toys/other/mkswap.c

/* mkswap.c - Format swap device.
 *
 * Copyright 2009 Rob Landley <rob@landley.net>

USE_MKSWAP(NEWTOY(mkswap, "<1>1", TOYFLAG_SBIN))

config MKSWAP
  bool "mkswap"
  default y
  help
    usage: mkswap DEVICE

    Sets up a Linux swap area on a device or file.
*/

#include "toys.h"

void mkswap_main(void)
{
  int fd = xopen(*toys.optargs, O_RDWR), pagesize = sysconf(_SC_PAGE_SIZE);
  off_t len = fdlength(fd);
  unsigned int pages = (len/pagesize)-1, *swap = (unsigned int *)toybuf;

  // Write header. Note that older kernel versions checked signature
  // on disk (not in cache) during swapon, so sync after writing.

  swap[0] = 1;
  swap[1] = pages;
  xlseek(fd, 1024, SEEK_SET);
  xwrite(fd, swap, 129*sizeof(unsigned int));
  xlseek(fd, pagesize-10, SEEK_SET);
  xwrite(fd, "SWAPSPACE2", 10);
  fsync(fd);

  if (CFG_TOYBOX_FREE) close(fd);

  printf("Swapspace size: %luk\n", pages*(unsigned long)(pagesize/1024));
}