make it possible for UNION fs to be loaded via LKM - instead of

having some #ifdef UNION code in vfs_vnops.c, introduce variable
'vn_union_readdir_hook' which is set to address of appropriate
vn_readdir() hook by union filesystem when it's loaded & mounted

sys/fs/union/union.h

@@ -1,4 +1,4 @@
-/*	$NetBSD: union.h,v 1.1 2003/03/16 08:26:51 jdolecek Exp $	*/
+/*	$NetBSD: union.h,v 1.2 2003/03/17 09:11:30 jdolecek Exp $	*/
 
 /*
  * Copyright (c) 1994 The Regents of the University of California.
@@ -122,6 +122,7 @@ extern struct vnode *union_lowervp __P((struct vnode *));
 extern void union_newlower __P((struct union_node *, struct vnode *));
 extern void union_newupper __P((struct union_node *, struct vnode *));
 extern void union_newsize __P((struct vnode *, off_t, off_t));
+int union_readdirhook(struct vnode **, struct file *, struct proc *);
 
 #define	MOUNTTOUNIONMOUNT(mp) ((struct union_mount *)((mp)->mnt_data))
 #define	VTOUNION(vp) ((struct union_node *)(vp)->v_data)

sys/fs/union/union_subr.c

@@ -1,4 +1,4 @@
-/*	$NetBSD: union_subr.c,v 1.1 2003/03/16 08:26:52 jdolecek Exp $	*/
+/*	$NetBSD: union_subr.c,v 1.2 2003/03/17 09:11:30 jdolecek Exp $	*/
 
 /*
  * Copyright (c) 1994 Jan-Simon Pendry
@@ -40,7 +40,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: union_subr.c,v 1.1 2003/03/16 08:26:52 jdolecek Exp $");
+__KERNEL_RCSID(0, "$NetBSD: union_subr.c,v 1.2 2003/03/17 09:11:30 jdolecek Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -100,7 +100,9 @@ union_init()
 void
 union_done()
 {
-	/* Nothing */
+	
+	/* Make sure to unset the readdir hook. */
+	vn_union_readdir_hook = NULL;
 }
 
 static int
@@ -1153,3 +1155,45 @@ union_diruncache(un)
 		un->un_dircache = 0;
 	}
 }
+
+/*
+ * This hook is called from vn_readdir() to switch to lower directory
+ * entry after the upper directory is read.
+ */
+int
+union_readdirhook(struct vnode **vpp, struct file *fp, struct proc *p)
+{
+	struct vnode *vp = *vpp, *lvp;
+	struct vattr va;
+	int error;
+
+	if (vp->v_op != union_vnodeop_p)
+		return (0);
+
+	if ((lvp = union_dircache(vp, p)) == NULLVP)
+		return (0);
+
+	/*
+	 * If the directory is opaque,
+	 * then don't show lower entries
+	 */
+	error = VOP_GETATTR(vp, &va, fp->f_cred, p);
+	if (error || (va.va_flags & OPAQUE)) {
+		vput(lvp);
+		return (error);
+	}
+		
+	error = VOP_OPEN(lvp, FREAD, fp->f_cred, p);
+	if (error) {
+		vput(lvp);
+		return (error);
+	}
+	VOP_UNLOCK(lvp, 0);
+	fp->f_data = (caddr_t) lvp;
+	fp->f_offset = 0;
+	error = vn_close(vp, FREAD, fp->f_cred, p);
+	if (error)
+		return (error);
+	*vpp = lvp;
+	return (0);
+}

sys/fs/union/union_vfsops.c

@@ -1,4 +1,4 @@
-/*	$NetBSD: union_vfsops.c,v 1.1 2003/03/16 08:26:54 jdolecek Exp $	*/
+/*	$NetBSD: union_vfsops.c,v 1.2 2003/03/17 09:11:31 jdolecek Exp $	*/
 
 /*
  * Copyright (c) 1994 The Regents of the University of California.
@@ -44,7 +44,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: union_vfsops.c,v 1.1 2003/03/16 08:26:54 jdolecek Exp $");
+__KERNEL_RCSID(0, "$NetBSD: union_vfsops.c,v 1.2 2003/03/17 09:11:31 jdolecek Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -259,6 +259,11 @@ union_mount(mp, path, data, ndp, p)
 	printf("union_mount: from %s, on %s\n",
 	    mp->mnt_stat.f_mntfromname, mp->mnt_stat.f_mntonname);
 #endif
+
+	/* Setup the readdir hook if it's not set already */
+	if (!vn_union_readdir_hook)
+		vn_union_readdir_hook = union_readdirhook;
+
 	return (0);
 
 bad:

sys/kern/vfs_vnops.c

@@ -1,4 +1,4 @@
-/*	$NetBSD: vfs_vnops.c,v 1.65 2003/03/16 08:26:48 jdolecek Exp $	*/
+/*	$NetBSD: vfs_vnops.c,v 1.66 2003/03/17 09:11:30 jdolecek Exp $	*/
 
 /*
  * Copyright (c) 1982, 1986, 1989, 1993
@@ -41,7 +41,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: vfs_vnops.c,v 1.65 2003/03/16 08:26:48 jdolecek Exp $");
+__KERNEL_RCSID(0, "$NetBSD: vfs_vnops.c,v 1.66 2003/03/17 09:11:30 jdolecek Exp $");
 
 #include "fs_union.h"
 
@@ -65,6 +65,10 @@ __KERNEL_RCSID(0, "$NetBSD: vfs_vnops.c,v 1.65 2003/03/16 08:26:48 jdolecek Exp
 #include <fs/union/union.h>
 #endif
 
+#if defined(LKM) || defined(UNION)
+int (*vn_union_readdir_hook) (struct vnode **, struct file *, struct proc *);
+#endif
+
 #ifdef VERIFIED_EXEC
 #include <sys/verified_exec.h>
 
@@ -440,46 +444,17 @@ unionread:
 	if (error)
 		return (error);
 
-#ifdef UNION
+#if defined(UNION) || defined(LKM)
-{
+	if (count == auio.uio_resid && vn_union_readdir_hook) {
-	extern struct vnode *union_dircache __P((struct vnode *));
+		struct vnode *ovp = vp;
 
-	if (count == auio.uio_resid && (vp->v_op == union_vnodeop_p)) {
+		error = (*vn_union_readdir_hook)(&vp, fp, p);
-		struct vnode *lvp;
-
-		lvp = union_dircache(vp);
-		if (lvp != NULLVP) {
-			struct vattr va;
-
-			/*
-			 * If the directory is opaque,
-			 * then don't show lower entries
-			 */
-			error = VOP_GETATTR(vp, &va, fp->f_cred, p);
-			if (va.va_flags & OPAQUE) {
-				vput(lvp);
-				lvp = NULL;
-			}
-		}
-		
-		if (lvp != NULLVP) {
-			error = VOP_OPEN(lvp, FREAD, fp->f_cred, p);
-			if (error) {
-				vput(lvp);
-				return (error);
-			}
-			VOP_UNLOCK(lvp, 0);
-			fp->f_data = (caddr_t) lvp;
-			fp->f_offset = 0;
-			error = vn_close(vp, FREAD, fp->f_cred, p);
 		if (error)
 			return (error);
-			vp = lvp;
+		if (vp != ovp)
 			goto unionread;
 	}
-	}
+#endif /* UNION || LKM */
-}
-#endif /* UNION */
 
 	if (count == auio.uio_resid && (vp->v_flag & VROOT) &&
 	    (vp->v_mount->mnt_flag & MNT_UNION)) {

sys/sys/vnode.h

@@ -1,4 +1,4 @@
-/*	$NetBSD: vnode.h,v 1.105 2003/03/17 09:06:40 jdolecek Exp $	*/
+/*	$NetBSD: vnode.h,v 1.106 2003/03/17 09:11:29 jdolecek Exp $	*/
 
 /*
  * Copyright (c) 1989, 1993
@@ -440,6 +440,11 @@ extern struct vnodeop_desc	*vnodeop_descs[];
  */
 extern struct simplelock	mntvnode_slock;
 
+/*
+ * Union filesystem hook for vn_readdir().
+ */
+extern int (*vn_union_readdir_hook) (struct vnode **, struct file *, struct proc *);
+
 /*
  * This macro is very helpful in defining those offsets in the vdesc struct.
  *