On Debian Linux 2.6.31.4 up to 2.6.31.6 with CIFS 1.60 the file size can't requested over system call stat(). Errno would be set to 75: Value too large for defined data type. Is this a problem with 32Bit int and 64Bit int of large file support over CIFS? The error is reproduceable on small and large files. On Linux 2.6.30.9 with CIFS 1.58 it works. Please have a look over the test program. If the file is copied to local device or ramdisk the test program returns the correct file size. All programs, own build and GNU tools, on the system, which are using stat(), fstat() or lstat() over CIFS mounts are failing, sometimes crashing because of memalloc of wrong file size.
The client is a Linux system with above errors, the server is a Windows XP Professional system or Windows XP Embedded system with SP2 installed.

#include <fcntl.h>      /* open */ 
#include <unistd.h>     /* exit */
#include <stdio.h>
#include <memory.h>
#include <time.h>
#include <stdlib.h>
#include <stdarg.h>
#include <ctype.h>


#include <sys/ioctl.h>  /* ioctl */
#include <sys/types.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/time.h>


#include <errno.h>

int main(int argc, char *argv[])
{
  off_t size;
  struct stat filestat;

  errno = 0;
  stat(argv[1],&filestat);
  size=filestat.st_size;

  printf("file %s size %d errno=%d\n sizeof(off_t)=%d sizeof(stat)=%d\n\n",
    argv[1],(int)size, errno, sizeof(off_t), sizeof(filestat));

}