From owner-freebsd-fs  Mon Sep 23 08:59:07 1996
Return-Path: owner-fs
Received: (from root@localhost)
          by freefall.freebsd.org (8.7.5/8.7.3) id IAA18960
          for fs-outgoing; Mon, 23 Sep 1996 08:59:07 -0700 (PDT)
Received: from godzilla.zeta.org.au (godzilla.zeta.org.au [203.2.228.19])
          by freefall.freebsd.org (8.7.5/8.7.3) with ESMTP id IAA18935
          for <fs@FreeBSD.org>; Mon, 23 Sep 1996 08:58:57 -0700 (PDT)
Received: (from bde@localhost) by godzilla.zeta.org.au (8.7.6/8.6.9) id BAA24393 for fs@freebsd.org; Tue, 24 Sep 1996 01:56:37 +1000
Date: Tue, 24 Sep 1996 01:56:37 +1000
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199609231556.BAA24393@godzilla.zeta.org.au>
To: fs@FreeBSD.org
Subject: untangling dirent macros
Sender: owner-fs@FreeBSD.org
X-Loop: FreeBSD.org
Precedence: bulk

I found that cd96660_vnops.c and devfs_vnops.c use the deprecated
compatibility header <sys/dir.h>.  Several other places include it but
don't actually use it.  <sys/dir.h> attempts to include the application
header <dirent.h>, but because of the bogus -I$S/sys in the kernel
Makefile, it actually includes <sys/dirent.h>.  This works because kernel
sources really want <sys/dirent.h> anyway.  When I removed -I$S/sys,
<sys/dir.h> started including the application header.  This worked too.

cd96660_vnops.c and devfs_vnops.c only need the DIRSIZ() macro from
<sys/dir.h>.  ufs avoids <sys/dir.h> by having its own copy of the
macro in <ufs/ufs/dir.h>, where the macro describes the on-disk layout.
The on-disk layout happens to be suitable for returning almost directly
in ufs_readdir(), at least on 32-bit machines (I think there might be
alignment problems for future(?) 64-bit machines).  I think a version
of the macro that gives minimal padding of the name for readdir()
should be defined in <sys/dirent.h> and all the names should be unique.
Maybe rename the ufs version UFS_DIRSIZ().  Maybe <machine/dirent.h>
is required to sometimes specify 64-bit alignment.

There is a similar problem with DIRBLKSIZE.  It is defined as 1024 in
<dirent.h>, but the kernel normally never sees or uses that.  ufs uses
DEV_BSIZE=512.  nfs_serv.c and nfs_vnops.c include <ufs/ufs/dir.h> so that
they can misuse the ufs value.  ext2fs_lookup.c includes <ufs/ufs/dir.c>
so that it can misuse the ufs value and lots more ufs stuff.  I think
a generic value for this should be defined in <sys/dirent.h>.

Bruce