#define _GNU_SOURCE

#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

#include <stdio.h>
#include <string.h>
#include <malloc.h>

int main(int argc, char* argv[])
{
  int fd;
  unsigned long long int const size = 4096 * 1024;
  unsigned int const size_page = 1024;
  unsigned long long int offset = 0;
  unsigned int offset_page = 0;

  //char* buffer = valloc(size);
  //memset(buffer, 0, size);

  if (argc != 2) {
    printf("usage: %s <filename>\n", argv[0]);
    return 0;
  }

  fd = open(argv[1], O_RDWR | O_CREAT | O_TRUNC | O_LARGEFILE /*| O_DIRECT*/, 0644);
  if (fd < 0) {
    perror("open");
    return 0;
  }

#ifdef ABUSE
  pwrite64(fd, "" , 1, offset + size);
#else
  ftruncate64(fd, offset + size);
#endif

  char* mapping = (char*)mmap64(0, size, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_POPULATE | MAP_NONBLOCK, fd, offset);
  memset(mapping, 'a', size);

  for (;;) {
    offset += size;
    offset_page += size_page;

#ifdef ABUSE
    pwrite64(fd, "", 1, offset + size);
#else
    ftruncate64(fd, offset + size);
#endif

    //munmap(mapping, size);
    //mapping = (char*)mmap64(0, size, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_POPULATE | MAP_NONBLOCK, fd, offset);
    remap_file_pages(mapping, size, 0, offset_page, MAP_NONBLOCK);

    memset(mapping, 'a', size);
  }

  close(fd);

  return 0;
}