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#include <stdio.h>
#include <unistd.h>
#include <sys/swap.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
/* XXX This needs to be obtained from kernel headers. See b/9336527 */
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)
{
int err = 0;
int fd;
ssize_t len;
off_t swap_size;
int pagesize;
struct linux_swap_header sw_hdr;
if (argc != 2) {
fprintf(stderr, "Usage: %s <filename>\n", argv[0]);
return -EINVAL;
}
fd = open(argv[1], O_WRONLY);
if (fd < 0) {
err = errno;
fprintf(stderr, "Cannot open %s\n", argv[1]);
return err;
}
pagesize = getpagesize();
/* Determine the length of the swap file */
swap_size = lseek(fd, 0, SEEK_END);
if (swap_size < MIN_PAGES * pagesize) {
fprintf(stderr, "Swap file needs to be at least %dkB\n",
(MIN_PAGES * pagesize) >> 10);
err = -ENOSPC;
goto err;
}
if (lseek(fd, 0, SEEK_SET)) {
err = errno;
fprintf(stderr, "Can't seek to the beginning of the file\n");
goto err;
}
memset(&sw_hdr, 0, sizeof(sw_hdr));
sw_hdr.version = 1;
sw_hdr.last_page = (swap_size / pagesize) - 1;
len = write(fd, &sw_hdr, sizeof(sw_hdr));
if (len != sizeof(sw_hdr)) {
err = errno;
fprintf(stderr, "Failed to write swap header into %s\n", argv[1]);
goto err;
}
/* Write the magic header */
if (lseek(fd, pagesize - MAGIC_SWAP_HEADER_LEN, SEEK_SET) < 0) {
err = errno;
fprintf(stderr, "Failed to seek into %s\n", argv[1]);
goto err;
}
len = write(fd, MAGIC_SWAP_HEADER, MAGIC_SWAP_HEADER_LEN);
if (len != MAGIC_SWAP_HEADER_LEN) {
err = errno;
fprintf(stderr, "Failed to write magic swap header into %s\n", argv[1]);
goto err;
}
if (fsync(fd) < 0) {
err = errno;
fprintf(stderr, "Failed to sync %s\n", argv[1]);
goto err;
}
err:
close(fd);
return err;
}
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