new files to support layered file systems. to be used in a bit.

mostly from work by Bill Studenmund - wrstuden at netbsd

5 files changed, 1925 insertions, 0 deletions

diff --git a/sys/miscfs/genfs/layer.h b/sys/miscfs/genfs/layer.h
new file mode 100644
index 00000000000..c2e4451c16e
--- /dev/null
+++ b/sys/miscfs/genfs/layer.h
@@ -0,0 +1,167 @@
+/*	$OpenBSD: layer.h,v 1.1 2003/05/12 20:58:40 tedu Exp $ */
+/*	$NetBSD: layer.h,v 1.4 2001/06/07 13:32:46 wiz Exp $	*/
+
+/*
+ * Copyright (c) 1999 National Aeronautics & Space Administration
+ * All rights reserved.
+ *
+ * This software was written by William Studenmund of the
+ * Numerical Aerospace Simulation Facility, NASA Ames Research Center.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the National Aeronautics & Space Administration
+ *    nor the names of its contributors may be used to endorse or promote
+ *    products derived from this software without specific prior written
+ *    permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NATIONAL AERONAUTICS & SPACE ADMINISTRATION
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE ADMINISTRATION OR CONTRIB-
+ * UTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
+ * OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/*
+ * Copyright (c) 1992, 1993
+ *	The Regents of the University of California.  All rights reserved.
+ *
+ * This code is derived from software donated to Berkeley by
+ * Jan-Simon Pendry.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ *    must display the following acknowledgement:
+ *	This product includes software developed by the University of
+ *	California, Berkeley and its contributors.
+ * 4. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ *	from: Id: lofs.h,v 1.8 1992/05/30 10:05:43 jsp Exp
+ *	@(#)null.h	8.2 (Berkeley) 1/21/94
+ */
+
+#ifndef _MISCFS_GENFS_LAYER_H_
+#define _MISCFS_GENFS_LAYER_H_
+
+struct layer_args {
+	char	*target;		/* Target of loopback  */
+	struct	export_args	export;	/* network export info */
+};
+
+#ifdef _KERNEL
+
+struct layer_node;
+
+LIST_HEAD(layer_node_hashhead, layer_node);
+
+struct layer_mount {
+	struct mount		*layerm_vfs;
+	struct vnode		*layerm_rootvp;	/* Ref to root layer_node */
+	struct netexport	layerm_export;	/* export info */
+	u_int			layerm_flags;	/* mount point layer flags */
+	u_int			layerm_size;	/* size of fs's struct node */
+	enum vtype		layerm_tag;	/* vtag of our vnodes */
+	int				/* bypass routine for this mount */
+				(*layerm_bypass)(void *);
+	int			(*layerm_alloc)	/* alloc a new layer node */
+				(struct mount *, struct vnode *,
+				    struct vnode **);
+	int			/* ops for our nodes */
+				(**layerm_vnodeop_p)(void *);
+	struct layer_node_hashhead	/* head of hash list for layer_nodes */
+				*layerm_node_hashtbl;
+	u_long			layerm_node_hash; /* hash mask for hash chain */
+	struct simplelock	layerm_hashlock; /* interlock for hash chain. */
+};
+
+#define	LAYERFS_MFLAGS		0x00000fff	/* reserved layer mount flags */
+#define	LAYERFS_MBYPASSDEBUG	0x00000001
+
+/*
+ * A cache of vnode references
+ */
+struct layer_node {
+	LIST_ENTRY(layer_node)	layer_hash;	/* Hash list */
+	struct vnode	        *layer_lowervp;	/* VREFed once */
+	struct vnode		*layer_vnode;	/* Back pointer */
+	unsigned int		layer_flags;	/* locking, etc. */
+};
+
+#define	LAYERFS_RESFLAGS	0x00000fff	/* flags reserved for layerfs */
+
+/*
+ * The following macros handle upperfs-specific locking. They are needed
+ * when the lowerfs does not export a struct lock for locking use by the
+ * upper layers. These macros are inteded for adjusting the upperfs
+ * struct lock to reflect changes in the underlying vnode's lock state.
+ */
+#define	LAYERFS_UPPERLOCK(v, f, r)	do { \
+	if ((v)->v_vnlock == NULL) \
+		r = lockmgr(&(v)->v_lock, (f), &(v)->v_interlock, curproc); \
+	else \
+		r = 0; \
+	} while (0)
+
+#define	LAYERFS_UPPERUNLOCK(v, f, r)	do { \
+	if ((v)->v_vnlock == NULL) \
+	    r = lockmgr(&(v)->v_lock, (f) | LK_RELEASE, &(v)->v_interlock, curproc); \
+	else \
+		r = 0; \
+	} while (0)
+
+#define	LAYERFS_UPPERISLOCKED(v, r)	do { \
+	if ((v)->v_vnlock == NULL) \
+		r = lockstatus(&(v)->v_lock); \
+	else \
+		r = -1; \
+	} while (0)
+
+#define	LAYERFS_DO_BYPASS(vp, ap)	\
+	(*MOUNTTOLAYERMOUNT((vp)->v_mount)->layerm_bypass)((ap))
+
+extern struct vnode *layer_checkvp(struct vnode *vp, char *fil, int lno);
+
+#define	MOUNTTOLAYERMOUNT(mp) ((struct layer_mount *)((mp)->mnt_data))
+#define	VTOLAYER(vp) ((struct layer_node *)(vp)->v_data)
+#define	LAYERTOV(xp) ((xp)->layer_vnode)
+#ifdef LAYERFS_DIAGNOSTIC
+#define	LAYERVPTOLOWERVP(vp) layer_checkvp((vp), __FILE__, __LINE__)
+#else
+#define	LAYERVPTOLOWERVP(vp) (VTOLAYER(vp)->layer_lowervp)
+#endif
+
+#endif /* _KERNEL */
+#endif /* _MISCFS_GENFS_LAYER_H_ */
diff --git a/sys/miscfs/genfs/layer_extern.h b/sys/miscfs/genfs/layer_extern.h
new file mode 100644
index 00000000000..892b637f0a7
--- /dev/null
+++ b/sys/miscfs/genfs/layer_extern.h
@@ -0,0 +1,122 @@
+/*	$OpenBSD: layer_extern.h,v 1.1 2003/05/12 20:58:40 tedu Exp $ */
+/*	$NetBSD: layer_extern.h,v 1.5 2001/12/06 04:29:23 chs Exp $	*/
+
+/*
+ * Copyright (c) 1999 National Aeronautics & Space Administration
+ * All rights reserved.
+ *
+ * This software was written by William Studenmund of the
+ * Numerical Aerospace Simulation Facility, NASA Ames Research Center.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the National Aeronautics & Space Administration
+ *    nor the names of its contributors may be used to endorse or promote
+ *    products derived from this software without specific prior written
+ *    permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NATIONAL AERONAUTICS & SPACE ADMINISTRATION
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE ADMINISTRATION OR CONTRIB-
+ * UTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
+ * OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+/*
+ * Copyright (c) 1992, 1993, 1995
+ *	The Regents of the University of California.  All rights reserved.
+ *
+ * This code is derived from software donated to Berkeley by
+ * Jan-Simon Pendry.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ *    must display the following acknowledgement:
+ *	This product includes software developed by the University of
+ *	California, Berkeley and its contributors.
+ * 4. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ */
+
+/*
+ * Routines defined by layerfs
+ */
+
+/* misc routines in layer_subr.c */
+int	layerfs_init(struct vfsconf *);
+void	layerfs_done(void);
+int	layer_node_alloc(struct mount *, struct vnode *, struct vnode **);
+int	layer_node_create(struct mount *, struct vnode *, struct vnode **);
+struct vnode *
+	layer_node_find(struct mount *, struct vnode *);
+#define LOG2_SIZEVNODE	7		/* log2(sizeof struct vnode) */
+#define LAYER_NHASH(lmp, vp) \
+	(&((lmp)->layerm_node_hashtbl[(((u_long)vp)>>LOG2_SIZEVNODE) & \
+		(lmp)->layerm_node_hash]))
+
+/* vfs routines */
+int	layerfs_start(struct mount *, int, struct proc *);
+int	layerfs_root(struct mount *, struct vnode **);
+int	layerfs_quotactl(struct mount *, int, uid_t, caddr_t,
+			     struct proc *);
+int	layerfs_statfs(struct mount *, struct statfs *, struct proc *);
+int	layerfs_sync(struct mount *, int, struct ucred *, struct proc *);
+int	layerfs_vget(struct mount *, ino_t, struct vnode **);
+int	layerfs_fhtovp(struct mount *, struct fid *, struct vnode **);
+int	layerfs_checkexp(struct mount *, struct mbuf *, int *,
+	    struct ucred **);
+int	layerfs_vptofh(struct vnode *, struct fid *);
+int	layerfs_sysctl(int *, u_int, void *, size_t *, void *, size_t,
+	   struct proc *);
+
+/* VOP routines */
+int	layer_bypass(void *);
+int	layer_getattr(void *);
+int	layer_inactive(void *);
+int	layer_reclaim(void *);
+int	layer_print(void *);
+int	layer_strategy(void *);
+int	layer_bwrite(void *);
+int	layer_bmap(void *);
+int	layer_lock(void *);
+int	layer_unlock(void *);
+int	layer_islocked(void *);
+int	layer_fsync(void *);
+int	layer_lookup(void *);
+int	layer_setattr(void *);
+int	layer_access(void *);
+int	layer_open(void *);
+int	layer_getpages(void *);
+int	layer_putpages(void *);
diff --git a/sys/miscfs/genfs/layer_subr.c b/sys/miscfs/genfs/layer_subr.c
new file mode 100644
index 00000000000..5b5ed9eaaac
--- /dev/null
+++ b/sys/miscfs/genfs/layer_subr.c
@@ -0,0 +1,401 @@
+/*	$OpenBSD: layer_subr.c,v 1.1 2003/05/12 20:58:40 tedu Exp $ */
+/*	$NetBSD: layer_subr.c,v 1.11 2002/02/20 06:16:22 enami Exp $	*/
+
+/*
+ * Copyright (c) 1999 National Aeronautics & Space Administration
+ * All rights reserved.
+ *
+ * This software was written by William Studenmund of the
+ * Numerical Aerospace Simulation Facility, NASA Ames Research Center.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the National Aeronautics & Space Administration
+ *    nor the names of its contributors may be used to endorse or promote
+ *    products derived from this software without specific prior written
+ *    permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NATIONAL AERONAUTICS & SPACE ADMINISTRATION
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE ADMINISTRATION OR CONTRIB-
+ * UTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
+ * OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+/*
+ * Copyright (c) 1992, 1993
+ *	The Regents of the University of California.  All rights reserved.
+ *
+ * This code is derived from software donated to Berkeley by
+ * Jan-Simon Pendry.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ *    must display the following acknowledgement:
+ *	This product includes software developed by the University of
+ *	California, Berkeley and its contributors.
+ * 4. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ *	from: Id: lofs_subr.c,v 1.11 1992/05/30 10:05:43 jsp Exp
+ *	@(#)null_subr.c	8.7 (Berkeley) 5/14/95
+ */
+
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/proc.h>
+#include <sys/time.h>
+#include <sys/vnode.h>
+#include <sys/mount.h>
+#include <sys/namei.h>
+#include <sys/malloc.h>
+#include <miscfs/specfs/specdev.h>
+#include <miscfs/genfs/layer.h>
+#include <miscfs/genfs/layer_extern.h>
+
+#define	NLAYERNODECACHE 16
+
+/*
+ * layer cache:
+ * Each cache entry holds a reference to the lower vnode
+ * along with a pointer to the alias vnode.  When an
+ * entry is added the lower vnode is VREF'd.  When the
+ * alias is removed the lower vnode is vrele'd.
+ */
+
+/*
+ * Initialise cache headers
+ */
+int
+layerfs_init(struct vfsconf *v)
+{
+#ifdef LAYERFS_DIAGNOSTIC
+	printf("layerfs_init\n");		/* printed during system boot */
+#endif
+	return (0);
+}
+
+/*
+ * Free global resources of layerfs.
+ */
+void
+layerfs_done()
+{
+#ifdef LAYERFS_DIAGNOSTIC
+	printf("layerfs_done\n");		/* printed on layerfs detach */
+#endif
+}
+
+/*
+ * Return a locked, VREF'ed alias for lower vnode if already exists, else 0.
+ */
+struct vnode *
+layer_node_find(mp, lowervp)
+	struct mount *mp;
+	struct vnode *lowervp;
+{
+	struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp);
+	struct layer_node_hashhead *hd;
+	struct layer_node *a;
+	struct vnode *vp;
+
+	/*
+	 * Find hash base, and then search the (two-way) linked
+	 * list looking for a layer_node structure which is referencing
+	 * the lower vnode.  If found, the increment the layer_node
+	 * reference count (but NOT the lower vnode's VREF counter)
+	 * and return the vnode locked.
+	 */
+	hd = LAYER_NHASH(lmp, lowervp);
+loop:
+	simple_lock(&lmp->layerm_hashlock);
+	for (a = hd->lh_first; a != 0; a = a->layer_hash.le_next) {
+		if (a->layer_lowervp == lowervp && LAYERTOV(a)->v_mount == mp) {
+			vp = LAYERTOV(a);
+			simple_unlock(&lmp->layerm_hashlock);
+			/*
+			 * We must be careful here as the fact the lower
+			 * vnode is locked will imply vp is locked unless
+			 * someone has decided to start vclean'ing either
+			 * vp or lowervp.
+			 *
+			 * So we try for an exclusive, recursive lock
+			 * on the upper vnode. If it fails, vcleaning
+			 * is in progress (so when we try again, we'll
+			 * fail). If it succeeds, we now have double
+			 * locked the bottom node. So we do an explicit
+			 * VOP_UNLOCK on it to keep the counts right. Note
+			 * that we will end up with the upper node and
+			 * the lower node locked once.
+			 */
+			if (vget(vp, LK_EXCLUSIVE | LK_CANRECURSE, curproc)) {
+				printf ("layer_node_find: vget failed.\n");
+				goto loop;
+			}
+			VOP_UNLOCK(lowervp, 0, curproc);
+			return (vp);
+		}
+	}
+
+	simple_unlock(&lmp->layerm_hashlock);
+	return NULL;
+}
+
+
+/*
+ * Make a new layer_node node.
+ * Vp is the alias vnode, lowervp is the lower vnode.
+ * Maintain a reference to lowervp.
+ */
+int
+layer_node_alloc(mp, lowervp, vpp)
+	struct mount *mp;
+	struct vnode *lowervp;
+	struct vnode **vpp;
+{
+	struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp);
+	struct layer_node_hashhead *hd;
+	struct layer_node *xp;
+	struct vnode *vp, *nvp;
+	int error;
+	extern int (**dead_vnodeop_p)(void *);
+
+	if ((error = getnewvnode(lmp->layerm_tag, mp, lmp->layerm_vnodeop_p,
+			&vp)) != 0)
+		return (error);
+	vp->v_type = lowervp->v_type;
+	vp->v_flag |= VLAYER;
+
+	xp = malloc(lmp->layerm_size, M_TEMP, M_WAITOK);
+	if (vp->v_type == VBLK || vp->v_type == VCHR) {
+		MALLOC(vp->v_specinfo, struct specinfo *,
+		    sizeof(struct specinfo), M_VNODE, M_WAITOK);
+		vp->v_hashchain = NULL;
+		vp->v_rdev = lowervp->v_rdev;
+	}
+
+	vp->v_data = xp;
+	xp->layer_vnode = vp;
+	xp->layer_lowervp = lowervp;
+	xp->layer_flags = 0;
+	/*
+	 * Before we insert our new node onto the hash chains,
+	 * check to see if someone else has beaten us to it.
+	 * (We could have slept in MALLOC.)
+	 */
+	if ((nvp = layer_node_find(mp, lowervp)) != NULL) {
+		*vpp = nvp;
+
+		/* free the substructures we've allocated. */
+		FREE(xp, M_TEMP);
+		if (vp->v_type == VBLK || vp->v_type == VCHR)
+			FREE(vp->v_specinfo, M_VNODE);
+
+		vp->v_type = VBAD;		/* node is discarded */
+		vp->v_op = dead_vnodeop_p;	/* so ops will still work */
+		vrele(vp);			/* get rid of it. */
+		return (0);
+	}
+
+	simple_lock(&lmp->layerm_hashlock);
+
+	/*
+	 * Now lock the new node. We rely on the fact that we were passed
+	 * a locked vnode. If the lower node is exporting a struct lock
+	 * (v_vnlock != NULL) then we just set the upper v_vnlock to the
+	 * lower one, and both are now locked. If the lower node is exporting
+	 * NULL, then we copy that up and manually lock the upper node.
+	 *
+	 * LAYERFS_UPPERLOCK already has the test, so we use it after copying
+	 * up the v_vnlock from below.
+	 */
+
+	vp->v_vnlock = lowervp->v_vnlock;
+	LAYERFS_UPPERLOCK(vp, LK_EXCLUSIVE, error);
+
+	if (error) {
+		/*
+		 * How did we get a locking error? The node just came off
+		 * of the free list, and we're the only routine which
+		 * knows it's there...
+		 */
+		vp->v_vnlock = &vp->v_lock;
+		*vpp = NULL;
+
+		/* free the substructures we've allocated. */
+		FREE(xp, M_TEMP);
+		if (vp->v_type == VBLK || vp->v_type == VCHR)
+			FREE(vp->v_specinfo, M_VNODE);
+
+		vp->v_type = VBAD;		/* node is discarded */
+		vp->v_op = dead_vnodeop_p;	/* so ops will still work */
+		vrele(vp);			/* get rid of it. */
+		return (error);
+	}
+	/*
+	 * NetBSD used to do an inlined checkalias here. We do not, as
+	 * we never flag device nodes as being aliased. The lowervp
+	 * node will, when appropriate, be flaged as an alias.
+	 */
+
+	*vpp = vp;
+	VREF(lowervp);	/* Take into account reference held in layer_node */
+	hd = LAYER_NHASH(lmp, lowervp);
+	LIST_INSERT_HEAD(hd, xp, layer_hash);
+	uvm_vnp_setsize(vp, 0);
+	simple_unlock(&lmp->layerm_hashlock);
+	return (0);
+}
+
+
+/*
+ * Try to find an existing layer_node vnode refering
+ * to it, otherwise make a new layer_node vnode which
+ * contains a reference to the lower vnode.
+ *
+ * >>> we assume that the lower node is already locked upon entry, so we
+ * propagate the lock state to upper node <<
+ */
+int
+layer_node_create(mp, lowervp, newvpp)
+	struct mount *mp;
+	struct vnode *lowervp;
+	struct vnode **newvpp;
+{
+	struct vnode *aliasvp;
+	struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp);
+
+	if ((aliasvp = layer_node_find(mp, lowervp)) != NULL) {
+		/*
+		 * layer_node_find has taken another reference
+		 * to the alias vnode and moved the lock holding to
+		 * aliasvp
+		 */
+#ifdef LAYERFS_DIAGNOSTIC
+		vprint("layer_node_create: exists", aliasvp);
+#endif
+	} else {
+		int error;
+
+		/*
+		 * Get new vnode.
+		 */
+#ifdef LAYERFS_DIAGNOSTIC
+		printf("layer_node_create: create new alias vnode\n");
+#endif
+
+		/*
+		 * Make new vnode reference the layer_node.
+		 */
+		if ((error = (lmp->layerm_alloc)(mp, lowervp, &aliasvp)) != 0)
+			return error;
+
+		/*
+		 * aliasvp is already VREF'd by getnewvnode()
+		 */
+	}
+
+	/*
+	 * Now that we have VREF'd the upper vnode, release the reference
+	 * to the lower node. The existance of the layer_node retains one
+	 * reference to the lower node.
+	 */
+	vrele(lowervp);
+
+#ifdef DIAGNOSTIC
+	if (lowervp->v_usecount < 1) {
+		/* Should never happen... */
+		vprint("layer_node_create: alias", aliasvp);
+		vprint("layer_node_create: lower", lowervp);
+		panic("layer_node_create: lower has 0 usecount.");
+	}
+#endif
+
+#ifdef LAYERFS_DIAGNOSTIC
+	vprint("layer_node_create: alias", aliasvp);
+#endif
+	*newvpp = aliasvp;
+	return (0);
+}
+
+struct vnode *
+layer_checkvp(vp, fil, lno)
+	struct vnode *vp;
+	char *fil;
+	int lno;
+{
+	struct layer_node *a = VTOLAYER(vp);
+#ifdef notyet
+	/*
+	 * Can't do this check because vop_reclaim runs
+	 * with a funny vop vector.
+	 *
+	 * WRS - no it doesnt...
+	 */
+	if (vp->v_op != layer_vnodeop_p) {
+		printf ("layer_checkvp: on non-layer-node\n");
+#ifdef notyet
+		while (layer_checkvp_barrier) /*WAIT*/ ;
+#endif
+		panic("layer_checkvp");
+	}
+#endif
+	if (a->layer_lowervp == NULL) {
+		/* Should never happen */
+		int i; u_long *p;
+		printf("vp = %p, ZERO ptr\n", vp);
+		for (p = (u_long *) a, i = 0; i < 8; i++)
+			printf(" %lx", p[i]);
+		printf("\n");
+		/* wait for debugger */
+		panic("layer_checkvp");
+	}
+	if (a->layer_lowervp->v_usecount < 1) {
+		int i; u_long *p;
+		printf("vp = %p, unref'ed lowervp\n", vp);
+		for (p = (u_long *) a, i = 0; i < 8; i++)
+			printf(" %lx", p[i]);
+		printf("\n");
+		/* wait for debugger */
+		panic ("layer with unref'ed lowervp");
+	}
+#ifdef notnow
+	printf("layer %p/%d -> %p/%d [%s, %d]\n",
+	        LAYERTOV(a), LAYERTOV(a)->v_usecount,
+		a->layer_lowervp, a->layer_lowervp->v_usecount,
+		fil, lno);
+#endif
+	return a->layer_lowervp;
+}
diff --git a/sys/miscfs/genfs/layer_vfsops.c b/sys/miscfs/genfs/layer_vfsops.c
new file mode 100644
index 00000000000..68970c8ca8f
--- /dev/null
+++ b/sys/miscfs/genfs/layer_vfsops.c
@@ -0,0 +1,285 @@
+/*	$OpenBSD: layer_vfsops.c,v 1.1 2003/05/12 20:58:40 tedu Exp $ */
+/*	$NetBSD: layer_vfsops.c,v 1.5 2001/11/15 09:48:21 lukem Exp $	*/
+
+/*
+ * Copyright (c) 1999 National Aeronautics & Space Administration
+ * All rights reserved.
+ *
+ * This software was written by William Studenmund of the
+ * Numerical Aerospace Simulation Facility, NASA Ames Research Center.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the National Aeronautics & Space Administration
+ *    nor the names of its contributors may be used to endorse or promote
+ *    products derived from this software without specific prior written
+ *    permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NATIONAL AERONAUTICS & SPACE ADMINISTRATION
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE ADMINISTRATION OR CONTRIB-
+ * UTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
+ * OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+/*
+ * Copyright (c) 1992, 1993, 1995
+ *	The Regents of the University of California.  All rights reserved.
+ *
+ * This code is derived from software donated to Berkeley by
+ * Jan-Simon Pendry.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ *    must display the following acknowledgement:
+ *	This product includes software developed by the University of
+ *	California, Berkeley and its contributors.
+ * 4. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ *	from: Id: lofs_vfsops.c,v 1.9 1992/05/30 10:26:24 jsp Exp
+ *	from: @(#)lofs_vfsops.c	1.2 (Berkeley) 6/18/92
+ *	@(#)null_vfsops.c	8.7 (Berkeley) 5/14/95
+ */
+
+/*
+ * generic layer vfs ops.
+ */
+
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/time.h>
+#include <sys/proc.h>
+#include <sys/vnode.h>
+#include <sys/mount.h>
+#include <sys/namei.h>
+#include <sys/malloc.h>
+#include <miscfs/genfs/layer.h>
+#include <miscfs/genfs/layer_extern.h>
+
+/*
+ * VFS start.  Nothing needed here - the start routine
+ * on the underlying filesystem will have been called
+ * when that filesystem was mounted.
+ */
+int
+layerfs_start(mp, flags, p)
+	struct mount *mp;
+	int flags;
+	struct proc *p;
+{
+
+	return (0);
+	/* return VFS_START(MOUNTTOLAYERMOUNT(mp)->layerm_vfs, flags, p); */
+}
+
+int
+layerfs_root(mp, vpp)
+	struct mount *mp;
+	struct vnode **vpp;
+{
+	struct vnode *vp;
+
+#ifdef LAYERFS_DIAGNOSTIC
+	printf("layerfs_root(mp = %p, vp = %p->%p)\n", mp,
+	    MOUNTTOLAYERMOUNT(mp)->layerm_rootvp,
+	    LAYERVPTOLOWERVP(MOUNTTOLAYERMOUNT(mp)->layerm_rootvp));
+#endif
+
+	/*
+	 * Return locked reference to root.
+	 */
+	vp = MOUNTTOLAYERMOUNT(mp)->layerm_rootvp;
+	if (vp == NULL) {
+		*vpp = NULL;
+		return (EINVAL);
+	}
+	VREF(vp);
+	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, curproc);
+	*vpp = vp;
+	return 0;
+}
+
+int
+layerfs_quotactl(mp, cmd, uid, arg, p)
+	struct mount *mp;
+	int cmd;
+	uid_t uid;
+	caddr_t arg;
+	struct proc *p;
+{
+
+	return VFS_QUOTACTL(MOUNTTOLAYERMOUNT(mp)->layerm_vfs,
+				cmd, uid, arg, p);
+}
+
+int
+layerfs_statfs(mp, sbp, p)
+	struct mount *mp;
+	struct statfs *sbp;
+	struct proc *p;
+{
+	int error;
+	struct statfs mstat;
+
+#ifdef LAYERFS_DIAGNOSTIC
+	printf("layerfs_statfs(mp = %p, vp = %p->%p)\n", mp,
+	    MOUNTTOLAYERMOUNT(mp)->layerm_rootvp,
+	    LAYERVPTOLOWERVP(MOUNTTOLAYERMOUNT(mp)->layerm_rootvp));
+#endif
+
+	memset(&mstat, 0, sizeof(mstat));
+
+	error = VFS_STATFS(MOUNTTOLAYERMOUNT(mp)->layerm_vfs, &mstat, p);
+	if (error)
+		return (error);
+
+	/* now copy across the "interesting" information and fake the rest */
+	sbp->f_flags = mstat.f_flags;
+	sbp->f_bsize = mstat.f_bsize;
+	sbp->f_iosize = mstat.f_iosize;
+	sbp->f_blocks = mstat.f_blocks;
+	sbp->f_bfree = mstat.f_bfree;
+	sbp->f_bavail = mstat.f_bavail;
+	sbp->f_files = mstat.f_files;
+	sbp->f_ffree = mstat.f_ffree;
+	if (sbp != &mp->mnt_stat) {
+		memcpy(&sbp->f_fsid, &mp->mnt_stat.f_fsid, sizeof(sbp->f_fsid));
+		memcpy(sbp->f_mntonname, mp->mnt_stat.f_mntonname, MNAMELEN);
+		memcpy(sbp->f_mntfromname, mp->mnt_stat.f_mntfromname, MNAMELEN);
+	}
+	strncpy(sbp->f_fstypename, mp->mnt_vfc->vfc_name, MFSNAMELEN);
+	return (0);
+}
+
+int
+layerfs_sync(mp, waitfor, cred, p)
+	struct mount *mp;
+	int waitfor;
+	struct ucred *cred;
+	struct proc *p;
+{
+
+	/*
+	 * XXX - Assumes no data cached at layer.
+	 */
+	return (0);
+}
+
+int
+layerfs_vget(mp, ino, vpp)
+	struct mount *mp;
+	ino_t ino;
+	struct vnode **vpp;
+{
+	int error;
+	struct vnode *vp;
+
+	if ((error = VFS_VGET(MOUNTTOLAYERMOUNT(mp)->layerm_vfs, ino, &vp))) {
+		*vpp = NULL;
+		return (error);
+	}
+	if ((error = layer_node_create(mp, vp, vpp))) {
+		vput(vp);
+		*vpp = NULL;
+		return (error);
+	}
+
+	return (0);
+}
+
+int
+layerfs_fhtovp(mp, fidp, vpp)
+	struct mount *mp;
+	struct fid *fidp;
+	struct vnode **vpp;
+{
+	int error;
+	struct vnode *vp;
+
+	if ((error = VFS_FHTOVP(MOUNTTOLAYERMOUNT(mp)->layerm_vfs, fidp, &vp)))
+		return (error);
+
+	if ((error = layer_node_create(mp, vp, vpp))) {
+		vput(vp);
+		*vpp = NULL;
+		return (error);
+	}
+
+	return (0);
+}
+
+int
+layerfs_checkexp(mp, nam, exflagsp, credanonp)
+	struct mount *mp;
+	struct mbuf *nam;
+	int *exflagsp;
+	struct ucred**credanonp;
+{
+	struct	netcred *np;
+	struct	layer_mount *lmp = MOUNTTOLAYERMOUNT(mp);
+
+	/*
+	 * get the export permission structure for this <mp, client> tuple.
+	 */
+	if ((np = vfs_export_lookup(mp, &lmp->layerm_export, nam)) == NULL)
+		return (EACCES);
+
+	*exflagsp = np->netc_exflags;
+	*credanonp = &np->netc_anon;
+	return (0);
+}
+
+int
+layerfs_vptofh(vp, fhp)
+	struct vnode *vp;
+	struct fid *fhp;
+{
+
+	return (VFS_VPTOFH(LAYERVPTOLOWERVP(vp), fhp));
+}
+
+int
+layerfs_sysctl(name, namelen, oldp, oldlenp, newp, newlen, p)
+	int *name;
+	u_int namelen;
+	void *oldp;
+	size_t *oldlenp;
+	void *newp;
+	size_t newlen;
+	struct proc *p;
+{
+	return (EOPNOTSUPP);
+}
diff --git a/sys/miscfs/genfs/layer_vnops.c b/sys/miscfs/genfs/layer_vnops.c
new file mode 100644
index 00000000000..2b644098d09
--- /dev/null
+++ b/sys/miscfs/genfs/layer_vnops.c
@@ -0,0 +1,950 @@
+/*	$OpenBSD: layer_vnops.c,v 1.1 2003/05/12 20:58:40 tedu Exp $ */
+/*	$NetBSD: layer_vnops.c,v 1.10 2001/12/06 04:29:23 chs Exp $	*/
+
+/*
+ * Copyright (c) 1999 National Aeronautics & Space Administration
+ * All rights reserved.
+ *
+ * This software was written by William Studenmund of the
+ * Numerical Aerospace Simulation Facility, NASA Ames Research Center.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the National Aeronautics & Space Administration
+ *    nor the names of its contributors may be used to endorse or promote
+ *    products derived from this software without specific prior written
+ *    permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NATIONAL AERONAUTICS & SPACE ADMINISTRATION
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE ADMINISTRATION OR CONTRIB-
+ * UTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
+ * OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+/*
+ * Copyright (c) 1992, 1993
+ *	The Regents of the University of California.  All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * John Heidemann of the UCLA Ficus project.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ *    must display the following acknowledgement:
+ *	This product includes software developed by the University of
+ *	California, Berkeley and its contributors.
+ * 4. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ *	@(#)null_vnops.c	8.6 (Berkeley) 5/27/95
+ *
+ * Ancestors:
+ *	@(#)lofs_vnops.c	1.2 (Berkeley) 6/18/92
+ *	$Id: layer_vnops.c,v 1.1 2003/05/12 20:58:40 tedu Exp $
+ *	...and...
+ *	@(#)null_vnodeops.c 1.20 92/07/07 UCLA Ficus project
+ */
+
+/*
+ * Null Layer vnode routines.
+ *
+ * (See mount_null(8) for more information.)
+ *
+ * The layer.h, layer_extern.h, layer_vfs.c, and layer_vnops.c files provide
+ * the core implimentation of the null file system and most other stacked
+ * fs's. The description below refers to the null file system, but the
+ * services provided by the layer* files are useful for all layered fs's.
+ *
+ * The null layer duplicates a portion of the file system
+ * name space under a new name.  In this respect, it is
+ * similar to the loopback file system.  It differs from
+ * the loopback fs in two respects:  it is implemented using
+ * a stackable layers techniques, and it's "null-node"s stack above
+ * all lower-layer vnodes, not just over directory vnodes.
+ *
+ * The null layer has two purposes.  First, it serves as a demonstration
+ * of layering by proving a layer which does nothing.  (It actually
+ * does everything the loopback file system does, which is slightly
+ * more than nothing.)  Second, the null layer can serve as a prototype
+ * layer.  Since it provides all necessary layer framework,
+ * new file system layers can be created very easily be starting
+ * with a null layer.
+ *
+ * The remainder of the man page examines the null layer as a basis
+ * for constructing new layers.
+ *
+ *
+ * INSTANTIATING NEW NULL LAYERS
+ *
+ * New null layers are created with mount_null(8).
+ * Mount_null(8) takes two arguments, the pathname
+ * of the lower vfs (target-pn) and the pathname where the null
+ * layer will appear in the namespace (alias-pn).  After
+ * the null layer is put into place, the contents
+ * of target-pn subtree will be aliased under alias-pn.
+ *
+ * It is conceivable that other overlay filesystems will take different
+ * parameters. For instance, data migration or access controll layers might
+ * only take one pathname which will serve both as the target-pn and
+ * alias-pn described above.
+ *
+ *
+ * OPERATION OF A NULL LAYER
+ *
+ * The null layer is the minimum file system layer,
+ * simply bypassing all possible operations to the lower layer
+ * for processing there.  The majority of its activity centers
+ * on the bypass routine, though which nearly all vnode operations
+ * pass.
+ *
+ * The bypass routine accepts arbitrary vnode operations for
+ * handling by the lower layer.  It begins by examing vnode
+ * operation arguments and replacing any layered nodes by their
+ * lower-layer equivlants.  It then invokes the operation
+ * on the lower layer.  Finally, it replaces the layered nodes
+ * in the arguments and, if a vnode is return by the operation,
+ * stacks a layered node on top of the returned vnode.
+ *
+ * The bypass routine in this file, layer_bypass(), is suitable for use
+ * by many different layered filesystems. It can be used by multiple
+ * filesystems simultaneously. Alternatively, a layered fs may provide
+ * its own bypass routine, in which case layer_bypass() should be used as
+ * a model. For instance, the main functionality provided by umapfs, the user
+ * identity mapping file system, is handled by a custom bypass routine.
+ *
+ * Typically a layered fs registers its selected bypass routine as the
+ * default vnode operation in its vnodeopv_entry_desc table. Additionally
+ * the filesystem must store the bypass entry point in the layerm_bypass
+ * field of struct layer_mount. All other layer routines in this file will
+ * use the layerm_bypass routine.
+ *
+ * Although the bypass routine handles most operations outright, a number
+ * of operations are special cased, and handled by the layered fs. One
+ * group, layer_setattr, layer_getattr, layer_access, layer_open, and
+ * layer_fsync, perform layer-specific manipulation in addition to calling
+ * the bypass routine. The other group
+
+ * Although bypass handles most operations, vop_getattr, vop_lock,
+ * vop_unlock, vop_inactive, vop_reclaim, and vop_print are not
+ * bypassed. Vop_getattr must change the fsid being returned.
+ * Vop_lock and vop_unlock must handle any locking for the
+ * current vnode as well as pass the lock request down.
+ * Vop_inactive and vop_reclaim are not bypassed so that
+ * they can handle freeing null-layer specific data. Vop_print
+ * is not bypassed to avoid excessive debugging information.
+ * Also, certain vnode operations change the locking state within
+ * the operation (create, mknod, remove, link, rename, mkdir, rmdir,
+ * and symlink). Ideally these operations should not change the
+ * lock state, but should be changed to let the caller of the
+ * function unlock them. Otherwise all intermediate vnode layers
+ * (such as union, umapfs, etc) must catch these functions to do
+ * the necessary locking at their layer.
+ *
+ *
+ * INSTANTIATING VNODE STACKS
+ *
+ * Mounting associates the null layer with a lower layer,
+ * effect stacking two VFSes.  Vnode stacks are instead
+ * created on demand as files are accessed.
+ *
+ * The initial mount creates a single vnode stack for the
+ * root of the new null layer.  All other vnode stacks
+ * are created as a result of vnode operations on
+ * this or other null vnode stacks.
+ *
+ * New vnode stacks come into existance as a result of
+ * an operation which returns a vnode.  
+ * The bypass routine stacks a null-node above the new
+ * vnode before returning it to the caller.
+ *
+ * For example, imagine mounting a null layer with
+ * "mount_null /usr/include /dev/layer/null".
+ * Changing directory to /dev/layer/null will assign
+ * the root null-node (which was created when the null layer was mounted).
+ * Now consider opening "sys".  A vop_lookup would be
+ * done on the root null-node.  This operation would bypass through
+ * to the lower layer which would return a vnode representing 
+ * the UFS "sys".  layer_bypass then builds a null-node
+ * aliasing the UFS "sys" and returns this to the caller.
+ * Later operations on the null-node "sys" will repeat this
+ * process when constructing other vnode stacks.
+ *
+ *
+ * CREATING OTHER FILE SYSTEM LAYERS
+ *
+ * One of the easiest ways to construct new file system layers is to make
+ * a copy of the null layer, rename all files and variables, and
+ * then begin modifing the copy.  Sed can be used to easily rename
+ * all variables.
+ *
+ * The umap layer is an example of a layer descended from the 
+ * null layer.
+ *
+ *
+ * INVOKING OPERATIONS ON LOWER LAYERS
+ *
+ * There are two techniques to invoke operations on a lower layer 
+ * when the operation cannot be completely bypassed.  Each method
+ * is appropriate in different situations.  In both cases,
+ * it is the responsibility of the aliasing layer to make
+ * the operation arguments "correct" for the lower layer
+ * by mapping an vnode arguments to the lower layer.
+ *
+ * The first approach is to call the aliasing layer's bypass routine.
+ * This method is most suitable when you wish to invoke the operation
+ * currently being hanldled on the lower layer.  It has the advantage
+ * that the bypass routine already must do argument mapping.
+ * An example of this is null_getattrs in the null layer.
+ *
+ * A second approach is to directly invoked vnode operations on
+ * the lower layer with the VOP_OPERATIONNAME interface.
+ * The advantage of this method is that it is easy to invoke
+ * arbitrary operations on the lower layer.  The disadvantage
+ * is that vnodes arguments must be manualy mapped.
+ *
+ */
+
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/proc.h>
+#include <sys/time.h>
+#include <sys/vnode.h>
+#include <sys/mount.h>
+#include <sys/namei.h>
+#include <sys/malloc.h>
+#include <sys/buf.h>
+#include <miscfs/genfs/layer.h>
+#include <miscfs/genfs/layer_extern.h>
+
+
+/*
+ * This is the 08-June-99 bypass routine, based on the 10-Apr-92 bypass
+ *		routine by John Heidemann.
+ *	The new element for this version is that the whole nullfs
+ * system gained the concept of locks on the lower node, and locks on
+ * our nodes. When returning from a call to the lower layer, we may
+ * need to update lock state ONLY on our layer. The LAYERFS_UPPER*LOCK()
+ * macros provide this functionality.
+ *    The 10-Apr-92 version was optimized for speed, throwing away some
+ * safety checks.  It should still always work, but it's not as
+ * robust to programmer errors.
+ *    Define SAFETY to include some error checking code.
+ *
+ * In general, we map all vnodes going down and unmap them on the way back.
+ *
+ * Also, some BSD vnode operations have the side effect of vrele'ing
+ * their arguments.  With stacking, the reference counts are held
+ * by the upper node, not the lower one, so we must handle these
+ * side-effects here.  This is not of concern in Sun-derived systems
+ * since there are no such side-effects.
+ *
+ * New for the 08-June-99 version: we also handle operations which unlock
+ * the passed-in node (typically they vput the node).
+ *
+ * This makes the following assumptions:
+ * - only one returned vpp
+ * - no INOUT vpp's (Sun's vop_open has one of these)
+ * - the vnode operation vector of the first vnode should be used
+ *   to determine what implementation of the op should be invoked
+ * - all mapped vnodes are of our vnode-type (NEEDSWORK:
+ *   problems on rmdir'ing mount points and renaming?)
+ */ 
+int
+layer_bypass(v)
+	void *v;
+{
+	struct vop_generic_args /* {
+		struct vnodeop_desc *a_desc;
+		<other random data follows, presumably>
+	} */ *ap = v;
+	int (**our_vnodeop_p)(void *); 
+	struct vnode **this_vp_p;
+	int error, error1;
+	struct vnode *old_vps[VDESC_MAX_VPS], *vp0;
+	struct vnode **vps_p[VDESC_MAX_VPS];
+	struct vnode ***vppp;
+	struct vnodeop_desc *descp = ap->a_desc;
+	int reles, i, flags;
+
+#ifdef SAFETY
+	/*
+	 * We require at least one vp.
+	 */
+	if (descp->vdesc_vp_offsets == NULL ||
+	    descp->vdesc_vp_offsets[0] == VDESC_NO_OFFSET)
+		panic ("layer_bypass: no vp's in map.\n");
+#endif
+
+	vps_p[0] = VOPARG_OFFSETTO(struct vnode**,descp->vdesc_vp_offsets[0],ap);
+	vp0 = *vps_p[0];
+	flags = MOUNTTOLAYERMOUNT(vp0->v_mount)->layerm_flags;
+	our_vnodeop_p = vp0->v_op;
+
+	if (flags & LAYERFS_MBYPASSDEBUG)
+		printf ("layer_bypass: %s\n", descp->vdesc_name);
+
+	/*
+	 * Map the vnodes going in.
+	 * Later, we'll invoke the operation based on
+	 * the first mapped vnode's operation vector.
+	 */
+	reles = descp->vdesc_flags;
+	for (i = 0; i < VDESC_MAX_VPS; reles >>= 1, i++) {
+		if (descp->vdesc_vp_offsets[i] == VDESC_NO_OFFSET)
+			break;   /* bail out at end of list */
+		vps_p[i] = this_vp_p = 
+			VOPARG_OFFSETTO(struct vnode**,descp->vdesc_vp_offsets[i],ap);
+		/*
+		 * We're not guaranteed that any but the first vnode
+		 * are of our type.  Check for and don't map any
+		 * that aren't.  (We must always map first vp or vclean fails.)
+		 */
+		if (i && (*this_vp_p == NULL ||
+		    (*this_vp_p)->v_op != our_vnodeop_p)) {
+			old_vps[i] = NULL;
+		} else {
+			old_vps[i] = *this_vp_p;
+			*(vps_p[i]) = LAYERVPTOLOWERVP(*this_vp_p);
+			/*
+			 * XXX - Several operations have the side effect
+			 * of vrele'ing their vp's.  We must account for
+			 * that.  (This should go away in the future.)
+			 */
+			if (reles & VDESC_VP0_WILLRELE)
+				VREF(*this_vp_p);
+		}
+			
+	}
+
+	/*
+	 * Call the operation on the lower layer
+	 * with the modified argument structure.
+	 */
+	error = VCALL(*vps_p[0], descp->vdesc_offset, ap);
+
+	/*
+	 * Maintain the illusion of call-by-value
+	 * by restoring vnodes in the argument structure
+	 * to their original value.
+	 */
+	reles = descp->vdesc_flags;
+	for (i = 0; i < VDESC_MAX_VPS; reles >>= 1, i++) {
+		if (descp->vdesc_vp_offsets[i] == VDESC_NO_OFFSET)
+			break;   /* bail out at end of list */
+		if (old_vps[i]) {
+			*(vps_p[i]) = old_vps[i];
+			if (reles & VDESC_VP0_WILLUNLOCK)
+				LAYERFS_UPPERUNLOCK(*(vps_p[i]), 0, error1);
+			if (reles & VDESC_VP0_WILLRELE)
+				vrele(*(vps_p[i]));
+		}
+	}
+
+	/*
+	 * Map the possible out-going vpp
+	 * (Assumes that the lower layer always returns
+	 * a VREF'ed vpp unless it gets an error.)
+	 */
+	if (descp->vdesc_vpp_offset != VDESC_NO_OFFSET &&
+	    !(descp->vdesc_flags & VDESC_NOMAP_VPP) &&
+	    !error) {
+		/*
+		 * XXX - even though some ops have vpp returned vp's,
+		 * several ops actually vrele this before returning.
+		 * We must avoid these ops.
+		 * (This should go away when these ops are regularized.)
+		 */
+		if (descp->vdesc_flags & VDESC_VPP_WILLRELE)
+			goto out;
+		vppp = VOPARG_OFFSETTO(struct vnode***,
+		    descp->vdesc_vpp_offset,ap);
+		/*
+		 * Only vop_lookup, vop_create, vop_makedir, vop_bmap,
+		 * vop_mknod, and vop_symlink return vpp's. vop_bmap
+		 * doesn't call bypass as the lower vpp is fine (we're just
+		 * going to do i/o on it). vop_loookup doesn't call bypass
+		 * as a lookup on "." would generate a locking error.
+		 * So all the calls which get us here have a locked vpp. :-)
+		 */
+		error = layer_node_create(old_vps[0]->v_mount, **vppp, *vppp);
+	}
+
+ out:
+	return (error);
+}
+
+/*
+ * We have to carry on the locking protocol on the layer vnodes
+ * as we progress through the tree. We also have to enforce read-only
+ * if this layer is mounted read-only.
+ */
+int
+layer_lookup(v)
+	void *v;
+{
+	struct vop_lookup_args /* {
+		struct vnodeop_desc *a_desc;
+		struct vnode * a_dvp;
+		struct vnode ** a_vpp;
+		struct componentname * a_cnp;
+	} */ *ap = v;
+	struct componentname *cnp = ap->a_cnp;
+	int flags = cnp->cn_flags;
+	struct vnode *dvp, *vp, *ldvp;
+	int error, r;
+
+	dvp = ap->a_dvp;
+	*ap->a_vpp = NULL;
+
+	if ((flags & ISLASTCN) && (dvp->v_mount->mnt_flag & MNT_RDONLY) &&
+	    (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME))
+		return (EROFS);
+
+	ldvp = LAYERVPTOLOWERVP(dvp);
+	ap->a_dvp = ldvp;
+	error = VCALL(ldvp, ap->a_desc->vdesc_offset, ap);
+	vp = *ap->a_vpp;
+
+	if (error == EJUSTRETURN && (flags & ISLASTCN) &&
+	    (dvp->v_mount->mnt_flag & MNT_RDONLY) &&
+	    (cnp->cn_nameiop == CREATE || cnp->cn_nameiop == RENAME))
+		error = EROFS;
+	/*
+	 * We must do the same locking and unlocking at this layer as 
+	 * is done in the layers below us. It used to be we would try
+	 * to guess based on what was set with the flags and error codes.
+	 *
+	 * But that doesn't work. So now we have the underlying VOP_LOOKUP
+	 * tell us if it released the parent vnode, and we adjust the
+	 * upper node accordingly. We can't just look at the lock states
+	 * of the lower nodes as someone else might have come along and
+	 * locked the parent node after our call to VOP_LOOKUP locked it.
+	 */
+	if ((cnp->cn_flags & PDIRUNLOCK)) {
+		LAYERFS_UPPERUNLOCK(dvp, 0, r);
+	}
+	if (ldvp == vp) {
+		/*
+		 * Did lookup on "." or ".." in the root node of a mount point.
+		 * So we return dvp after a VREF.
+		 */
+		*ap->a_vpp = dvp;
+		VREF(dvp);
+		vrele(vp);
+	} else if (vp != NULL) {
+		error = layer_node_create(dvp->v_mount, vp, ap->a_vpp);
+	}
+	return (error);
+}
+
+/*
+ * Setattr call. Disallow write attempts if the layer is mounted read-only.
+ */
+int
+layer_setattr(v)
+	void *v;
+{
+	struct vop_setattr_args /* {
+		struct vnodeop_desc *a_desc;
+		struct vnode *a_vp;
+		struct vattr *a_vap;
+		struct ucred *a_cred;
+		struct proc *a_p;
+	} */ *ap = v;
+	struct vnode *vp = ap->a_vp;
+	struct vattr *vap = ap->a_vap;
+
+  	if ((vap->va_flags != VNOVAL || vap->va_uid != (uid_t)VNOVAL ||
+	    vap->va_gid != (gid_t)VNOVAL || vap->va_atime.tv_sec != VNOVAL ||
+	    vap->va_mtime.tv_sec != VNOVAL || vap->va_mode != (mode_t)VNOVAL) &&
+	    (vp->v_mount->mnt_flag & MNT_RDONLY))
+		return (EROFS);
+	if (vap->va_size != VNOVAL) {
+ 		switch (vp->v_type) {
+ 		case VDIR:
+ 			return (EISDIR);
+ 		case VCHR:
+ 		case VBLK:
+ 		case VSOCK:
+ 		case VFIFO:
+			return (0);
+		case VREG:
+		case VLNK:
+ 		default:
+			/*
+			 * Disallow write attempts if the filesystem is
+			 * mounted read-only.
+			 */
+			if (vp->v_mount->mnt_flag & MNT_RDONLY)
+				return (EROFS);
+		}
+	}
+	return (LAYERFS_DO_BYPASS(vp, ap));
+}
+
+/*
+ *  We handle getattr only to change the fsid.
+ */
+int
+layer_getattr(v)
+	void *v;
+{
+	struct vop_getattr_args /* {
+		struct vnode *a_vp;
+		struct vattr *a_vap;
+		struct ucred *a_cred;
+		struct proc *a_p;
+	} */ *ap = v;
+	struct vnode *vp = ap->a_vp;
+	int error;
+
+	if ((error = LAYERFS_DO_BYPASS(vp, ap)) != 0)
+		return (error);
+	/* Requires that arguments be restored. */
+	ap->a_vap->va_fsid = vp->v_mount->mnt_stat.f_fsid.val[0];
+	return (0);
+}
+
+int
+layer_access(v)
+	void *v;
+{
+	struct vop_access_args /* {
+		struct vnode *a_vp;
+		int  a_mode;
+		struct ucred *a_cred;
+		struct proc *a_p;
+	} */ *ap = v;
+	struct vnode *vp = ap->a_vp;
+	mode_t mode = ap->a_mode;
+
+	/*
+	 * Disallow write attempts on read-only layers;
+	 * unless the file is a socket, fifo, or a block or
+	 * character device resident on the file system.
+	 */
+	if (mode & VWRITE) {
+		switch (vp->v_type) {
+		case VDIR:
+		case VLNK:
+		case VREG:
+			if (vp->v_mount->mnt_flag & MNT_RDONLY)
+				return (EROFS);
+			break;
+		default:
+			break;
+		}
+	}
+	return (LAYERFS_DO_BYPASS(vp, ap));
+}
+
+/*
+ * We must handle open to be able to catch MNT_NODEV and friends.
+ */
+int
+layer_open(v)
+	void *v;
+{
+	struct vop_open_args *ap = v;
+	struct vnode *vp = ap->a_vp;
+	enum vtype lower_type = LAYERVPTOLOWERVP(vp)->v_type;
+
+	if (((lower_type == VBLK) || (lower_type == VCHR)) &&
+	    (vp->v_mount->mnt_flag & MNT_NODEV))
+		return ENXIO;
+
+	return LAYERFS_DO_BYPASS(vp, ap);
+}
+
+/*
+ * We need to process our own vnode lock and then clear the
+ * interlock flag as it applies only to our vnode, not the
+ * vnodes below us on the stack.
+ */
+int
+layer_lock(v)
+	void *v;
+{
+	struct vop_lock_args /* {
+		struct vnode *a_vp;
+		int a_flags;
+		struct proc *a_p;
+	} */ *ap = v;
+	struct vnode *vp = ap->a_vp, *lowervp;
+	int	flags = ap->a_flags, error;
+	struct proc *p = ap->a_p;
+
+	if (vp->v_flag & VXLOCK) /* XXX this is a disaster -tedu XXX */
+		return (0);
+
+	if (vp->v_vnlock != NULL) {
+		/*
+		 * The lower level has exported a struct lock to us. Use
+		 * it so that all vnodes in the stack lock and unlock
+		 * simultaneously. Note: we don't DRAIN the lock as DRAIN
+		 * decommissions the lock - just because our vnode is
+		 * going away doesn't mean the struct lock below us is.
+		 * LK_EXCLUSIVE is fine.
+		 */
+		if ((flags & LK_TYPE_MASK) == LK_DRAIN)
+			return (lockmgr(vp->v_vnlock, (flags & ~LK_TYPE_MASK) |
+			    LK_EXCLUSIVE, &vp->v_interlock, p));
+		else
+			return (lockmgr(vp->v_vnlock, flags, &vp->v_interlock, p));
+	} else {
+		/*
+		 * Ahh well. It would be nice if the fs we're over would
+		 * export a struct lock for us to use, but it doesn't.
+		 *
+		 * To prevent race conditions involving doing a lookup
+		 * on "..", we have to lock the lower node, then lock our
+		 * node. Most of the time it won't matter that we lock our
+		 * node (as any locking would need the lower one locked
+		 * first). But we can LK_DRAIN the upper lock as a step
+		 * towards decomissioning it.
+		 */
+		lowervp = LAYERVPTOLOWERVP(vp);
+		if (flags & LK_INTERLOCK) {
+			simple_unlock(&vp->v_interlock);
+			flags &= ~LK_INTERLOCK;
+		}
+		if ((flags & LK_TYPE_MASK) == LK_DRAIN) {
+			error = VOP_LOCK(lowervp, (flags & ~LK_TYPE_MASK) |
+			    LK_EXCLUSIVE, p);
+		} else {
+			error = VOP_LOCK(lowervp, flags, p);
+		}
+		if (error)
+			return (error);
+		if ((error = lockmgr(&vp->v_lock, flags, &vp->v_interlock, p))) {
+			VOP_UNLOCK(lowervp, 0, p);
+		}
+		return (error);
+	}
+}
+
+/*
+ */
+int
+layer_unlock(v)
+	void *v;
+{
+	struct vop_unlock_args /* {
+		struct vnode *a_vp;
+		int a_flags;
+		struct proc *a_p;
+	} */ *ap = v;
+	struct vnode *vp = ap->a_vp;
+	int	flags = ap->a_flags;
+	struct proc *p = ap->a_p;
+
+	if (vp->v_flag & VXLOCK)
+		return (0);
+
+	if (vp->v_vnlock != NULL) {
+		return (lockmgr(vp->v_vnlock, ap->a_flags | LK_RELEASE,
+		    &vp->v_interlock, p));
+	} else {
+		if (flags & LK_INTERLOCK) {
+			simple_unlock(&vp->v_interlock);
+			flags &= ~LK_INTERLOCK;
+		}
+		VOP_UNLOCK(LAYERVPTOLOWERVP(vp), flags, p);
+		return (lockmgr(&vp->v_lock, ap->a_flags | LK_RELEASE,
+		    &vp->v_interlock, p));
+	}
+}
+
+/*
+ * As long as genfs_nolock is in use, don't call VOP_ISLOCKED(lowervp)
+ * if vp->v_vnlock == NULL as genfs_noislocked will always report 0.
+ */
+int
+layer_islocked(v)
+	void *v;
+{
+	struct vop_islocked_args /* {
+		struct vnode *a_vp;
+	} */ *ap = v;
+	struct vnode *vp = ap->a_vp;
+
+	if (vp->v_vnlock != NULL)
+		return (lockstatus(vp->v_vnlock));
+	else
+		return (lockstatus(&vp->v_lock));
+}
+
+/*
+ * If vinvalbuf is calling us, it's a "shallow fsync" -- don't bother
+ * syncing the underlying vnodes, since they'll be fsync'ed when
+ * reclaimed; otherwise,
+ * pass it through to the underlying layer.
+ *
+ * XXX Do we still need to worry about shallow fsync?
+ */
+
+int
+layer_fsync(v)
+	void *v;
+{
+	struct vop_fsync_args /* {
+		struct vnode *a_vp;
+		struct ucred *a_cred;
+		int  a_flags;
+		off_t offlo;
+		off_t offhi;
+		struct proc *a_p;
+	} */ *ap = v;
+
+	return (LAYERFS_DO_BYPASS(ap->a_vp, ap));
+}
+
+
+int
+layer_inactive(v)
+	void *v;
+{
+	struct vop_inactive_args /* {
+		struct vnode *a_vp;
+		struct proc *a_p;
+	} */ *ap = v;
+	struct vnode *vp = ap->a_vp;
+	struct proc *p = ap->a_p;
+
+	/*
+	 * Do nothing (and _don't_ bypass).
+	 * Wait to vrele lowervp until reclaim,
+	 * so that until then our layer_node is in the
+	 * cache and reusable.
+	 *
+	 * NEEDSWORK: Someday, consider inactive'ing
+	 * the lowervp and then trying to reactivate it
+	 * with capabilities (v_id)
+	 * like they do in the name lookup cache code.
+	 * That's too much work for now.
+	 */
+	VOP_UNLOCK(vp, 0, p);
+
+	/* ..., but don't cache the device node. */
+	if (vp->v_type == VBLK || vp->v_type == VCHR)
+		vgone(vp);
+	return (0);
+}
+
+int
+layer_reclaim(v)
+	void *v;
+{
+	struct vop_reclaim_args /* {
+		struct vnode *a_vp;
+		struct proc *a_p;
+	} */ *ap = v;
+	struct vnode *vp = ap->a_vp;
+	struct layer_mount *lmp = MOUNTTOLAYERMOUNT(vp->v_mount);
+	struct layer_node *xp = VTOLAYER(vp);
+	struct vnode *lowervp = xp->layer_lowervp;
+
+	/*
+	 * Note: in vop_reclaim, the node's struct lock has been
+	 * decomissioned, so we have to be careful about calling
+	 * VOP's on ourself. Even if we turned a LK_DRAIN into an
+	 * LK_EXCLUSIVE in layer_lock, we still must be careful as VXLOCK is
+	 * set.
+	 */
+	/* After this assignment, this node will not be re-used. */
+	if ((vp == lmp->layerm_rootvp)) {
+		/*
+		 * Oops! We no longer have a root node. Most likely reason is
+		 * that someone forcably unmunted the underlying fs.
+		 *
+		 * Now getting the root vnode will fail. We're dead. :-(
+		 */
+		lmp->layerm_rootvp = NULL;
+	}
+	xp->layer_lowervp = NULL;
+	simple_lock(&lmp->layerm_hashlock);
+	LIST_REMOVE(xp, layer_hash);
+	simple_unlock(&lmp->layerm_hashlock);
+	FREE(vp->v_data, M_TEMP);
+	vp->v_data = NULL;
+	vrele (lowervp);
+	return (0);
+}
+
+/*
+ * We just feed the returned vnode up to the caller - there's no need
+ * to build a layer node on top of the node on which we're going to do
+ * i/o. :-)
+ */
+int
+layer_bmap(v)
+	void *v;
+{
+	struct vop_bmap_args /* {
+		struct vnode *a_vp;
+		daddr_t  a_bn;
+		struct vnode **a_vpp;
+		daddr_t *a_bnp;
+		int *a_runp;
+	} */ *ap = v;
+	struct vnode *vp;
+
+	ap->a_vp = vp = LAYERVPTOLOWERVP(ap->a_vp);
+
+	return (VCALL(vp, ap->a_desc->vdesc_offset, ap));
+}
+
+int
+layer_print(v)
+	void *v;
+{
+	struct vop_print_args /* {
+		struct vnode *a_vp;
+	} */ *ap = v;
+	struct vnode *vp = ap->a_vp;
+	printf ("\ttag VT_LAYERFS, vp=%p, lowervp=%p\n", vp, LAYERVPTOLOWERVP(vp));
+	VOP_PRINT(LAYERVPTOLOWERVP(vp));
+	return (0);
+}
+
+/*
+ * XXX - vop_strategy must be hand coded because it has no
+ * vnode in its arguments.
+ * This goes away with a merged VM/buffer cache.
+ */
+int
+layer_strategy(v)
+	void *v;
+{
+	struct vop_strategy_args /* {
+		struct buf *a_bp;
+	} */ *ap = v;
+	struct buf *bp = ap->a_bp;
+	int error;
+	struct vnode *savedvp;
+
+	savedvp = bp->b_vp;
+	bp->b_vp = LAYERVPTOLOWERVP(bp->b_vp);
+
+	error = VOP_STRATEGY(bp);
+
+	bp->b_vp = savedvp;
+
+	return (error);
+}
+
+/*
+ * XXX - like vop_strategy, vop_bwrite must be hand coded because it has no
+ * vnode in its arguments.
+ * This goes away with a merged VM/buffer cache.
+ */
+int
+layer_bwrite(v)
+	void *v;
+{
+	struct vop_bwrite_args /* {
+		struct buf *a_bp;
+	} */ *ap = v;
+	struct buf *bp = ap->a_bp;
+	int error;
+	struct vnode *savedvp;
+
+	savedvp = bp->b_vp;
+	bp->b_vp = LAYERVPTOLOWERVP(bp->b_vp);
+
+	error = VOP_BWRITE(bp);
+
+	bp->b_vp = savedvp;
+
+	return (error);
+}
+
+#if 0
+int
+layer_getpages(v)
+	void *v;
+{
+	struct vop_getpages_args /* {
+		struct vnode *a_vp;
+		voff_t a_offset;
+		struct vm_page **a_m;
+		int *a_count;
+		int a_centeridx;
+		vm_prot_t a_access_type;
+		int a_advice;
+		int a_flags;
+	} */ *ap = v;
+	struct vnode *vp = ap->a_vp;
+	int error;
+
+	/*
+	 * just pass the request on to the underlying layer.
+	 */
+
+	if (ap->a_flags & PGO_LOCKED) {
+		return EBUSY;
+	}
+	ap->a_vp = LAYERVPTOLOWERVP(vp);
+	simple_unlock(&vp->v_interlock);
+	simple_lock(&ap->a_vp->v_interlock);
+	error = VCALL(ap->a_vp, VOFFSET(vop_getpages), ap);
+	return error;
+}
+
+int
+layer_putpages(v)
+	void *v;
+{
+	struct vop_putpages_args /* {
+		struct vnode *a_vp;
+		voff_t a_offlo;
+		voff_t a_offhi;
+		int a_flags;
+	} */ *ap = v;
+	struct vnode *vp = ap->a_vp;
+	int error;
+
+	/*
+	 * just pass the request on to the underlying layer.
+	 */
+
+	ap->a_vp = LAYERVPTOLOWERVP(vp);
+	simple_unlock(&vp->v_interlock);
+	simple_lock(&ap->a_vp->v_interlock);
+	error = VCALL(ap->a_vp, VOFFSET(vop_putpages), ap);
+	return error;
+}
+#endif