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Re: Bug with the fsnamespace cache ???

On Fri, 28 Apr 2000, Leigh Stoller wrote :
> I forget what version of the oskit are you running, cause the current impl
> uses a COM wrapper around oskit_dir_t, implemented by the fsnamespace
> cache. The posix unlink chains to this. This is in
> oskit/fsnamespace/src/dir_wrapper.c. 
> 

...

> If you do have this version of the code, then something is indeed wrong.
> Perhaps a reference count error.
> 

I am running version 20000202 of OSKit. The wrapper is present. But...
I have debugged a short code more carefully :

/* This name because it is plugged where there should be a command prompt. */
void read_command( void ) {
    int r ;
    r = open( "toto", O_CREAT|O_WRONLY ) ;
    fprintf( stdout, "open1 %d\n", r ) ;
    r = unlink( "toto" ) ;
    fprintf( stdout, "unlink %d\n", r ) ;
    r = open( "toto", O_RDONLY ) ;
    fprintf( stdout, "open2 %d", r ) ;
    return ;
}

The output produced is (if toto exist before the execution of this code) :
open1 3
unlink 0
open2 4

The awaited result is (and it is the case if toto does not exist before
the execution of the code) :
open1 3
unlink 0
open2 -1

While the debug, I saw that the wrapper was not installed on the directory
(file fsnamespace/src/fsnamespace.c) :

static OSKIT_COMDECL
fsnamespace_lookup(oskit_fsnamespace_t *f, const char *filename,
		   int flags, struct oskit_file **out_file)
{
	struct fsobj	*fs = (struct fsobj *) f;
	oskit_file_t	*file;
	oskit_error_t	rc;
	int		isdir;

	assert(fs->count);

	/*
	 * Do a pathname lookup using the current root and cwd.
	 */
	rc = fsn_lookup(fs, filename, flags, &isdir, &file);
	if (rc)
		return rc;

#if	defined(FSCACHE) && defined(THREAD_SAFE)
	/*
	 * In the multithreaded model, must wrap up directories so that
	 * cache consistency can be maintained. See the dir_wrapper code.
	 * Fortunately, most operations are on files, not directories.
	 */
	if (isdir) {
		oskit_dir_t	*dir;

		rc = fsn_wrap_dir(fs->fsnimpl, (oskit_dir_t *) file, &dir);
		
		/*
		 * Release reference since the wrapper took a ref.
		 */
		oskit_file_release(file);
		
		if (rc) 
			return rc;

		file = (oskit_file_t *) dir;
	}
#endif
	*out_file = file;
	return 0;
}


I think there are at least two errors :
- Our code is not multithreaded. The wrapper MUST be installed even if the
code is not multithreaded. I think the test defined(THREAD_SAFE) should
not be done there.
- Only directory looked up with the namespace are wrapped up. Is the home
directory wrapped up ?

	Simon.
References: