocks parameter optional added Wed Feb  8 10:33:43 1995.
  *
  * Version 1 swap area code (for kernel 2.1.117), aeb, 981010.
  *
  * Sparc fixes, jj@ultra.linux.cz (Jakub Jelinek), 981201 - mangled by aeb.
  * V1_MAX_PAGES fixes, jj, 990325.
  *
  * 1999-02-22 Arkadiusz Mi¶kiewicz <misiek@misiek.eu.org>
  * - added Native Language Support
  *
  *  from util-linux -- adapted for busybox by
  *  Erik Andersen <andersen@codepoet.org>. I ripped out Native Language
  *  Support, made some stuff smaller, and fitted for life in busybox.
  *
  */

 #include <stdio.h>
 #include <unistd.h>
 #include <string.h>
 #include <fcntl.h>
 #include <stdlib.h>
 #include <sys/ioctl.h>			/* for _IO */
 #include <sys/utsname.h>
 #include <asm/page.h>			/* for PAGE_SIZE and PAGE_SHIFT */
 				/* we also get PAGE_SIZE via getpagesize() */
 #include "busybox.h"

 #ifndef _IO
 /* pre-1.3.45 */
 enum { BLKGETSIZE = 0x1260 };
 #else
 /* same on i386, m68k, arm; different on alpha, mips, sparc, ppc */
 #define BLKGETSIZE _IO(0x12,96)
 #endif

 static char *device_name = NULL;
 static int DEV = -1;
 static long PAGES = 0;
 static int check = 0;
 static int badpages = 0;
 #if ENABLE_FEATURE_MKSWAP_V0
 static int version = -1;
 #else
 #define version 1
 /* and make sure that we optimize away anything which would deal with checking
  * the kernel revision as we have v1 support only anyway.
  */
 #undef KERNEL_VERSION
 #define KERNEL_VERSION(p,q,r) 1
 #define get_linux_version_code() 1
 #endif

 /*
  * The definition of the union swap_header uses the constant PAGE_SIZE.
  * Unfortunately, on some architectures this depends on the hardware model,
  * and can only be found at run time -- we use getpagesize().
  */

 static int pagesize;
 static unsigned int *signature_page;

 static struct swap_header_v1 {
 	char bootbits[1024];		/* Space for disklabel etc. */
 	unsigned int swap_version;
 	unsigned int last_page;
 	unsigned int nr_badpages;
 	unsigned int padding[125];
 	unsigned int badpages[1];
 } *p;

 static inline void init_signature_page(void)
 {
 	pagesize = getpagesize();

 #ifdef PAGE_SIZE
 	if (pagesize != PAGE_SIZE)
 		bb_error_msg("Assuming pages of size %d", pagesize);
 #endif
 	signature_page = (unsigned int *) xmalloc(pagesize);
 	memset(signature_page, 0, pagesize);
 	p = (struct swap_header_v1 *) signature_page;
 }

 static inline void write_signature(char *sig)
 {
 	char *sp = (char *) signature_page;

 	strncpy(sp + pagesize - 10, sig, 10);
 }

 #define V0_MAX_PAGES	(8 * (pagesize - 10))
 /* Before 2.2.0pre9 */
 #define V1_OLD_MAX_PAGES	((0x7fffffff / pagesize) - 1)
 /* Since 2.2.0pre9:
    error if nr of pages >= SWP_OFFSET(SWP_ENTRY(0,~0UL))
    with variations on
 	#define SWP_ENTRY(type,offset) (((type) << 1) | ((offset) << 8))
 	#define SWP_OFFSET(entry) ((entry) >> 8)
    on the various architectures. Below the result - yuk.

    Machine	pagesize	SWP_ENTRY	SWP_OFFSET	bound+1	oldbound+2
    i386		2^12		o<<8		e>>8		1<<24	1<<19
    mips		2^12		o<<15		e>>15		1<<17	1<<19
    alpha	2^13		o<<40		e>>40		1<<24	1<<18
    m68k		2^12		o<<12		e>>12		1<<20	1<<19
    sparc	2^{12,13}	(o&0x3ffff)<<9	(e>>9)&0x3ffff	1<<18	1<<{19,18}
    sparc64	2^13		o<<13		e>>13		1<<51	1<<18
    ppc		2^12		o<<8		e>>8		1<<24	1<<19
    armo		2^{13,14,15}	o<<8		e>>8		1<<24	1<<{18,17,16}
    armv		2^12		o<<9		e>>9		1<<23	1<<19

    assuming that longs have 64 bits on alpha and sparc64 and 32 bits elsewhere.

    The bad part is that we need to know this since the kernel will
    refuse a swap space if it is too large.
 */
 /* patch from jj - why does this differ from the above? */
 #if defined(__alpha__)
 #define V1_MAX_PAGES           ((1 << 24) - 1)
 #elif defined(__mips__)
 #define V1_MAX_PAGES           ((1 << 17) - 1)
 #elif defined(__sparc_v9__)
 #define V1_MAX_PAGES           ((3 << 29) - 1)
 #elif defined(__sparc__)
 #define V1_MAX_PAGES           (pagesize == 8192 ? ((3 << 29) - 1) : ((1 << 18) - 1))
 #else
 #define V1_MAX_PAGES           V1_OLD_MAX_PAGES
 #endif
 /* man page now says:
 The maximum useful size of a swap area now depends on the architecture.
 It is roughly 2GB on i386, PPC, m68k, ARM, 1GB on sparc, 512MB on mips,
 128GB on alpha and 3TB on sparc64.
 */

 #define MAX_BADPAGES	((pagesize-1024-128*sizeof(int)-10)/sizeof(int))

 static inline void bit_set(unsigned int *addr, unsigned int nr)
 {
 	unsigned int r, m;

 	addr += nr / (8 * sizeof(int));

 	r = *addr;
 	m = 1 << (nr & (8 * sizeof(int) - 1));

 	*addr = r | m;
 }

 static int bit_test_and_clear(unsigned int *addr, unsigned int nr)
 {
 	unsigned int r, m;

 	addr += nr / (8 * sizeof(int));

 	r = *addr;
 	m = 1 << (nr & (8 * sizeof(int) - 1));

 	*addr = r & ~m;
 	return (r & m) != 0;
 }

 static void page_ok(int page)
 {
 	if (ENABLE_FEATURE_MKSWAP_V0) {
 		bit_set(signature_page, page);
 	}
 }

 static void check_blocks(void)
 {
 	unsigned int current_page;
 	int do_seek = 1;
 	char *buffer;

 	buffer = xmalloc(pagesize);
 	current_page = 0;
 	while (current_page < PAGES) {
 		if (!check && version == 0) {
 			page_ok(current_page++);
 			continue;
 		}
 		if (do_seek && lseek(DEV, current_page * pagesize, SEEK_SET) !=
 			current_page * pagesize)
 			bb_error_msg_and_die("seek failed in check_blocks");
 		if ((do_seek = (pagesize != read(DEV, buffer, pagesize)))) {
 			current_page++;
 			if (version == 0)
 				bit_test_and_clear(signature_page, current_page);
 			else {
 				if (badpages == MAX_BADPAGES)
 					bb_error_msg_and_die("too many bad pages");
 				p->badpages[badpages] = current_page;
 			}
 			badpages++;
 			continue;
 		}
 		page_ok(current_page++);
 	}
 	if (ENABLE_FEATURE_CLEAN_UP)
 		free(buffer);
 	if (badpages > 0)
 		printf("%d bad page%s\n", badpages, (badpages==1)?"":"s");
 }

 static long valid_offset(int fd, int offset)
 {
 	char ch;

 	if (lseek(fd, offset, 0) < 0)
 		return 0;
 	if (read(fd, &ch, 1) < 1)
 		return 0;
 	return 1;
 }

 static int find_size(int fd)
 {
 	unsigned int high, low;

 	low = 0;
 	for (high = 1; high > 0 && valid_offset(fd, high); high *= 2)
 		low = high;
 	while (low < high - 1) {
 		const int mid = (low + high) / 2;

 		if (valid_offset(fd, mid))
 			low = mid;
 		else
 			high = mid;
 	}
 	return (low + 1);
 }

 /* return size in pages, to avoid integer overflow */
 static inline long get_size(const char *file)
 {
 	int fd;
 	long size;

 	fd = bb_xopen3(file, O_RDONLY, 0);
 	if (ioctl(fd, BLKGETSIZE, &size) >= 0) {
 		size /= pagesize / 512;
 	} else {
 		size = find_size(fd) / pagesize;
 	}
 	close(fd);
 	return size;
 }

 int mkswap_main(int argc, char **argv)
 {
 	char *tmp;
 	struct stat statbuf;
 	int sz;
 	int maxpages;
 	int goodpages;
 #ifdef __sparc__
 	int force = 0;
 #endif

 	init_signature_page();		/* get pagesize */

 	bb_opt_complementally = "?"; /* call bb_show_usage internally */
 	sz = bb_getopt_ulflags(argc, argv, "+cfv:", &tmp);
 	if (sz & 1)
 		check = 1;
 #ifdef __sparc__
 	if (sz & 2)
 		force = 1;
 #endif
 #if ENABLE_FEATURE_MKSWAP_V0
 	if (sz & 4) {
 		version = bb_xgetlarg(tmp, 10, 0, 1);
 	} else {
 		if (get_linux_version_code() < KERNEL_VERSION(2, 1, 117))
 			version = 0;
 		else
 			version = 1;
 	}
 #endif

 	argv += optind;
 	argc -= optind;

 	goodpages = pagesize / 1024; /* cache division */
 	while (argc--) {
 		if (device_name) {
 			PAGES = bb_xgetlarg(argv[0], 0, 10, sz * goodpages) / goodpages;
 			argc = 0; /* ignore any surplus args.. */
 		} else {
 			device_name = argv[0];
 			sz = get_size(device_name);
 			argv++;
 		}
 	}

 	if (!device_name) {
 		bb_error_msg_and_die("error: Nowhere to set up swap on?");
 	}
 	if (!PAGES) {
 		PAGES = sz;
 	}

 #if 0
 	maxpages = ((version == 0) ? V0_MAX_PAGES : V1_MAX_PAGES);
 #else
 	if (!version)
 		maxpages = V0_MAX_PAGES;
 	else if (get_linux_version_code() >= KERNEL_VERSION(2,2,1))
 		maxpages = V1_MAX_PAGES;
 	else {
 		maxpages = V1_OLD_MAX_PAGES;
 		if (maxpages > V1_MAX_PAGES)
 			maxpages = V1_MAX_PAGES;
 	}
 #endif
 	if (PAGES > maxpages) {
 		PAGES = maxpages;
 		bb_error_msg("warning: truncating swap area to %ldkB",
 				PAGES * goodpages);
 	}

 	DEV = bb_xopen3(device_name, O_RDWR, 0);
 	if (fstat(DEV, &statbuf) < 0)
 		bb_perror_msg_and_die("%s", device_name);
 	if (!S_ISBLK(statbuf.st_mode))
 		check = 0;
 	else if (statbuf.st_rdev == 0x0300 || statbuf.st_rdev == 0x0340)
 		bb_error_msg_and_die("Will not try to make swapdevice on '%s'", device_name);

 #ifdef __sparc__
 	if (!force && version == 0) {
 		/* Don't overwrite partition table unless forced */
 		unsigned char *buffer = (unsigned char *) signature_page;
 		unsigned short *q, sum;

 		if (read(DEV, buffer, 512) != 512)
 			bb_error_msg_and_die("fatal: first page unreadable");
 		if (buffer[508] == 0xDA && buffer[509] == 0xBE) {
 			q = (unsigned short *) (buffer + 510);
 			for (sum = 0; q >= (unsigned short *) buffer;)
 				sum ^= *q--;
 			if (!sum) {
 				bb_error_msg("Device '%s' contains a valid Sun disklabel.\n"
 "This probably means creating v0 swap would destroy your partition table\n"
 "No swap created. If you really want to create swap v0 on that device, use\n"
 "the -f option to force it.", device_name);
 				return EXIT_FAILURE;
 			}
 		}
 	}
 #endif

 	if (version == 0 || check)
 		check_blocks();
 	if (version == 0 && !bit_test_and_clear(signature_page, 0))
 		bb_error_msg_and_die("fatal: first page unreadable");
 	if (version == 1) {
 		p->swap_version = version;
 		p->last_page = PAGES - 1;
 		p->nr_badpages = badpages;
 	}

 	goodpages = PAGES - badpages - 1;
 	if (goodpages <= 0)
 		bb_error_msg_and_die("Unable to set up swap-space: unreadable");
 	printf("Setting up swapspace version %d, size = %ld bytes\n",
 		   version, (long) (goodpages * pagesize));
 	write_signature((version == 0) ? "SWAP-SPACE" : "SWAPSPACE2");

 	sz = ((version == 0) ? 0 : 1024); /* offset */
 	if (lseek(DEV, sz, SEEK_SET) != sz)
 		bb_error_msg_and_die("unable to rewind swap-device");
 	goodpages = pagesize - sz; /* cache substraction */
 	if (write(DEV, (char *) signature_page + sz, goodpages)
 		!= goodpages)
 		bb_error_msg_and_die("unable to write signature page");

 	/*
 	 * A subsequent swapon() will fail if the signature
 	 * is not actually on disk. (This is a kernel bug.)
 	 */
 	if (fsync(DEV))
 		bb_error_msg_and_die("fsync failed");
 	if (ENABLE_FEATURE_CLEAN_UP) {
 		close(DEV);
 		free(signature_page);
 	}
 	return EXIT_SUCCESS;
 }
	/* vi: set sw=4 ts=4: */
	/*
	* mkswap.c - set up a linux swap device
	*
	* (C) 1991 Linus Torvalds. This file may be redistributed as per
	* the Linux copyright.
	*/

	/*
	* 20.12.91 - time began. Got VM working yesterday by doing this by hand.
	*
	* Usage: mkswap [-c] [-vN] [-f] device [size-in-blocks]
	*
	* -c for readability checking. (Use it unless you are SURE!)
	* -vN for swap areas version N. (Only N=0,1 known today.)
	* -f for forcing swap creation even if it would smash partition table.
	*
	* The device may be a block device or an image of one, but this isn't
	* enforced (but it's not much fun on a character device :-).
	*
	* Patches from jaggy@purplet.demon.co.uk (Mike Jagdis) to make the
	* size-in-blocks parameter optional added Wed Feb 8 10:33:43 1995.
	*
	* Version 1 swap area code (for kernel 2.1.117), aeb, 981010.
	*
	* Sparc fixes, jj@ultra.linux.cz (Jakub Jelinek), 981201 - mangled by aeb.
	* V1_MAX_PAGES fixes, jj, 990325.
	*
	* 1999-02-22 Arkadiusz Mi¶kiewicz <misiek@misiek.eu.org>
	* - added Native Language Support
	*
	* from util-linux -- adapted for busybox by
	* Erik Andersen <andersen@codepoet.org>. I ripped out Native Language
	* Support, made some stuff smaller, and fitted for life in busybox.
	*
	*/

	#include <stdio.h>
	#include <unistd.h>
	#include <string.h>
	#include <fcntl.h>
	#include <stdlib.h>
	#include <sys/ioctl.h> /* for _IO */
	#include <sys/utsname.h>
	#include <asm/page.h> /* for PAGE_SIZE and PAGE_SHIFT */
	/* we also get PAGE_SIZE via getpagesize() */
	#include "busybox.h"

	#ifndef _IO
	/* pre-1.3.45 */
	enum { BLKGETSIZE = 0x1260 };
	#else
	/* same on i386, m68k, arm; different on alpha, mips, sparc, ppc */
	#define BLKGETSIZE _IO(0x12,96)
	#endif

	static char *device_name = NULL;
	static int DEV = -1;
	static long PAGES = 0;
	static int check = 0;
	static int badpages = 0;
	#if ENABLE_FEATURE_MKSWAP_V0
	static int version = -1;
	#else
	#define version 1
	/* and make sure that we optimize away anything which would deal with checking
	* the kernel revision as we have v1 support only anyway.
	*/
	#undef KERNEL_VERSION
	#define KERNEL_VERSION(p,q,r) 1
	#define get_linux_version_code() 1
	#endif

	/*
	* The definition of the union swap_header uses the constant PAGE_SIZE.
	* Unfortunately, on some architectures this depends on the hardware model,
	* and can only be found at run time -- we use getpagesize().
	*/

	static int pagesize;
	static unsigned int *signature_page;

	static struct swap_header_v1 {
	char bootbits[1024]; /* Space for disklabel etc. */
	unsigned int swap_version;
	unsigned int last_page;
	unsigned int nr_badpages;
	unsigned int padding[125];
	unsigned int badpages[1];
	} *p;

	static inline void init_signature_page(void)
	{
	pagesize = getpagesize();

	#ifdef PAGE_SIZE
	if (pagesize != PAGE_SIZE)
	bb_error_msg("Assuming pages of size %d", pagesize);
	#endif
	signature_page = (unsigned int *) xmalloc(pagesize);
	memset(signature_page, 0, pagesize);
	p = (struct swap_header_v1 *) signature_page;
	}

	static inline void write_signature(char *sig)
	{
	char sp = (char ) signature_page;

	strncpy(sp + pagesize - 10, sig, 10);
	}

	#define V0_MAX_PAGES (8 * (pagesize - 10))
	/* Before 2.2.0pre9 */
	#define V1_OLD_MAX_PAGES ((0x7fffffff / pagesize) - 1)
	/* Since 2.2.0pre9:
	error if nr of pages >= SWP_OFFSET(SWP_ENTRY(0,~0UL))
	with variations on
	#define SWP_ENTRY(type,offset) (((type) << 1) \| ((offset) << 8))
	#define SWP_OFFSET(entry) ((entry) >> 8)
	on the various architectures. Below the result - yuk.

	Machine pagesize SWP_ENTRY SWP_OFFSET bound+1 oldbound+2
	i386 2^12 o<<8 e>>8 1<<24 1<<19
	mips 2^12 o<<15 e>>15 1<<17 1<<19
	alpha 2^13 o<<40 e>>40 1<<24 1<<18
	m68k 2^12 o<<12 e>>12 1<<20 1<<19
	sparc 2^{12,13} (o&0x3ffff)<<9 (e>>9)&0x3ffff 1<<18 1<<{19,18}
	sparc64 2^13 o<<13 e>>13 1<<51 1<<18
	ppc 2^12 o<<8 e>>8 1<<24 1<<19
	armo 2^{13,14,15} o<<8 e>>8 1<<24 1<<{18,17,16}
	armv 2^12 o<<9 e>>9 1<<23 1<<19

	assuming that longs have 64 bits on alpha and sparc64 and 32 bits elsewhere.

	The bad part is that we need to know this since the kernel will
	refuse a swap space if it is too large.
	*/
	/* patch from jj - why does this differ from the above? */
	#if defined(__alpha__)
	#define V1_MAX_PAGES ((1 << 24) - 1)
	#elif defined(__mips__)
	#define V1_MAX_PAGES ((1 << 17) - 1)
	#elif defined(__sparc_v9__)
	#define V1_MAX_PAGES ((3 << 29) - 1)
	#elif defined(__sparc__)
	#define V1_MAX_PAGES (pagesize == 8192 ? ((3 << 29) - 1) : ((1 << 18) - 1))
	#else
	#define V1_MAX_PAGES V1_OLD_MAX_PAGES
	#endif
	/* man page now says:
	The maximum useful size of a swap area now depends on the architecture.
	It is roughly 2GB on i386, PPC, m68k, ARM, 1GB on sparc, 512MB on mips,
	128GB on alpha and 3TB on sparc64.
	*/

	#define MAX_BADPAGES ((pagesize-1024-128*sizeof(int)-10)/sizeof(int))

	static inline void bit_set(unsigned int *addr, unsigned int nr)
	{
	unsigned int r, m;

	addr += nr / (8 * sizeof(int));

	r = *addr;
	m = 1 << (nr & (8 * sizeof(int) - 1));

	*addr = r \| m;
	}

	static int bit_test_and_clear(unsigned int *addr, unsigned int nr)
	{
	unsigned int r, m;

	addr += nr / (8 * sizeof(int));

	r = *addr;
	m = 1 << (nr & (8 * sizeof(int) - 1));

	*addr = r & ~m;
	return (r & m) != 0;
	}

	static void page_ok(int page)
	{
	if (ENABLE_FEATURE_MKSWAP_V0) {
	bit_set(signature_page, page);
	}
	}

	static void check_blocks(void)
	{
	unsigned int current_page;
	int do_seek = 1;
	char *buffer;

	buffer = xmalloc(pagesize);
	current_page = 0;
	while (current_page < PAGES) {
	if (!check && version == 0) {
	page_ok(current_page++);
	continue;
	}
	if (do_seek && lseek(DEV, current_page * pagesize, SEEK_SET) !=
	current_page * pagesize)
	bb_error_msg_and_die("seek failed in check_blocks");
	if ((do_seek = (pagesize != read(DEV, buffer, pagesize)))) {
	current_page++;
	if (version == 0)
	bit_test_and_clear(signature_page, current_page);
	else {
	if (badpages == MAX_BADPAGES)
	bb_error_msg_and_die("too many bad pages");
	p->badpages[badpages] = current_page;
	}
	badpages++;
	continue;
	}
	page_ok(current_page++);
	}
	if (ENABLE_FEATURE_CLEAN_UP)
	free(buffer);
	if (badpages > 0)
	printf("%d bad page%s\n", badpages, (badpages==1)?"":"s");
	}

	static long valid_offset(int fd, int offset)
	{
	char ch;

	if (lseek(fd, offset, 0) < 0)
	return 0;
	if (read(fd, &ch, 1) < 1)
	return 0;
	return 1;
	}

	static int find_size(int fd)
	{
	unsigned int high, low;

	low = 0;
	for (high = 1; high > 0 && valid_offset(fd, high); high *= 2)
	low = high;
	while (low < high - 1) {
	const int mid = (low + high) / 2;

	if (valid_offset(fd, mid))
	low = mid;
	else
	high = mid;
	}
	return (low + 1);
	}

	/* return size in pages, to avoid integer overflow */
	static inline long get_size(const char *file)
	{
	int fd;
	long size;

	fd = bb_xopen3(file, O_RDONLY, 0);
	if (ioctl(fd, BLKGETSIZE, &size) >= 0) {
	size /= pagesize / 512;
	} else {
	size = find_size(fd) / pagesize;
	}
	close(fd);
	return size;
	}

	int mkswap_main(int argc, char **argv)
	{
	char *tmp;
	struct stat statbuf;
	int sz;
	int maxpages;
	int goodpages;
	#ifdef __sparc__
	int force = 0;
	#endif

	init_signature_page(); /* get pagesize */

	bb_opt_complementally = "?"; /* call bb_show_usage internally */
	sz = bb_getopt_ulflags(argc, argv, "+cfv:", &tmp);
	if (sz & 1)
	check = 1;
	#ifdef __sparc__
	if (sz & 2)
	force = 1;
	#endif
	#if ENABLE_FEATURE_MKSWAP_V0
	if (sz & 4) {
	version = bb_xgetlarg(tmp, 10, 0, 1);
	} else {
	if (get_linux_version_code() < KERNEL_VERSION(2, 1, 117))
	version = 0;
	else
	version = 1;
	}
	#endif

	argv += optind;
	argc -= optind;

	goodpages = pagesize / 1024; /* cache division */
	while (argc--) {
	if (device_name) {
	PAGES = bb_xgetlarg(argv[0], 0, 10, sz * goodpages) / goodpages;
	argc = 0; /* ignore any surplus args.. */
	} else {
	device_name = argv[0];
	sz = get_size(device_name);
	argv++;
	}
	}

	if (!device_name) {
	bb_error_msg_and_die("error: Nowhere to set up swap on?");
	}
	if (!PAGES) {
	PAGES = sz;
	}

	#if 0
	maxpages = ((version == 0) ? V0_MAX_PAGES : V1_MAX_PAGES);
	#else
	if (!version)
	maxpages = V0_MAX_PAGES;
	else if (get_linux_version_code() >= KERNEL_VERSION(2,2,1))
	maxpages = V1_MAX_PAGES;
	else {
	maxpages = V1_OLD_MAX_PAGES;
	if (maxpages > V1_MAX_PAGES)
	maxpages = V1_MAX_PAGES;
	}
	#endif
	if (PAGES > maxpages) {
	PAGES = maxpages;
	bb_error_msg("warning: truncating swap area to %ldkB",
	PAGES * goodpages);
	}

	DEV = bb_xopen3(device_name, O_RDWR, 0);
	if (fstat(DEV, &statbuf) < 0)
	bb_perror_msg_and_die("%s", device_name);
	if (!S_ISBLK(statbuf.st_mode))
	check = 0;
	else if (statbuf.st_rdev == 0x0300 \|\| statbuf.st_rdev == 0x0340)
	bb_error_msg_and_die("Will not try to make swapdevice on '%s'", device_name);

	#ifdef __sparc__
	if (!force && version == 0) {
	/* Don't overwrite partition table unless forced */
	unsigned char buffer = (unsigned char ) signature_page;
	unsigned short *q, sum;

	if (read(DEV, buffer, 512) != 512)
	bb_error_msg_and_die("fatal: first page unreadable");
	if (buffer[508] == 0xDA && buffer[509] == 0xBE) {
	q = (unsigned short *) (buffer + 510);
	for (sum = 0; q >= (unsigned short *) buffer;)
	sum ^= *q--;
	if (!sum) {
	bb_error_msg("Device '%s' contains a valid Sun disklabel.\n"
	"This probably means creating v0 swap would destroy your partition table\n"
	"No swap created. If you really want to create swap v0 on that device, use\n"
	"the -f option to force it.", device_name);
	return EXIT_FAILURE;
	}
	}
	}
	#endif

	if (version == 0 \|\| check)
	check_blocks();
	if (version == 0 && !bit_test_and_clear(signature_page, 0))
	bb_error_msg_and_die("fatal: first page unreadable");
	if (version == 1) {
	p->swap_version = version;
	p->last_page = PAGES - 1;
	p->nr_badpages = badpages;
	}

	goodpages = PAGES - badpages - 1;
	if (goodpages <= 0)
	bb_error_msg_and_die("Unable to set up swap-space: unreadable");
	printf("Setting up swapspace version %d, size = %ld bytes\n",
	version, (long) (goodpages * pagesize));
	write_signature((version == 0) ? "SWAP-SPACE" : "SWAPSPACE2");

	sz = ((version == 0) ? 0 : 1024); /* offset */
	if (lseek(DEV, sz, SEEK_SET) != sz)
	bb_error_msg_and_die("unable to rewind swap-device");
	goodpages = pagesize - sz; /* cache substraction */
	if (write(DEV, (char *) signature_page + sz, goodpages)
	!= goodpages)
	bb_error_msg_and_die("unable to write signature page");

	/*
	* A subsequent swapon() will fail if the signature
	* is not actually on disk. (This is a kernel bug.)
	*/
	if (fsync(DEV))
	bb_error_msg_and_die("fsync failed");
	if (ENABLE_FEATURE_CLEAN_UP) {
	close(DEV);
	free(signature_page);
	}
	return EXIT_SUCCESS;
	}