/*
   try-lfs1.c -- one of LFS subsystem tests
   by Matti Aarnio <matti.aarnio@sonera.fi>

   This test-program tries for largest writable offset in the
   current filesystem.

   While the system in Linux may allow file sizes up to 1 TB,
   the filesystem where this program is run at to produce its
   "lfs-test.dat" file, might not support all that much...

   For example all triply-indirected classical UNIX filesystems
   have inherent limitation from following formula:

     B = filesystem block size (0.5k, 1k, 2k, 4k)

     Max block number = 10 + B/4 + (B/4)^2 + (B/4)^3

   Highest term of the polynome for the filesize is thus:

     (B^4)/64

   and next highest (e.g. largest factor for an "epsilon") is:

     (B^3)/16

   or

     4/B

   part of the highest term.


     B    MaxIndirection

   0.5k       1 GB + epsilon1
   1.0k      16 GB + epsilon2
   2.0k     256 GB + epsilon3
   4.0k    4096 GB + epsilon4

   The last one is, of course, more than 32-bit system will be
   able to address with PGOFF_SHIFT = 9 ...

*/

#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>

#ifndef O_LARGEFILE
# define O_LARGEFILE     0100000 /* i386 only ! */
#endif

extern loff_t llseek(int fd, loff_t pos, int whence);

#define LFS "lfs-test.dat"

int main()
{
  int fd;
  loff_t off, pos;
  int rc;

  fd = open(LFS,O_RDWR|O_CREAT|O_TRUNC|O_LARGEFILE,0644);
  if (fd < 0) {
    perror("open('"LFS"',O_RDWR|O_CREAT|O_TRUNC|O_LARGEFILE,0644)");
    exit(88);
  }

  off = 0LL;

  while (1) {
    off += 0x2000000LL; /* 32 MB */
    pos = llseek(fd, off - 4LL, SEEK_SET);
    if (pos == (loff_t)-1) {
      fprintf(stdout,"llseek(fd,off,SEEK_SET) off=%Ld; errno=%s\n",
	      off,strerror(errno));
      break;
    }
    fprintf(stdout,"llseek(fd,off,SEEK_SET) new pos = %Ld\n",pos);
    if (write(fd,"01234567",8) != 8) {
      perror("write(fd,'....',8) failed");
      break;
    }
  }
  close(fd);
  exit(99);
}