RE: Was able to reproduce "cp: cannot stat file.x: Input/output error"

["David Dabbs" <david@dabbs.net>]

> -----Original Message-----
> From: Hans Reiser [mailto:reiser@namesys.com]
> Sent: Saturday, August 07, 2004 11:18 PM
> To: David Dabbs
> Subject: Re: Was able to reproduce "cp: cannot stat file.x: Input/output
> error"
> 

> >
> How about, code was X, now it is Y, with just the relevant parts of the
> code cited?

Probably the most significant change to mongo sources is how it generates
file names. Mongo.pl had a hard coded value of 6 for the "max_fname"
parameter passed to reiser_fract_tree. I made this a parameter one can
specify on the mongo command line. I passed it a value of 23.

In addition, reiser_fract_tree.c now generates file names (not directories)
with extensions. Before, every file name generated had none. Here is the
original and modified code.


CODE WAS
/* generate a unique filename */
void get_name_by_number(num_t this_files_number, char * str, char type)
{
  double rnd;
  char t[16];
  /* We need to generate filenames of different lengths */
  rnd=rand();
  rnd=rnd/RAND_MAX*max_fname+1;
  sprintf (t, "%%c%%0%ulu",(int) rnd );
  sprintf (str, t, type, this_files_number);

}

NOW CODE IS

/* generate a unique filename */
void get_name_by_number(num_t this_files_number, char * str, char type)
{
  double rnd;
  char t[16];
  /* We need to generate filenames of different lengths */
  rnd=rand();
  rnd=rnd/RAND_MAX*max_fname+1;
  if( type == 'f' ) 
    sprintf (t, "%%c%%0%ulu.%c",(int) rnd, '`'+(char)rnd );
  else
    sprintf (t, "%%c%%0%ulu",(int) rnd );


  sprintf (str, t, type, this_files_number);

}

Backtick is the character immediately preceding 'a', so passing a value for
max_fname that generates a character greater than 'z' might generate an
extension character that might be a shell metacharacter. Hence my earlier
warning about using this parameter.

Finally, I added two phases to mongo. MKDIRS and MKFILES. The first makes
directories from a static list of directories cat-ted from a file. MKFILES
does the same, except with files. The files are created by executing the
following code taken directory from reiser_fract_tree:

/* make a file of a specified size */
void make_file(int size, char * fname)
{ 
  char string [1025] = {0};
  char * str = string;
  int fd = 0;
  int error;
  static num_t this_files_number = 1;

  /* open the file, and deal with the various errors that can occur */

  if ((fd = open(fname, g_flags, 0666)) == -1 ) {
    if (errno == ENOSPC) {
      if (!already_whined) {
	printf("reiser-2021A: out of disk (or inodes) space, will keep
trying\n");
	already_whined = 1;	/* we continue other file creation in out of
				   space conditions */
      }
      return;
    }
    /*  it is sometimes useful to be able to run this program more than once
	inside the same directory, and that means skipping over filenames
that
	already exist.  Thus we ignore EEXIST, and pay attention to all
	else. */
    if ( errno == EEXIST) {	/* just skip existing file */
      return;
    }
    perror ("open");
    exit (errno);
  }

  /* close the file */
  if (close(fd)) {
    perror("close() failed");
    exit(errno);
  }
}

Since the above code simply opens and closes the file, every file created is
zero length, and it creates _many_ zero-length files. Before, all files
created during a mongo run had some content, though I'd need to go back and
check the size distribution function to be sure. 


Finally, there is the bit about mounting and unmounting. Mongo.pl first
unmounts the target filesystem, then runs the proper mkfs command, mounted
the filesystem, ran df to get the block usage, then unmounted the
filesystem. To run each phase, mongo calls the function mongo_launcher,
which mounted the filesystem, ran the command for N iterations, then
unmounted the filesystem.

I made the following changes, see http://dabbs.net/reiser4/mongopl.html for
more context.

In 

init_fsys: 
   don't unmount the filesystem after mkfs * df.

mongo_launcher:
   don't call &mount_fsys; at beginning and &umount_fsys; at end of each
phase


Only umount_fsys at end of function mongo.


David