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#include <fcntl.h>
#include <linux/fs.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/swap.h>
#include <sys/types.h>
/* This is not in a uapi header. */
struct linux_swap_header {
char bootbits[1024]; /* Space for disklabel etc. */
uint32_t version;
uint32_t last_page;
uint32_t nr_badpages;
unsigned char sws_uuid[16];
unsigned char sws_volume[16];
uint32_t padding[117];
uint32_t badpages[1];
};
#define MAGIC_SWAP_HEADER "SWAPSPACE2"
#define MAGIC_SWAP_HEADER_LEN 10
#define MIN_PAGES 10
int mkswap_main(int argc, char **argv)
{
if (argc != 2) {
fprintf(stderr, "Usage: %s <filename>\n", argv[0]);
return EXIT_FAILURE;
}
int fd = open(argv[1], O_RDWR);
if (fd < 0) {
fprintf(stderr, "Cannot open %s: %s\n", argv[1], strerror(errno));
return EXIT_FAILURE;
}
/* Determine the length of the swap file */
off64_t swap_size;
struct stat sb;
if (fstat(fd, &sb)) {
fprintf(stderr, "Couldn't fstat file: %s\n", strerror(errno));
return EXIT_FAILURE;
}
if (S_ISBLK(sb.st_mode)) {
if (ioctl(fd, BLKGETSIZE64, &swap_size) < 0) {
fprintf(stderr, "Couldn't determine block device size: %s\n", strerror(errno));
return EXIT_FAILURE;
}
} else {
swap_size = sb.st_size;
}
int pagesize = getpagesize();
if (swap_size < MIN_PAGES * pagesize) {
fprintf(stderr, "Swap file needs to be at least %d KiB\n", (MIN_PAGES * pagesize) >> 10);
return EXIT_FAILURE;
}
struct linux_swap_header sw_hdr;
memset(&sw_hdr, 0, sizeof(sw_hdr));
sw_hdr.version = 1;
sw_hdr.last_page = (swap_size / pagesize) - 1;
ssize_t len = write(fd, &sw_hdr, sizeof(sw_hdr));
if (len != sizeof(sw_hdr)) {
fprintf(stderr, "Failed to write swap header into %s: %s\n", argv[1], strerror(errno));
return EXIT_FAILURE;
}
/* Write the magic header */
if (lseek(fd, pagesize - MAGIC_SWAP_HEADER_LEN, SEEK_SET) < 0) {
fprintf(stderr, "Failed to seek into %s: %s\n", argv[1], strerror(errno));
return EXIT_FAILURE;
}
len = write(fd, MAGIC_SWAP_HEADER, MAGIC_SWAP_HEADER_LEN);
if (len != MAGIC_SWAP_HEADER_LEN) {
fprintf(stderr, "Failed to write magic swap header into %s: %s\n", argv[1], strerror(errno));
return EXIT_FAILURE;
}
if (fsync(fd) < 0) {
fprintf(stderr, "Failed to sync %s: %s\n", argv[1], strerror(errno));
return EXIT_FAILURE;
}
close(fd);
return EXIT_SUCCESS;
}
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