mkswap.c

Util-linux 软件包包含许多工具。其中比较重要的是加载、卸载、格式化、分区和管理硬盘驱动器

	return (r & m) != 0;
}

static void
usage(void) {
	fprintf(stderr,
		_("Usage: %s [-c] [-v0|-v1] [-pPAGESZ] /dev/name [blocks]\n"),
		program_name);
	exit(1);
}

static void
die(const char *str) {
	fprintf(stderr, "%s: %s\n", program_name, str);
	exit(1);
}

static void
page_ok(int page) {
	if (version==0)
		bit_set(signature_page, page);
}

static void
page_bad(int page) {
	if (version == 0)
		bit_test_and_clear(signature_page, page);
	else {
		if (badpages == MAX_BADPAGES)
			die(_("too many bad pages"));
		p->badpages[badpages] = page;
	}
	badpages++;
}

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

	buffer = malloc(pagesize);
	if (!buffer)
		die(_("Out of memory"));
	current_page = 0;
	while (current_page < PAGES) {
		if (!check) {
			page_ok(current_page++);
			continue;
		}
		if (do_seek && lseek(DEV,current_page*pagesize,SEEK_SET) !=
		    current_page*pagesize)
			die(_("seek failed in check_blocks"));
		if ((do_seek = (pagesize != read(DEV, buffer, pagesize)))) {
			page_bad(current_page++);
			continue;
		}
		page_ok(current_page++);
	}
	if (badpages == 1)
		printf(_("one bad page\n"));
	else if (badpages > 1)
		printf(_("%lu bad pages\n"), badpages);
}

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

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

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

	low = 0;
	for (high = 1; high > 0 && valid_offset (fd, high); high *= 2)
		low = high;
	while (low < high - 1) {
		const off_t 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 unsigned long
get_size(const char  *file) {
	int	fd;
	unsigned long	size;

	fd = open(file, O_RDONLY);
	if (fd < 0) {
		perror(file);
		exit(1);
	}
	if (ioctl(fd, BLKGETSIZE, &size) >= 0) {
		int sectors_per_page = pagesize/512;
		size /= sectors_per_page;
	} else {
		size = find_size(fd) / pagesize;
	}
	close(fd);
	return size;
}

static int
isnzdigit(char c) {
	return (c >= '1' && c <= '9');
}

int
main(int argc, char ** argv) {
	struct stat statbuf;
	int i;
	unsigned long maxpages;
	unsigned long goodpages;
	unsigned long sz;
	off_t offset;
	int force = 0;
	char *block_count = 0;
	char *pp;

	program_name = (argc && *argv) ? argv[0] : "fsck.minix";
	if ((pp = strrchr(program_name, '/')) != NULL)
		program_name = pp+1;

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

	if (argc == 2 &&
	    (!strcmp(argv[1], "-V") || !strcmp(argv[1], "--version"))) {
		printf(_("%s from %s\n"), program_name, util_linux_version);
		exit(0);
	}

	for (i=1; i<argc; i++) {
		if (argv[i][0] == '-') {
			switch (argv[i][1]) {
				case 'c':
					check=1;
					break;
				case 'f':
					force=1;
					break;
				case 'p':
					pp = argv[i]+2;
					if (!*pp && i+1 < argc)
						pp = argv[++i];
					if (isnzdigit(*pp))
						user_pagesize=atoi(pp);
					else
						usage();
					break;
				case 'v':
					version = atoi(argv[i]+2);
					break;
				default:
					usage();
			}
		} else if (!device_name) {
			device_name = argv[i];
		} else if (!block_count) {
			block_count = argv[i];
		} else
			usage();
	}

	init_signature_page();	/* get pagesize */

	if (!device_name) {
		fprintf(stderr,
			_("%s: error: Nowhere to set up swap on?\n"),
			program_name);
		usage();
	}
	if (block_count) {
		/* this silly user specified the number of blocks
		   explicitly */
		char *tmp;
		int blocks_per_page = pagesize/1024;
		PAGES = strtoul(block_count,&tmp,0)/blocks_per_page;
		if (*tmp)
			usage();
	}
	sz = get_size(device_name);
	if (!PAGES) {
		PAGES = sz;
	} else if (PAGES > sz && !force) {
		fprintf(stderr,
			_("%s: error: "
			  "size %lu is larger than device size %lu\n"),
			program_name,
			PAGES*(pagesize/1024), sz*(pagesize/1024));
		exit(1);
	}

	if (version == -1) {
		/* use version 1 as default, if possible */
		if (PAGES <= V0_MAX_PAGES && PAGES > V1_MAX_PAGES)
			version = 0;
		else if (linux_version_code() < MAKE_VERSION(2,1,117))
			version = 0;
		else if (pagesize < 2048)
			version = 0;
		else
			version = 1;
	}
	if (version != 0 && version != 1) {
		fprintf(stderr, _("%s: error: unknown version %d\n"),
			program_name, version);
		usage();
	}

	if (PAGES < 10) {
		fprintf(stderr,
			_("%s: error: swap area needs to be at least %ldkB\n"),
			program_name, (long)(10 * pagesize / 1000));
		usage();
	}

	if (version == 0)
		maxpages = V0_MAX_PAGES;
	else if (linux_version_code() >= MAKE_VERSION(2,3,4))
		maxpages = PAGES;
	else if (linux_version_code() >= MAKE_VERSION(2,2,1))
		maxpages = V1_MAX_PAGES;
	else
		maxpages = V1_OLD_MAX_PAGES;

	if (PAGES > maxpages) {
		PAGES = maxpages;
		fprintf(stderr,
			_("%s: warning: truncating swap area to %ldkB\n"),
			program_name, PAGES * pagesize / 1000);
	}

	DEV = open(device_name,O_RDWR);
	if (DEV < 0 || fstat(DEV, &statbuf) < 0) {
		perror(device_name);
		exit(1);
	}

	/* Want a block device. Probably not /dev/hda or /dev/hdb. */
	if (!S_ISBLK(statbuf.st_mode))
		check=0;
	else if (statbuf.st_rdev == 0x0300 || statbuf.st_rdev == 0x0340)
		die(_("Will not try to make swapdevice on '%s'"));

#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)
			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) {
				fprintf(stderr, _("\
%s: 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.\n"),
					program_name, device_name);
				exit(1);
			}
		}
	}
#endif

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

	goodpages = PAGES - badpages - 1;
	if ((long) goodpages <= 0)
		die(_("Unable to set up swap-space: unreadable"));
	printf(_("Setting up swapspace version %d, size = %llu kB\n"),
		version, (unsigned long long)goodpages * pagesize / 1000);
	write_signature((version == 0) ? "SWAP-SPACE" : "SWAPSPACE2");

	offset = ((version == 0) ? 0 : 1024);
	if (lseek(DEV, offset, SEEK_SET) != offset)
		die(_("unable to rewind swap-device"));
	if (write(DEV,(char*)signature_page+offset, pagesize-offset)
	    != pagesize-offset)
		die(_("unable to write signature page"));

	/*
	 * A subsequent swapon() will fail if the signature
	 * is not actually on disk. (This is a kernel bug.)
	 */
#ifdef HAVE_fsync
	if (fsync(DEV))
		 die(_("fsync failed"));
#endif
	return 0;
}